Subjects -> EARTH SCIENCES (Total: 771 journals)
    - EARTH SCIENCES (527 journals)
    - GEOLOGY (94 journals)
    - GEOPHYSICS (33 journals)
    - HYDROLOGY (29 journals)
    - OCEANOGRAPHY (88 journals)

GEOPHYSICS (33 journals)

Showing 1 - 31 of 31 Journals sorted alphabetically
Acta Geologica Polonica     Open Access  
Artificial Intelligence in Geosciences     Open Access   (Followers: 6)
Chinese Journal of Geophysics     Full-text available via subscription   (Followers: 1)
Contributions to Geophysics and Geodesy     Open Access   (Followers: 1)
Energy Geoscience     Open Access  
Eos, Transactions American Geophysical Union     Open Access   (Followers: 5)
Geodesy and Cartography     Open Access   (Followers: 2)
Geodesy and Cartography : The Journal of Committee on Geodesy of Polish Academy of Sciences     Open Access   (Followers: 2)
Geodesy and Geodynamics     Open Access  
Geofísica internacional     Open Access  
Geology, Geophysics and Environment     Open Access   (Followers: 1)
GEOMATICA     Hybrid Journal  
Geomechanics and Geophysics for Geo-Energy and Geo-Resources     Hybrid Journal  
Geophysical Research Letters     Full-text available via subscription   (Followers: 179)
GeoScience Engineering     Open Access  
Geothermal Energy     Open Access   (Followers: 5)
GIScience & Remote Sensing     Open Access   (Followers: 54)
Greenhouse Gases : Science and Technology     Hybrid Journal   (Followers: 4)
Interpretation     Hybrid Journal   (Followers: 1)
Journal of Earth Sciences and Geotechnical Engineering     Open Access   (Followers: 4)
Journal of Environmental & Engineering Geophysics     Hybrid Journal   (Followers: 3)
Journal of Remote Sensing & GIS     Full-text available via subscription   (Followers: 38)
Journal of the Earth and Space Physics     Open Access   (Followers: 9)
Near Surface Geophysics     Open Access   (Followers: 1)
New Zealand Journal of Geology and Geophysics     Hybrid Journal   (Followers: 6)
NRIAG Journal of Astronomy and Geophysics     Open Access   (Followers: 4)
Physics and Chemistry of the Earth, Parts A/B/C     Hybrid Journal   (Followers: 10)
Research in Geophysics     Open Access   (Followers: 5)
Results in Geophysical Sciences     Open Access  
Reviews of Geophysics     Full-text available via subscription   (Followers: 49)
Transportation Geotechnics     Full-text available via subscription   (Followers: 1)
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Interpretation
Number of Followers: 1  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 2324-8858 - ISSN (Online) 2324-8866
Published by Society of Exploration Geophysicists Homepage  [3 journals]
  • The controlling effect of chair-shaped slope break landforms on
           sedimentation in continental faulted basins: A case study in the
           Xilinhaolai area, Baiyinchagan depression, Erlian Basin, China

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      Abstract: AbstractTo reveal the geomorphic characteristics of the gentle slope zone in a continental faulted basin and its control on sedimentary systems, we have performed the geomorphic units division and comprehensive analysis of seismic facies, well-log facies, and core facies in the Xilinhaolai area in the western area of the Baiyinchagan depression, North China. The results find that the gentle slope in the Xilinhaolai area developed a chair-shaped slope break, which includes four geomorphic segments: steep slope of the depression margin (SSDM), shallow-water gentle slope (SWGS), deepwater steep slope (DWSS), and depression center. The chair-shaped slope break controlled the distribution of the sand body by controlling the water depth and hydrodynamic type of sedimentation. The SSDM was a favorable place for the deposition of beach bars. It has become a good oil reservoir not only because of its shallow burial and good physical properties but also because of the location configured with stepped faults. On the SWGS, the active river current and lake waves caused the deposition of large-scale braided river deltas and shoal bars, which are already the main oil and gas areas discovered in the Xilinhaolai area. On the DWSS, a large-scale slump turbidite fan developed and became a very favorable oil and gas reservoir near the oil and gas source rock. The slumped turbidite fans on the DWSS and the shoal bar on the SSDM are potentially favorable reservoirs for future oil exploration.
      PubDate: Fri, 29 Jul 2022 00:00:00 GMT
       
  • Can I, should I be a reviewer'

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      PubDate: Fri, 29 Jul 2022 00:00:00 GMT
       
  • Introduction to special section: Machine learning for image-based geologic
           interpretation

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      PubDate: Mon, 25 Jul 2022 00:00:00 GMT
       
  • Introduction to special section: Multienergy resources in super Ordos
           Basin

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      Abstract: The Ordos Basin is an important superimposed sedimentary basin in Central China, covering an area of more than 320,000 km2. The basin has evolved from a Lower Paleozoic marine carbonate basin to Upper Paleozoic coal-bearing basin, and to Mesozoic-Cenozoic continental craton basin, forming a complete tectonic cycle and depositional successions from marine to lacustrine system. The Ordos Basin is rich in oil, natural gas, helium, coal, uranium, geothermal, and other energy resources. In recent years, great progress has been made in petroleum exploration and development in the Ordos Basin, which makes it the largest oil and gas producing basin in China. The new oil and gas are mainly extracted from unconventional reservoirs such as coal measure strata, tight sandstone, and shale.
      PubDate: Thu, 21 Jul 2022 00:00:00 GMT
       
  • Heterogeneous characteristics and controlling factors of oil bearing of
           the Chang 7 shale in the Ordos Basin

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      Abstract: AbstractOil-bearing evaluation is the key issue of shale oil geologic exploration, which affects the mobility and effective development of the remaining oil in the shale system. To study the oil content and its controlling factors of shale in Chang 7 member of the Yanchang Formation in the Ordos Basin, we take the core of well H317 as the main research object, analyze the oil-bearing characteristics of shale by conventional rock pyrolysis and multistep pyrolysis experimental methods, and analyze the change characteristics of the elements by handheld X-ray fluorescence. The results indicate that the organic heterogeneity of Chang 7 shale in well H317 is obvious. It can be divided into upper shale and lower shale with 2467 m as the boundary. The upper shale has low total organic carbon (TOC), poor kerogen type, and slightly low oil content, but strong mobility. The lower shale has high TOC, good kerogen type, and good oil content, but poor mobility. The content and type of organic carbon in shale have obvious control effect on oil bearing and mobility. Differences in paleosedimentary environment control the formation of original sedimentary organic matter. During the lower shale deposition period, the climate was humid and the terrigenous input was relatively weak, high paleoproductivity and strong reducing water effectively preserved the original sedimentary organic matter, and finally formed an organic-rich interval with high TOC. Early diagenesis further altered the abundance and type of original organic matter.
      PubDate: Wed, 20 Jul 2022 00:00:00 GMT
       
  • Machine-learning-based automatic well-log completion and generation:
           Examples from the Ordos Basin, China

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      Abstract: AbstractOilfields have large amounts of old well-logging data, some of which were possibly lost or distorted for borehole situation, limiting the use of well-logging in formation evaluation. Machine-learning algorithms provide possibility to complete or correct bad quality logging, even to generate new loggings. We took 50 wells in the Ordos Basin, a prolific hydrocarbon production basin, as an example to complete and generate well- loggings. We applied three algorithms, such as random forest (RF), extreme gradient boosting (XGBoost), and deep neural network (DNN) algorithm, for well-logging curve completion experiments. We generated resistivity loggings including deep investigate lateral resistivity log (RILD) and medium investigate lateral resistivity log (RILM) using four loggings, e.g. the spontaneous potential (SP), gamma ray (GR), acoustic log (AC), and electrical resistivity log (R4). After data preprocessing, we used training data sets and validation data sets, accounting for 90% and 10% of all database, respectively, to complete and generate well-logs. The results reveal that the XGBoost algorithm has a better effect on well-log completion if the parameters used are sufficiently optimized with experience, whereas the DNN algorithm has great advantages if large sufficient amounts of well-log data sets are available in the training sets. In this experiment, the accuracy of results by RF algorithm is better than those by XGBoost algorithm because the optimized parameters are difficult to guarantee without experience, and better than that, by DNN algorithms in which the input number of wells is less than 300 and may not be sufficient. In addition, RF algorithm has wider expansibility, higher efficiency, lower computation requirements, and better generalization ability. Our work provides a better understanding of the conditions and function of the application of different machine-learning algorithms to well-logging completion and generation.
      PubDate: Wed, 20 Jul 2022 00:00:00 GMT
       
  • Introduction to special section: Recent advances in lacustrine
           moderate-low maturity shale oil exploration and development

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      PubDate: Thu, 14 Jul 2022 00:00:00 GMT
       
  • Lisbon Field: Geology of microseepage

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      Abstract: AbstractCertain satellite sensors can be used for mineral identification and thus detection of alteration indicative of hydrocarbon microseepage. However, care must be taken when placing these results into context because alteration also can be due to other factors. The authors review the rationale for multiscale and multispectral image selection as well as the benefit of iterative processing, to highlight alteration within a given formation. The authors determine using remote sensing results integrated with other geologic information to confirm that alteration exists, compare results with a conceptual microseepage model, reconcile alteration pattern and extent with the geologic setting and trap timing, and appraise the potential that other factors may have caused alteration. The authors used geologic information from the well-studied Lisbon Field including, but not limited to, geochemistry, petrography and diagenetic studies, and paleo-structure reconstruction. We evaluated whether the alteration model made sense by assessing the thermal history and estimating volumetrics and seepage rate based on the geologic setting and extent of alteration. The results confirm that the alteration at the Lisbon Field is compatible with hydrocarbon microseepage as its principal cause, however, it cannot rule out the possibility that some of it may be due to hydrothermal fluid migration.
      PubDate: Thu, 14 Jul 2022 00:00:00 GMT
       
  • Applicability of decision tree-based machine learning models in the
           prediction of core-calibrated shale facies from wireline logs in the late
           Devonian Duvernay Formation, Alberta, Canada

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      Abstract: AbstractWell logs provide insight into stratigraphically compartmentalized rock properties and are a cost-effective alternative to core. The identification of reservoir (and nonreservoir) facies in core, and their calibration to well-log response has traditionally relied on expert domain knowledge and is inherently inconsistent. Such analyses are time-consuming, tedious, error prone, and often biased due to a lack of objectivity. Automated lithologic interpretations from wireline logs appear to be a promising solution for identifying and understanding depositional complexity within a reservoir. Using the Duvernay Formation in the Western Canada Sedimentary Basin as a case study, the authors evaluate the applicability of decision tree-based machine learning (ML) methods in the prediction of core-calibrated facies and/or facies association distributions within wireline logs. The authors use three independent decision tree-based ML models to predict (1) facies (FACM), (2) facies associations (FAM), and (3) reservoir rock (RESM) from wireline logs. Model accuracies are 60.3%, 88.1%, and 88.1% for FACM, FAM, and RESM, respectively, but individual class F1 scores range from 0 to 0.92. The authors attribute discrepancies in individual class performance to interval thickness, sample proportion of training data, and distinguishability of the output class. Classes thicker than 3 m and encompassing at least 16% of the training data set have F1 scores greater than 0.60. The authors attribute exceptions to these general cutoffs to the ability to recognize diagnostic sedimentologic features observed in core. Results from this study help in understanding stratigraphic complexity in the absence of core aiding in subsurface characterization of reservoirs.
      PubDate: Thu, 14 Jul 2022 00:00:00 GMT
       
  • Laminar structure differences and heterogeneities in reservoirs in
           continental organic-rich shales: The Cretaceous Nenjiang Formation in the
           Songliao Basin

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      Abstract: AbstractShale has a unique laminar structure that is currently the focus of considerable interest and a great deal of research in the academic community and industry. Studies have focused primarily on the differences among laminar combinations, whereas only a few have investigated the structure of individual lamina. In this study, we use typical organic-rich shale from the Cretaceous Nenjiang Formation in the Songliao Basin as an example and analyze each individual lamina of the shale on a millimeter scale. We have investigated heterogeneities among the different laminae by using X-ray fluorescence analysis, rock slicing, laser scanning confocal microscopy, field emission scanning electron microscopy, total organic carbon (TOC), rock pyrolysis, X-ray diffraction mineral analysis, electronic computer tomography (nano-CT), nitrogen adsorption, and other experimental methods. Four laminar units — composed of clay minerals, feldspar-quartz, and calcite — are distinguished based on their different levels of Ca, K, and Fe. We designate these units as UA, UB, UC, and UD (from the top to bottom in the formation). The palaeoenvironment, organic geochemical parameters, and mineral compositions of the different laminar structures are “two-stage” in character. From UD to UA, TOC values indicate a slightly decreasing trend, whereas the calcite content indicates a substantial increase, which is related to gradual reduction in the paleodepth, increasing aridity of the climate, increase of salinity, and decrease of reducibility during the sedimentary period. Different laminae correspond to different pore structures. The pore types in units UC and UD are mainly clay mineral-related pores and pyrite intergranular pores. In contrast, calcite dissolution pores are common in units UA and UB. Nitrogen adsorption and nano-CT data indicate that the pore development degree and pore size of organic matter in units UC and UD are better than those of units UA and UB. The porosity of UD is 2.6 times higher than that of UA. Laminae have an important influence on shale quality. The traditional approach to shale evaluation takes laminar combinations in shale strata as the research unit. Switching the focus to the heterogeneity of individual lamina could help in the selection of “sweet spots” and identification of optimal locations for shale oil exploration and development.
      PubDate: Wed, 06 Jul 2022 00:00:00 GMT
       
  • Introduction to special section: CO 2 geologic storage and utilization:
           Recent advances and future perspectives

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      Abstract: Sequestration of CO2 in geologic formations is one of the most promising solutions for mitigating the effects of point-sourced carbon emissions on the global climate. Geologic formations have the potential to store vast amounts of injected CO2, captured from industrial sources, safely over geologic time. Nevertheless, the subsurface properties and flow characteristics of these “reservoirs” can vary substantially from what is desired or understood in typical oil and gas exploration strategies. In response to the global and financial challenges and opportunities associated with excess CO2 emissions, several industrial sectors, the scientific community, and various international governmental entities have begun to heavily invest in geologic storage.
      PubDate: Wed, 06 Jul 2022 00:00:00 GMT
       
  • Introduction to special section: Formation integrity and borehole
           stability

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      PubDate: Wed, 06 Jul 2022 00:00:00 GMT
       
  • Backthrust play of the Chernyshev swell, Timan-Pechora Basin: Reentry into
           a legacy exploration site based on multidisciplinary study

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      Abstract: AbstractWe have developed a new interpretation of the Povarnitsa High, located in the southern part of the transition zone between the Chernyshov swell and the Kosyu-Rogov trough in the Polar Urals foreland. Petroleum exploration in this area took place in the 1980s and resulted only in an uneconomical oil deposit. Reprocessing and reinterpretation of vintage data and a newly acquired 3D seismic survey along with nonseismic geophysical data provided new insight into the geologic setting of the area. It found a subthrust extension of the Povarnitsa High, overlain by a backthrust sheet floored by upper Ordovician evaporites. This backthrust sheet interpretably resulted from the squeezing of the salt diapir during the late Permian contraction. Stratal patterns of the Silurian-Carboniferous section adjacent to the salt structures suggest early precontraction initiation of the halokinetic deformation, which influenced the distribution of reservoirs such as reefs and oolites. We consider the salt-cored subthrust structural culmination a principal hydrocarbon prospect. It includes multiple reservoir-seal pairs in the Silurian-Permian section at depths ranging from 1 to 4 km. The updated structural model of the Povarnitsa High area suggests that the vintage wells penetrated prospective intervals at the periphery of the closure approximately 1 km downdip from the subthrust crest of the prospect.
      PubDate: Thu, 30 Jun 2022 00:00:00 GMT
       
  • Machine learning delineation of buried igneous features from the offshore
           Otway Basin in southeast Australia

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      Abstract: AbstractMagmatic rocks are frequently encountered during hydrocarbon exploration in rift-related sedimentary basins. As magmatic rocks may contribute positively and negatively to the hydrocarbon systems, their spatiotemporal distribution and structural elements are crucial for exploration in frontier basins. With the proliferation and increased density of seismic reflection data, various subsurface magmatic features can be discriminated and illuminated via conventional interpretation approaches, such as attribute extraction, opacity rendering, or geo-body extraction. However, these manual interpretation techniques are labor-intensive, subject to interpreter bias, and often bottleneck with respect to time data delivery. A supervised machine learning approach could efficiently resolve these issues by amalgamating suitable seismic attributes, such as energy, reflection strength, texture, and similarity, and automatically delineating these magmatic features in 3D seismic reflection data. Our machine learning neural network (NN) classified igneous features from nonigneous features in two different seismic surveys within the natural laboratory of the offshore Otway Basin, southeast Australia. This multilayer perception NN designed in this study resulted in an optimized igneous probability meta-attribute cube that could effectively reveal the extension and distribution of igneous features and several structural elements in the study area. We have developed the detailed workflow of this artificial neural network and observed the efficiency of this approach in different seismic surveys. These results illustrate the potential of the NN in imaging other complex igneous features from 3D seismic data in the Otway Basin and worldwide.
      PubDate: Thu, 30 Jun 2022 00:00:00 GMT
       
  • Rock-mechanical properties and in situ stress state of the Upper
           Cenomanian Mishrif limestone reservoir, Zubair oil field, southern Iraq

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      Abstract: AbstractRock-mechanical properties and tectonic stress state have crucial implications for reservoir stability, drilling, and production optimization. We have developed the first ever in situ stress analysis focused on the Mishrif reservoir from the supergiant Zubair oil field, southern Iraq. We interpreted an overall hydrostatic pore pressure gradient of 9.8 MPa/km and a vertical stress (σv) gradient of 22.17 MPa/km in the Upper Cenomanian Mishrif limestone formation. We inferred a Poisson’s ratio of 0.27–0.31, a Young’s modulus of 27–38 MPa, a coefficient of internal friction range of 0.66–0.76, and estimated a uniaxial compressive strength (UCS) range of 35–70 MPa with a low cohesive strength of 7.8–9.8 MPa from compressional sonic slowness data. We established fitting relationships between the dynamic and static elastic properties from the core-based triaxial test measurements and used the same for estimating the minimum (σhmin) and maximum (σhmax) horizontal stress magnitudes by poroelastic horizontal strain model. We validated the reservoir σhmin with the mini-frac-based fracture closure pressure and interpreted its gradient as 14.5–15.9 MPa/km, whereas we calculated the σhmax gradient as 19.5–23 MPa/km. We interpreted C-quality breakouts from four-arm caliper data and deciphered a northeast–southwest σhmax orientation (N45°E–N70°E). Using the compressive failure criteria, we constrained the reservoir σhmax by stress polygon analysis against the estimated UCS ranges and concluded a normal fault to strike-slip transitional tectonic stress state (σv ≥ σhmax > σhmin) in the Mishrif reservoir.
      PubDate: Thu, 30 Jun 2022 00:00:00 GMT
       
  • 3D magnetic characterization of the Aimorés structure (Brazil) aiming to
           identify interpretation elements under cover: Impact crater or circular
           intrusion'

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      Abstract: AbstractThe Aimorés intrusive complex (AIC), located in the Araçuaí belt (Brazil), has been characterized for many years as the Aimorés Impact Crater due to its topographic features, such as the circular morphology and the ring-shaped rim. Detailed geologic mapping finds a zoned igneous intrusion composed of granite and charnockite rocks in the outer rims, whereas the central part of the structure is covered by overburden. In the absence of direct evidence under the center of the structure, uncertainty remains and there is ambiguity about the geologic interpretation of the area. For this reason, we have used magnetic data to investigate the AIC structure in the subsurface. We explore the different possibilities of geologic scenarios for this region, namely, a pluton with eroded center, a zoned intrusion, a simple impact crater, and a complex impact crater through a synthetic study. Our synthetic tests revealed zoned intrusion and simple impact crater as possible geologic scenarios. Then, in the next stage, we characterize the AIC in three dimensions to unveil the subsurface geometry of the magnetic rocks. The inverted model found the geometry of a high susceptibility ring-shaped body that extends at 4 km depth, pointing to a circular zoned intrusion as the more likely interpretation. Our study has revealed two new geologic features in the study area: (1) the presence of two distinct zones under the central depression cover of the AIC and (2) a new zoned body at southeast of the AIC, which has not been mapped previously because of the overburden. We find the efficacy of using magnetic data for mapping postcollisional intrusions potentially associated with lithium mineralization in subsurface.
      PubDate: Wed, 29 Jun 2022 00:00:00 GMT
       
  • Identifying minor faults on top of coalfield Ordovician limestone stratum
           using seismic attributes derived from azimuthally stacked data

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      Abstract: AbstractIdentifying geologic faults has always been the primary aim of geophysical prospecting work in coalfields. However, identifying minor faults of the top Ordovician limestone stratum (in coalfield areas) remains a significant challenge. As parts of the work described herein, we build a geologic model with a fault located on top of the Ordovician limestone stratum in a coalfield. We use a 2D seismic profile obtained by means of forward modeling in a numerical simulation (by azimuth) process, to fit seismic attributes to a general ellipse equation. The seismic attributes derived from these azimuthally stacked data sets have found that, at the fault locations, the maximum amplitude decreases, whereas the minimum amplitude increases. Fitting the seismic attributes according to the least-squares method for the maximum and minimum amplitudes by azimuth produces ellipses that fitted well to the fault plane and could be used to determine fault plane characteristics. Specifically, the major axis of the ellipses runs parallel to the faults’ strike. At a given fault dip angle, eccentricity (e) can be used to qualitatively determine fault throw and fault dip. The larger the value of eccentricity (e), the greater the fault throw and fault dip. Finally, the validity of this azimuth analysis method is verified by application to actual seismic data.
      PubDate: Wed, 29 Jun 2022 00:00:00 GMT
       
  • Impact of CO 2 generated from coal-measure source rocks on physical
           properties of reservoirs — A case study of the Sulige gas field in the
           Ordos Basin, Northwest China

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      Abstract: AbstractWe did have done thermal simulation experiments on coal-measure source rocks, carbon and oxygen isotope analysis of calcite cement in tight sandstone reservoirs, as well as uniform temperature and composition determination of fluid inclusions to illustrate the relationship between the gas generation of coal-measure source rocks and reservoir densification. Coal-measure source rocks produce a considerable amount of CO2 during the entire thermal simulation experiment, especially in the initial stage with the carbon isotope of CO2 ranging from −21.2‰ to −11.6‰, which indicates organic origin. The carbon isotope value of CO2 becomes heavier as the degree of thermal maturation increases. The carbon isotope of calcite cements in the tight sandstone reservoirs of the lower Shihezi Formation is in the range of −13‰ to −4.7‰, which may have the same origin as the CO2 produced during the gas generation of coal-measure source rocks. CO2 derived from coal-measure source rocks can promote the formation of cement, which may be a key reason for the densification of sandstone reservoirs. The fluid inclusions related to oil and gas charging which are mainly methane and carbon dioxide also can confirm this conclusion. At the same time, the CO2 also will impact the dissolution of potash feldspar, albite, and other minerals as well as the reprecipitation of clay minerals, resulting in a more complicated variation of porosity and permeability. CO2 is of great significance in improving oil recovery and the application of carbon capture, utilization, and storage. Studying the influence of CO2 generated from coal-measure source rocks on the physical properties of reservoirs can provide guidance for the mechanism of CO2 storage in the ground.
      PubDate: Wed, 29 Jun 2022 00:00:00 GMT
       
  • Skeletonization and impermeability characterization of discontinuity
           interface for reservoir with sandstone compartment

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      Abstract: AbstractIn the process of fluvial sedimentary evolution, mudstone interlayer is frequently developed in the interval of sandstone deposition, forming a reservoir of sandstone compartment. Some generally nonpermeable or semipermeable interlayers become discontinuity interfaces of a reservoir, which is one of the causes for the complexity in the distribution of remaining oil. The degree of the impermeability of the discontinuity interface on fluid flow is critical to the development of hydrocarbons. The discontinuity interface, a small-scale reservoir discontinuity comparing with the fault, is generally below the seismic vertical resolution (λ/4). The key to the study of the discontinuity interface is to characterize the variation of plane characteristics of sediments between isochronous seismic horizons. Therefore, we can extract seismic attributes between isochronous seismic horizons to analyze the subtle changes of seismic data, which reflect the distribution of the discontinuity interfaces. In the experiment of gradient vector to detect discontinuity interface in seismic attribute, the authors find that the width of the discontinuity interface is caused by the “lens” shape of the sandstone itself. This phenomenon is an indicator of the impermeability of the discontinuity interface. Here, we have developed a two-step method. First, we use the erosion operator of mathematical morphology to locate the skeleton of the discontinuity interface with the steering of the gradient direction. Second, we measured the width of the discontinuity interface to indicate its impermeability. The application to a field data set demonstrates that the results of this proposed method are consistent with the production data of the wells. The proposed method characterizes the reservoir heterogeneity refined from sandstone sets to a single sandstone bed, which improves the resolution of seismic geologic interpretation.
      PubDate: Wed, 29 Jun 2022 00:00:00 GMT
       
  • Geochemical characteristics and shale oil exploration potential of the
           Da’anzhai Member in the Sichuan Basin, southwest China

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      Abstract: AbstractBased on the analysis of the organic geochemical characteristics of the shale in the Da’anzhai Member in the Sichuan Basin, southwest China, we discuss the hydrocarbon generation potential, hydrocarbon expulsion efficiency (EH), and oil-bearing properties to identify the dominant exploration direction for shale oil. The results indicate that: (1) the Da’anzhai shale has low organic matter content and high maturity with the average total organic carbon (TOC) content of 1.27% and average vitrinite reflectance (Ro) of 1.29%, (2) the EH of the Da’anzhai shale ranges from 0% to 92% with an average value of 72%, (3) the lower limit of TOC for shale commercial production is 1.5%, which is lower than any current standard in China and North America, and (4) shale oil in the center lacustrine basin is more enriched compared with the outskirts of the basin with TOC>1.5%, Ro < 1.25%, EH < 67%, and oil saturation index > 100 mg/(g·TOC). These results indicate that the prospects for shale oil exploration in the central basin are optimistic and should be the key exploration area for shale oil in the future.
      PubDate: Thu, 23 Jun 2022 00:00:00 GMT
       
  • Estimation of horizontal stresses from wellbore failures in strike-slip
           tectonic regime: A case study from the Ordovician reservoir of the
           Tinzaouatine field, Illizi Basin, Algeria

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      Abstract: AbstractWe present a geomechanical analysis of the Ordovician reservoir from the Tinzaouatine field situated in the prolific Illizi Basin, eastern Algeria. The sandstone reservoir has a hydrostatic pore pressure gradient (9.95 MPa/km). We analyzed a cumulative of 300 m of acoustic image log data and identified the coexistence of B-quality extensive drilling-induced tensile failures (DITFs) and compressive failures, i.e., breakouts (BOs), indicating a mean maximum horizontal stress (SHMax) orientation of N140°E. We used a combined BO and DITF-based solution to estimate horizontal stress magnitudes when the two failure types coexist. Based on the C-quality minifrac measurements, we interpreted the minimum horizontal stress (Shmin) gradient as 17.4–17.47 MPa/km, whereas the new approach indicates an Shmin range of 17.31–18.67 MPa/km. Using the BO width and DITF-based approaches, we inferred an SHMax gradient range of 28.37–38.59 MPa/km within the studied reservoir. Based on the relative stress magnitudes, we infer a strike-slip tectonic stress regime in the studied field.
      PubDate: Tue, 21 Jun 2022 00:00:00 GMT
       
  • Downhole microseismic data interpretation for media anisotropy evaluation
           with limited acquisition geometry in Western Siberia

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      Abstract: AbstractWe have evaluated the results of processing and interpretation for one of the first projects in Russia for downhole microseismic monitoring of hydraulic fracturing in Western Siberia. The data are characterized by large distance to the acquisition array and noisy recordings. We illustrate that preliminary quality control of microseismic array installation is a useful tool that may predict some of the issues and help to promote better acquisition quality. Therefore, it is important to reiterate the significance of the supervision for microseismic field measurements, especially when the technology is tested in new regions. Despite limited acquisition aperture and a comparatively small number of observed microseismic events, it is possible to derive valuable interpretation results from the data set. The geometry of the event locations suggests significant unplanned development of the hydraulic fractures, including a significant shift of the fracture from the initiation point. Records with clear S-wave splitting allowed us to determine arrival times of P waves and two S waves for several microseismic events. Arrival times were then used for simultaneous kinematic inversion for microseismic-event location and anisotropic velocity-model update (layered transversely isotropic with the vertical axis of symmetry model). We estimate significant anisotropy from microseismic data. Thomsen parameters ε and γ are well constrained, whereas parameter δ is constrained only for one of the layers.
      PubDate: Wed, 15 Jun 2022 00:00:00 GMT
       
  • Recurrent autoencoder model for unsupervised seismic facies analysis

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      Abstract: AbstractMachine learning-based automatic seismic facies analysis has increased significantly over the past few decades. The key is to select the most representative features (such as the commonly used poststack amplitude data or the induced seismic attributes) as the input of the different machine learning algorithms. As an advanced branch of machine learning, deep learning can be used to extract the discriminatively deep features from seismic data similar to those used in image classification. In this study, we havedeveloped an unsupervised seismic facies analysis method by using a recurrent autoencoder model. First, we have constructed and trained an autoencoder architecture combined with long short-term memory-based recurrent operation. Its main aim is to learn the deep discriminative features by taking the windowed poststack seismic data as the input time series data. This type of unsupervised learning takes advantage of the no labeling requirement of seismic data. In addition, the recurrent operation is beneficial in delineating the time-sequential characteristics of seismic data. Second, we have taken the learned features as the input of simple K-means clustering and analyzed the corresponding seismic facies. In other words, the clustering is executed in the learned feature space (learned feature-based clustering). Real data results have demonstrated that our method reveals more details than the original amplitude-based K-means clustering, depending on the cluster calibration. In particular, according to the known natural gamma-ray logs and lithological descriptions of five wells, different amounts of sandstone and mudstone deposit are more accurately discriminated, which is substantially informative in reservoir prediction and hydrocarbon exploration. Furthermore, the estimated average silhouette scores have quantitatively shown the effectiveness of our method.
      PubDate: Wed, 15 Jun 2022 00:00:00 GMT
       
  • Influencing factors and identification method of low-resistivity pay zone
           in Jurassic, Huanxian area, Ordos Basin

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      Abstract: AbstractHuanxian area is in the west of the Ordos Basin and contains a widely distributed Jurassic low-resistivity pay zone. Due to the lack of a systematic summary of the influencing factors of the Jurassic low-resistivity pay zone in this location, oilfield engineers have not established a logging rapid identification method, increasing the complexity of oilfield exploration and development. Therefore, we reveal the main influencing factors and propose a corresponding logging identification method. Through a groundwater chemical composition test, phase permeability experiment, cast thin-section analysis, seismic data, and logging data, we have obtained the groundwater salinity, irreducible water saturation, clay mineral content, tectonic amplitude, and resistivity and apparent resistivity index of sandstone. The results of the correlation analysis indicated that the groundwater salinity is the main control factor for the development of the Jurassic low-resistivity pay zone in the study area, whereas other factors (such as irreducible water saturation) are secondary influencing factors. We have created a crossplot for groundwater salinity versus sandstone resistivity to identify the Jurassic low-resistivity pay zone based on clarifying the main control factor. The identification accuracy of this crossplot has reached approximately 65% through oil testing conclusions in the study area. To further improve the application, we have replaced sandstone resistivity with an apparent resistivity index in the crossplot. As a result, we have improved the identification accuracy of the Jurassic low-resistivity pay zone to more than 80%, which can meet the production demand. The results of this study can provide technical support for the exploration and development of the Jurassic low-resistivity pay zone, which is significant for optimizing various oil and gas resource production structures and coproduction methods in this location.
      PubDate: Mon, 13 Jun 2022 00:00:00 GMT
       
  • Seismic interpretation pitfalls caused by interference effects,
           exemplified by seismic modeling of outcropping chalk successions

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      Abstract: AbstractInterference and inherent resolution limitations are well-recognized problems in reflection seismic data and have over time led to misinterpretations. Acquisition of seismic data containing a broad range of frequencies, including high frequencies, does not solve this problem but merely moves the problem to a finer scale. Forward seismic modeling of known geologic scenarios is a valuable tool for studying anticipated seismic responses of successions with a given set of geologic and/or rock physical characteristics and for predicting interpretational challenges. We perform finite-difference-based seismic forward modeling on a conceptual geologic model derived from outcropping chalk sections in southeast Denmark and evaluate possible pitfalls that may hamper interpretation of seismic data acquired from strata with similar characteristics. We demonstrate that interbedded strata with contrasting physical properties and variable thickness can result in interference effects resembling faults and fractures. The result has significance for characterization, e.g., geothermal sites, potential CO2 storage targets, groundwater reservoirs, and hydrocarbon exploration sites, in which the proper imaging of faults and fractures from seismic data is an essential task.
      PubDate: Mon, 13 Jun 2022 00:00:00 GMT
       
  • Heterogeneity of pore-throat structures and petrophysical properties of
           tight sandstone and its influence on seepage: A case study of sandstone in
           the Yanchang Formation, Ordos Basin, China

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      Abstract: AbstractTight sandstone reservoirs are characterized by poor petrophysical properties, strong pore-throat structures, and heterogeneous permeability, which prevent oilfield water flooding. We take the tight sandstone reservoir of the Yanchang Formation in Ordos Basin as an example, select samples from the Chang 6 and Chang 8 members in the HX block for constant-rate mercury injection and single-core and combined-core model water-flooding tests, and discuss the effects of heterogeneous pore-throat structures and petrophysical properties on the seepage of the tight sandstone. Constant-rate mercury injection tests found that the permeability of the tight sandstone was controlled by the throats. Compared with the pore structures, the throat structures were more heterogeneous, and the samples with more heterogeneous throats were more permeable. Therefore, in addition to the morphology of the pore-throat structures, the heterogeneity of the throats also was used to evaluate the seepage. When applying the water-flooding tests with the combined-core model, the water absorption capacity of the high-permeability core with a high permeability contrast (7.5) was greater than that of the high-permeability core with a low permeability contrast (3.6). Moreover, by comparing the results from the water-flooding experiment for the same core between a single-core and the combined-core model, the loss of the oil displacement efficiency (70.7%) of the low-permeability core in the combined-core model with a high permeability contrast (7.5) was much higher than that (29.8%) of the low-permeability core in the combined-core model, which had a low permeability contrast (3.6). The water absorption percentage and the recovery of the low-permeability core in the combined-core model with a high permeability contrast were lower, indicating that after water flooding, the remaining oil in the low-permeability reservoir in the area with a strong permeability heterogeneity was enriched. Such enrichment may increase the exploitation potential of tight reservoirs.
      PubDate: Fri, 10 Jun 2022 00:00:00 GMT
       
  • Gas-bearing reservoir distribution in a volcanic environment: Case of the
           Yingcheng Formation, China

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      Abstract: AbstractAs a special type of lithologic body, gas-bearing strata, composed of rhyolite, an igneous rock with a volcanic composition, are characterized by deep burial, complex lithology, poor stratification, and a complicated gas-bearing distribution. These characteristics lead to difficulties in the prediction of gas-bearing reservoir parameters and thus restrict the exploration and exploitation of such reservoirs. The unique and complex volcanic model contains different types of facies and subfacies because the volcanic eruption usually experiences different explosion-effusion periods. Our study focuses on the vertical and lateral gas-bearing reservoir distribution in a volcanic environment in the Cretaceous Yingcheng Formation of the Songnan Gas Field, using seismic facies-controlled nonlinear stochastic inversion to integrate the volcanic facies information. First, we built the volcanic facies model for the Songliao Basin to introduce the comprehensive characteristics of the volcanic facies during a volcanic eruption and analyzed the well-tie logging facies and seismic facies to guide the facies analysis of the target layer. Then, based on this facies analysis, we depicted the gas-bearing reservoir in detail through the use of seismic facies-controlled nonlinear random inversion. Finally, we predicted the distribution of the gas-bearing reservoir by the inversion results. The predicted results were found to agree well with the actual drilling data. The inversion method effectively predicts the velocity distribution of the gas-bearing reservoir, which provides a good foundation for the subsequent description of gas-bearing reservoirs in the Yingcheng Formation.
      PubDate: Tue, 07 Jun 2022 00:00:00 GMT
       
  • Quantitative analysis of paleoenvironment of Qingshankou Formation in
           northern Songliao Basin, Northeastern China

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      Abstract: AbstractThe Qingshankou Formation in the Songliao Basin of northeastern China is an important layer for unconventional oil exploration. To solve the problem of the main controlling factors of shale oil enrichment, to quantitatively analyze the paleosalinity, paleoclimate, paleoredox environment, provenance, and lake productivity, and to clarify the relationship between sedimentary environment and total organic carbon, we have analyzed quantitative reconstruction of the sedimentary environment by using comprehensive analysis of multiple indicators with major and trace elements, fossils, and biomarkers. The results are as follows: the paleosalinity index w(Sr)/w(Ba) ratio is 0.4–4, the w(B)/w(Ga) value is 0.7–8.5, and the w(Pr)/w(Ph) value is 0.8–2.8, which mainly stand for fresh brackish to saline water. The paleoclimate CIW′ (Chemical index of weathering, CIW = [A12O3/(AI203 + CaO+Na20)] × 100 [molecular proportions]) value is 90–100, indicating a warm and humid climate. The redox index w(V)/w((V + Ni)) value is 0.54–0.89, which mainly belongs to the dysoxic environment. The provenance input of terrigenous debris index w(Ti)/w(Al) value is 0.026–0.034, mainly standing for low terrigenous debris input. The production index CAL (enrichment degree of Cu) value is 1–3, belonging to high production. We conclude that the humid climate, the fresh brackish to saline and dysoxic water, and the high lake production provide favorable geologic conditions for biological reproduction and then provide a foundation for the formation, enrichment, and preservation of organic matter. The quantitative reconstruction of the paleoenvironment of the Qingshankou Formation has theoretical significance for Gulong shale oil exploration and development.
      PubDate: Mon, 06 Jun 2022 00:00:00 GMT
       
  • P-wave reflectivity parameterization and nonlinear inversion in terms of
           Young’s modulus and Poisson ratio

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      Abstract: AbstractYoung’s modulus and Poisson ratio are essential parameters for rock brittleness evaluation. At present, prestack inversions of these parameters mostly adopt linear approximation, whereas the nonlinear inversion methods that are based on the exact Zoeppritz equation are seldomly conducted. Nevertheless, in the case of large incident angles and high-impedance contrast, the nonlinear equation has higher accuracy than the linear approximation. It is more in line with the nature of geophysical inversion problems, and it describes the variation of formations’ elastic parameters better than the linear approximation does. Therefore, based on the exact solution of the Zoeppritz equation, we have parameterized and derived a new nonlinear reflection coefficient equation using nonlinear Young’s modulus, Poisson ratio, and density (YPD) as variables. Subsequently, by combining the inverse operator algorithm with the YPD equation, we develop a new nonlinear amplitude-variation-with-offset inversion scheme. This approach can robustly extract Young’s modulus and Poisson ratio from seismic data and identify shale-gas sweet spot locations within the reservoir, as well as predict reservoir fluid properties. We have tested the accuracy and applicability of this approach with synthetic and real data examples.
      PubDate: Thu, 02 Jun 2022 00:00:00 GMT
       
  • Coal and shale distributions on half-graben slopes: A case study of the
           Eocene Pinghu Formation in Xihu Sag, East China Sea

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      Abstract: AbstractSteep and gentle slopes in a half-grabben basin often form oil source rocks of coal and shale. However, which source rock is dominant and what the relation is with the slope type and sedimentary facies are not clear. The Pinghu Formation in Xihu Sag is a half-graben basin with coal seam as the main source rock. Five condensate reservoirs have been found in its west slope, with several wells and 3D seismic data, which makes it possible to study the relationship between slope types and source rocks. We have used logging data, lithologic identification statistics, and seismic inversion to reconstruct the sedimentary facies and paleoslopes in the western Xihu Sag and have analyzed the variations in the proportions of coal and shale in the study area and their relationships with the facies, slope types, and subsag. The results indicate that the upper slope contained a higher proportion of coal than the lower slope. In contrast, the lower slope contained more shale than the upper slope. Coal is dominant in the delta plain and front facies, whereas shales are dominant in the prodelta facies. Although the proportions of coal and shale vary among the southern hinged margin, the central escarpment margin, and the northern hinged margin, the thicknesses of the coal and shale increases northward, independent of the rift margin type. These variations may be related to the filling of the delta from north to south during the deposition of the Eocene Pinghu Formation. These results also suggest that there were no substantial differences in the depositional slopes and water depths of the hinged and escarpment margins. The abundance of shales in the lower slope and at the center of the depression suggest that, in addition to coal, shales should have contributed to petroleum generation in Xihu Sag.
      PubDate: Thu, 02 Jun 2022 00:00:00 GMT
       
  • Nanoindentation investigation of mechanical and creep properties of
           continental Triassic Yanchang Formation shale, Ordos Basin

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      Abstract: AbstractThe mechanical and creep properties of shale have a great impact on wellbore stability and artificial fracturing performance during shale gas exploration. We have applied nanoindentation to study the preceding two aspects of the lacustrine Triassic Yanchang Formation shale in Ordos Basin on the microscale, which is the representative exploration target for shale gas occurring in continental shales in China. A massive nanoindentation campaign finds that the Yanchang shale is highly mechanically heterogeneous in local areas but statistically homogeneous in large areas. The sequentially increasing indentation loads (5–400 mN) result in a two-stage change of values of Young’s modulus and hardness, i.e., descending first and then remaining steady with a turning point at approximately 300 mN, which suggests that the large indentation load of not less than 300 mN can detect the mechanical response of bulk shale on the microscale. In addition, the indentation tests reveal a strong anisotropy of mechanical properties of Yanchang shale, as the measured Young’s modulus and hardness in the bedding plane parallel are much larger than those in the bedding plane normal direction. Furthermore, the Yanchang shale presents strong creep behavior and weak fracture toughness, which are different from those of current gas-producing marine shales worldwide. We attribute this to the higher content of clay minerals and relatively more loose texture of the Yanchang shale. In particular, the creep strain-rate sensitivity (m) is calculated to be 0.102–0.134, suggesting that the dominant deformation mechanism of the lacustrine Yanchang shale may be dislocation creep.
      PubDate: Thu, 02 Jun 2022 00:00:00 GMT
       
  • Assessment of CO 2 storage potential in reservoirs with residual gas using
           deep learning

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      Abstract: AbstractCO2 injection into the underlying water leg of depleted hydrocarbon reservoirs is a desirable option for carbon storage as demonstrated by existing industrial-scale storage projects in these geologic environments. This study sheds light on the effect of residual methane on the CO2 storage efficiency as a screening criterion for selecting a water-bearing zone of a depleted gas reservoir to store CO2. Using compositional reservoir simulations, we have evaluated the impact of residual methane on the injectivity, operational pressure, and long-term CO2 trapping efficiency during injection and postinjection stage in a reservoir model representative of the so-called “HC sand” gas reservoir in the High Island 24L field located in the offshore Texas State Waters. Results suggest that the presence of residual hydrocarbon gas negatively affects CO2 residual and dissolution trapping because it enhances the injectivity and pressure management arising from the increased mobility of CO2 plume in the vicinity of the injection zone due to its mixing with the resident residual hydrocarbon gas. We further investigate the application of artificial neural network (ANN)-based proxy models for fast-track modeling of CO2 storage in geologic structures associated with depleted gas reservoirs, aiming at the prediction of CO2 trapping efficiency. We then use the developed ANN model to perform Monte Carlo simulations for quantifying the uncertainty of geologic and reservoir parameters on CO2 trapping efficiency in these formations. It becomes evident that the residual hydrocarbon saturation is a key screening criterion for the storage site selection. The developed data-driven model can offer a robust and fast tool for screening the water-bearing zone of the depleted gas reservoirs by evaluating the efficiency of CO2 storage.
      PubDate: Wed, 25 May 2022 00:00:00 GMT
       
  • Generating a labeled data set to train machine learning algorithms for
           lithologic classification of drill cuttings

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      Abstract: AbstractDespite significant developments in the past few years in the application of machine learning algorithms for the lithologic classification of rock samples, publicly available labeled data sets are very scarce. We open source a fully labeled data set containing more than 16,000 scanning electron microscopy (SEM) images of drill cutting samples—mounted on thin sections—from a low-permeability reservoir in western Canada. We develop a simplified image processing workflow to segment and isolate the rock chips into individual SEM images, which in turn are used to identify, classify, and quantify rock types based on textural characteristics. In addition, using this data set, we explore the use of convolutional neural networks (CNNs) as a baseline tool for acceleration and automatization of rock-type classification. Without significant modifications to popular CNN models, we obtain an accuracy of approximately 90% for the test set. Results demonstrate the potential of CNN as a fast approach for lithologic classification in low-permeability siltstone reservoirs. In addition to making the data set publicly available, we believe our workflow to segment and isolate drill cutting samples in individual images of rock chips will facilitate future research of drill cuttings properties (e.g., lithology, porosity, and particle size) using machine learning algorithms.
      PubDate: Wed, 25 May 2022 00:00:00 GMT
       
  • Integrated detection and investigation of bad borehole section in the
           Wolfcamp Formation in the Midland Basin using machine learning,
           petrophysics, and core characterization

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      Abstract: AbstractThe quality of formation evaluation and reservoir estimates depends a lot on the quality of open hole logs, which is intricately tied to the borehole geometry and stand-offs. Bad borehole sections cause interesting patterns on wireline logs that can result in multiple interpretations. We have conducted an automated identification of bad borehole sections (>50 ft [15 m] thick) in multiple wells in the Wolfcamp Formation in the Midland Basin of the United States and investigated the causalities behind the unstable borehole section. The wells impacted by bad hole conditions appear to be within a particular region of the northern Midland Basin, and the bad hole condition impacts a specific zone in the Wolfcamp D. We consider well logs as multivariate time series (or depth series), where they share interdependencies to a large extent. We use this concept and unsupervised multivariate time series clustering to automatically identify bad borehole sections. Our proposed workflow simultaneously clusters the wireline logs, resulting in a large labeled regional-scale data set that can be further used for log quality assurance, processing, and petrophysical modeling. More importantly, we investigate the reasons behind the borehole washout, integrating sedimentology and geochemical data. Thick borehole washout sections are related to the presence of a significant amount of clay (>73 wt%, a mixture of smectite and illite) in the Wolfcamp D. The results also indicate that the manual editing of wireline logs and even supervised machine learning-based log reconstruction (commonly known as a missing log prediction problem) can lead to erroneous and inconsistent interpretation of subsurface characteristics. Such exercise can be meaningless if derived models are not validated with the ground truth (preserved subsurface rocks).Geologic feature:Clay-rich unstable borehole sectionLog appearance:Large-to-small caliper response associated with erratic density and neutron porosity logsFeatures with similar appearance:Gypsum, siderite nodules, and tool failureFormation:Wolfcamp FormationAge:WolfcampianLocation:Northern Midland Basin, Texas, USAWell data:Obtained from the IHSAnalysis tools:Unsupervised machine learning, core description, geochemistry, and petrophysical inversion modeling
      PubDate: Tue, 24 May 2022 00:00:00 GMT
       
  • Fault enhancement comparison among coherence enhancement, probabilistic
           neural networks, and convolutional neural networks in the Taranaki Basin
           area, New Zealand

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      Abstract: AbstractFault identification is a critical component of seismic interpretation. During the past 25 years, coherence, curvature, and other seismic attributes sensitive to faults improved seismic interpretation, but human interaction is still required to generate a complete fault interpretation. Today, image enhancement of fault-sensitive attributes, multiattribute fault analysis using shallow learning, and deep-learning algorithms based on extensive training and convolutional neural networks (CNNs) are promising fault interpretation workflows. We have compared three workflows to test fault-detection capabilities; these include image enhancement, probabilistic neural networks (PNNs), and CNNs. We compared results to human-interpreted faults as our ground truth for a merged 3D seismic survey acquired in the Taranaki Basin, New Zealand. We extracted fault surfaces from the results of the workflows using them as seed points for an active contour method. Extracted faults are then compared to the human-interpreted surface using the Hausdorff distance. Data conditioning, including spectral balancing and structure-oriented filtering, improved the performance of all three workflows. Although all three approaches produce enhanced fault volumes, we find differences in fault location and different artifacts (mispredicted faults). Because all three methods exhibit “false positive” predictions, the enhanced multispectral coherence method produces faults and stratigraphic edges in the final image, including residual stair-step artifacts. In our implementation, PNN produces many salt-and-pepper artifacts through the resulting image, suggesting that we might need to include better training data or reduce the volume size to reduce the number of relevant classes to obtain an improved classification. The CNN algorithm is trained with synthetic data that provide rapid results, correctly identifying larger faults, but missing smaller faults and, in some cases, misclassifying mass-transport deposits and angular unconformities as being faults.
      PubDate: Thu, 19 May 2022 00:00:00 GMT
       
  • Quantifying the sensitivity of seismic facies classification to seismic
           attribute selection: An explainable machine-learning study

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      Abstract: AbstractDuring the past two decades, geoscientists have used machine learning (ML) to produce a more quantitative reservoir characterization and discover hidden patterns in their data. However, as the complexity of these models increases, the sensitivity of their results to the choice of the input data becomes more challenging. Measuring how the model uses the input data to perform either a classification or regression task provides an understanding of the data-to-geology relationships which indicates how confident we are in the prediction. To provide such insight, the ML community has developed local interpretable model-agnostic explanations (LIME) and Shapley additive explanations (SHAP) tools. In this study, we train a random forest architecture using a suite of seismic attributes as input to differentiate among mass transport deposits (MTDs), salt, and conformal siliciclastic sediments in a Gulf of Mexico data set. We apply SHAP to understand how the model uses the input seismic attributes to identify target seismic facies and examine in what manner variations in the input, such as adding band-limited random noise or applying a Kuwahara filter, impact the model predictions. During our global analysis, we find that the attribute importance is dynamic, and it changes based on the quality of the seismic attributes and the seismic facies analyzed. For our data volume and target facies, attributes measuring changes in dip and energy show the largest importance for all cases in our sensitivity analysis. We note that to discriminate between the seismic facies, the ML architecture learns a “set of rules” in multiattribute space, and overlap among MTDs, salt, and conformal sediments might exist based on the seismic attribute analyzed. Finally, using SHAP at a voxel scale, we understand why certain areas of interest were misclassified by the algorithm and perform an in-context interpretation to analyze how changes in the geology impacted the model predictions.
      PubDate: Thu, 19 May 2022 00:00:00 GMT
       
  • Experimental investigation on dynamic and static rock mechanical behavior,
           failure modes, and sequences of frequent interbedded sand and shale
           reservoirs

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      Abstract: AbstractHigh variability in diagenetic strength and rock mechanical properties in interbedded sand and shale necessitates a sustained interest in the study of the dynamic and static rock mechanical behavior and failure modes. We have analyzed the rock mechanical behavior, rupture characteristics, and sequences of the clastic reservoirs of the Xu 5 member, Western Sichuan Depression, China. The results indicate that the Xu 5 shale can produce longer plastic creep behavior than tight sandstone at the same load rate. This causes greater stresses to build up inside the shale than in adjacent sandstone formations. The average internal friction angle of sandstone is 43°, whereas the average internal friction angle of shale is 33°. The failure modes of the Xu 5 member sandstone are mainly brittle-tensile failure and brittle X-type shear failure. We observed that the tensile rupture is dominant, accounting for approximately 75.2%. Shale failure forms mainly include plastic-tensile failure and X-type shear failure, in which shear failure accounts for approximately 67.9%. The sequence of failures of similar clastic reservoirs is generally tensile failure or tensile-shear failure to extension failure. We found that the Xu 5 shale has high plasticity, and the stress conditions required for its failure are higher and more complicated. In addition, our test results indicate that, for the same lithology, the tensile failure is the initial rupture rather than shear failure.
      PubDate: Thu, 19 May 2022 00:00:00 GMT
       
  • Semisupervised salt segmentation using mean teacher

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      Abstract: AbstractDetecting subsurface salt structures from seismic images is important for seismic structural analysis and subsurface modeling. Recently, deep learning has been successfully applied in solving salt segmentation problems. However, most of the studies focus on supervised salt segmentation and require numerous accurately labeled data, which are usually laborious and time-consuming to collect, especially for the geophysics community. We have adopted a semisupervised framework for salt segmentation, which requires only a small amount of labeled data. In our method, adopting the mean teacher method, we train two models sharing the same network architecture. The student model is optimized using a combination of supervised loss and unsupervised consistency loss, whereas the teacher model is the exponential moving average of the student model. We introduce the unsupervised consistency loss to better extract information from unlabeled data by constraining the network to give consistent predictions for the input data and its perturbed version. We train and test our novel semisupervised method on synthetic and real data sets. Results demonstrate that our semisupervised salt segmentation method outperforms the supervised baseline when there is a lack of labeled training data.
      PubDate: Thu, 19 May 2022 00:00:00 GMT
       
  • Accelerating core characterization and interpretation through deep
           learning with an application to legacy data sets

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      Abstract: AbstractCore descriptions provide an essential element of ground truth to subsurface reservoir characterizations, but adequate core characterization and interpretation require a significant time commitment from geoscientists because they are usually done manually. Moreover, core characterizations and interpretations often are inconsistent because they are made at different times by different people. We have used deep-learning segmentation networks, trained using worldwide data sets labeled by specialists, to infer lithofacies and structural features on core images. These networks are not intended to provide perfect core descriptions, but rather to provide high-level fully digital characterizations that can be quickly checked for quality and manually fixed if needed. This ensures that all available and relevant data can be used and relieves geoscientists from the most repetitive characterization tasks to allow them to focus on more complex and value-adding integration and interpretation. We test the previously trained networks in legacy public data from a UK field as an example. There are more than 1300 m of released core images in the field, together with multiple vintages of fault interpretations, that significantly differ from one another. Integrating core and seismic-scale structural characterizations is critical because the best reservoir facies are the most prone to deform via permeability-reducing processes. Detailed structural characterization and identification of individual structural features achieved through deep learning provide an unprecedented amount of data to highlight areas where the seismic-scale fault interpretations and core-scale structural interpretations are inconsistent, yielding valuable insights to validate fault interpretation.
      PubDate: Thu, 19 May 2022 00:00:00 GMT
       
  • Coupling relationship between current in-situ stress and natural fractures
           of continental tight sandstone oil reservoirs

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      Abstract: AbstractWe have integrated rock mechanics and acoustic experiments, full-wave array acoustic testing, formation microscanner image logging, and hydraulic-fracturing data to evaluate the coupling relationship between current in-situ stress and natural fractures. We used the data of the Yanchang Formation in the DL block of the western Ordos Basin, China, as an example. Our results find that the Yanchang Formation mainly develops high-angle fractures and vertical fractures. Furthermore, the in-situ stress state of the target sandstone strata satisfies σv>σH>σh. Nearly vertical and high-angle fractures are formed in the environment when σv is the maximum principal stress. Therefore, the current in-situ stress state of the target layer matches the induced fractures (longitudinal tensile-induced fractures) and natural fractures. As the buried depth increases, the difference between the horizontal maximum and minimum stresses (σH−σh) has a tendency to first decrease and then increase, and its conversion depth is approximately 2000 m. Natural fractures are not developed in the distributary bay (the lowest horizontal stress area) and the thick sand area in the middle of the main river channel (the largest horizontal stress area). Natural fractures are mainly developed on the two wings of the main channel, and their horizontal stress is approximately 2–4 MPa lower than the central part of the main channel. We determined a correlation between fractures and sedimentary facies, and we have an important reference value for improving the drilling success rate of tight oil reservoirs. Furthermore, our study provides insights into the prediction of fractures and sweet spots for further exploration and hydraulic fracturing activities in the studied area and elsewhere in continental tight sandstone reservoirs.
      PubDate: Wed, 18 May 2022 00:00:00 GMT
       
  • The mobility of continental shale oil by gas flooding and influencing
           factors based on displacement-nuclear magnetic resonance instruments

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      Abstract: AbstractThe efficient development of shale oil is a challenging problem for researchers. Conventional experiments for characterizing fluid distribution encounter a bottleneck because of the special composition, complex pore structure, and unclear fluid occurrence in shale oil reservoirs. Targeting continental shale in eastern China, we used high-temperature and high-pressure displacement instruments combined with nuclear magnetic resonance instruments for the first time to evaluate the shale oil mobility under different gases (CH4, CO2, and N2) flooding for simulating “huff-n-puff” in the field. Results found that the gas flooding can significantly improve the mobility of shale oil. Compared with CH4 and N2, CO2 had obvious advantages in improving the mobility of shale oil. Under an injection pressure of 6.0 MPa, the experimental average movable ratio was 22.3%, and the theoretical maximum movable ratio was 39.3%. Organic matter abundance, mineral composition, sedimentary structures, and pore structure determine the movable ratio of gas flooding by affecting the permeable channel, phase state of the injected gas, and gas-oil contact. Gas flooding has broad prospects in the exploitation of continental shale oil considering difficult development and abundant gas source in the eastern basin of China.
      PubDate: Wed, 18 May 2022 00:00:00 GMT
       
  • Lower limits and controlling factors of the petrophysical properties of
           coal-measure sandstone oil reservoirs: A case study of the Jurassic
           Yan’an Formation in the Huanjiang area, Ordos Basin, China

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      Abstract: AbstractCoal-measure sandstone oil reservoirs of the Jurassic Yan’an Formation in the Ordos Basin, China, have strong heterogeneity. Reservoir quality is the core factor that determines the large-scale accumulation of hydrocarbons. Taking the Yan’an Formation in the Huanjiang area, Ordos Basin, as an example, we have calculated the lower limits of petrophysical properties based on empirical statistics, porosity and permeability intersections, mercury injections and irreducible water analysis, oil tests, oil-bearing property analysis, and distribution functions. In addition, we have investigated the main controlling factors of effective reservoirs in the Yan’an Formation. The results demonstrate that the lower limits of petrophysical properties of the effective reservoir in the Yan’an Formation display a gradually decreasing trend as the depth increases. Furthermore, we have obtained the functions of the lower limits of the petrophysical properties and the depth. Sedimentation and diagenesis have a significant control effect on the quality of reservoirs in the Yan’an Formation. High-quality reservoirs have mainly developed in the sedimentary microfacies of point sand bar and distributary channel sand bodies. The strong compaction and cementation in the diagenesis process are the internal reasons for the poor petrophysical properties of the Yan’an Formation reservoirs. Overall, the effect of compaction on the petrophysical properties of the reservoir is stronger than that of cementation, whereas the secondary dissolution pores significantly improve the petrophysical properties of the reservoir.
      PubDate: Wed, 18 May 2022 00:00:00 GMT
       
  • Simulation of tectonic stress field and prediction of tectonic fractures
           in shale reservoirs: A case study of the Ansai area in the Ordos Basin,
           China

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      Abstract: AbstractThe Chang 7 oil-bearing layers from the Ansai area of the Ordos Basin are abundant in oil and gas resources. These layers are chiefly comprised of shales interbedded with tight sandstone. In the regions where the exploration level is relatively low and the structures are gentle in the Ansai area, the distribution of fractures in shale reservoirs and tight sandstone reservoirs is significant for predicting sweet spots and determining the success rate of hydraulic fracturing. In this research, the results acquired from the scanning electron microscope (SEM), cores, thin sections, and image logging determined the developmental characteristics of fractures. Moreover, the Himalayan stress field was modeled using ANSYS, whereas the two-factor method is used to predict the distribution of tectonic fracture by combining stress field and fracture criterion. The results indicate a gradually decreasing trend of the maximum principal stress from east to west. The minimum principal stress in the western part is less than that in the eastern part. The differential stress that can indicate the degree of tectonic deformation ranges from 17 Mpa to 25 MPa. The fracture density ranges from 0 strip/m to 1.5 strip/m. In addition, the areas with more fractures are mainly located in the western and southeastern parts, where shale oil is relatively rich. Similarly, the comparison of different maps illustrates that the distribution of tectonic fracture is related to mechanical parameters and stress fields.
      PubDate: Wed, 18 May 2022 00:00:00 GMT
       
  • Fractal characteristics of the micropore throats in the shale oil
           reservoirs of the Chang 7 member of the Yanchang Formation, Ordos Basin

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      Abstract: AbstractWith the development of the global shale oil and gas revolution, shale oil has became an important replacement field to increase oil and gas reserves and production. The Chang 7 member of the Yanchang Formation in the Ordos Basin is an important shale oil exploration series in China. To study the micropore-throat structure characteristics of the Chang 7 member, we have conducted nuclear magnetic resonance (NMR) and high-pressure mercury intrusion (HPMI) experiments to analyze the pore-throat structure features of the Chang 7 reservoir, and we have considered fractal theory to study the fractal characteristics. The NMR results indicate that the T2 spectral morphology of the Chang 7 reservoir can be characterized by three main patterns encompassing early and late peaks with different amplitudes: the type 1 reservoir contains mostly small pores and few large pores, and the porosities of the small and large pores range from 4.16% to 9.04% and 0.70% to 2.40%, respectively; the type 2 reservoir contains similar amounts of small and large pores; and the type 3 reservoir contains few small pores and mostly large pores, while the porosities of the small and large pores range from 1.81% to 2.74% and 3.32% to 5.64%, respectively. The pore-throat structure parameters are obviously affected by the pore size distribution, which in turn influences the reservoir seepage characteristics of the reservoir. The micropore-throat structure of the reservoir exhibits obvious piecewise fractal characteristics and mainly includes dichotomous and trilateral fractals. The type 1 reservoirs are dominated by dichotomous fractals, and these two fractal types are equally distributed in the type 2 and 3 reservoirs. The fractal dimension of the pore throats of different scales exhibits a negative correlation with the corresponding porosity, but no correlation is observed with the permeability, indicating that the size of the reservoir determined by pore throats imposes a strong controlling effect on their fractal characteristics.
      PubDate: Wed, 18 May 2022 00:00:00 GMT
       
  • Multiattribute analysis of channel architectural elements within the
           deepwater Taranaki Basin, 3D Romney data

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      Abstract: AbstractThe Taranaki Basin is located offshore west of North Island, New Zealand. Within the study area, deepwater channel systems are present as a result of plate boundary movement and clastic deposition during the Plio-Pleistocene. Multiattribute analysis revealed a few interesting features that we identified and interpreted. After refining the horizon of focus, we have concluded some interpretations as noise, whereas others were confirmed as geologic deposits. In one funny-looking thing (FLT 1), we interpreted high energy and high sweetness response along the northwestern portion of the main channel body as a sand-rich levee deposit and, in a second funny-looking thing (FLT 2), scalloping and elongate “finger-like” geometries as noise. The visualization and interpretation of these features through seismic attributes allow for optimized exploration, and therefore an opportunity for hydrocarbon extraction, within the Taranaki Basin.Geologic feature:Deep marine channel system: sandy channel fill to the northwest (FLT 1); interesting features in the center of the time slice (FLT 2)Seismic appearance:Chaotic, discontinuous reflectors with a high-energy response (FLT 1); chaotic high-variance features (FLT 2)Alternative interpretations:Overlapping sand-dominated channel (FLT 1); crevasse splays, fan lobes, distributary channels, ravines, and incisions (FLT 2)Age:Plio-PleistoceneLocation:Taranaki Basin, western offshore North Island, New ZealandSeismic data:Provided by Anadarko Taranaki CompanyAnalysis tool:A 3D reflection seismic, geometric, and physical seismic attributes
      PubDate: Tue, 17 May 2022 00:00:00 GMT
       
  • 2D inversion of ultradeep electromagnetic logging measurements for
           look-ahead applications

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      Abstract: AbstractKnowing formation ahead of the drill bit can help with hydrocarbon exploration and production, especially for low-angle and vertical wells. The advent of electromagnetic look-ahead technology makes it possible to interrogate formations tens of feet ahead of the drill bit. The formation can be very complex, such as fault and unconformity. However, existing approaches to recover the formation rely primarily on the 1D forward solver, which presumes that the formation is layered and transversely isotropic. For complicated formation, it will give rise to incorrect resistivity distribution. As a consequence, we have investigated and implemented a 2D pixel-based inversion algorithm to interpret the measurements for complex scenarios. We conduct a sensitivity study to illustrate the differences between look-ahead applications and look-around applications. To improve the look-ahead ability, we propose an effective technique to incorporate the prior information. In addition, we develop several examples to demonstrate the performance of the 2D inversion algorithm. It is found that using prior information as a reference model in the objective function enhances inversion performance significantly, and the proposed method can reasonably reconstruct some complex structures.
      PubDate: Tue, 17 May 2022 00:00:00 GMT
       
  • Velocity modeling of supercritical pore fluids through porous media under
           reservoir conditions with applications for petroleum secondary migration
           and carbon sequestration plumes

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      Abstract: AbstractComputational methods to characterize secondary migration in porous media traditionally rely on fluid transport equations with assumptions of time invariance, such as flow-path modeling of buoyancy vectors, statistical percolation algorithms, capillary pressure curves, or a form of Darcy’s law, which presumes instantaneous fluid transport. However, in petroleum systems modeling, the timeframe of secondary migration from source to reservoir is important to quantify in relation to other geologic factors, such as the timing of petroleum generation, fault movement, and seal formation. In addition, quantifying migration velocities enables an estimation of the distance a plume of geologically sequestered carbon dioxide travels over time, as well as the identification of low-permeability strata appropriate for long-term containment. This study introduces a method to quantify transport velocities of supercritical fluids in low-permeability lithologies for a broad range of rock and fluid properties likely encountered in the sedimentary sequence. A time-dependent form of Darcy’s law for pressure-driven viscous flow through homogeneous isotropic porous media was used to model flow velocities within a carrier bed. Thermodynamic equations of state were used to determine thermophysical properties of supercritical pore fluids under reservoir pressures ranging from 0 MPa to 200 MPa (0–29,000 psi) to constrain the momentum equations. Three case studies were examined that (1) estimated fluid flow velocities of methane within the low-permeability Upper Jurassic Haynesville Formation, (2) defined permeability-based flow units to evaluate saline formations for long-term geologic carbon sequestration, and (3) calculated the migration distance of carbon dioxide plumes at the Decatur, Illinois injection and sequestration project.
      PubDate: Tue, 17 May 2022 00:00:00 GMT
       
  • Synthetic seismic data for training deep learning networks

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      Abstract: AbstractDeep learning is increasingly being used as a component of geoscience workflows for processing and interpreting seismic data. Training a supervised deep learning network is a data-hungry task: a significant number of data examples are needed and they must include labels. The data examples and their labels must have consistent patterns for the deep learning network to learn. Too few examples and/or poor-quality labels can lead to poor deep learning training results. One method to provide large quantities of training examples with high-quality labels is to create synthetic data. We discuss our techniques and experiences with our ongoing use of synthetic seismic data. We share our techniques as an open-source project concurrent with this paper at https://github.com/tpmerrifield/synthoseis. We hope that the geoscience community will share our enthusiasm for developing deep learning geoscience tools and for including synthetic seismic data in supervised deep learning training. We invite contributions from the geoscience community using the open-source model to collectively reduce the realism gap between synthetic data and field seismic data.
      PubDate: Tue, 17 May 2022 00:00:00 GMT
       
  • Perhydrous organic carbon logging evaluation method in shore and shallow
           lacustrine shale formations: A case study of the Mesozoic lacustrine shale
           in the western Sichuan Basin, China

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      Abstract: AbstractThe types of organic carbon in shore and shallow lacustrine shales are more diverse than those in marine formations. It is of great importance to establish log interpretation models of the separate types of organic carbon content for hydrocarbon generation potential estimation. First, we summarize the main rock types and their logging characteristics in the shore and shallow lacustrine shale reservoirs and analyze the types of organic carbon in shore and shallow lacustrine shales using core pyrolysis analysis and kerogen maceral microscopic identification. Second, we establish the calculation method of the total organic carbon (TOC) content in the lacustrine shale formation by regression analysis. Third, we divide the organic matter in shore and shallow lacustrine shales into two parts: perhydrous organic carbon (perhydrous macerals) with a higher hydrogen index, higher H/C atomic ratio, and stronger hydrocarbon generation potential and subhydrous organic carbon (subhydrous macerals) with a lower hydrogen index, lower H/C atomic ratio, and poorer hydrocarbon generation potential. Furthermore, we introduce the concept of the mixed skeleton, combined with the formation component triangular chart, and establish calculation methods for perhydrous and subhydrous organic carbon contents. Finally, we apply this method to the Mesozoic shore and lacustrine shale in the western Sichuan Basin, China. The application indicates that the kerogen types of the Mesozoic shore and shallow lacustrine formations in the western Sichuan Basin are mainly type III and type IIB kerogen with a low content of perhydrous macerals. The perhydrous organic carbon content calculated by the logging evaluation model is positively correlated with the perhydrous maceral content obtained by kerogen maceral microscopic identification and the oil generation potential S2 obtained by core pyrolysis analysis. Logging analysts should use the perhydrous organic carbon content to estimate the hydrocarbon generation potential of shore and shallow lacustrine shale formations.
      PubDate: Tue, 17 May 2022 00:00:00 GMT
       
  • Comparisons of pyrolysis parameters between source rocks and their
           clay-sized fractions: Implication for source material of hydrocarbon
           generation

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      Abstract: AbstractIn natural environments, organic-clay interactions are strong and cause organo-clay composites (a combination between organic matter [OM] and clay minerals) to be one of the predominant forms for OM occurrence, and their interactions greatly influence the hydrocarbon (HC) generation of OM within source rocks. However, despite occurring in nature, dominating the OM occurrence, and having unique HC generation ways, organo-clay composites have rarely been investigated as stand-alone petroleum precursors. To improve this understanding, we have compared the Rock-Eval pyrolysis parameters derived from more than 100 source rocks and their corresponding <2 μm clay-sized fractions (representing organo-clay composites). The results show that all of the Rock-Eval pyrolysis parameters in bulk rocks are closely positively correlated with those in their clay-sized fractions, but in clay-sized fractions the quality of OM for HC generation is poorer, in that the pyrolysable organic carbon levels and hydrogen index values are lower, whereas the residual organic carbon levels are higher than those in bulk rocks. Being integrated with the effects of organic-clay interactions on OM occurrence and HC generation, our results suggest that organo-clay composites are stand-alone petroleum precursors for HC generation occurring in source rocks, even if the source rocks exist in great varieties in their attributes. Our source material for HC generation comprehensively integrates the original OM occurrence and HC generation behavior in natural environments, which differs from kerogen and is much closer to the actual source material of HC generation in source rocks, and it calls for further focus on organic-mineral interactions in studies of petroleum systems.
      PubDate: Mon, 16 May 2022 00:00:00 GMT
       
  • Seismic clues into the origin of polygonal faulting and pockmarks in the
           Great South Basin, New Zealand

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      Abstract: DescriptionGeologic feature:Polygonal faulting and pockmarks in the Great South Basin New ZealandAppearance:Dense faulting among horizons in cross section and reflector concave features in seismic sectionsMap view appearance:Dense faulting and multiple circular featuresFeatures with a similar appearance:Tectonic faulting, mounds, syneresis, carbonate mounds, and dissolution featuresFormation:Rakiura Group, offshore, Great South Basin, southern New ZealandLocation:Great South Basin, southern side of the Southern Island in New ZealandAge:EoceneData sets: A 3D seismic reflection data, from New Zealand Petroleum and Minerals (NZP&M), New ZealandSeismic attributes:Variance, curvature, dip magnitude, and color blending
      PubDate: Mon, 16 May 2022 00:00:00 GMT
       
  • Determining shear failure gradient and optimum drilling mud window in the
           Ourhoud oil field, Berkine Basin, Algeria

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      Abstract: AbstractOptimum drilling mud window provides a workable downhole mud pressure range to prevent formation fluid influx, borehole instabilities, and fluid loss into the formation while drilling, and this can be achieved by a comprehensive geomechanical modeling using well data. We have integrated the wireline logs, drilling data, and measured downhole data to assess the vertical stress, pore pressure, minimum horizontal stress, and shear failure (SF) gradient of the 3400 m thick Mesozoic and Paleozoic succession in the Ourhoud field, Berkine Basin. We have interpreted the hydrocarbon pressure gradient in the Triassic Argilo-Greseux Inferieur reservoir as 0.32 psi/ft and found the overburden shales to be hydrostatically pressured (0.46 psi/ft). Poisson’s ratio-based minimum horizontal stress has a 0.73–0.80 psi/ft gradient, whereas frictional faulting theory provides a lower limit of 0.66 psi/ft. We have observed massive wash outs in the caliper logs against the Cretaceous shales, which is more prone to compressive failures. To address this wellbore failure, we have modeled SF gradient by Mohr-Coulomb rock failure criteria and compared the results with the mud pressure used in drilling. We have inferred that at least 10.5 ppg drilling mud weight is required to prevent such wellbore instabilities in the Mesozoic shales, whereas the minimum allowable mud weight for the Carboniferous shale is 10 ppg. Based on the interpreted pressure gradients, we have recommended an optimum downhole drilling window for the Ourhoud field, which will be helpful to deliver stable wellbores in future drilling campaigns.
      PubDate: Mon, 16 May 2022 00:00:00 GMT
       
  • Evaluation method of hydrocarbon yield of source rocks in open, semiopen,
           and closed systems: A case study on the K 1 qn Formation, northern
           Songliao Basin, China

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      Abstract: AbstractHydrocarbon yield of source rocks is an important parameter in the evaluation of oil and gas resources, and its value determines the potential of conventional and unconventional oil and gas resources. There is no oil cracking into gas in the thermal pyrolysis experiment data of an open system, whereas kerogen cracking into oil in a closed system is involved in the calculation of oil cracking into gas. However, most source rocks in sedimentary basins are a process of hydrocarbon generation and hydrocarbon expulsion, which could lead to insufficient understanding of hydrocarbon yield of source rocks. Based on the multiple thermal pyrolysis experiment data, three hydrocarbon generation kinetic models, and actual geologic data (burial history, thermal history, and hydrocarbon generation threshold), we established the evaluation method and chart of hydrocarbon yield of source rocks under open, semiopen, and closed systems by using the hydrocarbon generation kinetics method. The concept of degree of openness was proposed. From a closed system to an open system, the degree of openness increases gradually, and its value changes from 0 to 1. Taking the K1qn Formation in the northern Songliao Basin as an example, the hydrocarbon expulsion efficiency of the K1qn Formation source rock is approximately 70%, and it can be approximated as the degree of openness. Based on our method for evaluating hydrocarbon yield of source rocks, the charts of hydrocarbon yield of source rocks under open system, semiopen system with a degree of openness of 0.7, and closed system of the K1qn Formation in the northern Songliao Basin were established. The oil and gas yields of the K1qn Formation source rocks in a semiopen system with a degree of openness of 0.7 are approximately 540 and 105 mgHC/gTOC at a burial depth of 2000 m, respectively. Our results indicate that the hydrocarbon yield of source rocks in a semiopen system is closer to the hydrocarbon yield of source rocks under geologic condition. We use the thermal pyrolysis experiment data, hydrocarbon generation kinetics model, and geologic data to propose a very valuable evaluation method of hydrocarbon yield of source rock, which has a solid theoretical basis and strong applicability.
      PubDate: Mon, 16 May 2022 00:00:00 GMT
       
  • Study on the characteristics of organic-rich shale in the north area of
           Dongying depression

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      Abstract: AbstractIn recent years, shale oil shows have been found in Shahejie Formation in the northern part of Dongying depression. To investigate the characteristics of shale oil in the northern part of Dongying depression, we have carried out a comparative study on the reservoir, oil bearing, and compressibility of shale in the northern steep-slope zone of Dongying depression and shale in the center of depression based on the mineral composition, reservoir physical properties, and pyrolysis experiments of drilling cores. The results find that the steep-slope zone shale and the depression central shale have good shale oil development potential. Three kinds of lithofacies developed in the steep slope and four kinds of lithofacies developed in the sag center. Interbedded sandstone with different thickness widely developed in the steep slope of Dongying depression. The development of micro-meso pores in the shale matrix and cement of interparticle pores of sandstone made shale in the sag center higher porosity than that of shale in the steep slope. However, macropores of interbedded sandstone significantly improved the permeability of shale series in the steep slope. Shale oil in the steep slope has higher gas/oil ratio, better mobility, and higher free-hydrocarbon content than the shale oil in the sag center. We predicted that the shale in the steep-slope zone has better shale oil production than the shale in sag center combined the fracturing capacity analysis.
      PubDate: Mon, 16 May 2022 00:00:00 GMT
       
 
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