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PARAMETERS CONTROLLING THE GEOMETRY OF DETACHMENT AND FAULT-BEND FOLDS: INSIGHTS FROM 3D FINITE-ELEMENT MODELS APPLIED TO THE AHWAZ ANTICLINE IN THE DEZFUL EMBAYMENT, SW IRAN 控制拆离和断层弯曲褶皱几何结构的参数&应用于伊朗西南德祖尔湾AHWAZ背斜的三维有限元模型
IF 1.8 4区 地球科学 Q2 Earth and Planetary Sciences Pub Date : 2023-04-07 DOI: 10.1111/jpg.12834
Anis Khalifeh-Soltani, Mohammad R. Ghassemi, Seyed Ahmad Alavi, Mehdi Ganjiani

Fault-related folds are present in most tectonic settings and can serve as structural traps for hydrocarbons. These structures have therefore been widely studied by both structural and petroleum geologists using a range of techniques. Approaches include field- and seismic-based methods, and numerical and analogue modelling. Geomechanical models attempt to examine the mechanical and geometric features of folds.

This study investigates the effects of variations in a range of parameters, including detachment and ramp geometry, friction coefficient and internal friction angle, on the geometry and development of detachment folds and fault-bend folds. For this purpose, we ran seven series of numerical, 3D elastic-plastic finite element models using ABAQUS software (26 model runs in all). Each model set-up consisted of five layers whose mechanical properties were based on those of stratigraphic units in the Zagros fold-and-thrust belt, SW Iran. The models were labelled series A to F and series H. Models in series A investigated the impact of concave, convex, wavy and oblique detachment surfaces on the development of detachment folds; those in series D examined the role of ramp dip and of listric, oblique and wavy ramps on the development of fault-bend folds. Models in series B and E, and series C and F, examined the effects of variations in the friction coefficient and of the internal friction angle, respectively, on the development of these two classes of folds. Finally, hybrid models in series H were provided to evaluate the results.

Major results were as follows. Firstly, the geometry of modelled detachment and fault-bend folds was found to be influenced by the geometry of the associated ramps and detachment faults. Thus the crests of anticlines and the trough lines of synclines were located at points of maximum curvature and at inflexion points on a wavy detachment fault or wavy ramp, respectively. Second, two important additional factors controlling fold style were identified: the friction coefficient, and the presence of along-strike geometric variations in the ramp or the detachment fault. Layers with low friction coefficients and high internal friction angles formed detachment folds with thick hinges and thin limbs; conversely, layers with high friction coefficients and low internal friction angles created detachment folds with thick limbs and thin hinges. Application of the results to modelling of the Ahwaz anticline in the Dezful Embayment, SW Iran, was successful, and in general the modelled structure was consistent with that observed in the field.

断层相关褶皱存在于大多数构造环境中,可作为碳氢化合物的构造圈闭。因此,结构地质学家和石油地质学家使用一系列技术对这些结构进行了广泛的研究。方法包括基于现场和地震的方法,以及数值和模拟建模。地质力学模型试图检验褶皱的力学和几何特征。
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引用次数: 2
RESERVOIR CHARACTERIZATION OF THE PLIOCENE RED SERIES, LAM FIELD AND SURROUNDING AREAS, OFFSHORE WESTERN TURKMENISTAN 土库曼斯坦西部近海lam油田及周边地区上新世红色系储层特征
IF 1.8 4区 地球科学 Q2 Earth and Planetary Sciences Pub Date : 2022-12-22 DOI: 10.1111/jpg.12831
Aneesa Ijaz Rabbani, Sameer Al-Hajri, Khaula Shahid Hussain, Graham Blackbourn, Chuangchuang Qi, Abhijith Suboyin, Jassim Abubacker Ponnambathayil, Md Motiur Rahman, Mohamed Haroun, Muhammad A. Gibrata, Lamia Rouis, Yanfidra Djanuar

The sedimentology, petrography and reservoir potential of Pliocene sandstones within the Upper Red Series in the offshore LAM field, Western Turkmenistan, have been examined. Depositional settings are interpreted within the framework of the Red Series palaeoenvironments across the entire Turkmen sector of the Apsheron-Prebalkhan uplift zone, including its onshore extension to the east.

Examination of 81 m of core from three separate intervals suggests that the Red Series in the LAM field is the product of a fluvial-dominated delta system with associated floodplain deposits, periodically flooded by the saline waters of the South Caspian Lake. Relatively thick sandstones, up to around 5 m thick, are interpreted as channel and point-bar deposits of a meandering river system, with thinner and finer-grained sandstones and siltstones inferred to be crevasse-splay and interdistributary floodplain deposits. Floodplain mudstones display signs of desiccation, soil formation, plant rootlets and occasional thin layers of anhydrite. Intervals with marine trace-fossil assemblages record incursions of saline-lake waters. Conglomeratic layers at the base of thicker mudstone intervals may be associated with abrupt transgressions of the lake. The best reservoir qualities are associated with the fluvial channel and point-bar sandstones. Crevasse-splay and other overbank sandstones are of poorer quality, while intercalated floodplain to lacustrine claystone/siltstone units may constitute local seals.

Eighteen sandstone plug samples from the cored intervals were examined in thin-section and by XRD and SEM to assess how mineralogy, grain size and diagenesis affect reservoir quality. The samples consist predominantly of lithic arkoses and feldspathic litharenites; higher porosities, and therefore better reservoir potential, are associated with the feldspathic litharenites. Primary controls on porosity include compaction, clay-matrix content and calcite cementation. XRD data reveal the presence of illite, illite-smectite and chlorite. The presence of swelling clays has been the main cause of formation damage in the field.

The interpretation of meandering fluvial channels here is thought to represent the first published account of such channels within Pliocene reservoir rocks in the north of the South Caspian Basin. Previous accounts of the Red Series sandstones deposited onshore to the east have indicated deposition within braided channels of the palaeo-Amu Darya river delta plain, and alluvial-fan deposits sourced from uplands to the north. Deposition of the equivalent Productive Series by the palaeo-Volga in the Azerbaijan sector to the west has also been interpreted as having taken place within braided systems, although mixed or suspended-load fluvial channels ascribed to the contemporary Kura delta farther south may have been associated with a meandering system. Two palaeogeographic maps a

对土库曼斯坦西部海上LAM油田上部红系上新世砂岩的沉积学、岩石学和储层潜力进行了研究。沉积环境在Apsheron‐Prebalkhan隆起带整个土库曼地区的红色系列古环境框架内进行解释,包括其向东的陆上延伸。
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引用次数: 2
APPLICATION OF MUD GAS DATA AND LEAKAGE PHENOMENA TO EVALUATE SEAL INTEGRITY OF POTENTIAL CO2 STORAGE SITES: A STUDY OF CHALK STRUCTURES IN THE DANISH CENTRAL GRABEN, NORTH SEA 泥气数据和泄漏现象在评价潜在CO2储存区密封完整性中的应用&北海丹麦中央地堑白垩系结构研究
IF 1.8 4区 地球科学 Q2 Earth and Planetary Sciences Pub Date : 2022-12-22 DOI: 10.1111/jpg.12830
H.I. Petersen, F.W.H. Smit

Depleted chalk oilfields and chalk structures in the Danish Central Graben, North Sea, are potential CO2 storage sites. In most of these fields, the main reservoir is the Upper Cretaceous – Danian Chalk Group and the Eocene – Miocene mudstones of the Horda and Lark Formations constitute the primary seal. In a few fields, the reservoir is composed of the Lower Cretaceous Tuxen and Sola Formations. Here the main seal is assumed to be the Chalk Group which however has poor gas sealing characteristics; the Horda and Lark Formations constitute an efficient secondary seal although they are quite high in the section. This study documents a workflow that may help to evaluate the seal integrity of the structures from an integration of mud gas data from wells with seismic data. Mud gas data provide detailed information about the distribution and types of gas (biogenic or thermogenic) throughout the seal section and overburden. The presence of higher carbon number gases (C3–C5, propane to pentane) in the seal indicates migration of thermogenic gas into the thermally immature sealing mudstones; whereas the dominance of C1 (methane) and partly C2 (ethane) likely reflects the presence of in situ generated biogenic gas in the mudstones, thus indicating that there are no seal integrity issues. The vertical thermogenic gas migration front has been determined, and a “traffic light” indicator system has been used for seal integrity evaluation. Where no or minor migration of thermogenic gas into the primary seal has occurred and a primary seal >30 m thick is present, the seal is considered to have good matrix seal integrity (green). If some significant thermogenic gas migration has occurred into the primary seal but more than 30 m of primary seal is present above the thermogenic gas migration front, the seal integrity is reduced (yellow). In structures where thermogenic gas migration is recorded through the primary seal and into the overburden, seal integrity is considered to be poor (red). In areas where significant leakage of thermogenic gas has occurred into the seal, high density, low porosity carbonate beds frequently occur encapsulated within the sealing mudstones and are interpreted to be composed of methane-derived authigenic carbonates (MDACs). Seismic data show that there is a convincing correlation between leakage as indicated from mud gas data and the presence of vertical wipe-out zones (gas chimneys), bright zones (gas-charged sediments or MDACs), and depressions (pockmarks). In general, potential CO2 storage sites in the study area in tectonically inverted structures show good seal integrity, but this may locally be reduced and require additional analyses. Storage sites associated with salt diapirs generally show poor seal integrity and are likely to be poor candidates for CO2 storage. In combination, mud gas and seismic data are therefore powerful tools to investigate (

北海丹麦中央地堑的枯竭白垩油田和白垩构造是潜在的二氧化碳储存地。在大多数油田中,主要储层为上白垩纪-大年白垩系白垩岩群,Horda和Lark组的始新世-中新世泥岩构成了主要的盖层。在少数油田中,储层由下白垩纪的Tuxen和Sola组组成。此处假设主密封为白垩岩群,但其气体密封特性较差;Horda组和Lark组构成了有效的二次密封,尽管它们在剖面中相当高。这项研究记录了一个工作流程,该工作流程可能有助于通过将油井的泥气数据与地震数据相结合来评估结构的密封完整性。泥气数据提供了关于整个密封段和覆盖层的气体分布和类型(生物成因或热成因)的详细信息。密封中存在较高碳数气体(C3–C5,丙烷到戊烷),表明产热气体迁移到热未成熟的密封泥岩中;而C1(甲烷)和部分C2(乙烷)的优势可能反映了泥岩中存在原位生成的生物气,因此表明不存在密封完整性问题。已确定垂直产热气体运移前沿,并使用“红绿灯”指示系统进行密封完整性评估。如果没有或少量产热气体迁移到主密封中,并且存在>30m厚的主密封,则认为该密封具有良好的基质密封完整性(绿色)。如果一些显著的产热气体迁移到主密封中,但在产热气体运移前沿上方存在超过30m的主密封,则密封完整性会降低(黄色)。在记录了产热气体通过初级密封层迁移到覆盖层的结构中,密封层的完整性较差(红色)。在热成因气体大量泄漏到密封层的区域,高密度、低孔隙度的碳酸盐岩床经常出现在密封泥岩中,并被解释为由甲烷衍生的自生碳酸盐岩(MDAC)组成。地震数据表明,泥气数据显示的泄漏与垂直擦除区(气体烟囱)、亮区(充气沉积物或MDAC)和凹陷(麻点)的存在之间存在令人信服的相关性。一般来说,研究区域内构造倒转结构中的潜在CO2储存点显示出良好的密封完整性,但这可能会局部减少,需要进行额外的分析。与盐底辟相关的储存地点通常表现出较差的密封完整性,很可能是CO2储存的较差候选者。因此,泥浆气和地震数据相结合,是研究(古)泄漏现象的有力工具,并为地方和区域尺度的密封完整性评估提供支持。
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引用次数: 1
PETROLEUM SYSTEMS ANALYSIS OF THE EASTERN ARABIAN PLATE: CHEMOMETRICS BASED ON A REVIEW OF THE GEOCHEMICAL CHARACTERISTICS OF OILS IN JURASSIC – CENOZOIC RESERVOIRS 阿拉伯板块东部油气系统分析&基于侏罗系&新生代油气藏地球化学特征的化学计学研究
IF 1.8 4区 地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2022-12-22 DOI: 10.1111/jpg.12829
Alireza Baniasad, Ralf Littke, Qusay Abeed

This paper presents the results of an integrated geochemical study of oils in Jurassic – Cenozoic reservoirs in the eastern region of the Arabian Plate. The main objective was to analyze the active petroleum systems at a regional scale across the study area which extends from NE Iraq to SE Oman and includes the entire Persian Gulf. The dataset for the study consisted of more than 500 crude oil samples from 112 oil fields and 11 different reservoir units. This dataset was compiled from both the literature and re-evaluated geochemical and stable isotope analyses, augmented by new analytical studies.

The study documents regional variations and trends in the bulk and molecular properties and stable isotope ratios of the oil samples. Two overall clans and twelve genetic oil families and sub-families were distinguished using multivariate statistical analysis (chemometrics) based on biomarker parameters. The age, lithology, depositional setting and organic matter type of the respective source rocks for each family/sub-family was inferred from oil geochemical fingerprints.

The results provide insights into the key geological factors that control the number, size and geochemical character of oil fields in the eastern Arabian Plate. The geographical extent of the various oil families was assessed and used to evaluate charge access and to predict migration directions and migration pathways in the study area.

The results indicate the value of implementing multivariate statistical analysis on “big data” along with state-of-the-art geological petroleum systems analysis and interpretation of biomarker and oil composition data to investigate complex and extended petroleum systems.

本文介绍了阿拉伯板块东部侏罗系-新生代油气藏的综合地球化学研究结果。主要目的是分析从伊拉克东北部到阿曼东南部,包括整个波斯湾的研究区域内的活跃石油系统。该研究的数据集由来自112个油田和11个不同储层单元的500多个原油样本组成。该数据集是根据文献和重新评估的地球化学和稳定同位素分析汇编而成,并辅以新的分析研究。
{"title":"PETROLEUM SYSTEMS ANALYSIS OF THE EASTERN ARABIAN PLATE: CHEMOMETRICS BASED ON A REVIEW OF THE GEOCHEMICAL CHARACTERISTICS OF OILS IN JURASSIC – CENOZOIC RESERVOIRS","authors":"Alireza Baniasad,&nbsp;Ralf Littke,&nbsp;Qusay Abeed","doi":"10.1111/jpg.12829","DOIUrl":"10.1111/jpg.12829","url":null,"abstract":"<p>This paper presents the results of an integrated geochemical study of oils in Jurassic – Cenozoic reservoirs in the eastern region of the Arabian Plate. The main objective was to analyze the active petroleum systems at a regional scale across the study area which extends from NE Iraq to SE Oman and includes the entire Persian Gulf. The dataset for the study consisted of more than 500 crude oil samples from 112 oil fields and 11 different reservoir units. This dataset was compiled from both the literature and re-evaluated geochemical and stable isotope analyses, augmented by new analytical studies.</p><p>The study documents regional variations and trends in the bulk and molecular properties and stable isotope ratios of the oil samples. Two overall clans and twelve genetic oil families and sub-families were distinguished using multivariate statistical analysis (chemometrics) based on biomarker parameters. The age, lithology, depositional setting and organic matter type of the respective source rocks for each family/sub-family was inferred from oil geochemical fingerprints.</p><p>The results provide insights into the key geological factors that control the number, size and geochemical character of oil fields in the eastern Arabian Plate. The geographical extent of the various oil families was assessed and used to evaluate charge access and to predict migration directions and migration pathways in the study area.</p><p>The results indicate the value of implementing multivariate statistical analysis on “big data” along with state-of-the-art geological petroleum systems analysis and interpretation of biomarker and oil composition data to investigate complex and extended petroleum systems.</p>","PeriodicalId":16748,"journal":{"name":"Journal of Petroleum Geology","volume":"46 1","pages":"3-45"},"PeriodicalIF":1.8,"publicationDate":"2022-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49525906","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
GEOCHEMICAL CHARACTERISTICS OF CRUDE OILS FROM THE SHARARA-C OIL FIELD, MURZUQ BASIN, SOUTHWESTERN LIBYA 利比亚西南部穆尔祖克盆地SHARARA-C油田原油地球化学特征
IF 1.8 4区 地球科学 Q2 Earth and Planetary Sciences Pub Date : 2022-12-22 DOI: 10.1111/jpg.12832
Ramadan Musbah M. Saheed, Tatjana Šolević Knudsen, Musbah Abduljalil M. Faraj, Hans Peter Nytoft, Branimir Jovančićević

Crude oil samples from the Sharara-C oil field (Concession NC-115, Murzuq Basin, SW Libya) were analysed by organic geochemical methods in order to infer the geochemical characteristics of their respective source rocks. Aromatic hydrocarbons were analysed by gas chromatography – mass spectrometry (GC-MS), and gas chromatography – tandem mass spectrometry (GC-MS-MS) was used to analyse saturated biomarkers. The Sharara-C oils are interpreted to have been generated by marine shales containing mixed terrigenous and marine organic materials deposited in an intermediate (suboxic) environment. Age-specific biomarker ratios indicated that the oils are older than Cretaceous, and maturation-related parameters pointed to their high thermal maturity. Consistent with previous studies, source rocks are inferred to be “hot” shales in the Lower Silurian Tanezzuft Formation.

Almost all the parameter ratios calculated varied over a very narrow range, indicating that the investigated oils were compositionally similar. The only significant difference that was noted concerned the sterane/hopane ratios whose variation suggested that there was some variability in the composition of the source organic material.

The organic geochemical parameters determined for the Sharara-C crude oils were compared with published data on other crude oils from Concession NC-115. Almost all the parameters agreed well with previously published data on oils from this part of the Murzuq Basin. The greatest deviation concerned the values of some of the maturity parameters. This tended to confirm the conclusions of previous studies concerning the presence of a number of distinct oil families and sub-families in the Sharara oil field area which are genetically related but which have different maturities.

采用有机地球化学方法分析了Sharara - C油田(位于利比亚西南部Murzuq盆地NC - 115特许权)的原油样品,以推断其各自烃源岩的地球化学特征。芳烃采用气相色谱-质谱(GC - MS)分析,饱和生物标志物采用气相色谱-串联质谱(GC - MS - MS)分析。Sharara‐C油被解释为由海相页岩产生,其中含有陆相和海相混合的有机物质,沉积在中间(亚氧)环境中。特定年龄的生物标志物比值表明,这些油的年龄超过白垩纪,成熟度相关参数表明它们的热成熟度较高。与前人研究一致,推断烃源岩为下志留统Tanezzuft组的“热”页岩。
{"title":"GEOCHEMICAL CHARACTERISTICS OF CRUDE OILS FROM THE SHARARA-C OIL FIELD, MURZUQ BASIN, SOUTHWESTERN LIBYA","authors":"Ramadan Musbah M. Saheed,&nbsp;Tatjana Šolević Knudsen,&nbsp;Musbah Abduljalil M. Faraj,&nbsp;Hans Peter Nytoft,&nbsp;Branimir Jovančićević","doi":"10.1111/jpg.12832","DOIUrl":"10.1111/jpg.12832","url":null,"abstract":"<p>Crude oil samples from the Sharara-C oil field (Concession NC-115, Murzuq Basin, SW Libya) were analysed by organic geochemical methods in order to infer the geochemical characteristics of their respective source rocks. Aromatic hydrocarbons were analysed by gas chromatography – mass spectrometry (GC-MS), and gas chromatography – tandem mass spectrometry (GC-MS-MS) was used to analyse saturated biomarkers. The Sharara-C oils are interpreted to have been generated by marine shales containing mixed terrigenous and marine organic materials deposited in an intermediate (suboxic) environment. Age-specific biomarker ratios indicated that the oils are older than Cretaceous, and maturation-related parameters pointed to their high thermal maturity. Consistent with previous studies, source rocks are inferred to be “hot” shales in the Lower Silurian Tanezzuft Formation.</p><p>Almost all the parameter ratios calculated varied over a very narrow range, indicating that the investigated oils were compositionally similar. The only significant difference that was noted concerned the sterane/hopane ratios whose variation suggested that there was some variability in the composition of the source organic material.</p><p>The organic geochemical parameters determined for the Sharara-C crude oils were compared with published data on other crude oils from Concession NC-115. Almost all the parameters agreed well with previously published data on oils from this part of the Murzuq Basin. The greatest deviation concerned the values of some of the maturity parameters. This tended to confirm the conclusions of previous studies concerning the presence of a number of distinct oil families and sub-families in the Sharara oil field area which are genetically related but which have different maturities.</p>","PeriodicalId":16748,"journal":{"name":"Journal of Petroleum Geology","volume":"46 1","pages":"103-123"},"PeriodicalIF":1.8,"publicationDate":"2022-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43958983","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
QUARTZITIC SANDSTONES IN THE NAMURIAN AND LOWER WESTPHALIAN SUCCESSION OF THE SOUTHERN NORTH SEA: A NEW HIGH-PERMEABILITY CARBONIFEROUS RESERVOIR TYPE 北海南部纳穆里亚-下威斯特伐利亚演替中的石英砂岩:一种新的高渗透石炭系储层类型
IF 1.8 4区 地球科学 Q2 Earth and Planetary Sciences Pub Date : 2022-09-30 DOI: 10.1111/jpg.12824
G. A. Blackbourn, J. D. Collinson

Most of the potential sandstone reservoirs within the Namurian and lower Westphalian succession of the Southern North Sea Basin are originally feldspathic sands in which the feldspar has mainly been altered to microporous kaolinite clays. The sandstones provide a moderate porosity (typically 8-15%, depending mainly on grain size), but permeability is severely limited owing to the microporous nature of much of the porosity. Permeability is typically 1 mD or less, rising to a few tens of millidarcies in occasional coarse- and very coarse-grained sands. Predicting the presence of higher-permeability reservoir zones is therefore a critical exploration problem in these successions.

Quartzitic sands have been discovered in places, especially for example in the Trent field (block 43/24), where physical reworking of sands during the transgressions that preceded the deposition of marine bands removed much of the feldspar, so that less clay was formed during burial diagenesis. Although these sandstones display moderately elevated permeabilities, commonly several to several tens of millidarcies, they are usually fine-grained, which limits their reservoir potential.

A particular type of quartzitic sandstone reservoir has been identified quite widely within the Namurian and lower Westphalian succession of the Southern North Sea. This type is indistinguishable in terms of sedimentology and inferred detrital composition from the originally feldspathic facies which now form the widespread kaolinite-rich, low-permeability sandstones. However, it has a very low kaolinite content (commonly 1-2%, compared with a more usual 5-20%) so that these sandstones display permeabilities of the order of several hundred millidarcies.

Wireline log data from nineteen wells within UK Quadrants 43 and 44 have been examined, and all relevant core logged in order to compare the depositional settings of the quartzitic and non-quartzitic sandstones. Existing data from over 500 petrographic thin sections from the area have been reviewed and 78 new thin sections analysed to determine the petrographic controls on reservoir quality in both sandstone types. The diagenetic histories of each type have been interpreted. The dissolution of feldspars during diagenesis of the quartzitic sandstones, without a substantial residue of kaolinite or other aluminium-rich mineral, is attributed to the mobilisation of aluminium within organic complexes. This is thought to require the presence of certain organic acids.

北海盆地南部纳莫里统和下威斯特伐利亚统的潜在砂岩储层大多为长石砂岩,其中长石主要蚀变为微孔高岭石粘土。砂岩的孔隙度适中(通常为8-15%,主要取决于颗粒大小),但由于大部分孔隙的微孔性质,渗透率受到严重限制。渗透率一般为1md或更低,偶尔在粗粒和极粗粒砂岩中可达几十毫达。因此,预测高渗透率储层的存在是这些层序中一个关键的勘探问题。石英砂已在一些地方被发现,特别是在特伦特油田(43/24区块),在海相沉积之前的海侵期间,对砂岩进行了物理改造,移除了大部分长石,因此在埋藏成岩作用期间形成的粘土较少。虽然这些砂岩的渗透率适中,通常为几到几十毫达尔,但它们通常是细粒的,这限制了它们的储层潜力。一种特殊类型的石英砂岩储层在北海南部的纳穆里亚和下威斯特伐利亚演替中被广泛发现。从沉积学和推断出的碎屑成分来看,这种类型与原来的长石相难以区分,而长石相现在形成了广泛分布的富含高岭石的低渗透砂岩。然而,它的高岭石含量非常低(通常为1-2%,而更常见的是5-20%),因此这些砂岩的渗透率为几百毫达。研究人员检查了英国43和44象限内19口井的电缆测井数据,并对所有相关岩心进行了测井,以比较石英砂岩和非石英砂岩的沉积环境。对来自该地区的500多个岩石薄片的现有数据进行了审查,并分析了78个新的薄片,以确定岩石对两种砂岩类型的储层质量的控制。对各类型成岩历史进行了解释。石英砂岩成岩过程中长石的溶解,没有大量高岭石或其他富铝矿物的残留,这归因于有机配合物中铝的动员。这被认为需要某些有机酸的存在。
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引用次数: 0
THE AGE, ORIGIN AND CONTEXT OF RESERVOIR SANDSTONES UNDERLYING THE LOWERMOST SILURIAN “HOT” SHALES IN THE WEST OF THE SULTANATE OF OMAN 阿曼苏丹国西部下志留纪“热”页岩下储层砂岩的年龄、成因和背景
IF 1.8 4区 地球科学 Q2 Earth and Planetary Sciences Pub Date : 2022-09-30 DOI: 10.1111/jpg.12823
A.S.M. Al Ghafri, A.P. Heward, G.A. Booth, I.A. Abbasi

The age and origin of reservoir sandstones which underlie the lowermost Silurian “hot” shales of the Sahmah Formation in the west of Oman is controversial. Here we describe one such sandstone which was cored and interpreted based on geological well evidence, and which then had to be re-interpreted when definitive palynological results became available. The findings are enhanced when interpreted along with other deep wells in the area which have consistent palynological data.

The western part of the Sultanate of Oman is a tectonically stable intra-basinal high with low regional dips. In this area, the relief on the base-Silurian unconformity of >250 m appears to be greater than that beneath the Permo-Carboniferous unconformity which is well known for being highly erosive. The sandstones preserved beneath the base-Silurian unconformity vary in depositional environment and reservoir quality from well to well, depending on their age, degree of erosion and differences in regional subsidence.

There has been little evidence for the presence of Hirnantian-aged deposits in Oman to date. However, some of the erosion and deep incisions which affect deposits of the Upper Ordovician Hasirah Formation are almost certainly related to falling sea levels accompanying the Hirnantian glaciation, just as the presence of the “hot shale” source rocks in the overlying Sahmah Formation are likely to be related to rising sea-levels and anoxic conditions during the later deglaciation. Deformed strata in the Upper Ordovician deposits may reflect the instability of valley-sides cut into weakly-consolidated strata exposed during changes in sea-level.

The Sahmah oil play underlying the basal Silurian “hot” shales in Oman carries significant risks relating to the presence or absence of closures and reservoir, and the character, continuity and cementation of reservoir sandstones.

阿曼西部Sahmah组下志留系“热”页岩下储层砂岩的年龄和成因存在争议。在这里,我们描述了一个这样的砂岩,它是根据地质井的证据取芯和解释的,当有明确的孢粉学结果时,它必须重新解释。当与该地区其他具有一致孢粉学数据的深井一起解释时,这些发现得到了加强。阿曼苏丹国西部是一个构造稳定的盆内高地,区域性倾角低。在该地区,250 m的基底-志留系不整合面上的起伏大于以高侵蚀性著称的二叠-石炭系不整合面下的起伏。在基底-志留系不整合面下保存的砂岩,由于其年龄、侵蚀程度和区域沉降的差异,不同井间的沉积环境和储层质量各不相同。迄今为止,几乎没有证据表明阿曼存在赫南提安时期的矿床。然而,影响上奥陶统Hasirah组沉积的一些侵蚀和深切口几乎肯定与Hirnantian冰期期间海平面下降有关,正如上覆Sahmah组中“热页岩”烃源岩的存在可能与后来的冰期期间海平面上升和缺氧条件有关。上奥陶统地层中的变形地层可能反映了在海平面变化过程中暴露出来的谷边切割成弱固结地层的不稳定性。阿曼基础志留系“热”页岩下的Sahmah油区存在着巨大的风险,与闭包和储层的存在与否以及储层砂岩的性质、连续性和胶结性有关。
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引用次数: 1
ELECTROFACIES DEFINITION AND ZONATION OF THE LOWER CRETACEOUS BARRA VELHA FORMATION CARBONATE RESERVOIR IN THE PRE-SALT SEQUENCE OF THE SANTOS BASIN, SE BRAZIL 巴西桑托斯盆地盐下层序下白垩统barra velha组碳酸盐岩储层电相定义与分带
IF 1.8 4区 地球科学 Q2 Earth and Planetary Sciences Pub Date : 2022-09-30 DOI: 10.1111/jpg.12827
M. Molina Camargo, G. F. Chinelatto, M. Basso, A. C. Vidal

Lower Cretaceous carbonates in the pre-salt succession in the Santos Basin, eastern Brazil, are highly heterogeneous in terms of their reservoir characteristics as a result of depositional and diagenetic factors. Electrofacies have widely been used for reservoir zonation and, when allied with computer-based methods such as neural networks, may help with the study of such complex reservoir rocks and with the identification of high-quality reservoir zones. In this work, an unsupervised artificial neural network known as a self-organizing map (SOM) was used to carry out a zonation of the pre-salt carbonates in the Aptian Barra Velha Formation, the main reservoir unit in the Santos Basin. Available data included gramma-ray, neutron porosity, resistivity deep, sonic, density, photoelectric factor, total porosity and effective porosity profiles from 21 wells together with mineralogical models. Core descriptions and thin section images were used as additional data for the lithological characterization of the electrofacies and consequently for reservoir zonation. A total of four electrofacies were defined from the SOM application, and five reservoir zones were identified.

The characterization of the reservoir zones also considered the structural locations of the wells based on the relative depth to top- Barra Velha Formation; well locations were classified as structurally high, intermediate or low. Based on the reservoir zone characteristics, the results could be correlated with zonations in previous studies. A general tendency was noted for there to be an increase of finer-grained sediments in the formation in wells located in structural lows; packstone and mudstone facies were prevalent in these wells and were in general characterized as poor-quality reservoir rocks. By contrast, the shrubstones and grainstones which were more frequent in structurally high wells comprised higher quality reservoir rocks.

The basal reservoir zone showed wide lithological variation compared to the overlying reservoir zones. Grainstone-dominated facies were identified in the middle of the formation, and the uppermost reservoir zones were characterized by an upward increase in shrubstones and reworked grainstones which in general pointed to better quality reservoirs.

巴西东部桑托斯盆地下白垩统盐下碳酸盐岩受沉积和成岩因素影响,储层特征极不均匀。电相已被广泛用于储层划分,当与神经网络等基于计算机的方法相结合时,可以帮助研究这种复杂的储层岩石并识别优质储层。在这项工作中,一种被称为自组织图(SOM)的无监督人工神经网络被用于对Aptian Barra Velha组(Santos盆地的主要储层单元)的盐下碳酸盐岩进行分带。现有数据包括21口井的伽马、中子孔隙度、深部电阻率、声波、密度、光电系数、总孔隙度和有效孔隙度剖面以及矿物学模型。岩心描述和薄片图像被用作电相岩性表征的附加数据,从而用于储层分带。通过SOM应用,共确定了4个电相,并确定了5个储层。储层的表征还考虑了基于Barra Velha组顶部相对深度的井的构造位置;井位被划分为构造高、中、低。根据储层的区带特征,研究结果可以与前人的研究分区相关联。构造低洼井中,地层中细粒沉积物呈增加趋势;这些井以包岩和泥岩相为主,总体上属于劣质储层。而在构造高的井中较为常见的灌木岩和颗粒岩则构成了较优质的储集岩。与上覆储层相比,基底储层岩性差异较大。储层中部以颗粒岩为主,上部储层发育灌木岩和改造颗粒岩,储层质量总体较好。
{"title":"ELECTROFACIES DEFINITION AND ZONATION OF THE LOWER CRETACEOUS BARRA VELHA FORMATION CARBONATE RESERVOIR IN THE PRE-SALT SEQUENCE OF THE SANTOS BASIN, SE BRAZIL","authors":"M. Molina Camargo,&nbsp;G. F. Chinelatto,&nbsp;M. Basso,&nbsp;A. C. Vidal","doi":"10.1111/jpg.12827","DOIUrl":"10.1111/jpg.12827","url":null,"abstract":"<p>Lower Cretaceous carbonates in the pre-salt succession in the Santos Basin, eastern Brazil, are highly heterogeneous in terms of their reservoir characteristics as a result of depositional and diagenetic factors. Electrofacies have widely been used for reservoir zonation and, when allied with computer-based methods such as neural networks, may help with the study of such complex reservoir rocks and with the identification of high-quality reservoir zones. In this work, an unsupervised artificial neural network known as a self-organizing map (SOM) was used to carry out a zonation of the pre-salt carbonates in the Aptian Barra Velha Formation, the main reservoir unit in the Santos Basin. Available data included gramma-ray, neutron porosity, resistivity deep, sonic, density, photoelectric factor, total porosity and effective porosity profiles from 21 wells together with mineralogical models. Core descriptions and thin section images were used as additional data for the lithological characterization of the electrofacies and consequently for reservoir zonation. A total of four electrofacies were defined from the SOM application, and five reservoir zones were identified.</p><p>The characterization of the reservoir zones also considered the structural locations of the wells based on the relative depth to top- Barra Velha Formation; well locations were classified as structurally high, intermediate or low. Based on the reservoir zone characteristics, the results could be correlated with zonations in previous studies. A general tendency was noted for there to be an increase of finer-grained sediments in the formation in wells located in structural lows; packstone and mudstone facies were prevalent in these wells and were in general characterized as poor-quality reservoir rocks. By contrast, the shrubstones and grainstones which were more frequent in structurally high wells comprised higher quality reservoir rocks.</p><p>The basal reservoir zone showed wide lithological variation compared to the overlying reservoir zones. Grainstone-dominated facies were identified in the middle of the formation, and the uppermost reservoir zones were characterized by an upward increase in shrubstones and reworked grainstones which in general pointed to better quality reservoirs.</p>","PeriodicalId":16748,"journal":{"name":"Journal of Petroleum Geology","volume":"45 4","pages":"439-459"},"PeriodicalIF":1.8,"publicationDate":"2022-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49660597","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
SOURCE ROCK POTENTIAL OF THE UPPER TRIASSIC CHANG 7 MEMBER IN THE WESTERN ORDOS BASIN, CHINA 鄂尔多斯盆地西部上三叠统长7段烃源岩潜力
IF 1.8 4区 地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2022-09-30 DOI: 10.1111/jpg.12825
Guo Chen, Ning Wang, Shuai Yang, Xiaofeng Li, Pengfei Zhang, Yanqing Su

The Chang 7 member of the Upper Triassic Yanchang Formation is an important source rock in the Ordos Basin, NW China. Previous studies of the unit have in general focused on the relatively deep-water (∼25 m) anoxic, OM-rich lacustrine mudstones which form the main Mesozoic source rock at fields in the south of the basin. However, this paper presents an integrated geochemical investigation of the relatively shallow-water Chang 7 facies in a study area around Jiyuan field in the western part of the basin in order to evaluate its source rock potential. The results show that the Chang 7 source rock in the study area has a high content of Type II OM, and is interpreted to have been deposited in a suboxic-anoxic lacustrine setting with a mixed input of aquatic and terrigenous organic matter. The results of 1D modelling of a well in the study area showed that the Chang 7 member entered the oil generation window from the Middle Jurassic. Oil-oil correlations based on hierarchical cluster analysis and correspondence analysis showed that crude oils generated by deep-water Chang 7 source rocks from wells in the south of the basin can be distinguished from Soxhlet-extracted petroleum from reservoir sandstones in the study area. The compositional differences are inferred to be due to variations in source rock facies compositions. An oil – source rock correlation study showed that the shallower-water Chang 7 source rock in the western part of the basin generated the hydrocarbons in core extracts of reservoir sandstones from wells in this area. The shallow-water Chang 7 facies may therefore constitute an effective oil-prone source rock in the western Ordos Basin.

上三叠统延长组长7段是鄂尔多斯盆地重要的烃源岩。以前对该单元的研究一般集中在相对深水(~ 25 m)缺氧、富含om的湖相泥岩上,这些泥岩在盆地南部的油田形成了主要的中生代烃源岩。本文对盆地西部姬塬油田周边研究区较浅水长7相进行了综合地球化学调查,以评价其烃源岩潜力。结果表明:研究区长7烃源岩ⅱ型有机质含量高,沉积环境为亚缺氧湖泊环境,水、陆源有机质混合输入。研究区一口井的一维模拟结果表明,长7段从中侏罗统开始进入生油窗口。基于层次聚类分析和对应分析的油气对比结果表明,盆地南部长7深水烃源岩产出的原油与研究区储层砂岩中的soxhleet萃取原油可以区分。成分差异被推断是由于烃源岩相组成的变化。油源对比研究表明,盆地西部浅水长7烃源岩在本区井储层砂岩岩心萃取物中生成烃。因此,长7浅水相可能构成鄂尔多斯盆地西部有效的亲油烃源岩。
{"title":"SOURCE ROCK POTENTIAL OF THE UPPER TRIASSIC CHANG 7 MEMBER IN THE WESTERN ORDOS BASIN, CHINA","authors":"Guo Chen,&nbsp;Ning Wang,&nbsp;Shuai Yang,&nbsp;Xiaofeng Li,&nbsp;Pengfei Zhang,&nbsp;Yanqing Su","doi":"10.1111/jpg.12825","DOIUrl":"10.1111/jpg.12825","url":null,"abstract":"<p>The Chang 7 member of the Upper Triassic Yanchang Formation is an important source rock in the Ordos Basin, NW China. Previous studies of the unit have in general focused on the relatively deep-water (∼25 m) anoxic, OM-rich lacustrine mudstones which form the main Mesozoic source rock at fields in the south of the basin. However, this paper presents an integrated geochemical investigation of the relatively shallow-water Chang 7 facies in a study area around Jiyuan field in the western part of the basin in order to evaluate its source rock potential. The results show that the Chang 7 source rock in the study area has a high content of Type II OM, and is interpreted to have been deposited in a suboxic-anoxic lacustrine setting with a mixed input of aquatic and terrigenous organic matter. The results of 1D modelling of a well in the study area showed that the Chang 7 member entered the oil generation window from the Middle Jurassic. Oil-oil correlations based on hierarchical cluster analysis and correspondence analysis showed that crude oils generated by deep-water Chang 7 source rocks from wells in the south of the basin can be distinguished from Soxhlet-extracted petroleum from reservoir sandstones in the study area. The compositional differences are inferred to be due to variations in source rock facies compositions. An oil – source rock correlation study showed that the shallower-water Chang 7 source rock in the western part of the basin generated the hydrocarbons in core extracts of reservoir sandstones from wells in this area. The shallow-water Chang 7 facies may therefore constitute an effective oil-prone source rock in the western Ordos Basin.</p>","PeriodicalId":16748,"journal":{"name":"Journal of Petroleum Geology","volume":"45 4","pages":"395-415"},"PeriodicalIF":1.8,"publicationDate":"2022-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45362239","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
GEOCHEMICAL ANALYSES OF SEEP OILS IN THE SOUTHERN GAFSA BASIN, SW TUNISIA: REASSESSMENT OF REGIONAL HYDROCARBON POTENTIAL 突尼斯南部gafsa盆地渗漏油的地球化学分析:区域油气潜力的再评价
IF 1.8 4区 地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2022-09-30 DOI: 10.1111/jpg.12826
Kamel Dadi, Riadh Ahmadi, Anis Belhaj Mohamed, Chaouki Khalfi, Najwa Mbarki, Jamel Abdennaceur Ouali

The recent discovery of surface oil seeps in the Tamerza area in the west-central Gafsa Basin (southern Tunisia) has prompted a re-evaluation of the hydrocarbon potential of the region. In this paper, we report the results of analyses of seep oils by Rock-Eval pyrolysis (n = 6) and gas chromatography – mass spectrometry (n = 4). The goals of the study were to assess the composition of the seep oils, to investigate the relationship between the seep oils and potential source rocks, and to highlight the significance of the seep oils for oil exploration in the region.

In the Tamerza area, surface oil seeps have been recorded in numerous formations ranging between the Upper Cretaceous Abiod Limestone Formation and the lower Miocene Sehib Siltstone Formation. The results of this study showed that all the seep oil samples analysed in general had a similar geochemical fingerprint: for example, Pr/Ph values are lower than 1; a plot of Pr/n-C17 (0.27- 0.36) versus Ph/n-C18 (0.3-0.8) indicates a marine source rock deposited under reducing anoxic conditions; and Ts/(Ts+Tm) ratios indicate that the source rock was thermally mature. Correlation studies suggest that the oils originated from Cenomanian-Turonian shales corresponding to the informally-named Bahloul equivalent formation. Oil expulsion from this source rock at the seep locations is inferred to have ended by middle Miocene time. However the main phase of folding occurred here in the Pliocene – early Quaternary, and the resulting anticlinal folds are not therefore prospective structural traps for hydrocarbons because they developed after migration had already ceased. Stratigraphic traps and salt structures in the region may be of greater exploration interest.

A surface oil seep sample was also recovered from the Quaternary upper Segui Formation at Jebel Orbata in the east of the Gafsa Basin. Analysis of this oil sample showed that it has similar geochemical characteristics to the seep oils from the Tamerza area, but that it appears to have had a much more recent migration history. In the eastern Gafsa Basin, Pliocene – early Quaternary anticlinal structures could therefore constitute effective structural traps charged by the same Bahloul equivalent formation source rock.

最近在Gafsa盆地中西部(突尼斯南部)的Tamerza地区发现了地面石油渗漏,促使人们对该地区的碳氢化合物潜力进行了重新评估。本文报道了6种岩石热解法(n = 6)和4种气相色谱-质谱法(n = 4)对渗漏油的分析结果,目的是评价渗漏油的组成,探讨渗漏油与潜在烃源岩的关系,并强调渗漏油对该地区石油勘探的意义。在Tamerza地区,在上白垩统Abiod灰岩组和下中新统Sehib粉砂岩组之间的许多地层中都记录了地面石油渗漏。研究结果表明,所分析的渗漏油样品具有相似的地球化学指纹图谱:Pr/Ph值均小于1;Pr/n-C17比值(0.27 ~ 0.36)与Ph/n-C18比值(0.3 ~ 0.8)表明海相烃源岩沉积于还原性缺氧条件下;Ts/(Ts+Tm)比值表明烃源岩热成熟。对比研究表明,这些油来自于与非正式名称Bahloul等效地层相对应的Cenomanian-Turonian页岩。据推测,该烃源岩在渗漏部位的排油在中新世中期结束。然而,褶皱的主要阶段发生在上新世-早第四纪,由此产生的背斜褶皱是在运移已经停止后发育的,因此不是有前景的油气构造圈闭。该地区的地层圈闭和盐构造可能具有更大的勘探价值。在Gafsa盆地东部Jebel Orbata地区第四系Segui组上段也获得了地面溢油样品。对该石油样本的分析表明,它与塔默扎地区的渗漏油具有相似的地球化学特征,但它的迁移历史似乎更近。因此,在Gafsa盆地东部,上新世—早第四纪背斜构造可能构成有效的构造圈闭,由相同的Bahloul等效地层烃源岩充能。
{"title":"GEOCHEMICAL ANALYSES OF SEEP OILS IN THE SOUTHERN GAFSA BASIN, SW TUNISIA: REASSESSMENT OF REGIONAL HYDROCARBON POTENTIAL","authors":"Kamel Dadi,&nbsp;Riadh Ahmadi,&nbsp;Anis Belhaj Mohamed,&nbsp;Chaouki Khalfi,&nbsp;Najwa Mbarki,&nbsp;Jamel Abdennaceur Ouali","doi":"10.1111/jpg.12826","DOIUrl":"10.1111/jpg.12826","url":null,"abstract":"<p>The recent discovery of surface oil seeps in the Tamerza area in the west-central Gafsa Basin (southern Tunisia) has prompted a re-evaluation of the hydrocarbon potential of the region. In this paper, we report the results of analyses of seep oils by Rock-Eval pyrolysis (n = 6) and gas chromatography – mass spectrometry (n = 4). The goals of the study were to assess the composition of the seep oils, to investigate the relationship between the seep oils and potential source rocks, and to highlight the significance of the seep oils for oil exploration in the region.</p><p>In the Tamerza area, surface oil seeps have been recorded in numerous formations ranging between the Upper Cretaceous Abiod Limestone Formation and the lower Miocene Sehib Siltstone Formation. The results of this study showed that all the seep oil samples analysed in general had a similar geochemical fingerprint: for example, Pr/Ph values are lower than 1; a plot of Pr/n-C<sub>17</sub> (0.27- 0.36) versus Ph/n-C<sub>18</sub> (0.3-0.8) indicates a marine source rock deposited under reducing anoxic conditions; and Ts/(Ts+Tm) ratios indicate that the source rock was thermally mature. Correlation studies suggest that the oils originated from Cenomanian-Turonian shales corresponding to the informally-named Bahloul equivalent formation. Oil expulsion from this source rock at the seep locations is inferred to have ended by middle Miocene time. However the main phase of folding occurred here in the Pliocene – early Quaternary, and the resulting anticlinal folds are not therefore prospective structural traps for hydrocarbons because they developed after migration had already ceased. Stratigraphic traps and salt structures in the region may be of greater exploration interest.</p><p>A surface oil seep sample was also recovered from the Quaternary upper Segui Formation at Jebel Orbata in the east of the Gafsa Basin. Analysis of this oil sample showed that it has similar geochemical characteristics to the seep oils from the Tamerza area, but that it appears to have had a much more recent migration history. In the eastern Gafsa Basin, Pliocene – early Quaternary anticlinal structures could therefore constitute effective structural traps charged by the same Bahloul equivalent formation source rock.</p>","PeriodicalId":16748,"journal":{"name":"Journal of Petroleum Geology","volume":"45 4","pages":"417-437"},"PeriodicalIF":1.8,"publicationDate":"2022-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43222112","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
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Journal of Petroleum Geology
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