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    Change of physical properties at different heating rates, time and water content for oil shale
    XU Liangfa, MA Zhongliang, ZHENG Lunju, BAO Fang
    Petroleum Geology & Experiment    2018, 40 (4): 545-550.   DOI: 10.11781/sysydz201804545
    Abstract   PDF (689KB)  
    An oil shale in situ pyrolysis simulation experiment with different heating rates, heating time and water contents was carried out to assess the influences of these parameters on the physical properties of oil shale in situ conversion production. The physical properties of oil shale in situ conversion production were analyzed using nuclear magnetic resonance T2 spectra. The results showed that the slow heating rate (the increase of reaction time) was beneficial to the development of organic micro-pores, while the increase of heating rate was beneficial to the development of micro-cracks. With the increase of constant temperature time, the physical properties of oil shale can be improved, and small pores gradually develop into relatively larger pores. High-temperature water may be used as a catalyst, reactant and solvent to participate in the reaction. On the one hand, it is beneficial to react with organic matter to generate organic pores; on the other hand, high-temperature water may react with oil shale minerals, thus improving the physical properties of oil shale.
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    Pore characterization of shale in Shanxi Formation, Yan'an area, Ordos Basin
    WANG Zilong, GUO Shaobin
    Petroleum Geology & Experiment    2019, 41 (1): 99-107.   DOI: 10.11781/sysydz201901099
    Abstract   PDF (2336KB)  
    The shale reservoirs in the Upper Paleozoic Shanxi Formation in the Yan'an area of the Ordos Basin were studied. The whole porosity of the shale was characterized in detail using NMR, SEM, high pressure mercury intrusion, nitrogen adsorption and carbon dioxide adsorption. The Shanxi Formation in the Yan'an area mainly developed four types of porosity, i.e. fractures, intergranular, intragranular pores, and organic pores, with intragranular and organic pores in the majority. The T2 NMR curves are mostly single-peaked and almost unchanged after centrifugation, indicating that the samples are dominated by nano pores with poor connectivity. High pressure mercury intrusion, nitrogen adsorption and carbon dioxide adsorption experiments showed that the pore volume is mainly meso pores and macro pores, accounting for about 85% of the total pore volume, while micro pores only account for 15% of the total pore volume. The specific surface area is mainly provided by micro pores and meso pores, with micro pores accounting for 52% of the total specific surface area, followed by meso pores accounting for 48%. Macro pores can be neglected when the surface area is more than 99%. The pore morphology of the samples is mainly parallel plate pores with openings or slits at both ends.
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    Rock features and sedimentary environment of the fourth member of Dengying Formation in Hujiaba section of Ningqiang, northern Sichuan Basin
    GUO Xusheng, HU Dongfeng, DUAN Jinbao, WU Hao, LI Bisong
    Petroleum Geology & Experiment    2018, 40 (6): 749-756.   DOI: 10.11781/sysydz201806749
    Abstract   PDF (11048KB)  
    In the central Sichuan Basin, significant progress has been made in the exploration of natural gas around the Dengying Formation. However, the exploration in the northern Sichuan Basin is relatively low and the drilling data is scarce. The petrological characteristics of the field geological section and the analysis of the sedimentary environment are of great significance for oil and gas exploration. Based on the survey and systematic sampling analysis of the Dengying Formation, Hujiaba section, sedimentary stratigraphy, rock classification and sedimentary environment analyses were carried out using sedimentology and petrology. Our research showed that:(1) According to the rock types, algae content and shale content, the 4th member of Dengying Formation, Hujiaba section can be divided into upper and lower sub-sections, of which the upper sub-section is the main part of the bioherm-beach and reservoir development; (2) The carbonate rock types of the 4th member of Dengying Formation can be divided into three sub-classes of crystalline dolomite, algae dolomite and granular dolomite, and eight micro-classes; (3) The 4th member of Dengying Formation, Hujiaba section is generally deposited on the edge of the platform, which can be divided into four subfacies of table, interbank sea, algal mound and grain beach. (4) During the deposition period of the fourth member of Dengying Formation, the sea level is characterized by two cycles of transgression and regression. The types of sedimentary rocks are controlled by the sedimentary cycle and sea level which shows a sedimentary evolution process of table facies→interbank sea facies→bioherm-beach facies→interbank sea facies→bioherm-beach facies.
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    Geological characteristics of ‘strata-bound’ and ‘fault-controlled’ reservoirs in the northern Tarim Basin: taking the Ordovician reservoirs in the Tahe Oil Field as an example
    LU Xinbian, YANG Min, WANG Yan, BAO Dian, CAO Fei, YANG Debin
    Petroleum Geology & Experiment    2018, 40 (4): 461-469.   DOI: 10.11781/sysydz201804461
    Abstract   PDF (3422KB)  
    The marine facies carbonate reservoirs in the northern Tarim Basin were studied using high-resolution 3D seismic data, as well as a large amount of actual drilling data and dynamic production data. The carbonate fractured-and-vuggy reservoirs in the study area were distinguished into two types:strata-bound karst reservoir and fault-controlled karstic-fault reservoir. The former was developed in the buried hill of the paleokarst system in the northern Tarim Basin, which can be further divided into two subtypes:residual hill type and paleo-channel type. Reservoirs are characterized by "vertically superimposed and quasi-stratified distribution" on the macroscopic scale, and feature large changes in reservoir space, coexistence of caves, pores and fractures, relatively contiguous reservoir units, and complex oil-water relationships. The karstic-fault reservoir mainly developed in the covered area of Middle-Upper Ordovician, which is controlled by different ordered strike slip faults and related dissolutions. The karstic-fault reservoir is a special type of oil and gas reservoir existing in nature. It has unique hydrocarbon accumulation characteristics, such as different sections of accumulation along fault belt, across different strata vertically and discontinued distribution and so on. The karstic-fault reservoir is a new trap type and a new target in deep carbonate oil and gas exploration and development.
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    Reservoir characteristics and controlling factors in the contact metamorphic zone of hypabyssal intrusive rocks in the Qintong Sag, Northern Jiangsu Basin
    WU Jun, CHEN Kongquan, ZHANG Feng, SHEN Junjun, LIU Jinshuai, TAN Jing
    Petroleum Geology & Experiment    2018, 40 (3): 323-329.   DOI: 10.11781/sysydz201803323
    Abstract   PDF (2755KB)  
    Reservoir characteristics and controlling factors in the contact metamorphic zone of hypabyssal intrusive rocks are of a great significance for the exploration and development of magmatic oil reservoirs. The contact metamorphic zone of hypabyssal intrusive rocks was well preserved in the Shuaiduo-Maoshan areas of the Qintong Sag, Northern Jiangsu Basin, and is an ideal area to understand this mechanism. Systematic core and drill cuttings observations, well logging interpretation and borehole-seism-modulus integration techniques were conducted to evaluate spatial distribution regularities and dissect the characteristics of reservoir development in a typical contact metamorphic zone. Some favorable reservoirs in the contact metamorphic zone of intrusive rocks in the Qingtong Sag were predicted. The studies showed that wall rocks were altered by the influence of intrusive rocks, forming the contact metamorphic zone of intrusive rocks. The contact metamorphic zone has the characteristics of high natural gamma, medium sonic time difference, medium natural potential and high resistivity on logging curves. The contact metamorphic zone generally distributed above and below the intrusive rocks, and has a positive correlation with the thickness of intrusive rocks. In addition, the thickness of altered mudstones in the contact metamorphic zone is the main factor affecting the distribution of high quality reservoirs, and the high-quality reservoirs in the contact metamorphic zone near to volcanic sills are favorable for hydrocarbon accumulation.
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    Shale gas reservoir geology of the Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation in western Hubei and northeastern Chongqing
    ZHOU Zhi, ZHAI Gangyi, SHI Dishi, WANG Shengjian, GUO Tianxu, LIU Yimin, WANG Hao
    Petroleum Geology & Experiment    2019, 41 (1): 1-9.   DOI: 10.11781/sysydz201901001
    Abstract   PDF (6968KB)  
    The Upper Ordovician Wufeng Formation and the Lower Silurian Longmaxi Formation are important strata for shale gas exploration in the western Hubei and northeastern Chongqing area. At present, no breakthrough has been made in exploration, and the main factors controlling shale gas enrichment are unclear. The spatial and temporal distribution, geochemical features, reservoir properties and gas-bearing capacities of high-quality shale of deep-water continental shelf facies in the Wufeng-Longmaxi formations were studied based on the analysis of drill core and field outcrop data of well JD1 and its adjacent area in Jianshi area. Organic-rich shale was developed well in the Wufeng-Longmaxi formations. The organic-rich shale of deep-water continental shelf facies was mainly found in the Katian, Hirnantian and Rhuddanian stages, which featured substantial thickness, high TOC content, medium maturity, favorable reservoir conditions and medium burial depth, showing a good potential for shale gas enrichment. The organic-rich shale of deep-water continental shelf facies in the Katian, Hirnantian and Rhuddanian stages had a stable structure with few fractures, and a regional cap rock in the Middle and Lower Triassic and these are the main controls for shale gas enrichment in the Wufeng-Longmaxi formations in the western Hubei and northeastern Chongqing area.
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    Characteristics and dominating factors of lamellar fine-grained sedimentary rocks: A case study of the upper Es4 member-lower Es3 member, Dongying Sag, Bohai Bay Basin
    WANG Miao, LU Jianlin, ZUO Zongxin, LI Hao, WANG Baohua
    Petroleum Geology & Experiment    2018, 40 (4): 470-478.   DOI: 10.11781/sysydz201804470
    Abstract   PDF (2654KB)  
    A case study was made in the Dongying Sag to meet the needs of shale oil zone evaluation.The characteristics and dominating factors of lamellar fine-grained sedimentary rocks from the upper Es4 member to the lower Es3 member in the Dongying Sag were studied based on core and cast thin section observations combined with drilling and logging data. By comparing the lamellar fine-grained sedimentary rocks in ancient lakes with those in recent lakes, five types of laminae were identified, including silty, clay, carbonate, organic-rich and mixed ones. The origin and sedimentary environment of each type of laminae was analyzed. The study considered both macroscopic and microscopic features of laminae and the factors of sedimentary source, transport process and depositional environment, and made a conclusion that tectonic movement, climate change and source determined laminar characteristics as follows. (1) From the upper Es4 member to the lower Es3 member, the distribution zone of lamellar fine-grained sedimentary rocks migrates from east to west, which is compatible with the evolution tendency of the tectonic subsidence center. Different laminar types developed in different tectonic units. The organic-rich laminae are mainly distributed in the deep depression and the southern slope. The silty laminae occur in the central anticline and the southern slope. The carbonate laminae are distributed in the inner slope. The mixed laminae are found in the central anticline and the southern slope. The clay laminae are distributed widely in all the above mentioned tectonic units. (2) An arid climate led to high lake salinity and carbonate laminae were deposited. So the carbonate laminae are relevant to an arid climate. The organic-rich laminae tend to be deposited in damp climates, which are well-developed in lacustrine transgressive system tracts from the upper Es4 member to the lower Es3 member. (3) Provenance has a significant control on limestone laminae distribution. A development mode of lamellar fine-grained sedimentary rocks was proposed.
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    Basin types and hydrocarbon distribution in salt basins in the South Atlantic
    LIU Jingjing, WU Changwu, DING Feng
    Petroleum Geology & Experiment    2018, 40 (3): 372-380.   DOI: 10.11781/sysydz201803372
    Abstract   PDF (5242KB)  
    The salt basins in the South Atlantic are rift-passive continental margin superimposed basins.These basins have the same tectonic evolution history and similar characteristics of stratigraphic development, but the hydrocarbon distribution is extremely uneven.Based on the further subdivision of basin type, this paper discussed the distribution of hydrocarbon in the salt basins. First, according to the characteristics of stratigraphic structure which was deposited during the rift stage, the salt basins in the South Atlantic were divided into two kinds of basin:rift strata with characteristics of depressions and uplifts, and rift strata with monoclinic characteristics. According to the characteristics of stepped faults during the rift stage and the sedimentary characteristics during the stage of passive continental margin, each type can be subdivided into two subtypes. Second, based on the analysis of regional petroleum geological conditions, there are three hydrocarbon accumulation combinations in the study area, including pre-salt, post-salt Cretaceous and Tertiary hydrocarbon accumulation combinations, and this paper outlines accumulation models and the main controlling factors.Finally, from the point of view of the basin type, the difference of hydrocarbon accumulation conditions in different basins was pointed out, and the differences of hydrocarbon distribution in different basins were discussed. These results will guide further oil and gas exploration in the salt basins in the South Atlantic.
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    Micro-pore characteristics of shale from Wufeng-Longmaxi formations in Pingqiao area, Sichuan Basin
    WANG Yunhai
    Petroleum Geology & Experiment    2018, 40 (3): 337-344.   DOI: 10.11781/sysydz201803337
    Abstract   PDF (2508KB)  
    The microscopic pore characteristics of shale from the lower Wufeng-Longmaxi formations in the Pingqiao area of the Sichuan Basin were studied using argon ion polished sample scanning electron microscopy and nitrogen adsorption-desorption experiments. Organic-rich siliceous shale and carbonaceous shale micro-pores are dominated by organic pores and micro-cracks. The pore structure is relatively complex, with rich pore morphology and a wide range of pore sizes. Argon ion polishing scanning electron microscopy showed that the organic pores are mainly thin and partly belong to micro-pores. Nitrogen adsorption-desorption experiments showed that the shale has narrow parallel plate-like holes, a small number of conical plate holes and wedge-shaped holes with a poor connectivity, and regular open round holes and ink bottle-shaped holes with open ends. The specific surface area measured by nitrogen adsorption-desorption experiments was 9-32.6 m2/g, with an average of 18.0 m2/g, which was low. The pore diameters measured by the BET method were 3.23 to 4.35 nm, and the average pore volume by the BJH method was 0.016 5 cm3/g. The fine meso-pores were dominant, and they were biased toward the micro-pore boundary. According to the comprehensive analysis, the microscopic pores of shale reservoirs in the study area are mainly mesoporous, and meso-pores and micro-pores contribute most of the specific surface area.
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    Structure and sedimentary characteristics of the Meso-Cenozoic basin group along the Yangtze River in the Lower Yangtze region
    XU Xi, ZHU Xiaoying, SHAN Xipeng, XIAO Mengchu, SUN Lianpu, GAO Shunli
    Petroleum Geology & Experiment    2018, 40 (3): 303-314.   DOI: 10.11781/sysydz201803303
    Abstract   PDF (5936KB)  
    The basin group along the Yangtze River is an important part of the Meso-Cenozoic petroliferous basins in the Lower Yangtze region, which is also an important window for the study of the structure and tectono-sedimentary evolution of the Meso-Cenozoic basins in East China. There are nine relatively independent faulted basins from west to east in the Yangtze River's middle and lower reaches, including Poyang, Qianshan, Wanjiang, Quanjiao, Wuwei, Jurong-Nanling, Changzhou-Xuancheng, Liyang and Pinghu basins, which comprise a basin system or group in the plane, named the Lower Yangtze basin group. Sedimentary filling in the basins was divided into two stages including faulting from the Late Cretaceous to the Paleogene, and depression from the Neogene to the Quaternary. The former stage is characterized by the sedimentation of fluviolacustrine and delta facies, while the latter stage is marked by the deposition of fluvial facies. The fault basin system formed in the Late Oligocene, and a unified depression system formed in the Neogene along the Yangtze River. Due to the Neogene differential deformation, the basinal strata were differentially denuded, forming the modern geological setting of the sedimentary basins.
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