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2021 Vol. 43, No. 5

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2021, 43(5): 000-000.
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2021, 43(5): 00-00.
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Advances in basic research on the mechanism of deep marine hydrocarbon enrichment and key exploitation technologies
MA Yongsheng, LI Maowen, CAI Xunyu, XU Xuhui, HU Dongfeng, QU Shouli, LI Gensheng, HE Dengfa, XIAO Xianming, ZENG Yijin, RAO Ying, MA Xiaoxiao
2021, 43(5): 737-748. doi: 10.11781/sysydz202105737
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A basic research program on deep hydrocarbon resource accumulation mechanisms and key exploitation technologies was initiated by the National Natural Science Foundation of China at the beginning of 2020, to meet the theoretical and technological demands of deep hydrocarbon exploration and development in the Tarim, Sichuan and Ordos basins. This paper provided a review of the recent program progresses on (1) the reconstruction of prototypes and the transformation histories of three ancient cratons in China; (2) the petroleum accumulation and flow mechanisms in deep marine carbonate reservoirs and deep shale gas systems; (3) the geophysical theories and methods for imaging the deep structures and predicting the deep petroleum reservoirs; and (4) the new protocols and downhole tools for deep well drilling and completion. Brief comments were also made on the preliminary application of the recent program results in facilitating several breakthroughs in the deep petroleum exploration of the Tarim and Sichuan basins.
Accumulation conditions and controlling factors for the enrichment of shale oil and gas in the Jurassic Qianfoya Formation, Yuanba area, Sichuan Basin
GUO Xusheng, ZHAO Yongqiang, ZHANG Wentao, LI Yuping, WEI Xiangfeng, SHEN Baojian
2021, 43(5): 749-757. doi: 10.11781/sysydz202105749
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Taking key wells such as Yuanye 3 in the Yuanba area of the Sichuan Basin as examples, the accumulation conditions of continental shale oil and gas in the Middle Jurassic Qianfoya Formation in this area have been evaluated based on core observation and experimental analysis. The organic-rich mudstone of the Qianfoya Formation has high porosity and good oil and gas content. It is the main reservoir lithofacies type, while the physical properties of limestone and sandstone interlayers are relatively poorer. The pores are mainly inorganic ones, accounting for approximately 60% to 80% of the total porosity. Compared with marine shale, the proportion of micropores is lower and the content of macropores is higher, which is conducive to the production of shale oil and gas. The fourth section of the lower part of the second member of the Qianfoya Formation is dominated by organic-rich mudstone, with a high shale-to-stratum ratio, an average porosity of 5.43%, and an average total organic carbon (TOC) content of 1.72%. The free hydrocarbon content (S1) of frozen sample pyrolysis is 2.63 mg/g, and the average total gas content is 1.51 m3/t, showing a good oil-bearing property and favorable geological conditions for the formation of continental shale oil and gas. Comparative analysis with other wells has indicated that half-deep lacustrine facies is the most favorable sedimentary facies belt, providing basic material for oil and gas enrichment, and high maturity and fracture development is the important condition for oil and gas enrichment.
Main constrains and dynamic process of Ordovician hydrocarbon accumulation, central and western Tahe Oil Field, Tarim Basin
ZHAO Yongqiang, YUN Lu, WANG Bin, GENG Feng, LI Haiying, GU Yi, LIU Yongli
2021, 43(5): 758-766. doi: 10.11781/sysydz202105758
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Diversified types of oil and gas resources have been discovered in the Ordovician strata of central and western parts of the Tahe Oil Field, Tarim Basin. The formation contains oil in the vertical direction as a whole, and its accumulation process appeared to be extremely complicated. The dynamic process of oil and gas accumulation in the central and western parts of Tahe Oil Field were re-studied on the basis of combination of approaches including perspective of multiple reservoir-forming factors and their temporal and spatial dynamic configuration relationships, the discussion of typical reservoir profiles, thermal evolution of source rocks and consequent hydrocarbon generation history, paleo-structural evolution, hydrocarbon accumulation period and transport system, thus, a model of compound accumulation was established following an idea that paleo-structures and strike-slip faults together constrained reservoir formation and hydrocarbon generation as well as accumulation. Studies have shown that the main constrains for hydrocarbon accumulation in the study area includes the long-term hydrocarbon generation and expulsion from source rocks, multi-stage charging and accumulation and mixing transformation, paleo-structural controlling the migration and accumulation direction, vertical conduction and lateral adjustment by strike-slip faults, and multiple types of fractures and caves. The dynamic process of hydrocarbon accumulation has the characteristics of "vertical transportation, lateral accumulation, paleo-uplift controlling enrichment" in the early stage, and "in-situ hydrocarbon source, vertical migration and accumulation, and fault controlling enrichment" in the late stage. The mixed accumulation of oil and gas of different stages and different properties has created the present complex oil and gas appearance of the Ordovician strata. The heavy oil area was dominated by early accumulation, which was related to the high paleo-structures in the middle and late Caledonian periods, and the later charging was relatively weaker. The light oil area was dominated by late accumulation, mainly constrained by the vertical transport and short-range lateral adjustment of strike-slip faults. It is most developed in the NNE-trending fault zone and the intersection with the NNW-trending fault.
Maturity limit of sweet spot area for continental matrix type shale oil: a case study of lower Es3 and upper Es4 sub-members in Dongying Sag, Bohai Bay Basin
LI Zhiming, SUN Zhongliang, LI Maowen, CAO Tingting, QIAN Menhui, MA Xiaoxiao, LIU Peng, Bao Yunjie, JIANG Qigui, TAO Guoliang, ZHANG Jun, RUI Xiaoqing
2021, 43(5): 767-775. doi: 10.11781/sysydz202105767
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The matrix type shale oil will become the main contributer for increasing shale oil reserves and production in China. Maturity is an important factor for the controlling to the distribution of sweet spot area for matrix type shale oil. The vitrinite reflectance suppression ranges of continental organic rich shale with different organic matter type were analyzed, and the maturity limit of sweet spot area for continental matrix type shale oil was discussed taking the lower Es3 (third member of Shahejie Formation) and upper Es4 (fourth member of Shahejie Formation) sub-members of the Dongying Sag as a case study. The vitrinite reflectance suppression ranges of continental organic rich shale are positively correlated to organic matter types. The actual maturity (EqVRo) of organic matter rich shale of the lower Es3 in subsags of Dongying Sag was mainly at the range of 0.69%-1.05%, and that of the upper Es4 is mainly at the range of 0.74%-1.20%. Combining with the analysis of geological and engineering sweet spot conditions, the EqVRo of organic matter rich shale of both two sub-members range 0.74%-1.20%. The deeper areas of four sub-sags in the Dongying Sag all have favorable prospecting of commercial development for matrix type shale oil in the lower Es3 and upper Es4 sub-members.
Main controlling factors for the enrichment of shale oil and significant discovery in second member of Paleogene Funing Formation, Qintong Sag, Subei Basin
YAO Hongsheng, ZAN Ling, GAO Yuqiao, HUA Caixia, YU Wenduan, LUO Weifeng, MA Xiaodong
2021, 43(5): 776-783. doi: 10.11781/sysydz202105776
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Based on the study of hydrocarbon generation features, oil bearing property and reservoir property of shale in the second member of Paleogene Funing Formation in the Qintong Sag of the Subei Basin, the main controlling factors of shale oil enrichment were analyzed. Shale of the second member of Funing Formation in the Qintong Sag was featured by large-scale thickness and medium TOC content, which provided a material basis for shale oil enrichment. The vitrinite reflectance (%Ro) of shale in the second member of Funing Formation in the deep sag distributed between 0.9%-1.0%, indicating a moderate thermal evolution degree. Shale oil has the characteristics of light hydrocarbon, high gas-measured total hydrocarbon value and good fluidity. Few faults were developed, resulting in good preservation conditions and high formation pressure, which were conducive to hydrocarbon enrichment. High content of brittle minerals and well-developed lamella and natural fractures made formation fracturing easier. The continuous and large-area distribution of high-quality shale is the basis for oil and gas abundance. Preservation condition is the key factor to reservoir formation. The degree of evolution is a decisive factor of oil-bearing. High pressure, lamina development and high brittle mineral content are important factors for high yield. The shale oil in second member of Funing Formation in Shaduo area has the characteristics of low TOC content (1%), low gas oil ratio (40-80 m3/t) and high pressure (1.25 MPa). The success of this well has reduced the shale oil evaluation standard and threshold, and expanded the development space of shale oil.
Occurrence states and potential influencing factors of shale oil in the Permian Fengcheng Formation of Mahu Sag, Junggar Basin
YANG Zhifeng, TANG Yong, GUO Xuguang, HUANG Liliang, WANG Ziqiang, ZHAO Xinmei
2021, 43(5): 784-796. doi: 10.11781/sysydz202105784
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Taking the Permian Fengcheng Formation of the Mahu Sag of the Junggar Basin as an example, a systematic study of shale oil was carried out for the occurrence states and potential influencing factors by integrating various data including cores, well logging, X-ray diffraction, argon ion polishing and field emission-scanning electron microscopy (FE-SEM) observations, high-pressure mercury injection (HPMI), rock pyrolysis, and two-dimensional nuclear magnetic resonance (NMR) experiments. The shale oil of the Fengcheng Formation in the Mahu Sag mainly has two modes of occurrence: film-like adsorbed oil and infilled free oil. The main constrains for shale oil occurrence state include lithofacies association, mineral composition and reservoir space. Four lithofacies associations namely dolomitic shale, sandy shale-dolomitic siltstone, dolomite rock containing alkaline mineral-argillaceous siltstone, and siliceous dolomite rock-dolomitic siltstone were recognized in the shale reservoirs of the Fengcheng Formation. The mineral composition, reservoir space, micro-pore structure and shale oil occurrence states of different lithofacies appeared to be quite different. The contents of quartz, pyrite and organic matter were positively correlated with thermal cracking hydrocarbon (S2), and the contents of feldspar and dolomite showed a weak positive correlation with free hydrocarbon (S1). The free oil was mainly stored in mesopores and large pores, such as secondary dissolution pores and residual intergranular pores. The absorbed oil was mainly stored in mesopores and small pores, such as organic pores, intercrystallite pores and the surface of mineral particles. The mineral composition and pore-throat structure were dominant factors controlling the occurrence state of shale oil.
Sedimentary environment and organic matter enrichment of the Lower Cambrian Niutitang Formation shale, western Hunan Province, China
ZHU Qingmin, LU Longfei, PAN Anyang, TAO Jinyu, DING Jianghui, LIU Wangwei, LI Maowen
2021, 43(5): 797-809. doi: 10.11781/sysydz202105797
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The Lower Cambrian Niutitang Formation shale is an extremely crucial marine source rock developed at the mid-upper Yangtze block of China. To clarify the paleoenvironment and conditions which are responsible for organic matter enrichment of the Niutitang Formation shale in South China, a systematic study of petrology, organic geoche-mistry and elemental geochemistry was carried out by focusing on the Niutitang Formation shale in Yuanling, western Hunan Province. Results showed that the paleoclimate was transforming from dry-cold to warm-wet during deposition of Niutitang Formation. The level of biological productivity, the redox properties of water and the intensity of hydrothermal activity showed a consistent trend of low-high-medium-high from the early to the late stage of deposition. Rather than being controlled by a single factor, the enrichment of organic matter in the Niutitang Formation shale was the result of the mutual configuration and coupling of multiple factors such as paleoclimate, biological productivity, water redox properties, deposition rate and hydrothermal activity. The water was shallow and oxic with a low-level of productivity in the course of deposition of the lower Niutitang Formation, which was not conducive to the enrichment of organic matter. A large-scale of Early Cambrian transgression occurred during deposition of the medium Niutitang Formation, and the associated upwelling carried extensive substances such as nutrients and sulfates entered the surface water, which promoted the blooming of algae. The anoxic-euxinic environment at the bottom water was conducive to the preservation of organic matter. Although the degree of water oxidation increased during deposition of the upper Niutitang Formation, the strong hydrothermal activity triggered by the continuous extension of South China provided rich nutrients, which kept a high-level biological productivity. Meanwhile, the relatively high deposition rate led to organic matter insufficiently degraded, resulting in rapid burial, preservation and enrichment.
Recognition of origin of crude oil from well Yubei 1 in Tarim Basin and its significance
SUN Yongge, LU Qinghua, HE Yuxin, KONG Lishu, LIU Shaojie, GU Yi
2021, 43(5): 810-817. doi: 10.11781/sysydz202105810
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The oil source of the Lower Paleozoic petroliferous system in the Tarim Basin is still controversial. Based on the detailed analysis of the molecular isotopic geochemistry of the crude oil from well Yubei 1 in the Yubei area of the Tarim Basin, the oil source of the Lower Paleozoic petroliferous system in this area was studied by inversion ideas. The crude oil from well Yubei 1 was the superimposed product of two phases of accumulation, and the oil sources of the two phases were the products of the same set of Cambrian source rocks during the peak period of oil generation. The burial depth of Cambrian source strata in different areas could be the main factor leading to multiple phases of hydrocarbon charging. Crude oil accumulated in the early stage experienced severe biodegradation due to strata uplift and erosion, while oil in the late stage was well preserved. Although the biomarker assemblages and molecular isotopic compositions in the Yubei 1 oil can be generally correlated with oils from the Lower Paleozoic petroleum system in the central Tarim Basin, the distributions of aryl isoprenoids suggested that the depositional environment of the Cambrian source rock in the southern Tarim Basin could be different from that in the central Tarim Basin, which worth a further in-depth study.
Kinetics of oil-cracking of ultra-deep Ordovician oil in the North Shuntuoguole area of Tarim Basin and its geological implications
LI Huili, MA Anlai, CAI Xunyu, LIN Huixi, LI Jianjiao, LIU Jinzhong, ZHU Xiuxiang, WU Xian
2021, 43(5): 818-825. doi: 10.11781/sysydz202105818
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With the expansion to the deep strata for the exploration of marine oil and gas in the Tarim Basin, the upper limit of temperature for the occurrence of ultra-deep reservoirs has become a scientific concerning of organic geochemistry and petroleum geology. Thermal simulations of the ultra-deep Ordovician oil from well SB 7 in the North Shuntuoguole area of Tarim Basin were carried out using a gold-tube confined system under two different pressures of 50 and 90 MPa and two different heating rates of 2 and 20℃/h, respectively. According to the results of simulation experiments, Kinetics software was used to calculate the chemical kinetics, and the mass yield of gas generation during oil-cracking under different temperature and pressure conditions was compared, and its geological significance was discussed. Under different temperature and pressure stages, the same oil sample experienced a similar process of oil-cracking as well as of total volume and mass yield of gas generation. Heavier gas compounts were generated in the early stage of oil-cracking and further transformed to form methane in the later stage. Heating rates impacted greatly on oil-cracking processes. Under a higher heating rate, the oil-cracking process moved to higher temperature and the separate oil phase can be kept with a higher temperature limit. High pressures only played minor roles on oil-cracking. With the same heating rate, higher pressure negligibly suppressed oil-cracking in the early stage of oil-cracking, whereas in the later stage, higher pressure promoted oil-cracking a bit. The difference of oil-cracking process under different temperatures and pressures can be explained by the distribution of activation energy. The distribution of activation energy of C1-C5 gas mass yield of oil-cracking of well SB 7 is relatively more concentrated, suggesting that the "temperature window" of oil-cracking is relatively narrower. According to the thermal simulation and kinetics calculation results, the maximum temperature of oil phase in the block 1 in the North Shuntuoguole area is greater than 180℃, and oil phase can be maintained at a depth greater than 9 000 m.
Re-evaluation of hydrocarbon generation potential of the Upper Paleozoic coal-measure source rocks in the Hangjinqi area of Ordos Basin
NI Chunhua, ZHU Jianhui, LIU Guangxiang, WANG Fubin, JIA Huichong, ZHANG Wei, WU Yingli, MIAO Jiujun
2021, 43(5): 826-834. doi: 10.11781/sysydz202105826
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The Upper Paleozoic strata in the Hangjinqi area of the Ordos Basin are an important field to increase reserves and productions for the North China Oil and Gas Branch, SINOPEC. It is necessary to conduct a re-evaluation of hydrocarbon generation potential for the Upper Paleozoic coal-measure source rocks in time, which is favorable to provide theoretical support for further exploration and deployment. The organic geochemical and organic petrological approaches were carried out in this study and integrated with the physical simulation of hydrocarbon generation and expulsion from formation pore by thermal compression, numerical simulation of TSM basin resource evaluation and new exploration data, in order to systematically analyze and compare the sedimentary environment, quality and distribution of the Upper Paleozoic source rocks, and further to conduct the re-evaluation of hydrocarbon potential. The results indicated that the Upper Paleozoic source rocks of the south of the fault belts in the Hangjinqi area appeared to have characteristics of good quality, high evolution degree, and a great thickness, whereas those in the north part of the fault belts displayed the negative characteristics. As indicated by the physical and numerical simulation results, the Upper Paleozoic coal-measure source rocks in the Hangjinqi area displayed a total gas generation amount of 15.922×1012 m3. The gas generation intensity to the north of the fault belts was less than 1×109 m3/km2, whereas that to the south ranged (1.5-3.5)×109 m3/km2, which has provided a material basis for the generation of large and medium gas fields.
Fluid charging history in Ledong 10 area, Yinggehai Basin, revealed by CO2 inclusion characteristics
SHUI Leilei, GUO Laiyuan, XU Xinde, HUANG Xiangsheng, HUANG Heting, CHEN Shuwei, SONG Xiuzhang
2021, 43(5): 835-843. doi: 10.11781/sysydz202105835
Abstract(355) HTML (111) PDF-CN(42)
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The Cenozoic strata of Yinggehai Basin is rich in natural gas, and exploration breakthroughs have been achieved in the middle and deep strata of the basin in recent years. The discovery of gas fields in the Ledong 10 area had attracted concerning for the migration and accumulation of natural gas in lithologic reservoirs in the middle and deep strata of nondiapir structures. The natural gas reservoir in the Miocene Huangliu Formation in the Ledong 10 block appeared to have a high content of CO2. The characteristics and periods of CO2 migration to natural gas reservoirs were discussed by the approaches including Laser Raman spectroscopy and combined with inclusion petrographic observation. Five types of fluid inclusions were classified, including brine inclusions, CO2 inclusions, gas-phase CH4 inclusions, gas-mixed inclusions and gas-mixed brine inclusions. According to the homogenization temperature and density of CO2 inclusions measured by Laser Raman and microthermometry analysis, and combined with the estimation of the capture conditions of CO2 inclusions, sedimentary characteristics, burial history as well as isotopic composition of CO2, two-stage filling mode for CO2 gas reservoirs was then concluded. The first stage was high-density inorganic-origin CO2 charged between 1.4-0.9 Ma; the second stage was medium-density inorganic CO2 charged between 0.7-0.4 Ma.
Simulation experiment and mathematical model analysis for shale gas diffusion in nano-scale pores
ZOU Yu, WANG Guojian, LU Li, ZHU Huaiping, LIU Guangxiang, YUAN Yusong, YANG Haiyuan, JIN Zhijun
2021, 43(5): 844-854. doi: 10.11781/sysydz202105844
Abstract(449) HTML (92) PDF-CN(56)
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Gas diffusion in nano-scale porous media of deeply burried shale includes bulk diffusion (Fick and Knudsen diffusions) and surface diffusion. To reveal the migration mechanism of this process, the influence of temperature and pressure on diffusion coefficient needs to be quantitatively evaluated. A case study was made with the Cambrian Niutitang Formation in the Maoping area, Zigui, western Hubei, South China. Gas diffusion was simulated by isobaric diffusion experiments under different temperature and pressure conditions. The results indicated that: (1) The diffusion coefficient DF decreases with increasing of pressure (when the pressure is higher than 30 MPa, DF tends to be constant), and increases with increasing of temperature; (2) In the high temperature-pressure setting, DF is affected significantly by pressure and generally tends to decrease. Moreover, the impacts of temperature, pressure, porosity and lithology were quantitatively calculated, and a mathematical model of gas diffusion was established, which had comparable results with simulation experiment. The following conclusions were thus drawn: (1)Higher temperature will cause stronger molecular kinetic energy, resulting in increasing bulk and surface diffusion coefficients, while higher pressure will slightly strengthen the Fick and surface diffusions, but significantly limit the Knudsen diffusion, and cause lower total diffusion coefficient; (2) Larger pore size leads to stronger bulk diffusion, but weaker surface diffusion. Finally, according to the studies of a specific research block, high pressure setting is conducive to the preservation of nano-scale porous gas reservoir in shale, while the uplift accompanied by pressure release is the main stage of shale gas loss.
Evaluating the connectivity of shale gas wells by new rare element tracers
SHEN Baojian, PAN Anyang, ZHANG Jun, LU Longfei, QIAN Menhui, LU Shuanglong, DU Mingliang
2021, 43(5): 855-861. doi: 10.11781/sysydz202105855
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Three types of rare earth elements, Pr, Yb and Sm, in shale gas well and fracturing fluid, which showed a low content and are environmentally friendly and chemically stable, formed complexes with ethylenediamine tetra-acetic acid and di-picolinic acid, both of which were applied as tracers in the determination of the connectivity of shale gas wells. A case study was made in two shale gas wells (Jiaoye 66-Z1HF and Jiaoye 66-Z2HF) of the middle gas reservoir in the Jiaoye No. 66 extended platform well group in the Fuling shale gas field of SINOPEC. We first injected rare element tracer into the wells, and then evaluated the connectivity of the Jiaoye No. 66 extended platform after fracuring by monitoring whether there was rare element tracer in the tracer-injected wells and the flow-back fluid from adjacent wells, and finally discussed the feasibility of three-dimensional development of the lower, middle and upper gas layers of the Fuling shale gas field. The results of flow-back fluid monitoring showed that a high content of Sm tracer, which had been injected into well Jiaoye 66-Z2HF, was occasionally found in well Jiaoye 66-Z1HF, indicating that there might be a connection between the middle gas layers of the two wells. There is no abnormal Pr, Yb or Sm concentrations in the monitoring wells of the lower gas layers, indicating that they were not connected with the central gas layers. A high concentration of Sm tracer was detected in the mixed back-flow fluid samples of wells Jiaoye 5-S2 and Jiaoye 5-S3 in the upper gas layer, indicating that they were connected to the central gas layers. The present investigation has verified that rare element tracer technology is a facile and effective method for the connection determination between shale gas wells and has broad application prospects.
Experimental development and application of source rock thermal simulation for hydrocarbon generation and expulsion
HE Chuan, ZHENG Lunju, WANG Qiang, MA Zhongliang, MA Jianfei
2021, 43(5): 862-870. doi: 10.11781/sysydz202105862
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Simulation experiment was one of the most valuable methods for the study of hydrocarbon generation, expulsion and retention in source rocks. It was summarized in this paper that the progressing status and development significations of thermal simulation experiments. According to the open degree of reaction system, the experimental methods can be classified to three types, including open, closed and restricted systems. Cumulative generation and expulsion of oil and gas at a single temperature step and continuous generation and expulsion of oil and gas in multiple temperature steps were introduced. The main constrains included simulation temperature, pressure, time duration, sample morphology and inorganic reaction medium. The simulation experiments of hydrocarbon generation and expulsion have played an important role in clarifying the processes of oil and gas generation, expulsion and retention and their major controlling factors, establishing oil and gas evolution models of different types of sedimentary organic matter, evaluating the oil and gas resource potential of sedimentary basins, and performing oil and gas source comparison and correlation. The current hydrocarbon generation and expulsion simulation experiments have some limitations, and researches are needed in terms of experimental boundary conditions, physical simulation of hydrocarbon generation and accumulation of source-reservoir synergy, and dynamic calculation of hydrocarbon generation with various constrains.
Microstructure and SEM-Raman study of organic matter pore heterogeneity in shale
BAO Fang, YU Lingjie, RUI Xiaoqing, ZHANG Qingzhen, FAN Ming, MA Zhongliang
2021, 43(5): 871-879. doi: 10.11781/sysydz202105871
Abstract(356) HTML (203) PDF-CN(63)
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The characteristics and influencing factors of pore development in organic matters of shale are of great significance for shale gas exploration and production in China. The pore development in organic matters of shale has been found to be heterogeneous with SEM observation. However, due to the lack of effective approach for micro-scale research, the influencing factors of pore development of organic matter are still controversial. Black shale samples of the Longmaxi Formation of Pingqiao area of the Sichuan Basin were selected by this study and the heterogeneity of development and distribution of pores in organic matters were analyzed in detail from two-dimensional and three-dimensional levels by the means of Ar ion polishing SEM and FIB-SEM observation. The organic matters with different pore development degrees were divided into three levels, and the area occupancy and contribution to the pores of these three levels of organic matter were studied by MAPS. In this paper, the Raman spectrum of three levels of organic matter with different pore development were obtained by SEM-Raman. The main factors affecting the heterogeneity of pore development of organic matter were discussed in view of the differences of Raman parameters. The results showed that the intensity ratio of D peak to G peak of organic matter was different, which indicated that the order degree of aromatic structure of different organic matter was significantly different, proving that the main factor affecting the pore development in organic matter could be the composition of original organic matter. This method can be used to observe the pores of organic matter in micro area and analyze the molecular structure characteristics of organic matter macerals in-situ, and further clarifies the main influencing factors of pore development of organic matter.
Microscopic recognition of micro fossils in carbonate rocks based on convolutional neural network
YU Xiaolu, YE Kai, DU Chongjiao, GONG Hanning, MA Zhongliang
2021, 43(5): 880-885. doi: 10.11781/sysydz202105880
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The identification of microfossils in carbonate rocks with thin-section observation is of great significance for the study of sedimentary environment, but the traditional method by manual identification is highly experience required and is greatly affected by subjective factors.In this paper, a method for microscopic recognition of carbonate rocks based on ResNet convolutional neural network was introduced. Through image preprocessing, model design, model training etc., the intelligent recognition of fossils of organisms within thin section images were realized, and the recognition accuracy showed to be 86%.Meanwhile, an advanced YOLO(You Look Only Once) object detection model was proposed, which could realize the detection and recognition of the area where the organism locates in thin section image, and the recognition accuracy appeared to be 85%.This method verified the feasibility of using digital image processing algorithm and deep learning method to intelligently identify biological microscopic images of carbonate rocks.It can be regarded as a useful supplement to traditional manual identification methods and has certain practical application value.
Reconstruction of paleo-temperature and pressure of oil reservoirs based on PVTx simulation: problems, strategies and case studies
XI Binbin, JIANG Hong, XU Jin, CHEN Qianglu, YOU Donghua
2021, 43(5): 886-895. doi: 10.11781/sysydz202105886
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The PVTx simulation of fluid inclusions is a valuable method for the reconstruction of paleo-temperature and pressure of oil reservoir. Since the accurate composition of oil-bearing inclusion is very difficult to be obtained and the composition may be altered during secondary alteration processes, it may cause uncorrected results. Compared to oil-bearing inclusion, the composition of accompanied aqueous inclusion is relatively simple and could hardly be affected during secondary alteration processions. As a result, accompanied aqueous inclusions were applied to reconstruct the paleo-temperature and pressure of well SN 1 in the South Shuntuoguole area of Tarim Basin. Gas-oil-bitumen bearing inclusions and aqueous inclusions are co-existed in calcite veins of well SN 1. The homogenization temperatures of aqueous inclusions were higher than 170℃, and the homogenization pressure of aqueous inclusions is significantly fluctuating from 39.1 MPa to over 165.8 MPa. The unusually high homogenization temperature of aqueous inclusions may be caused by hydrothermal fluid activity while the fluctuation of homogenization pressure of aqueous inclusions may be caused by oil cracking. The lowest homogenization pressure of aqueous inclusion was applied to determine the charge time of hydrothermal fluid, which is Hercynian. The charging time of hydrothermal fluid is in accordance with the active time of NE-trending strike-slip faults in the South Shuntuoguole area. Thus, the co-existing aqueous inclusions potentially can be applied to reconstruct the paleo-temperature and pressure of oil reservoir to make up the deficiency of present methods.
Reconstruction of tectonic-burial evolution history of Sinian Dengying Formation in Sichuan Basin based on the constraints of in-situ laser ablation U-Pb date and clumped isotopic thermometer(Δ47)
HU Anping, SHEN Anjiang, CHEN Yana, ZHANG Jianyong, LIANG Feng, WANG Yongsheng
2021, 43(5): 896-905. doi: 10.11781/sysydz202105896
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Reliable evolution curve of tectonic-burial history is essential for the research of the source rock evolution, reservoir formation and hydrocarbon accumulation of target strata of basin. Previous publications reported the tectonic-burial evolution history curves established depending on regional geological setting, formation (denuded) thickness, and tectonic movements, which were uncertain due to the difference in such geological understandings. For the ancient marine carbonates in China, which have experienced multiple tectonic movement reformation, it is more difficult to reconstruct tectonic-burial evolution history. In this paper, based on the identification of carbonate cements and the establishment of diagenetic sequence, through coupling carbonate laser ablation U-Pb dating and clumped isotope (Δ47) thermometer, two understandings were proposed: (1) The tectonic-burial curves of the Sinian Dengying Formation in the Sichuan Basin were established under the constraints of absolute age and temperature, which avoided the problems of uncertainty of tectonic-burial history curves in previous studies; (2) The new tectonic-burial history curve provided critical reference for study on the source rock evolution, reservoir origin and hydrocarbon accumulation of the Sinian Dengying Formation of the Sichuan Basin, revealing three stages of hydrocarbon accumulation in the Dengying gas reservoir including Silurian, Permian and Yanshanian-Himalayan periods. The proposed method of reconstructing tectonic-burial evolution curve is not only suitable for the ancient marine carbonates which experienced multiple tectonic movement reformation, but is also promising for the study of source rock evolution, reservoir origin and hydrocarbon accumulation.
A simultaneous determination method for diamondoids and thiadiamondoids in condensate oil and its geological significance: taking condensate oil from central Tarim Basin as an example
FANG Chenchen, ZHAI Jia, HU Guoyi, GONG Deyu
2021, 43(5): 906-914. doi: 10.11781/sysydz202105906
Abstract(404) HTML (133) PDF-CN(40)
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Diamondoids and thiadiamondoids in crude oil samples have the similar diamond-like cage structures, which can reflect the thermal cracking and thermochemical sulfate reduction(TSR) effect during geological processes. Therefore, the simultaneous monitoring of diamondoids and thiadiamondoids cannot only improve the efficiency of sample analysis and the accuracy of quantitative results of thiadiamondoids, but also provide more reliable and extensive geochemical interpretation for the samples. In this paper, a simultaneous quantitative detection method of diamondoids and thiadiamondoids was proposed by the means of gas chromatography-triple quadrupole mass spectrometer (GC-MS-MS). By determining the parameters of precursor and product ions, scanning time and collision energy of the target compound, a simultaneous quantitative detection method was established for diamondoids and thiadiamondoids in condensate from the central Tarim Basin. Results showed that despite the contents of diamondoids of oils from the central Tarim Basin were different, the maturity degree on the other hand, were comparable as over mature, and some samples have experienced TSR.
Pyrolysis-gas chromatography-mass spectrometry analyses of oil-bearing fluid inclusions composition
CHEN Yan'e, ZHANG Zhirong, GREENWOOD Paul
2021, 43(5): 915-920. doi: 10.11781/sysydz202105915
Abstract(289) HTML (89) PDF-CN(52)
Abstract:
The molecular compositions of oil-bearing fluid inclusions (FIs) are valuable for the research of oil and gas accumulation; however, due to the very trace amount of materials included, the requirements of commercial instruments cannot be satisfied and thus custom designed instruments were needed for this method, which is difficult to be achieved and the application for the molecular composition of FIs have been limited. In this paper, three samples of oil-bearing FIs were analyzed by pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) to obtain their hydrocarbon composition. The first sample was a synthetic inclusion prepared by the occlusion of a small amount of crude oil from the Halibut oil field, the second sample was from Australian Jabiru oil field and the third sample was collected from the Tahe oil field in the northwestern China. A diverse range of aliphatic compounds, including n-alkanes, mono-, di- and tricyclic aromatic hydrocarbons and other components have been successively detected from these materials of which, the n-alkanes were monitored up to carbon numbers over C30. Also, the results showed that the method introduced here gave comparable molecular characteristics with data obtained from other traditional methods. The mature degree calculated from Py-GC-MS is very close to that of MCI method. However, it is also notable that the thermal maturity parameters calculated from the results of inclusion analysis were much lower than those of crude oil, indicating modification caused by late-stage alteration to oils in reservoir. As a conventional and easy performed analytical method specially designed for the degradation of macromolecule, the Py-GC-MS demonstrated here is also suitable for the analysis of FIs.
2021, 43(5): .
Abstract(118) PDF-CN(27)
Abstract:
2021, 43(5): 921-921.
Abstract(254) PDF-CN(31)
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