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2023 Vol. 45, No. 3

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2023, 45(3): .
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Abstract:
Strike-slip structures and hydrocarbon accumulation in complex fault blocks in Subei Basin
QIU Xuming, CHEN Wei, LI Heyong, DUAN Hongliang
2023, 45(3): 393-401. doi: 10.11781/sysydz202303393
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The research on basin formation and hydrocarbon generation and accumulation in the Subei Basin was carried out based on structural geometry and kinematic analyses. The Subei Basin has experienced three evolutionary stages: rift-subsiding, fault depression and depression. During the tectonic development dominated by extension and tension in the Himalayan period in the eastern China, there were echelon, pinnate, broom-like and other strike-slip fault combinations in the basin, and it has been found that oil reservoirs and traps were directionally arranged and closely related to strike-slip actions. The extension and strike-slip process controlled basin formation and evolution, which resulted in the oblique arrangement of sags, and formed multiple hydrocarbon generation sub-sags in each sag. The differential development characteristics of basin-controlling and sag-controlling faults controlled the main migration directions of oil and gas, forming three migration modes. The oil and gas migration patterns under the control of echelon and pinnate sag-controlling faults were quite different. The fault transform zone and structural high zone formed by secondary fault combination and formation deformation are important places for oil and gas enrichment, and many types of fault nose and fault block reservoirs were formed.
Assessment methods and potential of shale oil resources in China
GUO Qiulin, MI Shiyun, ZHANG Qian, WANG Jian
2023, 45(3): 402-412. doi: 10.11781/sysydz202303402
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In view of the large differences in type classification, assessment methods, evaluation parameters and resource potential prediction of shale oil in China, shale oil is classified into three categories: interlayer shale oil, pure shale oil and in-situ converted shale oil. According to the obviously different occurrence and formation characteristics of the three types of shale oil, the corresponding resource calculation method models, respectively named volume method, volume method based on pyrolysed hydrocarbon S1 content and hydrocarbon generation quantity method based on hydrogen index variation, were put forward, and the key parameters and their lowest threshold standards of each model were determined. Finally, the three categories of shale oil resources in the major basins in China were evaluated according to the unified parameter criterion. The in-place resources of pure shale oil, interlayer shale oil and in-situ converted shale oil are 145.4×108 t, 95.1×108 t and 708.2×108 t, respectively, and the recoverable resources are 9.4×108 t, 7.1×108 t and 460.3×108 t, respectively. The evaluation results show that China is rich in shale oil resources, which is an important replacement field to promote domestic crude oil production increase and stabilization.
Reservoir characteristics and controlling factors of Paleogene carbonate-rich shale in Dongying Sag, Bohai Bay Basin
XU Xiaoping
2023, 45(3): 413-421. doi: 10.11781/sysydz202303413
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In this paper, the mineralogical composition, sedimentary structure, laminar type, pore size distribution, pore volume, specific surface area, number of laminae and morphological characteristics of dissolution pores of the lacustrine shale from the upper sub-member of the fourth member of the Paleogene Shahejie Formation of the wells NY1 and FYP1 in the Dongying Sag of Bohai Bay Basin were finely characterized by a combination of core observation, thin section observation, nitrogen adsorption and X-ray diffraction. On this basis, the main lithofacies types and laminar characteristics, the pore size, pore volume and specific surface area of different lithofacies, and the pore and laminar characteristics of carbonate-rich shale in this area were summarized. The results show that there are four lithofacies types in the Dongying Sag: organic-rich laminated argillaceous limestone, organic-rich laminated sandy limestone, organic-bearing laminated sandy limestone and organic-bearing massive limestone. The microscopic features of the laminae are mainly flat, lenticular, interbedded and undulating. The measured nitrogen adsorption data show that the carbonate-rich shale in the Dongying Sag has a larger pore volume and specific surface area. At the same time, the development of dissolution pores and laminae allows the carbonate-rich shale to have higher storage capacity and horizontal permeability. Therefore, the carbonate-rich shale is a high quality reservoir in the Dongying Sag.
Experimental evaluation and hydrocarbon significance of natural fractures in Shunbei ultra-deep carbonate reservoir, Tarim Basin
LI Yingtao, RU Zhixing, DENG Shang, LIN Huixi, HAN Jun, ZHANG Jibiao, HUANG Cheng
2023, 45(3): 422-433. doi: 10.11781/sysydz202303422
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There are abundant hydrocarbon resources in the strike-slip fault-controlled ultra-deep carbonate reservoirs in the Shunbei area, Tarim Basin. Large strike-slip faults and natural fractures are the main storage space and flow channel of hydrocarbon resources. It is of great significance to study the natural fracture development characteristics in such reservoirs. 39 limestone samples and 7 dolomite samples from 5 wells in Shunbei area are taken as research objects. Through the analysis of thin section of lithofacies, fine description of natural fractures and brittleness test evaluation of core samples, the main controlling factors and influence laws of natural fracture development in Shunbei reservoir are studied. It is found that the reservoir lithology of Middle and Lower Ordovician Yingshan Formation and Yijianfang Formation in Shunbei area is dolomite and limestone, and the lithofacies include grainstone, wackestone, packstone, boundstone, muddy limestone, silicified limestone, silty-fine crystal dolomite and medium-coarse crystal dolomite. In limestone samples, muddy limestone has the highest brittleness index and natural fracture development density, while boundstone has the lowest brittleness index and natural fracture development density. In dolomite samples, the brittleness index of medium-coarse crystalline dolomite is higher than that of silty-fine crystal dolomite, and the coarser the grains are, the more developed the natural fractures are. There is a positive correlation between the natural fracture development density and the brittleness index of rock samples. The porosity, permeability and brittleness index of dolomite are higher than those of limestone. Under the same brittleness index, the fracture development ability of limestone is stronger. Therefore, the highly brittle section of limestone stratum is more likely to be the geological sweet spot in Shunbei area.
Controlling factors for effective reservoir development of Ordovician Kelimoli Formation in western Ordos Basin
LI Huimin, ZHAO Zhenyu, SONG Wei, ZHANG Tao, ZHAO Dangni, JIANG Tingting, ZHANG Li, CHEN Zhaobing
2023, 45(3): 434-442. doi: 10.11781/sysydz202303434
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In recent years, some progress has been made in the exploration of Ordovician natural gas in the western Ordos Basin, among which, the Ordovician Kelimoli Formation has the highest degree of natural gas accumulation. However, the controlling factors for effective reservoir development are complicated, leading to unsatisfactory exploration effect. Based on the data of core observation, thin section identification, drilling and logging, the development types and controlling factors of effective reservoir in the Kelimoli Formation were systematically studied, and a development model of effective reservoir was established. The results show that the effective reservoir types of Kelimoli Formation in the western Ordos Basin mainly include dolomite intercrystal (dissolved) pore, limestone karst fracture and structural micro-fracture, and marginal platform granular pore type reservoir is locally developed. The development of effective reservoir was mainly controlled by sedimentary facies, diagenesis, paleokarst weathering and tectonic movement. The tidal flat facies and marginal platform facies provided the material basis for the original reservoir of the Kelimoli Formation, and on this basis, the dolomite intercrystal (dissolved) pore and marginal platform granular pore reservoirs were formed in the early diagenesis. In the stage of burial diagenesis, recrystallization obviously reformed the original dolomite reservoir, and the crystal framework became more stable. New intercrystal (dissolved) pores were formed or underwent secondary recrystallization. At the same time, the original structure of marginal platform granular pores was damaged, filled or improved, and the present marginal platform residual granular pores were formed. Paleo-karst weathering controlled the development of fracture-vuggy reservoirs in the middle and upper parts of the Kelimoli Formation, and high-yield wells were mainly drilled in the upper groove direction of the karst slope groove zone and karst highlands. The multi-stage tectonic movement continuously transformed and controlled the development of micro-fracture system, forming porous media reservoirs distributed around the fault zone. Therefore, it is a favorable direction for further exploration to find favorable facies belts of tidal flat facies and marginal platform facies, updip positions of karst paleo-geomorphology or high positions of fault zone.
Shale lithofacies types and reservoir characteristics from Ordovician Wufeng Formation to the first sub-member of the first member of Silurian Longmaxi Formation, northeast Zhaotong area
REN Guanbao, CHEN Lei, JI Yubing, CHENG Qingsong
2023, 45(3): 443-454. doi: 10.11781/sysydz202303443
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Shale lithofacies has an important influence on shale reservoirs. It controls the hydrocarbon generation capacity, storage performance and fracturing performance of shale to a certain extent. In order to study the shale lithofacies characteristics, reservoir characteristics and evaluation of Wufeng-Longmaxi formations in the northeast Zhaotong area, a detailed research was carried out based on core, thin section, X-ray diffraction and various geochemical test data. Calcareous/siliceous mixed shale lithofacies, mixed shale lithofacies, clayey/siliceous mixed shale lithofacies, mixed siliceous shale lithofacies, clay-rich siliceous shale lithofacies are developed in the study area. There is a difference in the vertical distribution of lithofacies between the south and the north of the study area. The lithofacies from Wufeng Formation to the first sub-member of the first member of Longmaxi Formation (Long1-1 submember) presents the characteristics of transition from clayey shale lithofacies associa- tion to siliceous shale lithofacies association and then to mixed shale lithofacies association in the southern area, while the northern area shows a transition trend from mixed shale lithofacies association to siliceous shale lithofacies association and then to mixed shale lithofacies association. Horizontally, the lithofacies distribution is highly heterogeneous and has poor continuity. The reservoir characteristics of different lithofacies are different. Siliceous shale has good reservoir properties, with the characteristics of "high TOC content, high gas content and high brittle mineral content". The TOC content and gas content of clayey shale are high, but the content of brittle minerals is very low. The properties of mixed shale reservoirs are complex, and generally, the mixed shale reservoirs with high siliceous content have better properties. Based on TOC content, gas content and brittle mineral content, the shale lithofacies evaluation standard is established by combining analytic hierarchy process and entropy method, and the dominant lithofacies are determined. Mixed siliceous shale lithofacies, calcium-rich siliceous shale litho- facies, calcareous/siliceous mixed shale lithofaciesis are class Ⅰ dominant lithofacies; clay-rich siliceous shale lithofacies, mixed shale lithofacies and clayey/siliceous mixed shale lithofacies are class Ⅱ dominant lithofacies; mixed clayey shale lithofacies and silicon-rich clayey shale lithofacies are non-dominant lithofacies.
Differential deformation characteristics and genetic mechanism of boundary normal faults in Wangfu Fault Depression, Songliao Basin
ZHANG Xichen, LIU Xiaobo, DU Changjiang, ZHOU Danni, LI Qiang, ZHANG Hongxiang, LIANG Yan, LI Lei
2023, 45(3): 455-465. doi: 10.11781/sysydz202303455
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In order to reveal the differential deformation characteristics of the Wangfu Fault Depression in Songliao Basin and study the regularity of the deformation mechanism of boundary normal faults, this paper, based on the structural analysis and fault differential analysis, discusses the controlling factors and genetic mechanism of differential deformation of boundary normal faults in combination with the advantages of tectonophysical simulation in "continuous forward modeling" and "control variables". The results show that: (1) According to the intensity of fault activity, four regional tectonic evolution stages can be divided. The boundary normal faults in the west of Wangfu Fault Depression is the most active, but the dip angle of the faults gradually increases from north to south, showing a "convex" shape locally. (2) Combining tectonophysical simulation with actual geological background, it is showed that the shape of boundary normal fault was controlled by three main factors, including lateral lithologic change, syntectonic sedimentation and pre-existing uplift of basement. If boundary normal faults are developed in strata with different lithology at the same time, or accompanied by strong syntectonic sedimentation, the dip angle will change. In addition, the extension of the fault near the hard basement bulge will change its trend and continue to spread around the bulge top, resulting in the local appearance of "uplift".
Microscopic occurrence characteristics and seepage law of water bodies in gas reservoir under stress: a case study of tight reservoirs in the eighth member of Permian Shihezi Formation, Shenmu Gas Field, Ordos Basin
MA Yunfeng, ZHAO Jianguo, SUN Long, BAO Yuning, CAO Qingyun, GONG Xiaoke, CHEN Zhaobing, WANG Hengli
2023, 45(3): 466-473. doi: 10.11781/sysydz202303466
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In order to solve the problem that the pore structure and the microscopic occurrence characteristics of fluid change with stress in real time during the depletion development of tight gas reservoirs, the pore structure, water production and irreducible water distribution characteristics of tight reservoirs in the eighth member of Permian Shihezi Formation, Shenmu Gas Field, Ordos Basin under different stress conditions were quantitatively characterized, and the influence of stress on gas-water relative permeability was analyzed by using nuclear magnetic resonance (NMR), high-pressure mercury injection (HPMI) and displacement experiments. The results show that when effective stress increases from 7 MPa to 17 MPa, reservoir porosity decreases from 8.39% to 7.65%, and the maximum pore radius decreases from 38.3 μm to 35.2 μm among which, the number of pore throats in the range of 0.3-18.9 μm decreases the most. The number of pores involved in seepage decreases due to the decrease of pore throat size, the bound water saturation increases from 51.3% to 59.7%, and the distribution range of the size of bound water increases from 0.012-17.4 μm to 0.012-20.1 μm. The changes of pore structure and bound water distribution characteristics further reduce the relative permeability of both gas and water phases, the relative permeability of gas phase decreases from 0.481 to 0.283, and that of isotonic point decreases from 0.157 to 0.09.
Petroleum systems and resource potential in Sverdrup Basin, Arctic
LI Gang, HU Jingjing, BAI Guoping, ZHANG Kaixun, QIU Haihua, WANG Ruifeng
2023, 45(3): 474-485. doi: 10.11781/sysydz202303474
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The Sverdrup Basin is one of the important petroliferous basins in the Arctic. It has abundant oil and gas resources, but the exploration degree is relatively low. Based on the IHS database and literatures in the public domain, this paper documented the geological characteristics and distribution of oil and gas in the Sverdrup Basin, and classified the petroleum systems and hydrocarbon plays in the basin. The undiscovered hydrocarbons were eventually assessed by Monte Carlo simulation and the favorable exploration areas were predicted. The investigation results show that the discovered oil and gas accumulations are mainly distributed in the western area of the basin, which consists of Sabin and Edinburgh sub-basins. Oil and gas are mainly reserved in the Jurassic and Triassic clastic reservoirs. Two petroleum systems, which are the Paleozoic and Mesozoic systems, were identified in the basin. The Mesozoic petroleum system has a far greater exploration potential. Undiscovered recoverable reserves (mean value) in the Mesozoic petroleum system are 474.81 MMbbl (1 MMbbl=1×106 bbl, 1 bbl=0.137 t) of oil, 13 620.82 Bcf (1 Bcf=1×109 ft3, 1 ft3=0.028 3 m3) of natural gas and 63.66 MMbbl of condensate, amounting to 2 808.61 MMboe (3.85×108 t), of which the natural gas accounts for 80.82%. The Lower Jurassic structural hydrocarbon play in the western area of the basin, the Upper Triassic-Lower Jurassic structural hydrocarbon play in the Edinburgh sub-basin and the Upper Jurassic structural hydrocarbon play in the Sabine sub-basin are the most promising exploration areas.
Structural characteristics and exploration fields in passive continental margin basins of Central Atlantic
TIAN Naxin, WU Gaokui, LIU Jingjing, TAO Chongzhi, GAO Min, WANG Dapeng
2023, 45(3): 486-496. doi: 10.11781/sysydz202303486
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The petroleum resources of the passive continental margin basins in the Central Atlantic are rich, but the insufficient knowledge of basin structural characteristics and accumulation conditions in the area restricts the exploration of deepwater oil and gas. Based on the integral analysis of seismic, drilling, gravity anomalies and magnetic anomalies data, the basin structural characteristics and hydrocarbon accumulation conditions in deepwater area of the passive continental margin basins of the Central Atlantic are studied and the exploration fields are predicted with the Senegal and Scotia basins as key anatomical objects. It can be concluded that the passive continental margin basins of the Central Atlantic have experienced three evolution stages: the rift period, the transition period and the drift period, with corresponding development of three tectonic layers: the rift layer, the depression layer and the continental margin layer, and the basin structures are controlled by transform faults and basement properties. From Triassic to Early Jurassic rift period, a series of horst-graben structures were formed, and the sediments were mainly continental ones such as rivers, lakes and deltas. From Middle to Late Jurassic transition period, the marginal ridge or submarine uplift zone were developed due to the activity of transform faults, and a landward high terrain limited environment was formed due to the stretch, thinning and subsidence of the Paleozoic weak basement, providing a favorable condition for the development of source rocks in the depression layer. During Cretaceous drift period, platform margin reef and delta-slope floor fan reservoirs were developed. Both the deepwater slope floor fan in the Scotia Basin and the platform margin reef in the Senegal Basin have great exploration potential.
The essence of gypsum's influence on Tmax of source rocks: a case study of the Lower Ganchaigou Formation of Paleogene in western Qaidam Basin
QI Wen, CHEN Feng, FANG Peng, ZHANG Bin, GAO Shuo, HONG Zhibin, ZHANG Ping, WU Jia
2023, 45(3): 497-503. doi: 10.11781/sysydz202303497
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Geological observation and thermal simulation experiments have revealed that the peak period of hydrocarbon generation of gypsum-bearing mudstone is often advanced in sedimentary basins, but the correlation between the amount of advance and the content of gypsum is still not clear. In this study, the source rock powder samples with different gypsum content in the Lower Ganchaigou Formation from well S49-1 in the western Qaidam Basin were selected and extracted to remove soluble organic matter (SOM). Part of the extracted residue was pickled to remove carbonate. Rock pyrolysis analysis was performed on the original samples and the solid residue after two-step pretreatment. Compared to the Tmax of original samples, the Tmax was higher in the SOM-free residue but lower in the SOM-free and carbonate-free residue, showing that SOM and sulfate minerals (gypsum and anhydrite) in gypsum-bearing mudstone can promote the thermal evolution of organic matter. Although the latter has a more significant effect, it is not proportional to its sulfate content, indicating that the contact area of sulfate minerals and organic matter is more important to Tmax. The hypothesis was verified by the Tmax values of different proportions of kerogen and magnesium sulfate powder mixtures. Therefore, the occurrence state of sulfate minerals will directly affect the contact relationship between organic matter and sulfate, which in turn will affect the process of hydrocarbon generation in thermal evolution.
Cross-formational hydrocarbon accumulation of Cambrian sequences and its significance for natural gas exploration in eastern Sichuan Basin
SUN Ziming, LIU Guangxiang, BIAN Changrong, GUO Xiaowen, WANG Yanlei, HE Sheng
2023, 45(3): 504-516. doi: 10.11781/sysydz202303504
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It has not been clearly understood whether the hydrocarbon generated from the argillaceous sourcerocks of the Lower Cambrian Qiongzhusi Formation could upward pass through the regional cap rocks of the Lower-Middle Cambrian gypsum rocks and accumulate in the Middle-Upper Cambrian Xixiangchi Group reservoir, namely the cross-formational hydrocarbon accumulation, in the eastern Sichuan Basin. Therefore, the studies on the reservoir solid bitumen in the Xixiangchi Group and the sealing performance of the regional cap rocks of the Lower-Middle Cambrian gypsum rocks were carried out, and the cross-formational hydrocarbon accumulation of the Cambrian oil and gas and its significance for natural gas exploration were discussed. It was shown by synthetic studies that the reservoir solid bitumen in the Xixiangchi Group mainly originated from the argillaceous source rocks of the Lower Cambrian Qiongzhusi Formation. The sealing integrity of the regional cap rocks of the Lower-Middle Cambrian gypsum rocks was damaged to some extent by the reactivated basement faults and the large nascent faults in the Middle Permian to Middle Triassic though it had good sealing performance in geological times, which could provide convenient vertical pathways for the Cambrian cross-formational hydrocarbon accumulation in the eastern Sichuan Basin. Three evolutionary stages were built up about the Cambrian hydrocarbon migration and accumulation as follows. Stage 1 is the formation of the Cambrian pre-salt early paleo-reservoirs in the period ofthe Late Silurian to the Early Permian (S3-P1), stage 2 is the one of the Cambrian cross-formational hydrocarbon accumulation in the period of the Middle Permian to the Middle Triassic (P2-T2), and stage 3 is the formation of the Cambrian late paleo-gas reservoirs in the period of the Late Triassic to the Early Cretaceous (T3-K1). The cross-formational hydrocarbon accumulation is an important feature of hydrocarbon accumulation in multi-cycle superimposed basins, and the reactivated basement faults and the large nascent faults in the period of the MiddlePermian to the Middle Triassic are important clues to the Xixiangchi Group primary paleo-gas reservoirs. Identification and evaluation of the Xixiangchi Group primary paleo-gas reservoirs will be the key points and the main challenges to natural gas exploration in the study area.
Key geochemical evidence of "near-source accumulation" of tight oil: a case study of near-source assemblage of Triassic Yanchang Formation in Ordos Basin
XIAO Zhenglu, LI Yong, YU Jian, ZHANG Hai, LU Jungang, YIN Xiangdong, HAN Meimei
2023, 45(3): 517-527. doi: 10.11781/sysydz202303517
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The conclusion of "near-source accumulation" of tight oil is inferred based on the reservoir characte-ristics that crude oil is difficult to migrate laterally for a long distance in low-permeability reservoirs, yet there has been no direct geochemical evidence for a long time. Based on the analysis of the characteristics of source rocks and the source differences of oil in the near-source assemblage (Chang 6 member to Chang 81 sub-member) of the Tirassic Yanchang Formation in the Ordos Basin, this paper explores the geochemical basis of tight oil near-source accumulation and explains its cause. The results show that the crude oil in the near-source assemblage comes from the in-situ Chang 7 source rocks, and even the oil sources in the adjacent blocks are different. It is difficult for crude oil to undergo large-scale lateral migration in a tight reservoir. The biomarker compounds of Chang 7 source rocks in the Ordos Basin have significant differences in the plane and are distributed in a circularbelt along the sedimentary center. The oil source difference caused by the combination difference ofbiomarker compounds in different facies zones is the fundamental reason for the predecessors' discovery of "near-source accumulation" of tight oil. The "near-source accumulation" of tight oil has changed the previous view that oilsource correlation is a generalization of the whole basin and the source rocks of the same layer, and has important significance for the zoning and fine evaluation of different types of oil and gas resources in a single basin in the future.
Evaluation of laboratory comparison results of GC and GC-MS in petroleum geology industry
WEI Caiyun, MA Xingzhi, HU Guoyi, XU Huaixian, LIU Shaobo, WEI Jinhong, WENG Na, LÜ Yue
2023, 45(3): 528-536. doi: 10.11781/sysydz202303528
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In order to learn about the detection capability of GC (gas chromatography) and GC-MS (gas chromato-graphy-mass spectrometry) laboratories in the petroleum geology industry of China, improve the detection level of the laboratories and promote inter-industry exchanges, the Standardization Committee of Petroleum Geological Exploration organized a comparison study among the petroleum geology laboratories throughout the country. A total of 23 laboratories participated in this study. Total hydrocarbons, saturated hydrocarbon and aromatic hydrocarbon samples were selected, and the experimental method was specified according to relevant standards. The data quality of each laboratory was evaluated using the quartile robust statistical method. The results show that the data of the laboratories are stable and reliable, and the analysis results have good repeatability and reproducibility. The qualification rate of total hydrocarbons light hydrocarbon ratio parameters of GC is 95%, and the qualification rate of saturated hydrocarbon and aromatic hydrocarbon parameters is 97%. The qualification rate of saturated hydrocarbon parameters of GC-MS is 100%, and the qualification rate of aromatic parameters is 95%. The overall satisfaction rate is high. The main reasons for the problematic data and outliers of relevant parameters of some laboratories are the storage conditions, storage time, instrument model, test method, personnel operation errors, etc. It is suggested that the laboratories should strengthen quality control measures to further improve the GC and GC-MS detection capabilities.
Screening of functional monomers and preparation of molecularly imprinted polymers (MIPs) in molecularly imprinted polymers of steranes
MA Rong, YUAN Longmiao, LIU Yanhong, WANG Zhiyu, WU Yingqin
2023, 45(3): 537-548. doi: 10.11781/sysydz202303537
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To prepare molecularly imprinted polymers (MIPs) with specific selectivity for steranes, the prepolyme-rization system was screened by UV spectroscopy to determine the type, proportion and mode of action of functional monomers. In this study, the interaction intensities between three template molecules (cholesterol, β-sitosterol, deoxycholic acid) and four functional monomers (acrylic acid (AA), methacrylic acid (MAA), methyl methacrylate (MMA), and acrylamide (AM)) are compared respectively. The results show that the functional monomer AA can interact strongly with the three template molecules and form a stable prepolymerization system, so AA is selected as the functional monomer of MIPs. In addition, the UV spectral absorbance change and differential UV spectral analysis of different proportions of AA show that the optimal concentration ratios of the three template molecules to functional monomer AA are all 1:4, and the stable complex configurations formed are cholesterol-1AA, β-sitosterol-1AA and deoxycholic acid-3AA, respectively. The MIPs are successfully synthesized by precipitation polymerization using EDGMA as dispersant and AIBN as initiator, and the results of FTIR show that MIPs are well prepared. Therefore, this method can be used for the screening and preparation of MIPs functional monomers with specific selectivity for steranes, and provide technical support for the study of oil-source correlation between deep and ultra-deep source rocks.
Comparison of column chromatography and Ag+-thin layer chromatography for aromatic compounds in crude oil
WANG Ting, SONG Hao, WANG Ruilin, WEN Zhigang, HE Wenxiang, HE Jiahao, HE Changrong, LI Hongbo
2023, 45(3): 549-559. doi: 10.11781/sysydz202303549
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By comparing the separation effects and applicability of Ag+-thin layer chromatography (Ag+-TLC) and column chromatography on aromatic hydrocarbons with different ring numbers in crude oil, this article aims to provide theoretical support for the quantitative analysis of aromatics and isotope analysis of monomer hydrocarbon in organic geochemical research. The results showed that Ag+-TLC can better enrich monocyclic aromatics and differentiate the monocyclic aromatics of different isomers into different components, but has a poor effect in enriching palycyclic aromatics, which may lead to severe losses and possible peak interference. Column chromatography has better separation effects on dinuclear and polycyclic aromatic compounds. Therefore, Ag+-TLC, suitable for the fine separation of monocyclic aromatics, can be used to enrich alkylbenzenes and aryl isoprenoids, and meets the detection requirements for measuring their monomer hydrocarbon isotopes; while column chromatography can effectively enrich series of compounds such as naphthalene, phenanthrene, and triaromatic steroids, and meets the requirements for detecting the separating degree of monomeric hydrocarbon isotopes.
Molecular simulation of the displacement of shale gas in quartz slit by flue gas
QIAN Yingqiang, YANG Xue, LIU Xiaoqiang, LI Meijun, CHEN Zeqin, XUE Ying
2023, 45(3): 560-565. doi: 10.11781/sysydz202303560
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To study the efficiency of flue gas sequestration with enhanced shale gas recovery in quartz slit, Grand Canonical Monte Carlo (GCMC) and Molecular Dynamics (MD) simulations were adopted to investigate the influence of burial depth, formation water content and the injection ratio of flue gas on the recovery efficiency of shale gas (CH4) in quartz slit by flue gas (CO2/N2). The density distribution, loading, adsorption heat and interaction energy of each component were systematically analyzed to reveal their adsorption mechanisms and the recovery efficiency of CH4. It indicates that the loadings of mixed CH4 and N2 (ΓCH4 and ΓN2) exhibit negative correlation with formation water content. With the increasing burial depth, both ΓCH4 and ΓN2 increase at first and then tend to be constant when the burial depth is over 2 400 m. The maximum loading of CO2 (ΓCO2) occurs at the burial depth of 2 400 m. There is a positive correlation of ΓCO2 with formation water content when the burial depth is below 2 400 m, and a negative correlation when the burial depth is over 2 400 m. The recovery efficiency of CH4 (η) reaches the maximum point at the burial depth of 400-600 m, which increases with the increasing mole fraction of CO2 in flue gas, showing that CO2 in flue gas can promote the displacement of CH4 significantly.
Experiment and numerical simulation of water injection induced dynamic fractures in ultra-low permeability reservoirs
LIANG Weiwei, DANG Hailong, LIU Bin, ZHANG Tianlong, WANG Xiaofeng, HOU Binchi, CUI Pengxing, WANG Qian, ZHANG Fengyuan
2023, 45(3): 566-575. doi: 10.11781/sysydz202303566
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In order to further clarify the mechanism of water injection induced dynamic fractures in ultra-low permeability reservoirs and its influence on water injection development in ultra-low permeability reservoirs, the genetic mechanism and propagation process of dynamic fractures induced by water injection were expounded based on the laboratory experiments of water injection induced dynamic fractures. A numerical characterization method of water injection induced dynamic fractures was established, and the corresponding reservoir numerical simulation was researched. The results indicate that the water injection induced dynamic fractures include natural closure type, artificial fracturing induced type and super reservoir breakdown pressure type. The main growth mechanism of water injection induced dynamic fractures was that the continuous extension of the fractures developed in rocks or the existing fractures through repeated action of injection pressure and rock breakdown pressure or fracture propagation pressure. The improved water injection induced dynamic fracture experiment shows that the injection pressure presents the characteristics of repeated "up and down", and the injection pressure is the main controlling parameter for the rock to generate water injection induced dynamic fractures. The numerical simulation results verify that the bottom hole pressure of the injection well shows a periodic trend of "pressure-build rise and crack initiation drop". After the dynamic fracture was induced, the pressure and saturation fields in the fracture system change dynamically with the opening and extension of the dynamic fracture and the changes are mainly obvious along the fracture system, and the influence range on both sides of the fracture system is small.
Analysis of shale pore structure characteristics based on nitrogen adsorption experiment and fractal FHH model: a case study of 7th member of Triassic Yanchang Formation in Huachi area, Ordos Basin
AN Cheng, LIU Guangdi, SUN Mingliang, YOU Fuliang, WANG Zixin, CAO Yushun
2023, 45(3): 576-586. doi: 10.11781/sysydz202303576
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Abstract:
Pore structure, as the focus of shale reservoir research, has important influence on the occurrence of shale oil. In this paper, 10 shale core samples from the 7th member of Triassic Yanchang Formation (Chang 7 member) in Huachi area, Ordos Basin were selected to carry out scanning electron microscope (SEM) observation and low-temperature nitrogen adsorption experiment, and the fractal dimension was calculated to quantitatively characterize the pore structure of shale in the research area combined with fractal FHH model. On this basis, the relationship between fractal dimension and pore structure parameters and oil-bearing parameters was discussed, and the main influencing factors of pore development of shale in the Chang 7 member were determined. The results show that the shale of the Chang 7 member in Huachi area has high organic matter abundance, which are good-to-excellent source rocks mainly composed of quartz and clay minerals, with good oil-bearing property (up to the middle oil-bearing level) and mobility. The reservoir space is dominated by intergranular pores, intragranular pores and a small amount of organic pores. There are two types of pore morphology, namely, parallel plate-shaped slit+unilateral slit and ink bottle-shaped + parallel plate-shaped slit. The pores are mainly micropores and mesopores, with macropores less developed. Most samples have fractal characteristics. The fractal dimension D1 of small pores is between 2.264 7 and 2.714 9, and the fractal dimension D2 of large pores is between 2.373 3 and 2.77 7. Among them, D2 has a good correlation with surface area, pore volume, average pore diameter and S1, which can characterize the development characteristics of pore structure and oil-bearing property of shale, while D1 can only characterize the mobility of shale oil. The pore development of shale is mainly controlled by TOC and quartz content, and has a certain relationship with feldspar content, while clay mineral content is not the main influencing factor.
Application and discussion of expected monetary value (EMV) method in domestic shale gas block bidding
ZHAO Linjie, WANG Baohua, LI Hao, LIU Chaoying, ZHOU Xiaojin
2023, 45(3): 587-592. doi: 10.11781/sysydz202303587
Abstract(583) HTML (238) PDF-CN(39)
Abstract:
The result of mining right bidding, affected by many factors, has strong uncertainty. Especially in areas with low exploration degree, how to accurately carry out block economic evaluation is a key issue in current research. Based on the expected monetary value (EMV) method, this paper considers the "risk-value" two-factor model to quantify the geological risk, uses the probability distribution model to quantify the uncertainty of resources, defines the basis for the selection of key parameters, sorts out the economic evaluation scheme for shale gas blocks in areas with low exploration degree, and carries out the application to a shale gas block in the Guizhong Depression in Dianqiangui Basin, southern China. The results show that the method comprehensively considers multiple scenarios under different combinations of schemes, such as resource potential, engineering and technical conditions, development scheme, expected economic value, and oil and gas subsidy policies. The multiple sets of economic evaluation schemes formed can provide diversified block economic evaluation parameter data for decision makers, and can effectively guide the decision-making of block bidding scheme.
Droplet shape analyzer
2023, 45(3): 593-593.
Abstract(198) PDF-CN(33)
Abstract:

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