Shale oil resources are abundant on Earth,of which hybrid sedimentary shale(HSS)oil is an important component,including high and medium-low organic matter content(TOC).Oil content,especially the oiliness gradation,is ...Shale oil resources are abundant on Earth,of which hybrid sedimentary shale(HSS)oil is an important component,including high and medium-low organic matter content(TOC).Oil content,especially the oiliness gradation,is a key parameter for shale oil evaluation and numerous studies had been conducted.However,most studies concentrated on the HSS with high TOC,making oil content evaluation of the HSS with medium-low TOC challenging.The Paleocene Shahejie Formation(E2s)shale in Dongpu Depression is a typical HSS with low-moderate TOC,showing great shale oil resource potential.Integrated geochemical characterization of 270 core samples were conducted and results show that,the E2s shale has fairgood hydrocarbon generation potential,with TOC ranging from 0.06%to 3.6%(Avg.0.86%)andⅡ1-Ⅱ2 kerogen type in thermally mature.The hydrocarbon generation potential decreases with kerogen types changing from type I toⅢ,but S1C and the oil saturation index(OSI)(S1*100/TOC>100)increase from type I toⅡ1,and then decrease from typeⅡ2 toⅢ,indicating shale with typeⅡ2 kerogen have the greatest oil content.This is related to the diferences in hydrocarbon expulsion efciency caused by diferential hydrocarbon generation potential and pore-microfractures evolution among shales with diferent kerogen types.Signifcant oil micro-migration occurred in E2s shale,with micro-migration quantity(∆Q)ranging from-846 to 993 mg/g(Avg.-120 mg/g),and 90%and 10%shale exhibit hydrocarbon intra-micro-migration(∆Q<0)and extra-micro-migration(∆Q>0).The shale with typeⅡ2 kerogen has the greatest intra-micro-migration.Based on S1C,TOC and OSI values and their evolution pattern,shale oil resources were classifed into enriched,moderately enriched,less efcient and invalid resources,accounting for 11%,53%,16%and 21%respectively,with S1C thresholds of 3.5 and 0.5 mg/g,OSI threshold of 100 mg/g.Compared with previous grading criteria,the gradation criterion established in this study is relatively lower,which is mainly due to the lower TOC and clay mineral content in HSS.Enriched and moderately enriched resources are mainly shales with typeⅡ2 kerogen,followed by typeⅡ1 kerogen,and the E2s4 U and E2s3 L shale are the most favorable targets for further shale oil exploration.The established oiliness gradation criteria are applicable for the HSS with TOC in other parts of the world.展开更多
A large number of nanopores and complex fracture structures in shale reservoirs results in multi-scale flow of oil. With the development of shale oil reservoirs, the permeability of multi-scale media undergoes changes...A large number of nanopores and complex fracture structures in shale reservoirs results in multi-scale flow of oil. With the development of shale oil reservoirs, the permeability of multi-scale media undergoes changes due to stress sensitivity, which plays a crucial role in controlling pressure propagation and oil flow. This paper proposes a multi-scale coupled flow mathematical model of matrix nanopores, induced fractures, and hydraulic fractures. In this model, the micro-scale effects of shale oil flow in fractal nanopores, fractal induced fracture network, and stress sensitivity of multi-scale media are considered. We solved the model iteratively using Pedrosa transform, semi-analytic Segmented Bessel function, Laplace transform. The results of this model exhibit good agreement with the numerical solution and field production data, confirming the high accuracy of the model. As well, the influence of stress sensitivity on permeability, pressure and production is analyzed. It is shown that the permeability and production decrease significantly when induced fractures are weakly supported. Closed induced fractures can inhibit interporosity flow in the stimulated reservoir volume (SRV). It has been shown in sensitivity analysis that hydraulic fractures are beneficial to early production, and induced fractures in SRV are beneficial to middle production. The model can characterize multi-scale flow characteristics of shale oil, providing theoretical guidance for rapid productivity evaluation.展开更多
基金supported by the National Natural Science Foundation of China(U24B6002,42202133,U22B6004)CNPC Innovation Fund(2022DQ02-0106)+5 种基金Key Laboratory of Tectonics and Petroleum Resources of the Ministry of Education(TPR-2023-05)major science and technology projects of CNPC during the"14th five-year plan"(2021DJ0101)National Natural Science Foundation of China(41872148,42072174,42130803)Strategic Cooperation Technology Projects of the CNPC and CUPB(ZLZX2020-01-05)Sinopec Zhongyuan Oilfeld and CUPB Cooperation Project(31300027-23-ZC0613-0013)AAPG Foundation Grantsin-Aid Program(22272306).
文摘Shale oil resources are abundant on Earth,of which hybrid sedimentary shale(HSS)oil is an important component,including high and medium-low organic matter content(TOC).Oil content,especially the oiliness gradation,is a key parameter for shale oil evaluation and numerous studies had been conducted.However,most studies concentrated on the HSS with high TOC,making oil content evaluation of the HSS with medium-low TOC challenging.The Paleocene Shahejie Formation(E2s)shale in Dongpu Depression is a typical HSS with low-moderate TOC,showing great shale oil resource potential.Integrated geochemical characterization of 270 core samples were conducted and results show that,the E2s shale has fairgood hydrocarbon generation potential,with TOC ranging from 0.06%to 3.6%(Avg.0.86%)andⅡ1-Ⅱ2 kerogen type in thermally mature.The hydrocarbon generation potential decreases with kerogen types changing from type I toⅢ,but S1C and the oil saturation index(OSI)(S1*100/TOC>100)increase from type I toⅡ1,and then decrease from typeⅡ2 toⅢ,indicating shale with typeⅡ2 kerogen have the greatest oil content.This is related to the diferences in hydrocarbon expulsion efciency caused by diferential hydrocarbon generation potential and pore-microfractures evolution among shales with diferent kerogen types.Signifcant oil micro-migration occurred in E2s shale,with micro-migration quantity(∆Q)ranging from-846 to 993 mg/g(Avg.-120 mg/g),and 90%and 10%shale exhibit hydrocarbon intra-micro-migration(∆Q<0)and extra-micro-migration(∆Q>0).The shale with typeⅡ2 kerogen has the greatest intra-micro-migration.Based on S1C,TOC and OSI values and their evolution pattern,shale oil resources were classifed into enriched,moderately enriched,less efcient and invalid resources,accounting for 11%,53%,16%and 21%respectively,with S1C thresholds of 3.5 and 0.5 mg/g,OSI threshold of 100 mg/g.Compared with previous grading criteria,the gradation criterion established in this study is relatively lower,which is mainly due to the lower TOC and clay mineral content in HSS.Enriched and moderately enriched resources are mainly shales with typeⅡ2 kerogen,followed by typeⅡ1 kerogen,and the E2s4 U and E2s3 L shale are the most favorable targets for further shale oil exploration.The established oiliness gradation criteria are applicable for the HSS with TOC in other parts of the world.
基金This study was supported by the National Natural Science Foundation of China(U22B2075,52274056,51974356).
文摘A large number of nanopores and complex fracture structures in shale reservoirs results in multi-scale flow of oil. With the development of shale oil reservoirs, the permeability of multi-scale media undergoes changes due to stress sensitivity, which plays a crucial role in controlling pressure propagation and oil flow. This paper proposes a multi-scale coupled flow mathematical model of matrix nanopores, induced fractures, and hydraulic fractures. In this model, the micro-scale effects of shale oil flow in fractal nanopores, fractal induced fracture network, and stress sensitivity of multi-scale media are considered. We solved the model iteratively using Pedrosa transform, semi-analytic Segmented Bessel function, Laplace transform. The results of this model exhibit good agreement with the numerical solution and field production data, confirming the high accuracy of the model. As well, the influence of stress sensitivity on permeability, pressure and production is analyzed. It is shown that the permeability and production decrease significantly when induced fractures are weakly supported. Closed induced fractures can inhibit interporosity flow in the stimulated reservoir volume (SRV). It has been shown in sensitivity analysis that hydraulic fractures are beneficial to early production, and induced fractures in SRV are beneficial to middle production. The model can characterize multi-scale flow characteristics of shale oil, providing theoretical guidance for rapid productivity evaluation.
