Oil & Gas Geology ›› 2021, Vol. 42 ›› Issue (1): 41-53.doi: 10.11743/ogg20210104

• Petroleum Geology • Previous Articles     Next Articles

Characteristic differences and controlling factors of pores in typical South China shale

Zhenxue Jiang1,2(), Xin Li1,2, Xingmeng Wang1,2, Guozhen Wang1,2, Hengyuan Qiu1,2, Deyu Zhu1,2, Hongyang Jiang1,2   

  1. 1. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum(Beijing), Beijing 102249, China
    2. Unconventional Oil and Gas Science and Technology Research Institute, China University of Petroleum(Beijing), Beijing 102249, China
  • Received:2020-04-23 Online:2021-02-28 Published:2021-02-07

Abstract:

Sweet spot prediction in shale usually depends on a general evaluation of hydrocarbon potential of reservoirs against various sedimentary settings and a thorough investigation into the main controlling factors on reservoir development in different strata context.Despite a large-scale commercial development of shale gas in South China, the marine-continental transitional shale and continental shale in the region have not contributed much to the boom so far.To turn the scale, representative shales in southeastern (marine) and northeastern (continental) Sichuan Basin as well as central Hunan Province (transitional), were sampled and analyzed in their respective sedimentary settings, geochemical attributes, petrological features and pore structure characteristics, to clarify the major factors controlling the reservoir capacity.The results show that marine shale with Type I maceral from southeastern Sichuan Basin is transportable and potentially porous with organic matter pores.The most promising facies is the organic-rich siliceous shale characterized by high pore volume (PV) (0.026 cm3/g on average) and high specific surface area (SSA) (28.99 m2/g on average) and with the abundance of organic matter determining the storage capacity.The marine-continental transitional shale with Type Ⅲ maceral of inertia from the central Hunan Province is dominated by clay mineral pores.The most promising facies is organic-rich clay characterized by high PV (0.023 cm3/g on average) and low SSA (6.33 m2/g on average) and with Si/Al ratios (ideally 2/3) controlling the reservoir capacity.The continental shale with mixing organic matter macerals from the northeastern Sichuan Basin is dominated by clay minerals and organic matter pores.The most promising facies is organic-rich clay mixed with shale, characterized by medium PV (0.017 cm3/g on average) and SSA (11.90 m2/g on average) and with both sapropelic content (>60%) and mineral ratios controlling the reservoir capacity.In all, shales with different sedimentary settings and under differential diagenetic modification present distinctive reservoir properties that require tailor-made exploration strategy.

Key words: pore structure, organic matter pore, reservoir capacity, marine facies, shale reservoir, South China

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