鄂尔多斯盆地延安地区二叠系山西组页岩气源储特征及聚集规律

doi:10.12108/yxyqc.20240307

Lithologic Reservoirs ›› 2024, Vol. 36 ›› Issue (3): 72-83.doi: 10.12108/yxyqc.20240307

• PETROLEUM EXPLORATION • Previous Articles Next Articles

Source-reservoir characteristics and accumulation rules of shale gas of Permian Shanxi Formation in Yan'an area, Ordos Basin

DUAN Yifei^1,2, ZHAO Weiwei^1,2, YANG Tianxiang³, LI Fukang⁴, LI Hui^1,2, WANG Jianan^1,2, LIU Yuchen^1,2

1. School of Earth Sciences and Engineering, Xi'an Shiyou University, Xi'an 710065, China;
2. Shaanxi Key Laboratory of Petroleum Accumulation Geology, Xi'an Shiyou University, Xi'an 710065, China;
3. Gas Field Company, Shaanxi Yanchang Petroleum(Group)Co., Ltd., Yan'an 716000, Shaanxi, China;
4. Natural Gas Research Institute Branch, Shaanxi Yanchang Petroleum(Group)Co., Ltd., Xi'an 710065, China

Received:2023-02-15 Revised:2023-03-10 Online:2024-05-01 Published:2024-04-30

Abstract

Abstract: Permian Shanxi Formation has great exploration potential for shale gas in Yan’an area of Ordos Basin.By analyzing drilling, mud-logging and wire-logging data, combined with the analysis and laboratory data of shale samples, the source-reservoir characteristics and accumulation process of shale gas of Permian Shanxi Formation in Yan’an area were analyzed, and the accumulation mechanism of shale gas was discussed. The results show that:（1）The organic carbon（TOC）content of shale of Permian Shanxi Formation in Yan’an area of Ordos Basin is relatively high, with an average mass fraction of 2.12%. The main type of kerogen is type Ⅲ, with Ro ranging from 2.0% to 3.7%. It is in the high to over mature stage and high-quality source rocks.（2）The mineral composition of the shale of Shanxi Formation in the study area seems to be rich in clay, with an average mass fraction of clay minerals of 56.7%, which is conducive to the occurrence of adsorbed gas. There are mainly three types of reservoir spaces:inorganic mineral pores, organic pores, and micro-fractures. The gas content of rocks varies greatly due to the influence of different lithology combinations. The Shan 2 member has a higher gas content than Shan 1 member（with an average mass volume of 1.38 m³/t）. According to different lithology combinations, the source-reservoir configuration of shale gas of Shanxi Formation can be divided into three types:thick shale interbedded with thin sand layer, shale interbedded with siltstone and fine sandstone, and shale mixed with coal seam. Different source-reservoir configurations have different gas-bearing characteristics.（3）The shale gas is mainly in adsorbed state and free state in the study area, and is in a dynamic equilibrium state during the accumulation process, continuously transforming with the change of formation conditions. The accumulation process can be divided into three stages:In Early Jurassic, organic matter began to generate gaseous hydrocarbons, and shale gas began to adsorb and accumulate；During Middle-Late Jurassic, a large number of gaseous hydrocarbons were generated and expanded, gaseous hydrocarbons were discharged, fractures closed, and cyclic migration and accumulation occurred；In Early Cretaceous, organic matter reached a high-over mature stage, entering the final stage of hydrocarbon generation and expulsion, until the formation uplifted and hydrocarbon generation ended. The good sealing effect of shale provides a solid guarantee for the formation of shale gas reservoirs.

Key words: shale gas, source-reservoir configuration, adsorbed state, free state, accumulation rules, sealing effect, Shanxi Formation, Permian, Yan’an area, Ordos Basin

CLC Number:

TE122.1

DUAN Yifei, ZHAO Weiwei, YANG Tianxiang, LI Fukang, LI Hui, WANG Jianan, LIU Yuchen. Source-reservoir characteristics and accumulation rules of shale gas of Permian Shanxi Formation in Yan'an area, Ordos Basin[J].Lithologic Reservoirs, 2024, 36(3): 72-83.

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Source-reservoir characteristics and accumulation rules of shale gas of Permian Shanxi Formation in Yan'an area, Ordos Basin

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