Abstract
The geological conditions of shale gas accumulation, gas-bearing characteristics and shale gas preservational conditions of Doushantuo Formation in western Hubei Province was studied based on comprehensive analysis of drilling, outcrops, and testing data. The Doushantuo Formation in the study area can be divided into four members, and the black carbonaceous dolomite developed in the second Member of Doushantuo Formation (Z1d2) is the main shale gas reservoir. From west to east, the shallow shelf, basin and platform facies are developed in turn, and two isolated platforms are developed among the basin. On the plane, the depocenter is mainly developed in Zigui-Wufeng region, with the thickness of organic-rich strata more than 100 m, the areas with the TOC values greater than 1.0, are distributed in the Shengnongjialinqu-Zigui-Wufeng area. Overall, the TOC values are at the range of 0.5,-2.0, belonging to low to medium level, and Ro is mainly high maturity of 2.0,-3.5,. The Z1d2 is characterized by the dominated dolomite mineral, the calcareous shale, the ultralow-low porosity, and ultra-low permeability reservoir. The dolomite intergranular pores and clay mineral stratified pores are the most important pore types, and pyrite intercrystalline pores and organic matter pores are much more developed in the samples with high TOC value. The areas with the high gas content are limited only to the north of the Tianyangping fault and southern of the Huangling anticline with the gas content over 1.0 m3/t. It is believed that the shale gas accumulation in Doushantuo Formation is mainly influenced by the superposition of sedimentary facies and structural types. Basin and platform basin facies, stable structural belt, the footwall of reverse fault, and the area far away from regional normal faults with a buried depth of more than 2,000 m are conducive for shale gas accumulation. This paper also provides a scientific basis for further shale gas exploration and development of the Doushantuo Formation in western Hubei Province. It is proposed that favorable areas are mainly distributed in the Yangye-1 well block and Yiye-1 to Yidi-3 well block in the southeast margin of Huangling anticline.
Key words
shale gas, accumulation conditions, gas-bearing property, preservation condition, Doushantuo Formation, western Hubei Province
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Accumulation geological conditions and comprehensive evaluation of shale gas of Doushantuo Formation in western Hubei Province,middle Yangtze area[J]. Marine Origin Petroleum Geology. 2023, 28(2): 196-208
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