Oil & Gas Geology ›› 2021, Vol. 42 ›› Issue (4): 816-828.doi: 10.11743/ogg20210404

• Petroleum Geology • Previous Articles     Next Articles

Reservoir tightening process and its coupling relationship with hydrocarbon accumulation in the fourth member of Upper Triassic Xujiahe Formation in theWestern Sichuan Depression, Sichuan Basin

Liangbiao Lin1,2(), Yu Yu1,2,*(), Hongli Nan3, Hongde Chen1,2, Lei Liu1,2, Dong Wu1, Zhikang Wang1,2   

  1. 1. State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu, Sichuan 610059, China
    2. Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu, Sichuan 610059, China
    3. Exploration & Production Research Institute, Southwest Oil & Gas Company, SINOPEC, Chengdu, Sichuan 610041, China
  • Received:2020-10-10 Online:2021-08-28 Published:2021-08-27
  • Contact: Yu Yu E-mail:linliangbiao08@cdut.cn;yuyucdut@163.com

Abstract:

The Upper Triassic Xujiahe Formation in Western Sichuan Depression is rich in hydrocarbon resources and has been one of the major tight gas pay zones in the area. By focusing on the tight sandstone of the fourth member of the formation, this study aims to answer why the stone is so tight and what factors had affected its tightening-up process based on petrological characteristics, reservoir physical property and diagenesis analyses, which are also combined with hydrocarbon accumulation history to confirm a possible coupling relationship between the two processes. It reveals that compaction caused great porosity loss in the stone. However, it was the late-stage precipitation of carbonate cements in a semi-closed to a closed setting that played a key role in the process by reducing the porosity of high-quality reservoirs in the formation to less than 10 % during the middle and late stages of mesodiagenesis (corresponding to the Early Cretaceous). Fluid inclusions and laser Raman compositional analyses suggest two hydrocarbon accumulation periods, of which the second period (the Late Jurassic-Early Cretaceous) contributed more. It also suggests that when other types of reservoirs in the basin were entering the tightening-up stage, i.e. when their porosity was reduced to less than 10 %, hydrocarbon accumulation in the fourth member of Xujiahe Formation was still ongoing, indicating a precedence of reservoir tightening to hydrocarbon accumulation.

Key words: hydrocarbon accumulation, reservoir tightening process, tight sandstone, Xujiahe Formation, Western Sichuan Depression, Sichuan Basin

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