New breakthrough of natural gas exploration in the Qixia Formation of Middle Permian by Well Pingtan 1 in the southwestern Sichuan Basin and its implications
ZHANG Benjian, YIN Hong, LI Rongrong, XIE Chen, WANG Xiaoxing, PEI Senqi, HU Xin, YANG Hua, DENG Bo, CHEN Xiao, LI Xucheng
In 2020, Well Pingtan 1 in the southwestern Sichuan Basin drills into porous dolomite reservoirs of marginal platform belt in the Qixia Formation of Middle Permian and produces high-yield industrial gas, which indicates a new breakthrough of Middle Permian natural gas exploration in this area. In order to further understand the geological conditions of Qixia Formation and provide guidance for the natural gas exploration in this area, this paper studied hydrocarbon accumulation elements of this area (e.g. hydrocarbon source conditions, reservoir characteristics and preservation conditions) after analyzing the drilling results of Well Pingtan 1. Then, exploration potential and direction of Qixia Formation natural gas in this area were discussed. And the following research results were obtained. First, the Qixia Formation reservoirs in the southwestern Sichuan Basin are dominated by moderate and fine crystalline dolomite, and their reservoir spaces are mainly acted by dissolved vugs, intercrystalline pores, intergranular pores and fractures. They are fractured-porous reservoirs of low porosity and middle–low permeability, with locally developed high-porosity and high-permeability reservoirs. Their lateral distribution is controlled by marginal platform shoal and they are extensively distributed in the area of Qiongxi, Pingluoba, Mingshan and Hanwangchang. Second, the source rocks of Qixia Formation natural gas in this area are similar to those in Shuangyushi structure, and they are mainly composed of mud shale of Lower Cambrian Qiongzhusi Formation and marl of Middle Permian, among which the Qiongzhusi Formation is dominant. Third, this area is characterized by "double-layer structure" vertically, and the Triassic salt gypsum has regional sealing conditions and the Permian structural traps and structural-lithological traps are morphologically completed with good preservation conditions, which provide favorable sites for the accumulation of Qixia Formation natural gas. In conclusion, the Middle Permian in the southwestern Sichuan Basin is better in hydrocarbon accumulation conditions, and the breakthrough of Well Pingtan 1 reveals a good natural gas exploration potential of Qixia Formation dolomite reservoirs of marginal platform belt in the southwestern Sichuan Basin.
张本健,尹宏,李荣容,谢忱,汪晓星,裴森奇,胡欣,杨华,邓波,陈骁,李旭成. 四川盆地西南部平探1井中二叠统栖霞组天然气勘探新突破及其意义[J]. 天然气工业, 2020, 40(7): 34-41.
ZHANG Benjian, YIN Hong, LI Rongrong, XIE Chen, WANG Xiaoxing, PEI Senqi, HU Xin, YANG Hua, DENG Bo, CHEN Xiao, LI Xucheng. New breakthrough of natural gas exploration in the Qixia Formation of Middle Permian by Well Pingtan 1 in the southwestern Sichuan Basin and its implications. NATURAL GAS INDUSTRY, 2020, 40(7): 34-41.