Basic characteristics and exploration potential of shale gas in Longtan Formation of Upper Permian in eastern Sichuan Basin
(2.Research Institute of Petroleum Exploration and Production, SINOPEC Jianghan Oil Field Branch Company, Wuhan, Hubei 430223)
(3.Research Institute of Petroleum Exploration and Production, SINOPEC East China Branch Company, Nanjing, Jiangsu 210011)
(4.Research Institute of Petroleum Exploration and Production, SINOPEC Exploration Branch Company, Chengdu, Sichuan 610041)
【Abstract】Various types of sedimentary facies were developed during the Longtan period of the Late Permian, Sichuan Basin. To discover the shale gas exploration potential of belts with different sedimentary facies, a systematic analysis of shale gas generation conditions was carried out on the basis of different typical wells. The organic-rich shale developed in the Sichuan Basin during the Late Permian Longtan period was mainly distributed in tidal flat-lagoon and shelf facies. With complex lithological combinations, the tidal flat-lagoon facies shale was distributed in the Ziyang-Yongchuan-Qijiang areas. Mudstone, shale, and argillaceous carbonate rocks were interbedded with varying thickness and coal seams were also developed in all sections. Furthermore, it has the characteristics of “high TOC, clay and gas contents, and high porosity”. The main organic matter type is type Ⅲ. The shallow water, mixed shelf facies in the Longtan Formation was mainly distributed in the Guang’an-Changshou-Nanchuan area, with reduced coal seams and increased ash content. Coal seams were barely developed in the second member of the Longtan Formation. Its organic matter type is Ⅱ2–Ⅱ1, with stable thickness as well as medium TOC and brittle mineral contents. Gas logging was anomalous. The deep-water shelf facies in the Wujiaping Formation were mainly distributed in Shizhu-Wanxian and Guangyuan-Liangping. Coal seams were only developed at the bottom of the Wujiaping Formation. Moreover, the second member of the Wujiaping Formation is composed of siliceous shale and mudstone, which has the characteristics of “high TOC content, high brittle mineral content, high porosity, high gas content, and high gas saturation”. Its organic matter type is Ⅱ1, with widespread organic pores. It is currently the main strata for the exploration and development of Permian shale gas in the Sichuan Basin.
【Keywords】 shale gas; Longtan Formation; Wujiaping Formation; Permian; exploration potential; eastern Sichuan area;
NIE Haikuan,HE Zhiliang,LIU Guangxiang,et al.Status and direction of shale gas exploration and development in China[J].Journal of China University of Mining & Technology,2020,49(1):13-35.
CAO Qinggu,LIU Guangxiang,ZHANG Changjiang,et al.Sedimentary environment and its controlling on source rocks during Late Permian in Sichuan Basin[J].Petroleum Geology & Experiment,2013,35(1):36-41.
ZHAO Jianhua,JIN Zhijun,LIN Changsong,et al.Sedimentary environment of the Lower Cambrian Qiongzhusi Formation shale in the Upper Yangtze region[J].Oil & Gas Geology,2019,40(4):701-715.
 WANG Hongyan,SHI Zhensheng,QUN Zhao,et al.Stratigraphic framework of the Wufeng-Longmaxi shale in and around the Sichuan Basin,China:implications for targeting shale gas[J].Energy Geoscience,2020,1(3/4):124-133.
WEI Limin,WANG Yan,ZHANG Tiancao,et al.Main control factors of enrichment and high production of shale gas:a case study of Wufeng-Longmaxi Formation in Southern Sichuan[J].Fault-Block Oil and Gas Field,2020,27(6):700-704.
ZHANG Tao,LIN Juanhua,HAN Yueqing,et al.Pattern of hydrothermal dolomitization in the Middle Permian Maokou Formation,eastern Sichuan Basin,and its alteration on reservoirs herein[J].Oil & Gas Geology,2020,41(1):132-143.
ZHANG Aobo,TANG Dazhen,TAO Shu,et al.Analysis of geolo-gical background and development situation of typical oil/gas-bearing shales in China and America[J].Petroleum Geology and Recovery Efficiency,2019,26(1):37-45.
ZHANG Peng,HUANG Yuqi,YANG Junwei,et al.Main controlling factors of shale adsorption capacity of Longtan Formation in Northwest Guizhou[J].Fault-Block Oil and Gas Field,2019,26(2):162-167.
LIU Guangxiang,JIN Zhijun,DENG Mo,et al.Exploration potential for shale gas in the Upper Permian Longtan Formation in eastern Sichuan Basin[J].Oil & Gas Geology,2015,36(3):481-487.
ZHAO Peirong,GAO Bo,GUO Zhanfeng,et al.Exploration potential of marine-continental transitional and deep-water shelf shale gas in Upper Permian,Sichuan Basin[J].Petroleum Geology & Experiment,2020,42(3):335-344.
GUO Xusheng,HU Dongfeng,LIU Ruobing,et al.Geological conditions and exploration potential of Permian marine-continent transitional facies shale gas in the Sichuan Basin[J].Natural Gas Industry,2018,38(10):11-18.
TONG Chongguang.Relationship between Neotectonic movement and structural evolution and gas pools formation of Sichuan Basin[J].Journal of Chengdu University of Technology,2000,27(2):123-130.
LIN Liangbiao,CHEN Hongde,ZHU Lidong.Geochemical characteristics of silicalites from Wujiaping Formation in Shizhu,Chongqing[J].Journal of Mineralogy and Petrology,2010,30(3):52-58.
LIANG Bing,SHI Yingshuang,SUN Weiji,et al.Reservoir forming characteristics of “the three gases” in coal measure and the possibility of commingling in China[J].Journal of China Coal Society,2016,41(1):167-173.
ZHANG Hanrong.Gas content of the Silurian shale in the SE Sichuan Basin and its controlling factors[J].Natural Gas Industry,2016,36(8):36-42.
CHEN Feiran,WEI Xiangfeng,LIU Zhujiang,et al.Pore development characteristics and main controlling factors of the Permian marine-continent transitional shale in the Sichuan Basin[J].Natural Gas Geoscience,2020,31(11):1593-1602.
ZHANG Jizhen,LI Xianqing,WANG Yuan,et al.Accumulation conditions and reservoir characteristics of marine-terrigenous facies coal measures shale gas from Longtan Formation in south Sichuan Basin[J].Journal of China Coal Society,2015,40(8):1871-1878.
SUN Chao,YAO Suping.Pore structure and characterization methods of shale oil reservoir[J].Petroleum Geology and Recovery Efficiency,2019,26(1):153-164.
DENG Ende,YAN Zhihua,JIANG Bingren,et al.Reservoir characteristics of marine-continental shale gas in Upper Permian Longtan Formation,western Guizhou province[J].Petroleum Geology & Experiment,2020,42(3):467-476.
ZHANG Guangrong,NIE Haikuan,TANG Xuan,et al.Pyrite type and its effect on shale gas accumulation:a case study of Wufeng-Longmaxi shale in Sichuan Basin and its periphery[J].Petroleum Geology & Experiment,2020,42(3):459-466.
 CAO Taotao,XU Hao,LIU Guangxiang,et al.Factors influencing microstructure and porosity in shales of the Wufeng-Longmaxi formations in northwestern Guizhou,China[J].Journal of Petroleum Science and Engineering,2020,191:107181.
KUANG Lichun,DONG Dazhong,HE Wenyuan,et al.Geological characteristics and development potential of transitional shale gas in the east margin of the Ordos Basin,NW China[J].Petroleum Exploration and Development,2020,47(3):435-446.
CAO Taotao,LIU Guangxiang,CAO Qinggu,et al.Influence of maceral composition on organic pore development in shale:a case study of transitional Longtan Formation shale in eastern Sichuan basin[J].Oil & Gas Geology,2018,39(1):40-53.
DENG Ende,YI Tongsheng,YAN Zhihua,et al.Accumulation condition and shale gas potential of the marine-terrestrial transitional facies:a case study of Jinshacan 1 well of Longtan Formation in northern Guizhou[J].Journal of China University of Mining & Technology,2020,49(6):1166-1181.
HE Zhiliang,NIE Haikuan,LI Shuangjian,et al.Differential occurrence of shale gas in the Permian Longtan Formation of Upper Yangtze region constrained by plate tectonics in the Tethyan domain[J].Oil & Gas Geology,2021,42(1):1-15.
LIANG Xiwen,LI Le.Geological conditions and exploration potential for shale gas in Upper Permian Wujiaping Formation in the region of western Hubei-eastern Chongqing[J].Petroleum Geology & Experiment,2021,43(3):386-394.
GUO Shaobin,WANG Zilong,MA Xiao.Exploration prospect of shale gas with Permian transitional facies of some key areas in China[J].Petroleum Geology & Experiment,2021,43(3):377-385.