川东北普光地区下三叠统飞仙关组岩溶段的地质意义  

Geological significance of karst section of Lower Triassic Feixianguan Formation in Puguang area,Northeast Sichuan

作　　者：梁欣阳 付德奎 张宁[1] 高秋灵 张雄华[1] 陈建 Liang Xinyang;Fu Dekui;Zhang Ning;Gao Qiuling;Zhang Xionghua;Chen Jian(School of Earth Sciences,China University of Geosciences(Wuhan),Wuhan 430074,China;SINOPEC Zhongyuan Oilfield Puguang Branch,Dazhou Sichuan 653000,China;Henan University of Engineering,Zhenzhou 451191,China)

机构地区：[1]中国地质大学(武汉)地球科学学院,武汉430074 [2]中石化中原油田普光分公司,四川达州635002 [3]河南工程学院,郑州451191

出　　处：《地质科技通报》2022年第5期386-394,共9页Bulletin of Geological Science and Technology

基　　金：中国石油化工股份有限公司中原油田普光分公司项目“普光地区海相层序地层特征及控制因素研究”(31301845-20-ZC0613-0026)。

摘　　要：川东北地区飞仙关组发育碳酸盐岩储层,是普光气田天然气的主要产出层位。在飞仙关组四段的划分中,前人研究对飞一段与飞二段间是否存在不整合面这一问题有较大争议。对普光地区现有的4口钻井开展了岩心观察,在飞一-飞二段中部发现了岩溶角砾段,且在该段上下发现了一定的岩性分界面。飞一段底部为细晶白云岩,而飞一段顶部至飞二段开始发育鲕粒及模铸孔。采取PG104-1井岩心样品并进行了碳氧同位素测试,其碳同位素值普遍正偏,而氧同位素值均大于-5‰,指示相关流体为大气淡水流体,说明岩溶角砾段底部经历了一定时间的暴露,沉积间断发育。综合界面上下出现的碳氧同位素差异,模铸孔的出现及消失以及测井曲线的变化等因素,认为飞一段与飞二段的界限可以由因准同生岩溶而发育的岩溶角砾段划分并表征。Reservoir strata with carbonate rocks of Feixianguan Formation are the main output horizons of natural gas in Puguang Gas Field,Northeast Sichuan.As to the division of four members of Feixianguan Formation,the controversy regarding whether the T_(1)f_(1)member and T_(1)f_(2)member should be classified in the same third-order sequence appears.Based on the core observation of the existing drilling in Puguang area,the karst breccia section is found atthe middle of the T_(1)f_(1)-T_(1)f_(2)section,and there is a certain lithologic interface above and below it.The bottom of T_(1)f_(1)is fine-grained dolomite.From the top of T_(1)f_(1)to T_(1)f_(2),oolites and mould casting holes begin to develop.The carbon and oxygen isotope study in Well PG104-1 shows that the fluid environment is atmospheric freshwater fluid,which proves the development of quasi-syngenetic karst,while the oxygen isotope value is more than-5‰,indicating that the relevant fluid is atmospheric freshwater fluid,which proves that the bottom of the karst breccia section experiences a certain period of exposure and that a sedimentary discontinuity appears.Considering the differences in carbon and oxygen isotopes between the upper and lower interface,the emergence and disappearance of die casting holes and the changes in logging curves,it is considered that the boundary between T_(1)f_(1)and T_(1)f_(2)can be distinguished and characterized by karst breccia sections.This study provides an important basis for the study of the storage and migration of oil and gas in Feixianguan Formation.

关 键 词：飞仙关组 古岩溶 碳同位素 氧同位素 普光地区 

分 类 号：P642.25[天文地球—工程地质学]