河坝气藏飞仙关组三段储集岩特征及成岩作用

川东北河坝地区下三叠统飞仙关组三段发现气藏，显示飞仙关组三段（简称飞三段）具有良好的勘探潜力。利用岩心样品普通薄片、铸体薄片、阴极发光薄片、扫描电镜和电子探针观察，并结合部分样品的物性、微量元素分析等测试结果，对该区飞三段鲕粒碳酸盐岩的储层特征、成岩作用进行了研究。结果显示，河坝地区飞三段颗粒滩型沉积储层发育，但物性总体以中、低孔隙度-低渗透率为主，储集岩岩性主要为鲕粒灰岩、砂屑灰岩，粒内溶孔和铸模孔为主要的孔隙空间。飞三段储层主要的成岩作用为泥晶化、溶蚀、胶结、白云石化、压实压溶和破裂作用，其中储层的发育主要与准同生期的大气水选择性溶蚀、深埋条件下的菱锶矿胶结、鞍状白云石充填等相关的埋藏溶蚀作用及构造裂缝的发育有关。沉积准同生期的大气水溶蚀作用是飞三段颗粒碳酸盐岩孔隙发育的基础，白云石化、菱锶矿化、埋藏溶蚀等埋藏成岩作用有利于孔隙的改善，微古地貌高地及断裂、裂缝相对发育区可能为储层发育有利区。

Diagenesis and characteristics of reservoirs in the Member 3 of the Lower Triassic Feixianguan Formation in Heba gas field

Gas pools were found in the Member 3 of the Lower Triassic Feixianguan Formation in Heba area of the northeastern Sichuan Basin, indicating a great exploration potential in the Member 3 of the Lower Triassic Feixianguan Formation (T 1f 3 for short). Based on detailed microscopic, scanning electron microscopic and election microprobe observations of ordinary, mold and cathodoluminescence thin sections of core samples and combined with measurement results of porosity, permeability and trace element analysis of some samples, we examined diagenetic characteristics of carbonate reservoirs in the Member 3 of the Lower Triassic Feixianguan Formation in this area. The results showed that the Member 3 of the Feixianguan Formation is dominated by intra-platform shoal and inter-shoal deposits of open platform, of which the intra-platform shoal deposit is favorable for reservoir evolution. Main reservoir rocks are composed of oolitic limestones and calcarenite having intragranular dissolved pores and mould pores with low-porosity and low-permeability. The main kinds of diagenesis in reservoirs of the Member 3 of the Feixianguan Formation are micritization, dissolution, cementation or filling, compaction-pressolution, dolomitization and fracturing. The pore development of these grain carbonate reservoirs is affected by penecontemporaneous meteoric dissolution and burial dissolution, of which penecontemporaneous meteoric dissolution is a key factor that controls reservoir pore formation. Burial diagenesis including dolomitization, strontianite cementation or replacement and burial corrosion has greatly improved pores. Thus, favorable exploration zones in this area should be distributed in micro-paleogeomorphic upland and other places where faults and fractures are relatively developed.