川东北铁山坡构造飞仙关组气藏特征

CHARACTERISTICS OF FEIXIANGUAN FORMATION GAS POOL IN TIESHANPO STRUCTURE, NORTHEAST SICHUAN BASIN

铁山坡构造位于四川省宣汉县、万源市境内,区域构造位置属四川盆地川东北中隆高陡构造区双石庙构造群的西北部,为黄金口构造带北段的一个主体构造。该构造为南北两个反向逆断层夹持的断隆,存在3个局部高点。综合地震、地质、钻井、测井、岩心、测试及岩屑、气水的物化资料,研究了该构造下三叠统飞仙关组气藏的构造、储层、成藏特征。结果认为,该构造飞仙关组储层属台地边缘鲕滩相,经同生白云化、成岩溶蚀作用和造山运动,使得储层内孔、洞、缝比较发育;以粉晶灰岩及亮晶鲕粒云岩、石灰岩为主的储层物性较好,但非均质性也较强;气藏气水界面、含气面积准确,属裂缝—孔隙型储集空间、含气丰度高的大型气藏。越靠近该构造南翼,则储层孔隙越发育、有效储层厚度越大。

Tieshanpo structure is located within the boundary of Xuanhan County and Wanyuan City, Sichuan province. It is the major structure of the northern part of Huangjinkou structural zone and its regional structural location is in the northwestern part of Shuangshimiao structure group in Zhonglong steep structural belt, the northeastern Sichuan Basin. It is a faulted upfold between two opposite reverse faults and has three local structural highs. The seismic, geologic, drilling, logging, coring and testing data as well as the physicochemical data of cuttings and gas/water are integrated to study the characteristics of structure, reservoir and gas accumulation of the Lower Triassic Feixianguan Formation gas pool. The Feixianguan Formation reservoir is of oolitic beach facies on platform margin. Pores, cavities and fractures are well developed due to syngenetic dolomitization, diagenetic dissolution and orogeny. The reservoirs dominated by various limestone and dolomite have good poroperm characteristics but large heterogeneity. The gas-water contact and gas bearing area are accurately determined. It is a large gas pool with reservoir space of fracture-pore type and large gas abundance. Both the porosity and net pay increase toward its southern flank.