川西梓潼凹陷中下侏罗统气藏成藏条件

探讨川西梓潼凹陷中下侏罗统气藏的成藏条件,为区域气藏预测提供依据。对中下侏罗统气藏成藏主控因素的分析结果表明:下侏罗统暗色泥质岩生烃能力较弱,上三叠统须家河组第五段泥页岩层是该区侏罗系气藏的气源;侏罗系储层总体属于低孔低渗储层;以构造-岩性圈闭为主,须五地层在绵阳-江油-剑阁地区存在一条NE-SW向的尖灭线,易形成上超尖灭岩性气藏、不整合面相关气藏。研究区中下侏罗统气藏成藏主要控制因素为:储渗条件较好的储层和规模较大、形成较早的古隆起背景上的圈闭。勘探证实该区中下侏罗统具有潜在的前景,其中低幅凹中隆起区为中下侏罗统有利勘探区。

Research on accumulation conditions of Lower-Middle Jurassic gas reservoir of Zitong depression in West Sichuan,China

This paper approaches the hydrocarbon accumulation conditions of the Lower-Middle Jurassic gas reservoir in the Zitong depression of west Sichuan to provide the basis for predicting regional gas pools.Through statistics and analysis of the main controlling factors of hydrocarbon accumulation of the gas reservoir,this paper points out that the shale bed in Member 5 of Upper Triassic Xujiahe Formation is the main source rock of the Lower-Middle Jurassic gas reservoir.The dark argillaceous rock of Lower Jurassic is weak in the ability of generating hydrocarbon.The Jurassic reservoir overall has low porosity and low permeability,the structural-lithologic traps are main conditions for gas accumulation,and there is a NE-SW pinch-out line in the Mianyang-Jiangyou-Jiange area which is easy to form the super pinch-out lithologic gas reservoir.The reservoir with high porosity and high permeability and the earliest trap formed on uplift are main controlling factors for hydrocarbon accumulation.The Jurassic reservoirs in the low amplitude uplifted area have favorable conditions for hydrocarbon accumulation,so their exploration potential is large.