孤北低潜山煤成气疏导体系

针对济阳坳陷沾化凹陷中部孤北地区煤成气源岩与储集层在空间上分离的实际，提出了缝隙（断裂、裂缝）是该地区煤成气由气源岩向砂岩储层运移的重要途径，地层水是煤成气运移重要媒介的认识；通过对源岩有机地化分析﹑储层及盖层的物性分析﹑圈闭形成时间等成藏地质背景的研究,认为孤北低潜山气藏属于晚古生代自生自储型煤成气藏，具有较好的生﹑储﹑盖等地质条件，其源岩层与储层之间存在厚度在200 m以上的隔层;经分析岩心观察结果及裂缝发育特征,认为垂向和斜向裂缝是煤成气疏导的重要通道,并进行了天然气在缝隙输导体中的运移模拟实验,获得了天然气排驱地层水而最终聚集成藏的认识。

CARRIER SYSTEM FOR COAL-DERIVED GAS IN GUBEI LOW BURIED HILL RESERVOIRS OF ZHANHUA SAG, JIYANG DEPRESSION

In view of the fact that the source rocks are separate from the reservoirs of coal derived gas in Gubei area in the central of Zhanhua sag, Jiyang depression, fractures (faults and fissures) are believed to be the major pathways and formation water is thought to be the major carrier for the coal derived gas to migrate from the source rocks to the sandstone reservoirs. Based on a study of the geologic settings of hydrocarbon accumulation such as organic geochemistry of the source rocks, poroperm characteristics of the reservoirs and seals, and the timing of trap formation, it is recognized that the Gubei low buried hill gas reservoirs belong to the Late Paleozoic coal derived gas reservoirs with the source rocks and reservoir rocks occurring at the same layer and have relatively favorable source-reservoir-cap rock combinations with a seal over 200 m thick occurring between the source and reservoir rocks. Analysis of core observation results and features of fault development show that the vertical and oblique fractures act as the major pathways for migration of the coal derived gas. Simulation study is performed on migration of natural gas in the fracture carrier system and a conclusion is obtained that the natural gas accumulates after displacing the formation water.