济阳坳陷孤北低潜山煤成气成藏条件及特征

The Pool-Forming Condition and Character of Coal-Formed Gas in Gubei Deeply Buried Hill of Jiyang Depression

以往济阳坳陷所探明的天然气几乎均为油型气,为了打开济阳坳陷煤成气勘探局面,通过研究已获煤成气流的孤北低潜山成藏特征,在综合运用录井、岩心、地化分析、测井及地震等资料基础上,分析构造演化特征,结果显示:孤北低潜山上古生界经历了印支期抬升剥蚀、燕山期中生界沉积后的抬升剥蚀等多次改造,至喜山期受埕南及孤北断层控制大幅沉降沉积后在馆陶组沉积时期开始大量二次生气;而埕南、孤北断层明化镇组沉积早期停止活动更为气藏的保存提供了保障,该低潜山气源充足、储层条件好、盖层条件优越,具有形成煤成气藏的条件。结果认为:本区气藏具有自生自储、上生下储和上生侧储3种运聚方式,除孤北低潜山的上古生界气藏之外,该区的下古生界风化壳和该区以南孤岛凸起的下古生界也是煤成气藏勘探的重要领域。

The natural gas discovered in Jiyang depression came mostly from oil, but coal-formed gas will become the main target of exploration in the future. Gubei deeply buried hill is a key place to search for coal-formed gas from the Upper Palaeozoic. This deeply buried hill is abundant in oil resources, and has the suitable reservoir and excellent caprock, after all the favorable pool-forming conditions owing to favorable structural history. Uplifted and denudated during the Indonesian Stage, Uplifted and denudated after being deposited in the Mesozoic during the Yanshanian, the structural history which was controlled by the Chengnan and Gubei faults during the Himalayan Stage and deposited on a large scale, made the gas source rock of the Upper Palaeozoic begin to produce secondary generation of natural gas during the Guantao Formation, both faults ceased moving at that time, which was in favor of the conservation of the gas pool. The migration and gathering types of gas pool consist of source and reservoir in the same bed , upper-source and lower-reservoir. Upper-source and side-reservoir. Besides the Gubei deeply buried hill of the Upper Palaeozoic; the weathering crust of the Lower Palaeozoic and Gudao bulge in the Lower Palaeozoic are also important regions for coal-formed gas exploration.