岩性油藏成藏机理及运聚模式——以牛庄洼陷为例

在东营凹陷牛庄洼陷岩性体油藏油气分布及油源特征分析的基础上,从该区压力演化角度出发,应用隐蔽输导体系理论,分析了该区岩性油藏的成藏过程。结果表明:岩性体油藏多数为它源性多期幕式置换成藏。在区域性地层超压释放过程中,高压岩性体中地层水与早期充注的油气首先通过隐蔽输导体系向外部岩性体排出,在上部破裂岩性体中聚集成藏。高压岩性体在释放高压流体的同时,岩性体本身泄压;由于岩性体物性远好于周围泥、页岩,泄压往往较泥、页岩彻底,加之该区高压主要形成于泥、页岩烃源岩中,在下次超压释放前某一段时间,岩性体内部压力相对周围泥、页岩较低,此时高压破裂产生的断层和微裂缝还有部分尚未完全闭合,有利于油气聚集成藏。

Formation mechanism and accumulation model of lithologic reservoirs:a case study with Niuzhuang sub-sag

The process of hydrocarbon accumulation in the lithologic reservoirs in Niuzhuang sub-sag of Dongying depression has been analyzed in respects of hydrocarbon distribution,source rock characteristics,pressure evolution and subtle transport system.The result shows that most of the turbidite reservoirs are multistage episodic reservoirs with allochthonous source rocks.In regional overpressure releasing process,formation water and early charged hydrocarbon in the high pressure turbidite would first discharge via subtle transport system to external rocks and accumulate into upper fractured turbidite.The high pressure turbidite had much better petrophysical property than its surrounding mudstone and shale,therefore pressure release would be more thoroughly.In addition,high pressure mainly formed in mudstone and shale source rocks,the pressure of turbidite would be lower than surrounding mudstone and shale before next releasing.Meanwhile,part of the faults and fractures generated due to high pressure break had not closed yet,therefore were favorable for hydrocarbon accumulation.