裂谷盆地岩浆侵入对泥质围岩储集性能的影响——以东营凹陷纯西地区辉长岩为例

Influence of magma intrusion on reservoir features of surrounding mud rocks in rift basin-case study of gabbros in Chunxi area of Dongying Sag

岩浆侵入活动大大改变了其周围泥岩的储集性能,对油气聚集具有重要意义。通过岩心观察系统分析了东营凹陷纯西地区沙河街组侵入岩周围泥岩中裂缝的类型、特征和形成机理。岩浆侵入时的瞬时高压引起泥质围岩的脆性破裂,形成拉张和挤压裂缝;岩浆的高温一方面使周围泥岩产生水热增压和生烃增压而形成大量微裂缝,另一方面还使围岩中的矿物发生热变质作用,为后期形成构造裂缝奠定了基础。最终岩浆将周围泥岩由非储层变为特殊的、发育多种裂缝的较好储层。

Magma intrusion changed reservoir features of surrounding mud rocks greatly in rift basins, which has important significance on oil-gas accumulation. Types,characteristics and forming mechanism of the fractures in the surrounding mud rocks of irruptive rocks are researched systematically in the Shahejie Formation of Chunxi area in Dongying Sag according to core observation. The moment high pressure of magma intrusion caused brittle fracture of the surroundings mud rocks,and tension and compression fissures formed. High temperature of the magma increased pressure and generated a lot of microfissures in the surrounding mud rocks because of hydrothermal activity and hydrocarbon generation. And the high temperature made minerals in the mud rocks thermal metamorphism. It established the foundation for the tecto-clase formation at later period. Finally,the magma made the surrounding mud rocks special good reservoirs of various fissures.