蚀变对中基性火山岩储层的控制作用:以松辽盆地徐家围子断陷下白垩统营城组为例

利用岩芯、薄片和扫描电镜等资料,综合分析松辽盆地徐家围子断陷下白垩统营城组火山岩储集空间类型和火山岩蚀变控制因素。依据化学蚀变指数(CIA)、黏土矿物测试和岩石矿物特征,将蚀变程度划分为弱蚀变(CIA50)、中蚀变(50CIA60)、强蚀变(CIA60)三种。与蚀变作用有关的成岩作用类型包括:脱玻化作用、溶蚀作用及充填作用。研究结果表明,随着蚀变程度提升,基质脱玻化作用和岩石黏土矿化作用越强,次生孔隙越发育;脱玻化作用和溶蚀作用具明显改善储层物性特征,充填作用虽然降低储层物性,但黏土矿物充填物中存在晶间微孔,仍具有一定储集性能。

Controlling of alteration on intermediate and basic volcanic reservoirs: a case study of Lower Cretaceous Yingcheng Formation of Xujiaweizi fault depression,Songliao Basin

Reservoir space types and controlling factors of alteration of Yingcheng Formation volcanic rocks in Xujiaweizi depression were studied by core data, thin sections and scanning electric microscope. Based on chemical alteration index (CIA), clay mineral test and rock mineral characteristics, the intensity of alteration is divided into three types: weak alteration(CIA<50), moderate alteration(50< CIA< 60)and strong alteration(CIA>60). The types of diagenesis related to alteration include: devitrification, dissolution and filling. It is indicated from this research that more secondary pores were developed with the increasing of alteration intensity, devitrification of matrix and clay mineralization of rocks. Devitrification and dissolution can also improve the reservoir properties. Although cavity filling apparently reduced the reservoir properties, there are intergranular micropores in the infilling of clay minerals, which still has a certain reservoir performance.