柴达木盆地石灰沟地区下古生界碳酸盐岩储层特征及控制因素

The characteristics and controlling factors of the Lower Plaeozoic carbonate reservoirs in Shihuigou Area,Qaidam Basin

基于对柴达木盆地石灰沟地区下古生界野外剖面的踏勘实测及样品采集,综合应用薄片观察、扫描电镜,以及常规物性分析方法,对下古生界碳酸盐岩储层的储集特征及控制因素进行了研究。研究结果表明:储层原生孔隙不发育,物性相对较差,但次生孔隙,如溶蚀性孔洞、裂缝及孔洞-裂缝等孔隙类型优势发育;储层性质的控制因素主要为岩石组构、成岩演化和构造运动等。通过对各种因素的综合分析,认为储层的孔喉结构是以原生孔隙为基础,经后期复杂的成岩作用及多期构造叠加改造而成的;先期的溶蚀是受岩石组构控制的选择性溶蚀,而后期构造运动产生的缝隙是溶蚀性储层发育的关键因素。

Being an important type of reservoir in Qaidam Basin,carbonate reservoirs developed widely in the northeast of Qaidam Basin. Based on the field profile survey and samples collection of Lower Palaeozoic in Shihuigou Area of Qaidam Basin, the characteristics and controlling factors of the Lower Paleozoic carbonate reservoirs were studied by means of thin section observation, scanning electron microscopy(SEM) and conventional physical property analysis.The results show that the reservoir primary pore does not develop and the physical property is relatively poor.However, secondary pores such as the dissolution pore, fractures and other type of pore develop. The controlling factors of reservoir properties are selective dissolution, diagenesis and tectonic movement. Through comprehensive analysis of various factors, it is concluded that the pore throat structure of the reservoir is based on the primary pores and reformed by complex diagenesis and the superposition of multi-period tectonism in the later period. The early dissolution is the selective dissolution controlled by the rock fabric, while the crevice produced by the later tectonic movement is the key factor for the development of dissolution reservoir.