南堡凹陷周边寒武-奥陶系碳酸盐岩储层特征及成岩作用

FEATURES AND DIAGENESIS OF CAMBRIAN-ORDOVICIAN CARBONATE IN PERIPHERAL OF NANPU SAG

基于大量的薄片及岩心观察,运用电镜扫描、X射线衍射、物性分析、铸体压汞等手段,对寒武-奥陶系碳酸盐岩储层进行了研究,探讨了成岩作用特征及孔隙演化模式。表明灰岩和白云岩为碳酸盐岩储层的主要岩石类型,以孔、缝、洞为主要储集空间,由于受连通性以及充填作用的影响,构造裂缝的储集性能更为优越。储层基质孔隙差,白云石化作用、溶蚀作用、压实和压溶作用、胶结及充填作用以及构造作用为区内主要的成岩作用类型。碳酸盐岩孔隙演化主要经历了两个阶段:早期原生孔隙形成与收缩阶段、中晚期的次生缝、孔、洞发育与充填阶段;早期碳酸盐岩沉积时孔隙大,经初期成岩和埋藏后,失去了主要孔渗性能;中晚期的次生缝、孔、洞十分发育,但充填严重,晚期的构造缝及溶蚀孔、洞被部分保存。

Based on thin section and core, scanning electron microscope, X-ray diffraction, physical property analysis, casting section, Cambrian-Ordovician carbonate reservoir was studied, and the diagenesis and the porosity evolution pattern were discussed. It suggests that the main rock types of carbonate include limestone and dolomite. The primary reservoir space consists of hole, fissure and cave. As for the connectivity and filling, structural fracture is favorable for hydrocarbon accumulation. In this zone it is characterized by the lower matrix porosity for carbonate, which experienced many diagenesis stages, such as dolomitization, dissolution, compaction and pressure solution, cementation, filling, fracturing. Porosity evolution of Cambrian-Ordovician carbonate involves two stages, including porosity formation and shrinkage in the early stage, secondary fissure-hole-cave developing and filling in middle period and late stage. In early stage carbonate is characterized by big hole, but after the initial diagenesis and burial it loses most of the permeability. Yet in middle period and in late stage the secondary fissure-hole-cave of carbonate develops well but is filled heavily, the late tectonic fracture and dissolved pores and holes are preserved partly.