惠州凹陷东部珠海组储层碱性成岩作用及孔隙演化

根据铸体薄片、扫描电镜、粒度分析、X衍射等资料，对惠州凹陷东部珠海组储层的岩石学特征、成岩作用和孔隙演化过程进行分析研究。研究认为，惠州凹陷东部珠海组储层的岩石类型以岩屑砂岩、长石质岩屑砂岩、岩屑质石英砂岩和岩屑质长石砂岩为主，结构成熟度与成分成熟度较低。砂岩埋藏过程中经历了明显的碱性成岩作用:石英的溶蚀与交代、碳酸盐矿物胶结、伊利石和绿泥石的沉淀以及钠长石化等。碱性成岩作用对孔隙的影响包括:石英溶蚀形成次生溶孔、碳酸盐胶结物沉淀损失粒间孔隙、黏土矿物沉淀形成晶间微孔。研究区珠海组主要发育粒内溶孔和粒间溶孔，原生孔隙较少。储层现今处于中成岩阶段A期，早期经历了强烈的压实作用，使其孔隙度由原始孔隙度32.1%降低至8.8%。早成岩阶段为碱性成岩环境，石英溶蚀增孔约0.5%；碳酸盐、硫酸盐、伊利石等胶结物沉淀减孔约2.3%。中成岩阶段A期为酸性成岩环境，硅质、高岭石等胶结物沉淀减孔约1.2%；长石、岩屑等溶蚀增孔约4.3%。最终，储层演化至现今孔隙度10.1%。

Alkaline Diagenesis and Porosity Evolution of Zhuhai Formation Reservoirs in Eastern Huizhou Sag

The petrological characteristics， diagenesis and porosity evolution of Zhuhai Formation reservoirs in the eastern Huizhou Sag were studied based on data from thin sections， scanning electron microscopy， grain?size analysis and X?ray diffraction. The reservoir rock types are mainly lithic sandstone， feldspathic lithic sandstone， lithic quartz sandstone and lithic feldspathic sandstone with both low compositional and structural maturity. There is clear evidence of alkaline diagenesis during sandstone burial， such as quartz dissolution and metasomatism， carbonate cementation， precipitation of illite and chlorite， and albitization. The alkaline diagenesis has had many effects on pores， including quartz dissolution to form secondary solution pores， carbonate cement precipitation infilling intergranular pores and clay mineral precipitation forming intergranular micropores. The Zhuhai Formation in the study area now contains mainly intra?and intergranular dissolution pores， with fewer primary pores. The reservoirs are at the middle of stage A diagenesis， symptomatic of strong compaction. The original porosity has been reduced from 32.1% to 8.8%. The early diagenetic stage is evidence of an alkaline environment. During this stage， quartz dissolution increased the porosity by about 0.5%， and precipitation of carbonate， sulfate and illite cements reduced porosity by about 2.3%. The middle of stage A diagenesis represents an acidic environment， in which feldspar and debris dissolution increased porosity by about 4.3%. Quartz formed secondary overgrowth edges and kaolinite was precipitated， reducing porosity by about 1.2%. The final porosity is 10.1%.