川中高石梯地区龙王庙组深层白云岩孔隙类型、成因及演化

Porosity Types, Origin and Evolution of Deep-Dolostone of Lower Cambrian Longwangmiao Formation in the Gaoshiti Area in Central Part of Sichuan Basin, SW China

摘要: 川中高石梯地区寒武系龙王庙组是四川盆地天然气勘探生产的重要层位。根据岩心、薄片等资料，对高石梯地区龙王庙组深层白云岩孔隙类型、成因以及其演化进行了研究。龙王庙组白云岩宏观储集空间类型主要有溶蚀孔洞、裂缝，微观储集空间主要有原生的晶间孔、次生的粒间溶孔、晶间溶孔、粒内溶孔、铸模孔、微裂缝等。龙王庙组主要成岩作用经历了同生成岩阶段的胶结作用、白云石化作用、大气淡水溶蚀作用，初次埋藏阶段的压实作用、压溶作用、溶蚀作用、白云石胶结作用，表生成岩阶段的顺层岩溶作用，二次埋藏阶段的胶结作用、构造破裂作用、溶蚀作用、热液作用等。其中，控制有效孔隙的关键因素是沉积微地貌与同生成岩阶段的白云石化、大气水溶蚀作用的匹配关系，岩溶作用及埋藏期的溶蚀–热液作用等控制作用次之。

Abstract: The Cambrian Longwangmiao Formation in Gaoshiti area, central Sichuan Basin, is an important horizon for oil and gas exploration and research. According to the cores, thin-sections and logging data, researches have been done in terms of the deep dolomitic pore types, formation mechanism and evolution. The main macroscopic pore type in Longwangmiao Formation can be divided into dissolved vug and fissures. The microscopic pore types can be divided into primary intercrystalline pores, secondary intracrystalline dissolved pores, intergranular dissolved pores, intercrystalline dissolved pores and microfissures. In the syndiagenetic stage, the diagenesis underwent cementation, dolomitization, atmospheric freshwater dissolution. In the primary burial stage, it underwent compaction, pressure solution, dissolution and dolomitic cementation. In the supergene stage, it underwent parallel karstification, secondary burial cementation, tectonic fracturing, dissolution and hydrothermalism. Among these digenesis, the critical factor controlling the effective pores is the matching relation between sedimentary microtopography and syndiagenetic dolomitization and atmospheric freshwater dissolution, followed by karstification and dissolution-hydrothermalism of the burial period.