四川盆地中部嘉二段储层特征及成因

Characteristics and genesis of reservoirs in Lower Triassic Jialingjiang Formation,central Sichuan Basin,China

通过钻井、录井、测井及岩心等大量资料的综合分析,系统识别出鲕粒灰岩储层、砂屑云岩储层和粉晶云岩储层是四川盆地中部地区下三叠统嘉陵江组嘉第二段主要的碳酸盐岩储层。鲕粒灰岩储层以孤立的粒内溶孔和铸模孔为主要储集空间,孔隙间喉道欠发育,以微喉为主,中孔微喉的配置关系导致储层多表现为中孔低渗、渗透率偏低的特征;砂屑云岩储层以残余粒间孔和粒间溶孔为主要储集空间,孔隙间喉道发育,以缩颈喉道为主,较好的孔喉配置关系使储层多表现为中孔中渗、储渗能力较好的特征;粉晶云岩储层以晶间孔和晶间溶孔为主要储集空间,孔隙间喉道以片状喉道为主,孔喉配置关系较好,储层多表现为中孔中渗的特征。储层成因分析结果表明,沉积微相是储层形成的沉积基础,分别形成于鲕滩微相、砂屑滩微相和云坪微相中的鲕粒灰岩、砂屑云岩和粉晶云岩为储层的形成提供了早期物质基础;台地内次一级微地貌高地为储层形成提供了有益的微地貌条件;同生期大气淡水淋溶、原生粒间孔保存和白云岩化作用分别是鲕粒灰岩储层、砂屑云岩储层和粉晶云岩储层形成的关键。

Through a comprehensive analysis of the data on the drilling, logging and core in Member 2 of Lower Triassic Jialingjiang Formation （T1 j2 ）, the authors consider that oolitic limestone reservoirs, dolarenite reservoirs and crystal dolomite reservoirs are important reservoir types in T1 je of central Sichuan Basin. The oolitic limestone reservoirs are dominated by isolated intragranular solution holes and moldic pores in the reservoir space. Between the pores, there are less developed throats mainly being miniature, leading the reservoirs to manifest medium porosity and low permeability. The dolarenite reservoirs are dominated by residual intergranular pores and intergranular solution holes in the reservoir space. Between pores, there are well developed throats mainly being neck down, leading to the good reservoir capability with medium porosity and permeability. The powder crystal dolomite reservoirs are dominated by intercrystal pores and intercrystal solution holes in the reservoir space. Between the pores there are well developed throats mainly being lamellar, and the configuration relationship between pores and throats is better, and the reservoirs are characterized by medium porosity and permeability. The analysis result of the reservoir genesis shows that sedimentary microfacies are the precondition to form reservoirs. The oolitic limestone, psammitolite dolomites and crystal powder dolomites developing where all of those rocks in the microfacies of oolitic shoal, psammitolite shoal and dolomitic flat respectively, provide the material base for the formation of the reservoirs. A sub-microtopography highland in the platform can provide profitable conditions for the reservoir development. The syndiagenetic meteoric leaching is the key to form the oolitic limestone reservoirs, the preservation of primary intergranular pores is the key to form the dolarenite reservoirs, and the dolomitization is the key to form the powder crystal dolomite reservoirs.