高磨地区龙王庙组滩相储层特征及主控因素

Characteristics and main controlling factors of Lower Cambrian Longwangmiao Formation beach-facies reservoirs in Gaoshiti-Moxi area,central Sichuan Basin

通过岩心观察、薄片鉴定及物性测试等手段,认为高磨地区龙王庙组总体为低孔低渗型储层,局部为低孔高渗型储层。储集岩以砂屑云岩、鲕粒云岩、粉-细晶云岩和花斑状粉晶云岩为主。储集空间包括粒间溶孔、晶间(溶)孔、粒内溶孔及铸模孔、残余粒间孔、膏模孔、溶洞和裂缝。储层类型分为密集顺层溶洞型晶粒云岩储层(Ⅰ-1类)、溶洞型颗粒云岩储层(Ⅰ-2类)、针孔和孤立小洞型颗粒云岩储层(Ⅱ-1类)、针孔型晶粒云岩储层(Ⅱ-2类)、溶孔和零星小洞型"花斑状"晶粒云岩储层(Ⅲ类)(储层物性依次变差)。岩性、沉积微相、白云化作用和溶蚀作用是影响龙王庙组储层发育的关键因素。滩核的砂屑云岩及云坪的粉晶云岩最有利于储层发育。第一期准同生白云化作用利于孔隙的保存。准同生期溶蚀作用和表生期岩溶作用是龙王庙组产生大量溶孔溶洞的关键因素。埋藏岩溶作用进一步改善储集性能。

Based on the methods of core observation, identifying thin sections and physical property testing, it is indicated that the reservoir in Gaoshiti - Moxi area Longwangmiao Formation mainly belongs to the low porosi-ty ,low permeability reservoir, partly to the low porosity, high permeability reservoir. The reservoir is mainly composed of arene dolomite, oolitic dolomite, powder-crystal dolomite and u piebald ＂ powder＂ dolomite, and the reservoir spaces mainly include intergranular dissolved pores, intercrystalline dissolved pores, intragranular dis-solved pores and moldic pores, residual intergranular pores, gypsum mould pores, caves and fractures. The res-ervoirs can be subdivided into five types ： crystal grain dolostone reservoirs with dense bedding caves （ Type I -1） , grain dolostone reservoirs with caves （Type I - 2 ） , grain dolostone reservoirs with pinholes and sepa-rate caves （Type II - 1 ） , crystal grain dolostone reservoirs with pinholes （ Type II - 2 ） , “ piebald” crystal grain dolostone reservoirs with dissolved pores and separate caves （ Type IH ） （ the reservoir physical property varies worse and worse successively） . Lithology, sedimentary microfacies, dolomitization and karstification are the keys for the development of dolomite reservoir of Longwangmiao Formation. The arene dolomite of shoal core and powder dolomite of dolomite flat are the most important factors to the reservoir. The first penecontemporane- ous dolomitization is beneficial to pores reservation. Penecontemporaneous karstification and epigenesis karstifi-cation are the key factors to produce dissolved pores and caves. Burial karstification improves the reservoir per- fbrmance further.