四川盆地安岳特大型气田下寒武统龙王庙组优质储层形成的主控因素

间孔，平均孔隙度为4.24%，平均厚度为36m，属裂缝-孔洞型储层及裂缝-孔隙型储层。储层发育的岩相古地理背景为内缓坡相，发育的物质基础是颗粒碳酸盐岩，其纵向演化及横向展布受颗粒滩亚相的控制。龙王庙组优质储层形成的建设性因素包括:①颗粒碳酸盐岩的粒间孔奠定了储集空间形成的基础；②准同生期大气淡水的淋滤溶蚀作用形成了大规模发育的溶蚀孔洞；③同时或稍后发生的准同期白云岩化作用有利于早期孔隙的保存；④加里东期表生岩溶作用改善了储集性能；⑤构造破裂及埋藏溶蚀作用进一步改善了储集性能。储层经历的破坏性作用主要为胶结作用及压实作用，其次为热液矿物充填及沥青充填。沉积及成岩作用综合分析确认，龙王庙组优质储层形成的必要条件是发育颗粒滩，准同生期大气淡水淋滤溶蚀作用、早期白云岩化作用和加里东期的表生岩溶作用分别决定了大面积分布孔洞型储层的形成、早期形成孔隙的保存和最优质孔洞型储层的形成。因此，龙王庙组优质储层形成的主控因素是“优势相带+准同生期大气淡水淋滤溶蚀作用+准同生期白云岩化+表生岩溶作用”。

Main origins of high quality reservoir of Lower Cambrian Longwangmiao Formation in the giant Anyue Gasfield,Sichuan Basin,SW China

The reservoir lithology of Longwangmiao Formation of Lower Cambrian in Anyue giant gas field mainly includes residual granule dolomite and crystalline dolomite.The major reservoir space is dissolved vug,followed by residual intergranular pore and intercrystalline pore.The types of reservoir belong to fractured-vugs and fractured-pores with the average porosity of 4.24% and thickness about 36m.The vertical and horizontal distribution of the reservoir is controlled by grain shoal facies in inner-ramp and the material basis of which is grain carbonate rock.The constructive factors during the reservoir evolution include:(1)The intergranular pore of grain carbonate rocks lay a foundation of the reservoir space generation;(2)Penecontemporaneous atmospheric water eluviation results in the continuous distribution of large-area massive vugs;(3)Penecontemporaneous dolomitization was favorable for the preservation of earlier porosity;(4)Supergene karstification in Caledonian stage improved the reservoir performance;(5)Fracture cracking and burial dissolution improved the reservoir performance further.The destructive effects of the reservoir suffered are mainly cementation and compaction,and then the filling of hydrothermal minerals and bitumen.After sedimentation and diagenesis comprehensive analysis,the following recognitions are summarized.The necessary condition for the formation of high quality reservoir is grain shoal facies;Penecontemporaneous atmospheric water eluviation is the precondition for the formation of vuggy reservoir;Undergoing penecontemporaneous dolomitization is a prerequisite for the preservation of earlier porosity;Supergene karstification superposition is necessary for the formation of best reservoir.So the main controlling factors of high quality reservoir generation are “Advantage Facies+ Penecontemporaneous Atmospheric Water Eluviation+Penecontemporaneous Dolomitization+ Supergene Karstification”.