川中金华油田大安寨段介壳灰岩储集空间演化与油气关系

SHELL LIMESTONE RESERVOIR SPACE EVOLUTION AND ITS SIGNIFICANCE IN OIL AND GAS OF DAANZHAI MEMBER IN JINHUA OIL FIELD CENTRAL SICHUAN

金华油田位于四川盆地中部，其产层下侏罗统大安寨段介壳灰岩为滨湖高能生物介壳滩相沉积。介壳灰岩层薄、致密、非均质性强，属低孔、低渗孔隙—裂缝性储层。储集空间类型主要为次生溶蚀孔、洞、裂缝及微孔隙和微裂缝，其多期叠加即形成了独特的被致密岩体所遮挡的具有一定体积和连通范围的相对独立的储渗体圈闭，即孔隙—裂缝系统圈闭。储集空间演化分为同生—早成岩、中成岩、晚成岩和后生四个阶段，其中后两个阶段是形成油气藏的主要阶段。储集空间发育主要受成岩后生作用、构造作用等多重因素的控制。位于生油中心上倾方向早期形成的古隆起，由于来自生油岩的压释水和烃类化合物优先选择其储集空间发育的部位，并且阻碍了孔、洞、缝中次生矿物的沉淀，使储集空间得以保存，有利于油气聚集形成油气藏。

Jinhua oil field is located in the centre of Sichuan basin. The oil producing stratum belongs to Daanzhai Member of lower Jurassic. The sedimentary facies of the shell limestone is shore lacustrine shell beach with high energy hydrodynamic environment. The shell limestone is thin bed,compact and anisotropism, so the reservoir is of low porosity, low permeability and pore fracture character. The ma-jor pore types are secondary corrasion pore, cavern, kluftkarren, micropore and microfracture. The pores with multiage stack form reservoir permeability traps with some volume and interconnection. They are pore fracture system traps screened by tight rocks. Reservoir space.evolution is divided into syn earlydiagenetic, middlediagenetic, latediagenetic and epigenetic stage. Late two stages are main reservoir forming stages. The development of reservoir space is controlled by sedimentary microfa-cies, diagenetic structure and source reservoir factes combination. The pressure relief water, and hy-drocarbon compound from source rock first entered in the reservoir space of early palaeoupfold located in updip from source centre, and jammed secondary mineral precipitation in pore,cavern and fracture, made the reservoir space preserved. So oil and gas moved in the reservoir and accumulated in the traps.