川西雷口坡组四段上亚段储层特征及成因机理

Reservoir Characteristics and Genetic Mechanism of Upper Section of the Fourth Member of Leikoupo Formation in Western Sichuan

为明确川西雷口坡组四段上亚段储层特征及成因机理,基于野外露头、岩心、测井和地震等资料,结合实验分析数据,对其进行了系统分析。研究表明:川西雷口坡组四段上亚段储层岩性以微粉晶白云岩和藻纹层白云岩最为有利。平均孔隙度3.7%,平均渗透率9.31×10^(-3)μm^(2),下储层段物性明显好于上储层段。主要储集空间为成岩组构溶蚀孔洞。白云化及组构选择性溶蚀等建设性成岩作用主要发生于沉积-成岩早期。(藻)云坪是优质储层发育的沉积基础。准同生白云石化和溶蚀作用是优质储层发育的关键。优质储层多发育在向上变浅高频旋回中上部藻纹层中。储层发育有利区平面上在川西中部,呈北东—南西向展布。

The reservoir characteristics and genetic mechanism of the upper section of the fourth member of the Leikoupo Formation in western Sichuan was systematically analyzed on based on field outcrop,core,logging and seismic data,and experimental analysis data.Research shows that the most favorable lithology for this reservoir is microcrystalline dolomite and algal layered dolomite.Average porosity and average permeability of the reservoir is 3.7%and 9.31×10^(-3)μm^(2)separately,the physical properties of the lower section of the reservoir are significantly better than those of the upper section.The main storage space is diagenetic fabric dissolution pores.Constructive diagenesis such as dolomitization and fabric selective dissolution mainly occur in the early stages of sedimentation-diagenesis.Carbonate tidal flat is the sedimentary foundation for the development of high-quality reservoirs.The metascontemporaneous dolomitization of microorganisms is the key basic condition for the development of high-quality reservoirs in carbonate tidal flat.Quasicontemporaneous dolomitization and dissolution are key factors for the development of high-quality reservoirs.High-quality reservoirs are mostly developed in the upper and middle algal layers of high-frequency cycles.The favorable area is located in the central part of western Sichuan on the plane,extending in a northeast-southwest direction.