双鱼石构造栖霞组白云岩储层特征及主控因素

Characteristics and Main Controlling Factors of the Middle Permian Qixia Formation Reservoir in Shuangyushi Structure

针对川西北双鱼石构造栖霞组白云岩储层特征及主控因素问题,以野外剖面实测、岩芯观察描述及钻测井资料为基础,结合普通镜下薄片、铸体薄片、扫描电镜及阴极发光等分析手段,探讨储层发育特征及主控因素。结果表明,栖霞组储层沿龙门山山前带呈北东-南西向展布,厚度在10~40 m;储层以台地边缘滩相的晶粒白云岩和少量颗粒白云岩为主;储集空间类型以溶蚀孔(洞)为主,裂缝次之;孔隙度频率分布主要集中在1.0%~4.0%,渗透率主要集中在0.001~10.000 mD;储集类型主要为裂缝-孔隙(洞)型储层。栖霞组储层的发育及分布主要受沉积相带、沉积古地貌、成岩作用及后期构造破裂等因素控制,沉积作用提供了储层发育的物质基础;沉积古地貌则控制了高能颗粒滩相的分布范围;准同生期淡水淋滤溶蚀不但形成了大量的次生溶蚀孔洞,还提供了白云石化流体运移的通道;埋藏白云石化作用最大限度地继承和保存了早期的孔洞系统;后期构造破裂形成的裂缝则进一步连通了孔洞系统。

For the characteristics and main controlling factors of dolomite reservoir in Qixia Formation of Shuangyushi structure in northwestern Sichuan Basin,based on field outcrop,core and well logging data,combined thin section analysis,casting thin section,SEM,cathodoluminescence,this paper analyzes the development characteristics and main controlling factors of dolomite reservoirs in this area.The results show that the reservoirs are distributed in the NE-SW direction along the front of the Longmenshan mountain,with a thickness between 10 and 40 m.The reservoirs which develop in the shoal of platform margin facies are mainly crystalline dolomites,followed by a small amount of grain dolomites;The reservoir spaces are dominated by dissolution pores(vugs),followed by a small amount of cracks;The porosity of Qixia Formation reservoirs ranges from 1%to 4%,the permeability ranges from 0.001 mD to 10.000 mD;the reservoir types are mainly fracture-pore(vug)type.The development and distribution of reservoirs are controlled by sedimentary facies,sedimentary paleogeomorphology,diagenesis,and late tectonic fracture.Sedimentation provides the material basis for reservoir development and sedimentary highlands of paleogeomorphology control the distribution of high-energy shoal area;Penecontemporaneous atmospheric water eluviation not only forms a large number of secondary dissolution pores(vugs),but also provides migration pathway for the fluid of dolomitization;The early pores(vugs)are maximally inherited and preserved during the stage of the shallow burial dolomitization;The cracks formed by the late tectonic fracture further connect the pores(vugs)system.