川西北中泥盆统观雾山组储层特征及其主控因素

Reservoir Characteristics and Main Control Factors of Middle Devonian Guanwushan Formation in Northwest Sichuan

为明确川西北观雾山组储层特征及主控因素,通过野外剖面及岩心观察、铸体薄片鉴定、扫描电镜、阴极发光、微米CT扫描、孔渗及地球化学测试等对其进行了分析。研究表明:川西北观雾山组储层岩性主要为生物礁白云岩、生屑白云岩和角砾状细-中晶白云岩。主要储集空间为生物体腔孔、晶间孔和溶蚀孔洞。孔隙度平均值为2.58%,渗透率平均值为0.71×10^(-3)μm^(2)。储层发育主要受沉积相、白云石化及岩溶作用控制。台缘礁滩及台内高能滩是储层发育的有利相带。有序度、阴极发光、锶同位素和稀土元素特征表明,同生-准同生期白云石化作用形成储层基础。高频沉积旋回控制的准同生溶蚀和构造抬升控制的表生岩溶改造是储层形成的关键。埋藏成岩阶段烃类成熟释放的酸性流体对储层改造也有改善。

The reservoir characteristics and main controlling factors of the Guanwushan Formation in northwestern Sichuan were analyzed by means of field profile and core observation,casting thin section identification,scanning electron microscopy,cathodoluminescence,micrometer CT scanning,and porosity,permeability and geochemical characteristic testing.The results show that the reservoir of the Guanwushan Formation in northwestern Sichuan is mainly composed of biogenicreef dolomite,bioclastic dolomite and brecciated fine-medium crystalline dolomite.The storage space of the reservoir is mainly composed of biological cavities,intergranular pores and dissolution pores.Its average porosity is 2.58%,and the average permeability is 0.71×10^(-3)μm^(2).The development of the reservoir is mainly controlled by sedimentary facies,dolomitization and karstification.The platform edge reefs and high-energy tidal flats within the platform are favorable facies zones for reservoir development.The orderliness,cathodolum inescence,strontium isotopes,and rare earth element characteristics indicate that the dolomitization in the syngenetic to quasi-syngenetic period is the foundation for the formation of the reservoir,and the quasi-synchronous dissolution controlled by high-frequency sedimentary cycles and the surface karstification controlled by tectonic uplift are the key to the formation of the reservoir.The acidic fluids released by the maturation of hydrocarbons in the burial diagenesis stage improved the reservoir.