川中地区下二叠统白云岩储层特征及发育主控因素

CHARACTERISTICS AND MAIN DEVELOPMENT CONTROLLING FACTORS FOR LOWER PERMIAN DOLOMITE RESERVOIRS IN CHUANZHONG REGION

为进一步深化对川中地区下二叠统白云岩储层特征及发育主控因素的认识,利用研究区茅口组的岩心、岩屑、薄片鉴定、扫描电镜、碳氧同位素、阴极发光及流体包裹体分析等资料,采用地质分析与地化分析相结合的方法,从岩石学、岩石地球化学及储集空间发育特征等方面进行研究。研究结果表明:茅口组白云岩主要发育砂糖状白云岩、中—细晶白云石、角砾白云岩及少量灰质白云岩,储集空间以溶孔和溶洞为主,溶缝和粒内溶孔次之,白云岩形成过程几乎不受埋深的影响,没有或很少有淡水参与,主要形成于构造—热液环境;储层的岩性组成、白云化作用、构造作用及溶蚀作用是茅口组白云岩储层发育的主控因素,储层的岩性组成是白云岩储层发育的物质基础,适度白云化作用是储层发育的必要条件,构造作用是储层最终发育和空间展布的关键,溶蚀作用是白云岩储层空间展布的重要因素。

In order to further understand the characteristics and developmental controlling factors of Lower Permian dolomite reservoirs in Chuanzhong region,with the help of the data of Maokou Formation in the study area,such as core,cuttings,thin section identification,scanning electron microscopy,carbon and oxygen isotopes,cathodoluminescence and fluid inclusion analysis and so on,and moreoverthe combined method between thegeological and geochemical analyses,the researches were conducted on the petrology,rock geochemistry,reservoir space development characteristics and some other aspects. The study achievements show that the saccharoidal dolomite,medium-fine crystalline dolomite,breccia dolomite and a small amount of gray dolomite are mainly developed in Maokou Forma-tion,the reservoir spacesare mainly composed of dissolved pores and karst caves,the next are fissures and intragranular dissolved pores,the formation process of the dolomite is almost unaffected by the depth of the burial,and there is little or no involvement of the fresh water,mainly formed in the structural-hydrothermal environments; the lithological compositions,dolomitization,tectonism and dissolution are the principal controlling factors of the dolomite reservoirs developed in Maokou Formation,among them,the lithological compositionsare the material basis for the development of the dolomite reservoirs,the moderate dolomitization is the necessary condition for the development of the reservoirs,the tectonism is the key to the reservoirfinal development and spatial distribution,the dissolution is the important factor in the spatial distribution and spread of the dolomite reservoirs.