CHARACTERISTICS AND CONTROLLING FACTORS OF SANDSTONE RESERVOIR OF DONGYING FORMATION IN SHENXIAN DEPRESSION, JIZHONG SUB-BASIN

The sandstone reservoir of the Dongying Formation in the Shenxian Depression, Jizhong Sub-basin is primarily composed of feldspathic lithic sandstone and lithic sandstone of low maturity. This means that the deposits come from multiple provenances and are close to the provenances. According to the conventional core analysis data, thin sections and scanning electron microscopic (SEM) data, the main pore types of the reservoir include primary and secondary pores, of which the primary intergranular pores dominate. The porosity and permeability data in the study area shows that the reservoir mainly belongs to a kind of high-porosity and mid-permeability. According to the standard for reservoir evaluation in the Shenxian Depression, there are four types of reservoirs, and the reservoirs of Dongying Formation are mainly of type Ⅰand type Ⅱ. The Dongying Formation in the Shenxian Depression is mainly a braided stream facies, which is the key factor controlling the reservoirs sand types, distribution pattern and later stage diagenetic reconstruction. The properties of the reservoirs are controlled by both the processes of deposition and diagenesis. The reservoirs have undergone three types of diagenesis, i. e. mechanic compaction, cementation and dissolution, and the former two are the main factors controlling the pore evolution.