Study on fluid mobility in shale oil reservoirs considering mineral composition and stress sensitivity

Shale oil has gradually become an important alternative resource to conventional oil in the world. It is necessary to study the mineral and stress sensitive characteristics of shale oil reservoir to understand the mobility of reservoir fluid. In this paper, two representative shale cores with different components (type 1 layered limy dolostone and type 2 laminated dolomitic limestone) are selected. The effects of core minerals and stress sensitivity on reservoir fluid flow are compared and analyzed. The stress sensitivity of type 2 cores is higher than that of type 1 cores. The saturated oil content of type 1 cores under high temperature and pressure is significantly higher than that of type 2 cores. The imbibition results show that the Bohai drilling (BH) imbibition fluid has obvious imbibition displacement effect on the oil in the large pore (>100 nm) of the core, and the recovery rate is high. Halliburton (HL) imbibition fluid has more obvious imbibition displacement effect on oil in medium and small pores (10–100 nm), and the recovery rate is lower. Shale oil reservoirs with higher brittle mineral content have lower stress sensitivity and more mobile fluid, which is conducive to fracturing and imbibition displacement. However, the shale oil reservoir with high clay mineral content has strong stress sensitivity and poor fluid mobility, which is not conducive to the development of shale oil. This study pioneers the shale oil productivity evaluation from the perspective of mineralogy.