Experimental evaluation of the salt dissolution in inter-salt shale oil reservoirs

Abstract

By using salt dissolution experiment, imbibition experiment and high temperature and high pressure nuclear magnetic resonance (NMR) on-line test, the evaluation methods for salt dissolution of inter salt shale oil-bearing cores were established, and the effects of salt dissolution on spontaneous imbibition and permeability were analyzed. The intensity of salt dissolution is quantitatively evaluated by comparing the signal quantity and distribution characteristics of T2 spectrum (transverse relaxation time) measured at different times. In salt dissolution experiment, salt in the core is gradually dissolved as the injected water is continuously immersed in the core. The spontaneous imbibition experiment of inter-salt shale oil-bearing core can be divided into three stages: strong imbibition and weak salt dissolution, strong salt dissolution promoting imbibition, and weak salt dissolution and weak imbibition. The salt dissolution in spontaneous imbibition is very obvious, and the salt dissolution contributes more than 60% of recovery. The micro-pore structure in different cross sections or different parts of inter-salt shale oil-bearing core isn't uniform, and the pore volume, porosity and permeability increase after salt dissolution.