Nuclear magnetic resonance study on imbibition and stress sensitivity of lamellar shale oil reservoir

The imbibition phenomenon widely exists in the fracturing and production process of shale oil and gas. It is of great scientific and engineering significance to elaborate the mechanism of infiltration and its influencing factors. In this paper, the impact of imbibition fluid types is investigated, and the influence mechanism of fluid imbibition on matrix-bedding permeability is clarified. Results shown that (a). The total porosity of 18 # core under saturated formation water condition is 8.75%. The porosity of movable fluid is 7.36%. The total porosity under saturated strong acid is 9.74%. (b) The total porosity of shale under saturated formation water condition of 6–4 # core is 4.03%. The porosity of movable fluid is 3.73%. The total porosity under the condition of maximum damage of alkaline fluid is 3.47%. (c) Slick water has no effect on the total porosity of shale in the study area. The total porosity of 8 # core under saturated formation water is 3.19%. The porosity of movable fluid is 2.57%. •The impact of imbibition fluid types is investigated.•The response mechanism of imbibition fluid types of shale pore structure is revealed.•The influence mechanism of fluid imbibition on matrix-bedding permeability is clarified.