Experimental study on elastic development characteristics and imbibition mechanism of shale oil reservoirs at micro-nano scale

The elastic development characteristics of shale oil reservoirs varies significantly, and the basic research on the flow mechanism and the influence of different factors at pore scale is not yet in-depth, so macro analysis lacks strong support. Aiming at the continental shale oil reservoir in the Jiyang Depression of the Bohai Bay Basin in Eastern China, innovatively established natural pore structure model chips at micro-nano scale, and established a visualization experimental method for dynamically observing the entire stages including fracturing, soaking, and development. On this basis, the flow mechanism of elastic development and the influence of pore structure, wettability, and soaking time were researched. The results shown that during elastic development, enhanced imbibition promoted the diffusion of fracturing fluid to matrix pores, shortened the oil breakthrough time, and the fracturing fluid backflow rates decreased by 30% to 50%, effectively enhanced recovery. Water-wet was the imbibition foundation, and the imbibition efficiency of complex pore structures improved by 3% to 6%. Additionally, the imbibition efficiency was logarithmically linearly correlated with soaking time, proper soaking could improve the imbibition efficiency and production capacity. This research provides guidance for sweet spot evaluation and development plans optimization of shale oil reservoir.