Imbibition is an important mechanism for resource development in tight reservoirs. Scaling models describe the mathematical relationship between imbibition cumulative production and time, which is important when associating experiments with reservoir behavior. For tight reservoirs, diffusion and water sensitivity have a great influence on imbibition, and the scaling effect of the classical model is poor and needs to be modified. In this study, nuclear magnetic resonance (NMR) method was used to test the imbibition process of eight samples, and a new model considering diffusion and water sensitivity was proposed, and the scaling effect of the new model was verified by the experimental results. The results show that diffusion and water sensitivity have an important influence on the imbibition of tight reservoirs. A new parameter of imbibition diffusion radius is proposed. It has two characteristics. One is that it increases with the increase of imbibition recovery rate, which can reflect the diffusion capacity, and the other is that it decreases with the increase of small holes, which can reflect the influence of water sensitivity. Compared with the average radius used by the classic model, it can better describe the process of tight reservoir imbibition. The scaling effect of the new model modified with new parameters is better than that of the classic model, and the dispersion of imbibition curve is well eliminated, which can make laboratory imbibition data more conveniently used to guide reservoir production. The research results provide a new model and experimental reference for the development of unconventional oil and gas resources.
Keywords Tight oil, imbibition, scaling models, diffusion effect, water sensitivity