Quantitative Prediction Method for Post-Fracturing Productivity of Oil–Water Two-Phase Flow in Low-Saturation Reservoirs

The fluid properties of low-saturation reservoirs (LSRs) produced after fracturing are complex and diverse, which makes it difficult to predict the post-fracturing productivity of oil–water two-phase flow and results in a low prediction accuracy. Therefore, based on elliptical seepage theory and nonlinear steady-state seepage formula, a new method for predicting the post-fracturing productivity (PFP) of oil–water two-phase flow in vertical wells in LSRs after fracturing is proposed in this paper. The Li Kewen model is preferred for accurately calculating oil–water relative permeability. Based on the elliptical fracture morphology, a quantitative prediction model for the PFP of oil–water two-phase flow is established. This model incorporates a starting pressure gradient (SPG) to depict the non-Darcy flow seepage law in low-permeability reservoirs. Hydraulic fracturing fracture length, width and permeability are obtained using logging curves and fracturing data, and this model can be applied to the quantitative prediction of PFP of oil–water two-phase flow in LSRs. The research results show that the conformity rate of oil production is 77.5%, and that of water production is 73.2%, with an improvement of over 15% in the interpretation conformity rate. Compared with actual well test productivity, the mean absolute error of the oil productivity prediction is 3.51 t/d, and the mean absolute error of the water productivity prediction is 12.37 t/d, which meet the requirements of field productivity quantitative evaluation, indicating the effectiveness of this quantitative prediction method for predicting the PFP of oil–water two-phase flow.