Prediction of the Optimal Post-Fracturing Soaking Time in Multifractured Shale Gas/Oil Formations on the Basis of Modeling of Fluid Imbibition

Abstract

Post-fracturing fluid soaking is believed to significantly affect productivity of hydraulic-fractured horizontal wells in the oil and gas industry. It is highly desirable to know the optimal soaking time period to maximize well productivity. An analytical model was developed in this research to describe the dynamic spontaneous imbibition process in shale cracks owing to fluid soaking. The model was integrated with pressure falloff data to develop a mathematical approach for forecasting the optimal soaking time, which is defined as the time it takes for the fluid to reach the midpoint between two adjacent hydraulic fractures. The optimal soaking time depends on crack and fluid properties, including crack width, fluid contact angle, and interfacial tension (IFT). A case study from the data of Tuscaloosa Marine Shale (TMS) suggests that the optimal soaking time is 2–4 weeks if the fracturing spacing is 4–6 m. This work provides petroleum engineers with a quick-and-easy method for predicting the optimal soaking time to maximize their well productivity.