The Effects of Fracturing Fluid Imbibition on Fracture Conductivity in Tight Reservoirs

Field observations indicate that larger than 70% of injected water cannot be recovered due to fracturing fluids imbibition during shut-in periods. However, the effects of imbibition on fracture conductivity are still unclear. In this paper, the fracture conductivity and imbibition experiments are conducted, and the correlativity between fracturing fluid imbibition and fracture conductivity damage is analyzed to explore the micro mechanism. The study finds out that fracturing fluid imbibition can obviously reduce fracture conductivity, and the conductivity damage degree of shale is much higher than that of conventional reservoir. After fracturing fluid entering shale, the interaction between shale and fracturing fluids is so strong as to cause the strength weakness and creep aggravation, which results in proppant embedment and fracture conductivity reduction. The interaction strength is not related to imbibition rate, but it is positively correlated with driving force coefficient. The research is significant for a deep recognition on interaction between fracturing fluid and shale.