Flow physics of how surfactants can reduce water blocking caused by hydraulic fracturing in low permeability reservoirs

摘要

Significant amount of fracturing fluid is lost after hydraulic fracturing, and it is believed that the loss of fluid into the matrix can hinder the hydrocarbon production. One potential way to reduce this damage is to use surfactants. Robust surfactant formulations have been developed for chemical enhanced oil recovery (CEOR); similar screening methods are introduced in this study to reduce the water block in low permeability reservoirs. Here we present an experimental investigation based on a coreflood sequence that simulates fluid invasion, flowback, and hydrocarbon production within the rock near the fracture face. Real-time CT scans are applied to visualize the change of water saturation profile, which is then compared with the regaining of rock permeability. Different surfactants are used to test the effect of IFT reductions and formation of microemulsions; these are further compared in order to explore the best condition that maximizes the permeability enhancement. From this work, we recognize the main physical mechanism responsible for the potential enhancements after the use of surfactants, thus we suggest criteria to optimize the performance of surfactant additives for stimulating the low permeability gas/oil reservoirs.