Reducing Surfacel Tension to Improve Clean Up Efficiency of Hydraulically Fractured Wells - Does it Really Work? (SPE 154894)

The main purpose of applying surfactants for hydraulically fractured wells is to reduce interfacial tension (IFT) during the leak off process. Much of the research up to now has been concentrated in developing different types of such chemicals. However, in a recent numerical study (SPE-14414), we have shown that for many practical ranges of fracture permeability reducing IFT tends to decrease the cleanup efficiency process. Following our previous study, we have conducted a comprehensive sensitivity study to identify the effect of IFT over a wide range of variation of pertinent parameters, which controls the cleanup efficiency process. We have looked at the impact of matrix permeability (km), fracture permeability (kf) and fracture fluid injection volume. Over 200 runs were performed to evaluate the impact of these pertinent parameters for a single fractured well model. The results indicate that at the early stage of production the cleanup efficiency is almost independent of IFT, km and kf and relatively poor. At late stages of production and when kf is low, reducing IFT decreases the efficiency of cleanup. For high kf values, on the other hand, cleanup efficiency improves with such a reduction. For the cases with km values more than 0.001, the cleanup is more effective if IFT increases. Furthermore as km decreases the damage due to fracture fluid blockage becomes more sever. It is interesting to note that when km is less than 0.0001, cleanup efficiency always decreases with IFT for all different kf values indicating the severity of fracture fluid damage for very tight gas reservoirs. Increasing the fracture fluid injection volume did not significantly change the above trend. The results presented here help the industry in properly evaluating the added value of using surfactant for the hydraulically fractured wells during cleanup process.