Abstract

After hydraulic fracturing, the flow-back of fracturing fluid is necessary before the gas production starts. A review of fracture treatments indicates that the incomplete return of treating fluids is a reason for poor gas production. It is believed that the water blockage in tight sand limits flow-back in low permeable gas wells. In this paper, it is proposed to reduce water blockage effects by wettability alteration in a fracture plane surface by introducing a novel set of materials that alter the wettability of the sand from a largely water-wet state to a less water-wet state. Consequently, this decreases the water imbibition from fracture face into the matrix and also reduces the capillary holdup. Four different easy to obtain, non-hazardous materials namely, talc, polytetrafluoroethylene (PTFE), activated carbon and silica nanopowder were evaluated for their efficiency to alter the wettability using contact angle measurements and spontaneous imbibition tests. The results of such study indicate that the PTFE was the best material by improving the wettability by more than 90 degrees and decreasing the water imbibition rate by 7 times. However, if a non-polymer solution is required, talc is a good alternative with moderate results. It is a readily available mineral and non-toxic. To determine how these results translate in terms of incremental recovery of the flow-back and the gas production, a coupled fracture propagation model with multiphase reservoir simulation has also been performed. The results predict an overall increase of gas production and a better water flow-back.

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