Near-Fracture Capillary End Effect on Shale-Gas and Water Production
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Copyright 2018, Unconventional Resources Technology Conference (URTeC). Capillary end effect develops in tight gas and shale formations near hydraulic fractures during flow back of the fracturing treatment water and extends into the natural gas production period. In this study, a new multi-phase reservoir flow simulation model is used to understand the role the capillary end effect plays on the removal of the water from the formation and on the gas production. The reservoir model has a matrix pore structure mainly consisting of a network of micro-fractures and cracks under stress. The model simulates water-gas flow in this network with a capillary discontinuity at the hydraulic fracture-matrix interface. The simulation results show that the capillary end effect cause significant formation damage during the flow back and production period by holding the water volume and saturation near the fracture at higher levels than that based on only the spontaneous imbibition of water. The effect makes water less mobile, or trapped, in the formation during the flow-back and tends to block gas flow during the production. The stress change effects during the production are relatively less important. We showed that the capillary end effect cannot be removed completely but can be reduced significantly by controlling the wellbore flowing pressure and by altering the formation wettability.
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Proceedings of the 6th Unconventional Resources Technology Conference
