Abstract
In unconventional water-wet gas reservoirs with very low permeability, water entrapment or blockage can occur near the wellbore due to the capillary end effect, resulting in low gas production. A reduction in capillary forces through wettability alteration of reservoir rock surface is proposed as an effective approach to reduce water blockage and enhance gas production. The method can be applied to accelerating dewatering and preventing drilling and fracturing fluid leak-off as well. Analytical models for steady-state water-gas linear and radial flows are developed in the current paper. The effects of contact angle on capillary pressure and relative permeabilities have been included. The new model is validated using experimental data. Applications to fully and partially treated regimes show the competition between viscous and capillary effects on productivity of gas and water, which leads to an optimal contact angle for the maximum productivity index for each phase. This study shows the potential for optimising unconventional gas productivity through wettability control. Application of nanotechnology to rock wettability alteration is proposed.
