Study on a New System of Water Unlocking in Tight Sandstone Gas Reservoirs

Abstract

TIn order to solve the problem of water lock blockage in the wellbore of Daniudi gas field, the main surfactant APG and CG-1, CG-2, WR and other surfactants were used to produce co-energy and synergistic effect through the combination of multiple surfactants. The static properties of the agent were evaluated by measuring the interfacial tension, surface tension and contact Angle of the surfactant system. According to the physicochemical mechanism of the synergistic action of compound surfactants, the water lock of the combination of anionic surfactants and non-ionic surfactants is preferred. A new water unlocking agent system for tight gas reservoirs was developed: APG (0.3%) +CG-1(0.2%) +SYH (0.1%) +KCl (2%). The interfacial tension between the system and simulated oil was 9.61·10^-4 mN/m, the surface tension was 18.2 mN/m, and the gas/liquid/solid three-phase contact antenna was 99.4°. Daniudi tight core (core No. 602-14) was used to simulate the process of high temperature and high-pressure water lock damage. The permeability recovery rate after injection of waterproof lock agent is 25.36% compared with water lock damage.