Analysis and Evaluation of the Drying Effect in Tight Sandstone Reservoirs

Abstract

As hydraulic fracturing technology has been widely used in the exploitation of tight gas sandstone reservoirs, the retention of hydraulic fracturing fluid will cause water locking damage to tight gas sandstone reservoirs and it can seriously affect the development of gas reservoirs. Selective injection of drying agents into tight sandstone reservoirs can effectively decrease water saturation and improve gas seepage capacity. Based on the laboratory orthogonal experiments, the injection parameters of drying agents are optimized. Results show that the improvement of gas permeability reaches its best when the concentration of the main drying agent is 1g/L, the injection volume is 4 PV, the injection rate is 0.2 mL/min, the reaction time is 70 min, the reaction temperature is 120 °C, the injection volume of post-positioning fluid is 4 PV, and the reverse displacement time is 90 min. In addition, the higher the irreducible water saturation of the tight core, the greater the increment of gas phase permeability after drying reaction and the higher the degree of water saturation reduction.