Water blockage removal and productivity index enhancement by injecting thermochemical fluids in tight sandstone formations

Abstract

Several challenges are associated with hydrocarbon production from tight reservoirs. Tight reservoirs are characterized with low permeability which reduces the hydrocarbon flow into the wellbore. Water blockage is considered one of the main damaging mechanisms in tight reservoirs due to the increase of water saturation around the wellbore region and eventually decrease in the relative permeability of hydrocarbons. Acid fracturing or hydraulic fracturing are required to remove the damage and enhance the formation conductivity. This paper presents a new technique to remove the water blockage from tight formations and improve the formation productivity using thermochemical treatment. Chemicals that generate pressure and heat at reservoir conditions are used to remove the water bank from tight core samples to enhance the flow conditions. Coreflooding experiments, capillary pressure, and NMR measurements were conducted as well as routine core analysis. The impact of thermochemical treatment on improving the formation productivity was quantified. The productivity index for core samples were determined before and after the thermochemical flooding. The effect of thermochemical injection on reducing the capillary forces was analyzed by measuring the capillary pressure before and after the chemical treatment. The alteration in pore geometry due to the thermochemical flooding was evaluated using NMR measurements. The results of this study show that water blockage is a potential damage in tight gas reservoirs. Injecting thermochemical fluids into tight samples reduced the capillary forces and removed the water banking. Flooding tight core samples with thermochemical resulted in generating tiny fractures in the treated samples, which reduces the capillary forces by 55.6% after the chemical treatment. The in-situ generated heat and nitrogen gas during thermochemical treatment can result in removing the water blockage from tight formations utilizing the desiccation effect. Also, thermochemical treatment showed a significant improvement in the core conductivity. The productivity index of core samples increased by 94.3% due to the chemical flooding. This study introduces a new chemical treatment for removing the water blockage from tight formations using environmentally friendly fluids. Thermochemical treatment improved the productivity index by a factor of 1.94 and decreased the drawdown pressure by more than 80%. Consequently, the trapped water was removed, and the total hydrocarbon production significantly improved.