Experimental Study on Tight Sandstone Reservoir Gas Permeability Improvement Using Electric Heating

Abstract

Although tight sandstone gas formations are abundant in China, their single-well productivities and exploitation efficiencies are restricted by water blocking from drilling and completion. At present, shut-in, chemical additive application, and hydraulic fracturing are the common approaches applied to handle this problem. However, these approaches are also characterized by low efficiencies or even cause secondary damage. In this study, the impact of high temperatures (of up to 800 °C) on the microstructure of a tight sandstone, including water blocking and gas permeability, are investigated through the electric heating of a simulated wellbore. The results show that the threshold temperature for fracturing of the tight sandstone is approximately 450 to 600 °C. Many secondary microcracks emerged near the wellbore beyond this temperature, improving the gas permeability, with some microcracks visible even after cooling. The gas permeability of the formation after heating to 800 °C increased by 456% and 3992% compared with the initial gas permeability and the water-blocking impacted gas permeability, respectively. This study demonstrates that electric heating is a potential method for improving the permeability of tight gas formations.