Influence of stress and high-temperature treatment on the permeability evolution behavior of sandstone

Abstract

Permeability is an important property of rock in gas and oil exploration engineering; environmental temperature and geo-stress have great influence on it. This paper aims to analyze the influence of thermal treatment on the permeability of sandstone under triaxial compression. Based on the gas seepage tests on a sandstone specimen after different thermal treatment temperatures with different gas pressures, hydrostatic stresses and deviatoric stresses, the thermal effect on the physical properties of sandstone is firstly analyzed. The results show that the mass of the sandstone specimen decreases with the increase of temperature; some spalling damage and tensile cracks occur on the lateral surface of the specimen at 400 °C. According to the seepage test results with various gas pressures, an exponential relationship has been found between the permeability coefficient and temperature. The permeability coefficient is approximately 100 times as large as the initial value when the temperature increases from 20 °C to 800 °C. The permeability evolution of the heated sandstone under hydrostatic and deviatoric compression has also been analyzed. A simplified double-pore texture model is proposed which can describe well the permeability evolution of sandstone under compression with hydrostatic stress and deviatoric stress, and it can be helpful to estimate the permeability of thermally treated sandstone under elastic triaxial compression.