Experimental study on stress sensitivity of high-temperature and high-pressure sandstone gas reservoirs in Yingqiong Basin

Performing stress-sensitivity evaluation on a high-temperature and high-pressure gas reservoir is essential for correctly understanding the characteristics of physical property changes and reasonably designing the development scheme of a reservoir under stratum conditions. By focusing on six core samples with different physical properties in a gas field in the Yingqiong Basin, stress-sensitivity experiments have been conducted along with mercury intrusion porosimetry and X-ray diffraction measurements to study the relationship among porosity, permeability, and effective stress at a temperature of 140 degrees C and effective stress ranging from 2 MPa to 70 MPa. Our results showed that the stress-sensitivity curve characterized by three-stage segmentation is primarily affected by average pore radius and mineral composition but has no direct relation with porosity and permeability. Meanwhile, the stress sensitivity of permeability is mainly related to the average pore throat radius and mineral composition of core specimen. The smaller the pore throat radius and the higher the clay content, the stronger the stress sensitivity of permeability. Under high-temperature and high-pressure conditions, the stress sensitivities of permeability and porosity can be characterized by power functions although the stress sensitivity of permeability is about 2-11 times higher than that of porosity.