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°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.

To determine how fracture–vuggy structure, pressure, and injection–production mode influence displacement efficiency in the water flooding process in fracture–vuggy reservoirs, two types of models were built based on the characteristic of such reservoir: two fracture models with different fracture apertures and two fracture–vuggy models with different sizes of vugs. A series of two-phase fluid flow experiments was conducted to study oil and water distribution as well as flow pattern in the water flooding process. Results show that displacement efficiency is significantly influenced by injection–production mode and injection pressure. By contrast, its relationship with the size of vugs is insignificant. Under the same injection–production mode, high-to-low recovery that corresponds to model type includes the small fracture, large fracture, small vug, and large vug models. Under the same pore volume multiple, high-to-low recovery that corresponds to model includes the small fracture, small vug, large fracture, and large vug models.