Reservoir stress sensitivity and its influence on pressure response characteristics in deep fractured-vuggy reservoirs: a case study of the X deep fractured-vuggy reservoir

Although stress sensitivity and bottom-hole pressure analysis have been investigated extensively, the inherent reservoir heterogeneity leads to variability in stress sensitivity behavior and pressure response behavior across different reservoirs. Therefore it is considerable importance to establish a stress sensitivity characterization method tailored to the X deep carbonate reservoir and to elucidate its characteristic bottom-hole pressure behavior. Our study adopts a combined research approach that integrates laboratory experimentation with theoretical derivation to systematically analyze the stress sensitivity characteristics of X deep carbonate reservoirs, and a well test model suitable for X deep carbonate reservoirs was established. The influence of reservoir stress sensitivity on the bottom-hole pressure behavior was further examined. It is found that the flow regime of a vertical well in X fractured-vuggy reservoir includes eight flow stages, which are the wellbore storage stage, the skin stage, the first radial flow stage, the transition stage, the vug storage stage, the second radial flow stage, the vug-fracture crossflow stage, and the boundary-controlled flow stage. Furthermore, stronger stress sensitivity leads to a greater decline in permeability. Meanwhile, the higher the stress sensitivity, the greater the attenuation of permeability caused by changes in effective stress, and the stress sensitivity effect also increases accordingly. The bottomhole pressure drop corresponding to the same dimensionless time increases significantly, and the pressure derivative curve shows a noticeable upward bend. These findings provide a theoretical basis for the efficient development of X deep carbonate fractured-vuggy reservoirs.