A novel method for calculating the dynamic reserves of tight gas wells considering stress sensitivity is under consideration.

The accuracy of dynamic reserve calculation of gas storage is of great significance for the rational and efficient development of oil and gas fields and the system of gas well allocation. The reservoir in the Shaxi Temple gas field in the ZT block of northwestern Sichuan is tight and highly heterogeneous, with complex gas-water distribution and large differences in gas well test production rates, resulting in rapid decline rates. In order to accurately calculate the dynamic reserves of such tight, water-bearing gas wells, this study takes the water-bearing tight gas reservoirs in the ZT block of northwestern Sichuan as the research object. Experimental methods such as rock X-ray diffraction, constant rate mercury injection, and reservoir rock stress sensitivity were conducted. Based on the experimental results, the porosity and permeability of rock samples under effective stress conditions were corrected using bivariate linear regression. These corrected parameters were then incorporated into the water-gas material balance method to establish a new method for calculating dynamic reserves of water-bearing tight gas reservoirs under stress-sensitive conditions. The results show that: (1) the rock porosity ranges from 6.08% to 10.22%, permeability ranges from 0.035mD to 0.547mD, clay mineral content ranges from 6.58% to 19.14%, pore radius distribution ranges from 90μm to 180μm, throat radius distribution ranges from 0.61μm to 3.41μm, with significant differences in throat distribution, indicating poor reservoir fluid flow capacity and strong tightness; (2) after aging experiments, rock samples exhibit plastic deformation, with porosity and permeability unable to fully recover after pressure relief. The stress sensitivity curve of rock samples shows a two-stage characteristic, with moderate to strong stress sensitivity; (3) porosity stress sensitivity is mainly influenced by pore radius and mineral composition - larger pore radius and higher clay content lead to stronger stress sensitivity, with porosity loss rates ranging from 8.26% to 23.69%. Permeability stress sensitivity is mainly influenced by throat radius and mineral composition - smaller throat radius and higher clay content result in stronger stress sensitivity, with permeability loss rates ranging from 47.91% to 62.03%; (4) a comparative analysis between the traditional dynamic reserve calculation method for gas wells and the new method considering stress sensitivity shows a relative error between 0.90% and 2.41%, with the new method demonstrating better accuracy. This study combines physical experimental results with an effective stress model of reservoir rocks to develop a new method for calculating dynamic reserves of water-bearing tight gas reservoirs under effective stress conditions, providing experimental data and example calculation results to support subsequent dynamic evaluation of gas reservoirs and the establishment of rational well allocation plans.