Study on Stress Sensitivity Damage Evaluation in Tight Low-Permeability Gas Reservoirs

ABSTRACT: Current stress sensitivity evaluation experiments lack accuracy due to the absence of considering the dynamic impact of the slip effect. This paper uses a correction method for Klinkenberg permeability that accounts for the dynamic variation of the slip effect. Gas measurement evaluations are conducted using varying confining and pore pressure methods under in situ reservoir conditions, fitting permeability and effective stress, and establishing a stress-sensitive gas well productivity equation that considers eliminating the slip effect. The results indicate that as effective stress increases, the gas slip effect intensifies. The average damage rate of corrected permeability increases by 0.9% and 12.09% in the two methods, with the pore pressure variation method being closer to field conditions. The greater the stress sensitivity, the faster the decline in gas well productivity, and both excessively high or low bottom hole flowing pressure are detrimental to gas well production. By calculating data from a gas well in Linxing, the reasonable range of bottom hole flowing pressure is determined to be 13.07 MPa to 13.99 MPa, while the reasonable production pressure difference range is 1.29 MPa to 2.21 MPa. This provides effective guidance for the development of low permeability reservoirs and reservoir protection. 1. INTRODUCTION With the sustained and stable development of Chinese petroleum industry, the development focus has gradually shifted towards low-permeability oil and gas reservoirs as middle to high permeability reservoirs are gradually being developed and the proportion of low-permeability oil and gas reserves continues to increase. Currently, low-permeability oil and gas reservoirs account for a relatively high proportion of petroleum reserves in China and are the main source of petroleum and natural gas production at this stage. During the production of tight low-permeability gas reservoirs, the pore pressure in the reservoir decreases, causing deformation of the reservoir rock and compression of the internal flow channels within the rock, resulting in damage to reservoir permeability, which is one of the reasons for the decrease in production well capacity. The tight sandstone gas reservoirs in Linxing area are highly heterogeneous, with low porosity and permeability, and their high clay content makes them vulnerable to permeability damage caused by stress changes. Therefore, understanding the stress sensitivity of low-permeability reservoirs is of great significance for formulating reservoir protection measures and guiding the efficient development of oil and gas reservoirs.