Rock stress sensitivity in low-permeability gas reservoirs and its impact on productivity

Abstract

The relationship between permeability and effective stress could be found using the stress sensitivity test, and the stress sensitivity in the low-permeability gas reservoir was investigated. The productivity model could be deduced and the influences of stress sensitivity on the development of the low-permeability gas reservoirs were also discussed. The results show that the permeability of the core decreases as the effective stress increases and the permeability first quickly declines, then slows. The fitting relationship between permeability and effective stress conforms to the index relationship. The fitting relationship between the stress sensitivity coefficient and permeability accords with the power function relation and the stress sensitivity effect weakens as the original permeability increases. Based on the Darcy flow theory and the original permeability in the reservoir, the productivity model of the well, considering the effect of stress sensitivity, could be presented. The distribution curves of the pressure and permeability in the reservoir are funnel shaped. The pressure and permeability decline quickly as the original permeability or the gas well productivity increases. The stress sensitivity of the permeability in the conglomerate gas reservoir is obvious, indicating that the fluid pressure must be appropriately controlled and the difference in the production pressure should be maintained at a reasonable value during the development process.