Factors of Stability of Wells in Reservoirs of Underground Gas Storage Facilities

Abstract

Preserving the integrity of wells and preventing sand production processes are among the key problems in the operation of underground gas storage facilities. Previously, the authors have stated that a key role in the processes of destruction and sand production is played by changes in formation pressure in the reservoir as a whole, since it has a decisive influence on the magnitude of the stresses acting in the vicinity of the wells. This thesis differs from the point of view of many researchers who associate these negative processes with a change in the stress state in the bottomhole zone of the formation caused by drawdown/overbalance in wells. The main goal of the article is to study the influence of unequal components of the initial stress state, as well as elastic and strength anisotropy of reservoir rocks on the stability of wells. It is shown that the presence of unequal components of the initial stress state and elastic anisotropy can lead to stress concentrations on the well contour that differ significantly from the isotropic case. It is also shown that in the presence of strength anisotropy, a change in the location of the points of the beginning of well destruction can be observed. The calculations performed have been confirmed by experimental studies carried out on rocks of the Uvyazovsky underground gas storage facility under conditions of true triaxial independent loading.