GEOMECHANICAL JUSTIFICATION OF WELL CONSTRUCTION IMPROVEMENT WITH AN OPEN BOTTOM AT UNDERGROUND GAS STORAGES IN UNSTABLE RESERVOIR

Abstract

Background The features of the operation of wells in underground gas storages in water-bearing layers are considered. The urgency of ensuring stability of the bottom-hole formation zone and prevention of sand production is shown. Aims and Objectives The aim of the study is the geomechanical justification of technological actions for well bottom reconstruction directed to increase in technical and economic indexes of underground gas storages explotation and decrease of sand production. A key geological and technical action of complex technology of well bottom reconstruction of underground gas storages in unstable reservoir is the well bottom expansion. Results The research of a stressed state of the bottom-hole formation zone of the vertical well according to the Kasimovskoye Underground Gas Storage is executed. Rock stressed state model was carried out in the conditions of gravitational stress field in the rocks massif taking into account of gas nonlinear filtration under the binomial law at assumption of the plane deformation. The stress distribution in a bottom-hole formation zone in the conditions of standard and expanded diameters of open bottom of the vertical gas well is defined. With use of the Mohr-Coulomb criterion of strength defined values of radius of the rock plastic flow zone in the bottom-hole reservoir zone before and after well bottom reconstruction and their comparative assessment is also carried out. It is established that at twice expansion of well bottom diameter decrease by 2.6 times of width of rock plastic flow area in a bottom-hole formation zone increases its stability. Thus, expansion of open bottom diameter of the gas well in the productive layer interval had justify from rocks mechanics position. Such expansion is entering in the complex technology of vertical well reconstruction on underground gas storages in water-bearing reservoirs offered earlier by one of authors.