Depletion-induced Stress Changes in a HPHT Reservoir: Calibration and Verification of a Full-field Geomechanical Model

Abstract

Abstract The Kvitebjørn field is a high pressure and high temperature gas-condensate field offshore Norway seated at a depth of 4000 meters. The field is produced by pressure depletion and therefore many geomechanical risks are at hand. In order to be able to forecast the geomechanical risks a full three-dimensional finite element model of the Kvitebjørn field has been built. We use four types of field measurements for initialisation, calibration and verification of the model: Surface subsidence measurements at the platform location In-situ compaction measurements from radio-active marker loggin Material properties from core and log measurements Stress measurements from extended leak-off tests Repeated compaction logging and global positioning measurements are used to calibrate the deformations at the surface and the reservoir level. The geomechanical model is populated by material properties based on core and log measurements. Four extended leak-off tests have been performed at different stages of reservoir depletion. The main application of the model is to determine and predict the depletion-induced stress changes for the entire Kvitebjørn field, to assess geomechanical risks related to infill drilling and collapse of production wells. It is concluded that the calibration and verification of the geomechanical model giving confidence in the prediction of the depletion-induced stress changes and the related geomechanical consequences.