A workflow for infill well design: Wellbore stability analysis through a coupled geomechanics and reservoir simulator

Abstract

The traditional way of analyzing wellbore stability in depleted reservoirs is by assuming homogenous depletion and uniaxial strain. Then the analytical solution of stress path is obtained. Pore pressure depletion, however, is location and time dependent. The objective of this study is to develop a workflow for infill well design. More specifically, a wellbore stability analysis is developed for infill wells using a coupled geomechanics and reservoir simulator (CGRS) which considers lateral displacement and inhomogeneous depletion. Different shear failure criteria are utilized in a new CGRS wellbore stability model. The upper bounds of shear failure are given by Drucker-Prager Inscribes and Griffith Theory, while the lower bound is given by Drucker-Prager Circumscribe. CGRS wellbore stability model is compared with conventional wellbore stability model (based on the analytical solution of stress path). CGRS wellbore stability can quantify the influence of azimuth on minimum and maximum mud weight during the depletion when initial maximum horizontal stress equals minimum horizontal stress. In addition, CGRS can give the output of a location-dependent mud weight map for the entire reservoir. Neither of the above two functions can be realized by conventional wellbore stability model. Therefore, CGRS can provide dynamic information concerning where to drill, when to drill, and how to drill for infill wells.