Methods for FEM stress initialization based on stress functions, and application to a reservoir cross-section

Abstract

An accurate description of the in-situ stress field in a rock mass is crucial in different areas of geo-engineering such as: underground excavations, hydrocarbon extraction, CO2 storage, hydraulic fracture etc. In this paper, a novel methodology to numerically generate the in-situ stress state within the Finite Elements framework is presented. It involves two steps: 1) an estimate of the stress components is given for integration point of the discretization, and 2) global equilibrium is verified and re-balancing nodal forces are applied if needed. While the second step is a closed procedure based only on statics, the estimate of the in-situ stress field can be done in different ways in order to incorporate all the information available of the rock mass. In this paper, more traditional approaches are discussed and a new procedure based on the Airy stress function is described, in order to generate a stress state proposal at each Gauss point of the domain. Finally, the performance of different approaches is illustrated with a reservoir example.