ABSTRACT
Many gas fields are being produced in the northern Netherlands. Gas production causes changes in the in situ effective stress field, eventually leading to fault reactivation and induced seismicity. Induced seismicity has become a growing problem in the Netherlands in the past two decades. In order to obtain more fundamental insight in the mechanisms of induced seismicity, gas reservoirs are modelled using the finite element method. The geomechanical models are representative for most of the Rotliegend gas fields in the Netherlands. The influence of several key parameters on stress development and fault slip on a normal fault intersecting a disk-shaped gas reservoir are studied. Three significant parameters are presented in this paper:Young’s modulus and Poisson’s ratio of the surrounding rock and fault orientation in a 3D anisotropic tectonic stress field. For the modelled conditions, incorporating an extensional stress regime, it could be concluded that a surrounding rock which is relatively stiff in relation to the reservoir rock promotes both normal and reverse fault slip. A fault with a strike direction parallel to the largest horizontal tectonic stress incorporates the most critical stress development during gas depletion. Strike-slip does at most hardly contribute to the calculated fault slip.
