Modelling Methodology for the Analysis of Subsidence Induced by Exploitation of Gas Fields

This paper presents the modelling methodology, currently employed by ENI, to perform quantitative 3D finite element analyses of the subsidence that may be induced by exploitation of gas fields. It is based on an uncoupled approach that integrates the geomechanical model with both geological model and fluid-dynamic model. Its description is provided herein by means of a case-study, the results of which are validated by comparison with the surface displacement measurements recorded by GPS monitoring stations. As already shown in the last decade by the application of such workflow to several gas fields, also in the case-study at hand, it is apparent that the numerical model employed can simulate, with high accuracy, the hydro-mechanical response of the rock mass to the depletion of the contained reservoir-aquifer system. Finally, it is proposed an overview of some ongoing research projects which aim to further improve reliability and accuracy of the long-term forecast, by means of the enhancement of both constitutive model and numerical model itself.