Finite Element Modeling of Production-Induced Compaction and Subsidence in a Reservoir along Coastal Louisiana

Subsidence has caused significant wetland losses in coastal Louisiana because of various anthropogenic and geological processes. Releveling data from the National Geodetic Survey show that one of the governing factors in subsidence in coastal Louisiana is hydrocarbon production, which has led to the acceleration of spatial-and temporal-dependent subsidence. The production-induced reservoir compaction and land subsidence are investigated for a typical reservoir in the Valentine field in coastal Louisiana, for three cases within the framework of homogeneous poroelasticity, inhomogeneous poroelasticity, and inhomogeneous poroplasticity. The observed subsidence is first interpreted by the Geertsma analytical model for a disk-shaped reservoir embedded in a semi-infinite homogeneous elastic medium and then by an analytical inhomogeneous poroelastic model that considers layered stratigraphy. A three-dimensional uncoupled finite element model is set up and validated against the two analytical poroelastic models. A modified Cam-Clay model is then adopted to account for the plastic compaction of the reservoir in an inhomogeneous poroplastic case. The material properties are calibrated based on the subsidence in the field and available geomechanical data in other reservoirs in the Gulf of Mexico. The observed trend and magnitude of subsidence in the Valentine field can be approximately interpreted through finite element modeling in all the three cases after calibration. It is inferred that the governing compaction mechanism is plastic deformation instead of elastic deformation during fluid production in the Valentine field. The ratio of subsidence over compaction generally varies with different compaction mechanisms. The finite element models presented in this study can be applied to evaluate the production-induced compaction and subsidence in other reservoirs, and the results could be potentially useful to coastal restoration and management.