Regional-scale implementation of poroelastic solutions for subsidence analyses

Extensive exploitation of water resources and fossil fuels is known to lead to long-term, spatially distributed land subsidence. The resulting ground settlement can be a major cause of infrastructure damage and economic loss, especially in coastal areas where subsidence contributes to increased risk of flooding and ecosystem deterioration. Although from a geomechanical standpoint, rock compaction due to pore pressure decrease is the major driver of ground settlement, the spatiotemporal distribution of subsidence is affected by a number of factors, such as site heterogeneity, variability of reservoir geometry, porosity fluctuations, and local differences in depletion history at extraction wells. To account for these factors while maintaining reasonable adherence with the physics of the problem, this paper aims to incorporate simple poroelastic solutions of land subsidence into a regional model accounting for spatial variations of the controlling parameters. For this purpose, the classical Geertsma solution is used to replicate the subsidence induced around a well, while pore pressure diffusion analyses are employed to simulate the delay between depletion history and ground settlement. Superposition principles are then used to assess the interaction between neighboring wells, eventually obtaining a spatiotemporal map of the expected subsidence. The methodology is finally tested for simplified arrangements of extraction wells, as well as under coupled and uncoupled scenarios. The results demonstrate that hydro-mechanical couplings may lead to non-negligible nonlinear subsidence trends even in the presence of linear poromechanical properties, thus making spatially distributed models a useful resource for a first-order assessment of the progression of ground settlements across a large region.