Geomechanics-Coupled Simulation of Fines Migration in Offshore Unconsolidated Heavy Oil Reservoirs

Sand production usually occurs in offshore unconsolidated sandstone reservoirs. Comprehensively accounting for formation deformation and fluid flux effects on particle detachment from matrix rock, an offshore unconsolidated sandstone sand production model is proposed, coupling oil, water, mobile particle flow equations and a geomechanical model incorporating multiple mechanisms including particle detachment, plugging and deposition. The model is numerically solved using combined finite volume and finite element methods with the sequential fully implicit (SFI) algorithm. Good agreement with experimental data verifies the model's correctness. Subsequently, detailed analysis of key parameters was conducted based on a five-spot well pattern model, and history matching was successfully performed for a field data using the proposed model. The results indicate that particle detachment mainly occurs in the near-wellbore region with larger fluid flow velocity during production, leading to increased porosity and permeability. Meanwhile, particle deposition and plugging cause particle retention in the formation, resulting in decreased permeability and reduced daily particle production. The influence of deposition is significantly lower than that of plugging. The detachment and plugging coefficients emerge as critical parameters governing sand production performance and reservoir property evolution, requiring prioritized consideration during history matching, The history matching of offshore field data confirms the field applicability of the proposed model, which provides practical guidance for sand production simulation and efficient development in offshore unconsolidated sandstone reservoirs.