NONLINEAR INFLOW PERFORMANCE RELATIONSHIPS IN STRESS-SENSITIVE FRACTURED-POROUS RESERVOIRS: A CASE STUDY

Abstract

This study investigates the phenomenon of nonlinear fluid inflow in stress-sensitive fractured-porous reservoirs of the East-European Shelf. It is established that the deformation of the void structure under declining reservoir pressure leads to a significant loss of conductivity in the filtration channels of the Lower Carboniferous sequence. Based on the integrated application of the power-law filtration model and the binomial equation, the deviation of actual flow rates from the predictive values of the classic rigid-bed model is quantitatively substantiated. The research reveals that ignoring the stress-sensitivity factor leads to a flow rate overestimation of 21.4 % at an operating drawdown of 4.3 MPa, and up to 38.5 % at maximum pressure gradients. A nonlinearity index ( = 0.89) was determined, and the potential productivity index ( ≈ 15.63 m³/day·MPa) was calculated for hypothetical conditions without deformation. The identified nonlinearity is physically substantiated using the Hertzian contact theory, accounting for the elastic deformation of fracture surface asperities. The research identifies a critical "crossover point" at the 18th month of production, where the geomechanically optimized strategy ( = 4.3 MPa) begins to outperform aggressive depletion due to the preservation of fracture conductivity. The proposed optimization algorithm allows for a 12.4 % increase in NPV and an incremental recovery of 3000–5000 tons of oil per well by preventing irreversible formation damage. These findings are critically important for optimizing well performance, reducing OPEX, and preventing irreversible fracture closure at late stages of field development.