Numerical Simulation of Change in Reservoir Properties Arising from Near Oil Wellbore Damages

Abstract

Long down-time and colossus economic loss associated with frequent well shut down required for proper well test analysis near oil wellbore  damages has necessitated the use of numerical models for simulating change in reservoir properties. In the current study, change in reservoir properties has been simulated by formulating models involving modification of Darcy equation in an attempt to optimize reservoir pressure for  improved reservoir properties. The coupled transient linear partial differential equations (CTLPDE) models developed for predicting reservoir  properties such as porosity, permeability and water saturation profile were numerically solved using finite difference method implemented in  MATLAB and solution validated using field data perturbed with Gaussian noise of ±10%. The results obtained for CTLPDE models indicated initial  decrease in both water and oil pressure from 4550 psi and 350 psi to 4525 psi and 320 psi respectively. Both water and oil pressure subsequently  increased to 4530 psi and 325 psi and then remained constant. However, while water saturation (Sw) increased throughout the pressure regime;  0.730 through 0.735 to 0.739, oil saturation (So) decreased from 0.320 through 0.268 to 0.263. The results of the corresponding auxiliary equation  indicated increase in relative permeability of water (Krw) with Sw but decreased with increase in So, while relative permeability of oil (Kro) decreased  with increase in Sw but increased with So. Generally, however, for every value of either S_o or ?_? , ?_?? ≫ ?_??. Numerical simulation proved  to be effective in predicting reservoir behavior. The formulated models indicate drop in oil saturation as pressure depleted over time.