TECHNICAL EVALUATION OF SECONDARY OIL RECOVERY METHODS, A CASE STUDY ON ONE OF THE IRANIAN HPHT CARBONATE RESERVOIRS

The reservoir under study is a HPHT (high pressurehigh temperature) reservoir with high amount of H2S and asphaltene. It has more than 1 billion of recoverable oil as static geological model estimated but the problem is the only drive mechanism is Solution gas drive and it has no active aquifer so although it had good flow potential but what if it drops lower than bubble point pressure? Dynamic model showed it was to deplete quickly. By usingnew reservoir management techniques and enhanced oil recovery in order to pressure maintenance one can recover a lot more oil.The scope of this project was to evaluate in terms of impact of surface facilities, reserves and recovery factor of using gas injection and then different fluid composition for this field's gas injection 1. Water Injection 2. Rich gas corresponding to the associated separator gas to be re-injected to reservoir3. Lean gas corresponding to the associated separator gas to be re-injected to reservoir after condensate removal There are 40 wells in this fields and this was possibleto change function of production well to injector if needed. A team of Reservoir, Production, Process, Facility and Environmental engineers worked on the possibility of Secondary recovery by injection and its challenges. Simulation models were run for different scenariosand realizations and the best composition of injection fluid was selected by considering reservoir rock and fluid data and different injecting fluid compositionand different injection pressure. After comprehensive study and technical evaluation it was found that. Miscible gas injection was the bestscenario allowing 0.66 BSTB Recovery increase and 9 years longer plateau compared to natural depletion