Chemical EOR in a Strong Aquifer Driven Reservoir: From Concept towards Reality

Abstract

Abstract North Kuwait has vision to increase oil production from its major reservoir and it is planned to be achieved by covering the major reservoirs under the umbrella of enhanced oil recovery (EOR). Sabiriyah Lower Burgan (SALB) is the biggest sandstone reservoir in Sabiriyah field with high permeability and strong aquifer support. Paper describes steps planned from present development strategy of simply infill drilling to EOR to improve the production scenario in future. Primary recovery from reservoirs like SALB are expected to be good. Performance of the reservoir especially rise in water cut of SALB was analyzed which suggested that though primary recovery would be good but will take longer time to achieve. EOR screening was performed and suitable EOR methods were evaluated using mechanistic model. Screening considered target oil, water quality, permeability, oil viscosity, temperature, aquifer and injection capacity. Lab experiments were performed for the identified EOR processes and most suitable method was selected. EOR pilot area and pilot design performed to take it forward from concept stage towards reality. SALB Layered part is an acceptable candidate for EOR process due to favorable mobility ratio which reduces the need for mobility control agents, reservoir being mixed wet system which is encouraging for improving unit displacement efficiency and reservoir rock properties are conducive to most forms of EOR. Low salinity water, CO2, N2 and Chemical EOR methods were evaluated. Mechanistic model based Estimated Recovery factor range for these EOR methods indicated Chemical EOR, (A) SP as most effective EOR method. Lab experiments were performed for CO2, N2 and ASP. In Lab, miscible N2 flooding was not found feasible whereas CO2 flooding was feasible for either as CO2 or a blend of CO2/NGL. Coreflood experiments suggested surfactant-polymer or alkaline-surfactant-polymer pilot flood as promising EOR methods for SALB. KOC has planned to proceed with Chemical EOR with its further evaluation through single well chemical tracer test (SWCTT) as first step. A multi-well pilot was also recommended assuming a successful single wells tracer test which would provide a better understanding of chemical solution injectivity, oil recovery potential, chemical retention by the reservoir, effect of the water drive on alkaline-surfactant-polymer flood potential and operational issues. Target layer and likely area was identified for EOR pilot. EOR in a reservoir with strong aquifer drive has its own challenges but merits of SALB for enhancement of recovery are encouraging. The paper provides an insight of applicability of Chemical EOR in a large reservoir with strong aquifer that will pave the way for similar reservoirs in Kuwait and worldwide.