A Sector Model for IOR/EOR Process Evaluation

Abstract

Abstract The Tengiz field is a giant naturally fractured carbonate reservoir with 44° API oil and 12% H2S content. This work presents a methodology to construct a sector model for the Tengiz field which is used to evaluate IOR/EOR processes to increase oil recovery through the life of the field. Current development plans call for expansion of sour gas injection in the platform area of Tengiz. Additional long term focus is now directed towards the fractured slope region of the field. IOR/EOR is a natural alternative to supplement reservoir energy, improve recovery efficiency, and convert resources to reserves, then to production. Reservoir simulation requires using a dual porosity dual permeability model and equation of state to model PVT properties. Unlike most published sector models which are usually limited to a section of 5-spot pattern, this sector model covers 1/6 of the field area and is complicated by natural fractures, plant capacity limitations, complex production rules, existing sour gas injection, and high well count. This work presents a method to treat plant capacity limitations, boundary flux, edge wells, and compositional effects to replicate full field model performance and subsequently to generate alternative predictions. This model matches production/injection data of existing wells and the anticipated performance of future wells in the full field model. Matching parameters include oil production rate, GOR, flowing bottom-hole-pressure (BHP), saturation profile, and reservoir pressure profile at the field and well level. The BHP at all future development well locations are also matched. The sector model was also used to determine optimal well count of infill producer. The methodology to do so is discussed in this work as well. The on-going work and forward plan focus on evaluating the concentration profile of all injectants, impact of injection rate, gas production management, new development well locations, and interference among all wells. The success of sector model enables Tengizchevroil to run numerous IOR scenarios in a much shorter time frame so that only those prioritized runs can be evaluated on a full-field basis.