Polymer Injection in a Heavy Oil Reservoir under Strong Bottom Water Drive

Al Azri, Nasser Said (Petroleum Development Oman) | Al Ajmi, Widad (Petroleum Development Oman) | Kazzaz, Ahmed (Petroleum Development Oman) | Ramalingam, Sankaranarayanan (Petroleum Development Oman) | Morshidi, Abulaziz (Petroleum Development Oman) | De Kruijf, Alexander (Petroleum Development Oman) | Jamal, Esam Abubaker (Petroleum Development Oman) | Al Busaidi, Iman Khamis (Petroleum Development Oman) | Al Mahrouqi, Abdullah (Petroleum Development Oman) | AlKharusi, Badar (Petroleum Development Oman) | Brooks, David (Shell Intl. E&P Co.)

OnePetro 

Implementing Enhance Oil Recovery techniques in heavy oil reservoirs with strong bottom water drive has been a challenge in the oil industry. This paper describes an Enhanced Oil Recovery process in which polymer is injected into a clastic reservoir with a strong bottom aquifer drive bearing heavy-oil (250-500 cP). The high reservoir permeability (2-5 Darcy) enables stretching the viscosity limit of a standard polymer application.

The presence of a strong bottom aquifer maintains high reservoir pressure, which could provide a challenge to injectivity. The close proximity of injectors to the oil water contact reduces the efficiency of the polymer flood through water fingering, and polymer loss to the aquifer. To best understand details of the influence of aquifer on the recovery process, test different development scenarios and address key uncertainties, detailed simulation study was conducted. The simulation results showed that the optimum development concept which would help reduce impact of polymer loss to the aquifer would be to utilize the currently existing and future horizontal producers, augmented with additional infill horizontal injectors placed approximately mid-way in the oil column. Optimization of the development was performed using the simulation model where the polymer viscosity, slug size, and injector location were optimized for net present value.

Uncertainty analysis using the simulation model showed that factors such as poor injectivity, poor conformance control and high kv/kh ratio have negative impact on process efficiency. To address and mitigate these key risks and uncertainties a number of activities are underway. These activities include intensive laboratory tests, field injectivity test and a field trial where polymer is injected in newly drilled injectors. The paper discusses study to identify the optimum development concept, key uncertainties and associated risk reduction activities. Finally, this paper discusses the design and the surveillance aspects of the upcoming field trial.