Deploying Polymer Flood in a Secondary Recovery Mode using Horizontal Injectors in a Complex Heavy Oil Field in the South of the Sultanate of Oman

Abstract

Abstract Over the past decade, Petroleum Development Oman (PDO) has accumulated significant experience studying and applying polymer flooding under various oil reservoirs and field conditions. In addition to ongoing commercial polymer flooding in the Marmul oil field, the company is actively pursuing polymer projects in more complex and mature oil fields. To accelerate the deployment of these projects, PDO capitalizes on in-house, regional, and worldwide experience. This paper discusses the implementation of polymer flooding in Thayfut a heavy oil field (oil viscosity above 600 cP) in a complex Gharif formation with a thin oil column. The field is produced under the depletion mode with the pressure support supplied by the aquifer. Due to the significant mobility contrast between viscous oil and water, the production water cut has increased significantly, limiting the oil recovery. Polymer flooding with horizontal injectors (parallel to existing horizontal producers) was proposed to achieve higher oil recovery at lower greenhouse gas (GHG) emission intensity. Additionally, this paper describes the development concept, reservoir modeling, and forecasting details. The scope of surface development is also discussed regarding water supply options, polymer facility, and polymer distribution mode. It is demonstrated that applying polymer in a secondary mode offers significant benefits due to high remaining oil saturation, especially for fields with high permeable formation and oil viscosity. Laboratory and field data from similar projects were used to benchmark the inputs for the dynamic models that were used to forecast the oil recovery due to polymer flooding. Despite the encouraging oil production forecast due to the polymer flooding, several alternative development scenarios were investigated, including infill drilling and waterflooding. It was found that injecting polymer is the best option due to the highest ultimate oil recovery and lowest GHG emission intensity of produced oil. Polymer project economics is also advantageous, including the surface optimizations applied regarding polymer facility and distribution. The project is expected to accelerate the production peak, reduce decline, and allow better facility and urban planning design. This paper illustrates the application of polymer injection in a secondary mode in a complex Gharif reservoir with heavy oil. This method can lead to a new polymer application strategy in future PDO fields.