Surface and Subsurface Requirements for Successful Implementation of Offshore Chemical Enhanced Oil Recovery

Abstract

Summary Chemical enhanced oil recovery (EOR), including polymer and surfactant-based processes, is a method that operators consider to maximize oil recovery from onshore and offshore reservoirs. Because of the logistical, operational, and environmental differences and the footprint and required weight needed for additional injection and production equipment, offshore chemical EOR processes are challenged by greater complexity and costs as compared with onshore applications of the same technologies. Chemical EOR commonly requires large volumes of injection chemicals, as well as demulsifiers to break produced-water/oil emulsions and inhibitors to control scale, resulting in high shipment and storage costs. The use of seawater and/or produced water for injection of the chemicals into offshore fields mandates stringent processing of both streams to allow optimal injectivity, sweep efficiency, and chemical effectiveness in the reservoir. Offshore production of saleable oil and clean water requires space- and weight-efficient oil/water-separation equipment. Currently, conventional methods for processing produced fluids fall short in both efficiency and compactness. High offshore drilling costs lead to relatively large well spacing and more difficulty in monitoring the EOR subsurface process, and lead to restrictions on the number of disposal wells. Finally, environmental restrictions limit the overboarding of toxic or poorly biodegradable EOR chemicals. The industry is currently investigating the limiting factors pertinent to offshore chemical EOR. As a result of these efforts, new enabling chemistries and technologies are being examined for improving surface operations to allow cost-effective offshore chemical EOR to be performed in an environmentally sound and safe manner. Some of these recent chemical- and fluids-processing developments are described in this paper. Subsurface challenges to implementing offshore chemical EOR are also highlighted, along with potential solutions.