Plans for Chemical Enhanced Oil Recovery in a North Oman Carbonate Field

Abstract

Most of PDO's carbonate fields in North Oman have been producing for many years, initially on depletion in the early days but were quickly put on water injection to maintain reservoir pressure and safeguard long term ultimate recovery. As these fields mature into early middle age, EOR options have been under review to further increase recovery.Given the reservoir properties and the prevailing fluid & gas conditions for these carbonate fields, thermal technologies are not considered an optimal choice. Gas floods would potentially feature but were screened out due to the overall balance between gas requirements, cost and potential reward. Chemical floods with potentially attractive high recoveries were selected for further assessment.The goal is to demonstrate that chemical technology can produce economic incremental oil from a waterflooded carbonate reservoir containing a low-viscous light oil. The reservoir selected has undergone a successful waterflood implementation with good control on historical voidage and production allocation. The potential follow up chemical flood is then planned to be introduced in a phased manner. This starts with phase behaviour and core flow experiments in the lab to find a suitable chemical formulation to optimally mobilize waterflood residual oil. This is then followed by field trials such as a Single Well Chemical Field Test to back up lab experiments, extensive logging, a MicroPilot test and a planned potential multi-well pilot. Full field implementation is then dependant on the results of the earlier project phases and will have to balance against the perceived rewards, risk and cost. The results to date, learning's and key findings along with the selection strategy and challenges will be discussed in this paper. This study and field work will provide a foundation upon which the future potential for chemical flooding in North Oman carbonate fields can be evaluated and implemented.