Managing Micro-Emulsion and Scale During ASP Flooding for North Sabah Field EOR

Abstract

Alkaline Surfactant Polymer (ASP) flooding has been identified as one of the best EOR methods to further recover the trapped oil in Malaysian maturing fields. ASP flooding application promises a huge incremental recovery factor based on recent successful implementation on offshore fields in other part of the world. The application of ASP flooding has been identified for pilot in North Sabah reservoir which is currently flooded with seawater since March 2011. Despite the promising recovery factor from the pilot laboratory and simulation study with incremental recovery of >80% above waterflood, the ASP flooding success always comes with risks and challenges. Two major challenges behind the success of ASP flooding are the formation of scales near wellbore due to the high pH of the alkaline in the injection fluid and the tight micro-emulsion which produced back in separator vessel which contains surfactant breakthrough. The identified pilot North Sabah reservoir which is currently been flooded with seawater is expected to further worsen the scaling effect due to the high divalent cation concentration (i.e. Ca2+ and Mg2+) in seawater. In addition, the high seawater cut causes a very tight micro-emulsion which is very difficult to manage. These challenges cause formation damage which impact injectivity and flow assurance issue to the production facilities as well as impair the crude quality and sellability. This paper will discuss in great detail on the lab test results which was designed based on the reservoir simulation ASP flooding study in North Sabah reservoir. Based on the in-situ produced water and chemical breakthrough simulated, this paper describes the extent of emulsion and scale severity at various ASP to water ratio, extensive performance tests evaluating the demulsifier and the scale inhibitor and discusses on the challenges in finding the suitable demulsifier and scale inhibitor at the simulated breakthrough condition.