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Abstract

The Angsi field in the offshore Terengganu, Malaysia was identified as the candidate for the pilot project to evaluate the effectiveness of the Alkaline Surfactant (AS) process in improving oil ultimate recovery through the reduction of residual oil saturation. The pilot project entails the injection of AS chemical into Angsi I-68 reservoir and will use a Single Well Tracer Test (SWCT) to determine the residual oil saturation in water-flooded area. This is the first chemical Enhanced Oil Recovery (EOR) pilot project in Malaysia and the results are crucial to support the decision making for a future full field and AS technology implementation in Malaysia.

High reservoir temperature and high water salinity pushes the technical limit of AS application that adds complexity to the pilot design. The implementation of the pilot project in the offshore environment, on an unmanned satellite platform with limited space and facilities provide additional operational challenges to the project team. In addition, the utilization of new and volatile chemicals during the pilot requires an introduction of various field procedures to ensure the operation is carried out in a safe manner.

The paper showcases, the key challenges in the planning and execution of the first offshore AS pilot project in the region. This challenging task demands the multi-disciplinary team to work together to develop the project execution plan with attention to detail during pilot design, planning and operation. As a result, critical parameters such as: treatment sequence, field procedures, equipment requirements and layout, and logistics were considered. The pilot design and procedures that are crucial for a successful pilot operation were developed within the constraints imposed by the offshore environment.

Introduction

In their quest to increase oil ultimate recovery and extend field life, PETRONAS spearheaded various Enhanced Oil Recovery (EOR) initiatives in Malaysia. The Chemical Enhanced Oil Recovery (CEOR) was identified as one of the EOR process that has good potential for the field implementation to increase ultimate recovery in Malaysian oil fields. Consequently, a research project was carried out to evaluate various CEOR processes and to identify candidate reservoir for a possible pilot implementation. The encouraging result (14.6% OOIP incremental recovery) for alkaline-surfactant (AS) process has proved that there is potential for CEOR application at Malaysian oil fields despite the harsh environment (high temperature and high salinity) for CEOR process^1. The research has successfully identified suitable chemicals that can withstand the harsh environment and a suitable candidate reservoir for pilot implementation. The research works also included the design of AS formulation tailored to the test reservoir.

Subsequently, the CEOR pilot project was proposed and implemented at Angsi I-68 reservoir to evaluate the effectiveness of the AS process at reservoir condition in improving oil ultimate recovery through the reduction of residual oil saturation, S_or.

The AS technology combines synergistically, the interfacial tension reducing effect of added surfactants and those produced in the acidic crude oil by alkaline reaction of organic acids. AS flooding shows promise of being cost-effective because alkali, in addition to reinforcing the activity of surfactants, reduces the depletion of surfactant that occurs due to adsorption/retention in the reservoir ^2-3 .

The Angsi CEOR pilot project marked a significant milestone for the Malaysian oil and gas industry as it was the first CEOR project implementation in the country. The results of this pilot project are crucial in the future decision making for a large-scale full field and AS technology implementation with reduced technical risk. The result may be one of the keys in deciding the fate of the CEOR implementation in the Malaysian oilfields. In implementing this pilot project, together the team tackled and overcame significant technical and operational challenges.