Evaluating Chemical EOR Potential of St Joseph Field, Offshore Malaysia

Abstract This paper presents a systematic evaluation of enhanced oil recovery (EOR) potentials for St Joseph Field located in the offshore Malaysia. The field has been in production for 30 years, currently under gas injection and started injecting water in March 2011. Chemical EOR (cEOR) was identified as the most effective EOR process for maximizing ultimate recovery for St Joseph and the two nearby fields. This paper presents the key results of the St Joseph chemical EOR feasibility evaluation. It also discusses an integrated area development concept exploiting the synergies between the three fields of North Sabah, which is recognized as key to a successful cEOR development in the area. This study aimed to understand the size of prize in case of both polymer flood and Alkaline-Surfactant-Polymer (ASP) EOR scenarios using 3D full field models. One dimensional box and single well models were used to understand the physics of the EOR processes whereas the full field model was used to investigate the EOR subsurface development concepts, infill opportunities, injector/producer placements, slug size etc. It is anticipated that the proposed ASP flood will increase the ultimate recovery factor for the EOR targeted sands to circa 65%. Potential subsurface risks/uncertainties were also investigated. The chemical EOR process will involve handling a large volume of chemicals. This represents a major challenge in application of chemical EOR technologies in an offshore environment like St Joseph. Various facilities concepts were examined in detail. The selected concept is a combination of a mobile floating facility for the injection water treatment and chemical injection packages and a platform-based facility for processing the produced fluids/chemical. A pilot injection prior to full implementation has been planned to manage key subsurface/surface uncertainties and main challenges. The detailed studies of the pilot design and implementation are presented in a separate paper.