Accurate Reservoir Evaluation in Exploration Gas Wells: A Case Study in Malaysia Basin

Reservoir fluid composition and reservoir parameters characterization are fundamental for the accurate reservoir description during exploration phase and successful reservoir management in gas field development planning. Key reservoir fluid parameters namely hydrocarbon composition and Carbon Dioxide (CO2) are essential input to comprehensive production and reservoir engineering studies. The paper presents the exploration work done through three gas wells campaign in two main Malaysia basins. The formation is mainly thinly laminated sand-shale beds and the main objective for the operator is to acquire an early and quick identification of hydrocarbon prospect for appraisal wells planning. With that, compared to conventional PVT lab analysis which can easily take weeks to months to complete and full scale DST that offers higher operational complexity and cost, downhole fluid analysis was deployed. Downhole fluid analysis has successfully identified the reservoir fluid composition and properties for different fluid types. In this offshore Malaysia basin, high CO2 content was not expected geologically, high CO2 was measured in several sands of interest and this early identification on non-hydrocarbon prospect avoids unnecessary cost, time and operational risks. This work presents the successful downhole reservoir fluid identification in mobility range of 23.2 to as high as 5263.8 md/cP. The methodology, applications and suggested best practices applied throughout the campaign are presented in this paper.