A Strategic Approach for Accelerated Development and Economic Assessment of a Greenfield in the Sarawak Basin

Abstract Recently discovered Field A, situated among mature brownfields within the Sarawak Basin, represents a significant greenfield development opportunity for early monetization. The development team leveraged on extensive real-world data from analogous fields, resulting in fast-tracking the transition from exploration to development phase for this Field A. This paper presents the case study to deliver this plan, aiming to establish the field production profile and phased development concept. Given the stretched timeline of less than a year, the team began forecasting using a Material Balance or tank model approach targeting the main reservoirs. In the absence of well testing during the exploration phase, the team relied on benchmarking analyses using regional and brownfield data. Key parameters such as initial oil rate per string, permeability-thickness versus highest tested rate, recovery factor for the main reservoirs, productivity index, and drainage radius were derived from nearby fields. This benchmark analysis was included in the tank model predictions and the resulting production profiles for the base case scenario, which focuses on the major reservoirs with depletion recovery strategy. The overall greenfield development strategy integrates static and dynamic modelling to assess various development scenarios for primary and secondary recovery. The tank model approach facilitated the field recovery benchmarking and well count optimization. Further, with the static model delivery, a full field dynamic model is planned to comprehensively evaluate minor reservoirs and secondary recovery strategies. Due to the undeveloped nature of the field, reservoir engineering (RE) uncertainty analysis was conducted. The forecast range was designed to encompass risks and uncertainties, including contacts and structural uncertainties affecting connected and recoverable volumes, given the unknown strength of the aquifer and gas cap support. The current analysis, utilizing the tank model, incorporates sensitivity analysis to identify which parameters most significantly impact the forecasting results, particularly the recoverable volume. The full-field model will further evaluate uncertainty management strategies. Besides that, the team is also evaluating appraisal well requirements to gather more information and mitigate uncertainties, optimizing well location and completion strategy prior to execution. This approach expedited reservoir engineering work despite inherent uncertainties in greenfield projects. The comprehensive use of analog field data and benchmarking, combined with sensitivity analysis and uncertainty management, facilitated a robust and expedited development plan, ensuring a viable economic assessment for this greenfield. This fit-for-purpose methodology for resource evaluation followed by an appropriate development concept and economic assessment is quite generic and can be effectively applied to greenfield projects targeting early monetization across the oil and gas industry.