Successful Underbalanced Well Completion Operations in Depleted Carbonate Reservoir of Brown Gas Field a Case Study

Abstract One of the main goals for oil and gas operators is to optimize reservoir productivity and enhance the ultimate recovery from depleting fields. Underbalanced drilling stands out as a pivotal technology embraced globally to accomplish various objectives aimed at maximizing reservoir potential. Among these goals, the primary aims are to minimize formation damage, pinpoint favorable zones within the reservoir, and trim down overall well expenses. Drilling the reservoir section underbalanced but completing the well overbalanced significantly affects the overall productivity of the reservoir. In addition to that, well control and killing operations during drilling and completion phases exacerbate the issue, leading to prolonged well delivery timelines and escalated costs. In response, this study delves into the successful case study of the groundbreaking underbalance slotted liner running followed by underbalance completion operation. The primary objective of this case study was to complete the well in underbalanced mode from dry hole to completion by utilizing the state-of-the-art technology which helps in bolstering well productivity without damaging the reservoir integrity, contrasting with conventional overbalanced methods. Methodologically, underbalance completion operations relied on the utilization of rotating control devices and downhole deployment valves for precise control, offering advantages such as enhanced reservoir connectivity while posing a few challenges which are also discussed. Results showcased notable improvements compared to offset wells. The underbalanced approach reduced cumulative drilling and completion days by 25%, resulting in a cost saving of 17%. Most significantly, the comparison of flowing rates revealed a substantial gain of 34%, highlighting the efficacy of underbalance strategies in optimizing performance. The successful implementation of underbalance operations proved instrumental in achieving desired production rates by avoiding the extensive well killing operations and costly acid stimulation treatments, thus underscoring its pivotal role in reservoir management and productivity enhancement. This paper discusses the planning, design, execution, and lessons learnt in underbalanced drilling and completion operations in the subject field.