Formation Pressure While Drilling – Benefits of Real-time Decisions for Extended Reach Wells in Mature Field Revitalization
As the long term reservoirs of a producing field become depleted, in-fill drilling, targeting zones or fault blocks that were bypassed by the original wells, is often necessary in order to maintain production levels. Targeted zones are often remote, having little to no formation evaluation data available, and previously produced depleted horizons may need to be crossed in order to reach them. This poses two main challenges - the requirement for reservoir characterization in development wells that have limited formation evaluation options due to various factors, including high deviation, potential wellbore stability issues with narrow pressure windows, and the need to drill the well in a safe and efficient manner. This paper describes the use of Formation Pressure While Drilling (FPWD) measurements in an Extended Reach Drilling (ERD) in-fill campaign in the Andaman Sea, offshore Myanmar that assisted to boost the production as a part of the ongoing development of a mature gas field. The requirement to safely drill through combinations of unstable shale and depleted sand layers, while targeting virgin reservoir sands, made real-time formation pressure monitoring essential. FPWD measurements were used to determine the differential pressure required to optimize the Equivalent Circulating Density (ECD) in a narrow drilling margin and while selecting casing points where larger mud weight changes were required. Pressure depletion monitoring in producing horizons, sand connectivity testing, and fluid typing through gradient analysis also provided valuable inputs to the reservoir characterization and completion decisions. In addition, FPWD was used to aid geo-steering in one of the highly deviated wells in order to penetrate a major fault and appraise a virgin sand layer in a different fault block. FPWD significantly contributed to the success of the in-fill drilling project, revitalizing the declining gas field by boosting production. Real-time knowledge of formation pressure enabled the mitigation of wellbore stability issues by managing ECD, while optimizing the well trajectory. Evaluation benefits included confirming pressure depletion, sand connectivity and subsurface model predictions. The data also provided a basis to identify additional production enhancement opportunities by identifying virgin horizons for future side tracks and in-fill wells, thus contributing to the re-evaluation and further development plans for the field. Formation Pressure While Drilling measurements contributed in at least four ways combined to aid the revitalization of the mature field, enabling the Operator to complete the in-fill ERD campaign safely and enhance the resource assessment. The results in this paper indicate that the correct application of FPWD is a very valuable tool in revitalizing the mature fields and enabling the operating companies to complete in-fill drilling safely to increase the production level.
AAPG Datapages/Search and Discovery Article #90336 ©2018 AAPG Asia Pacific Region, The 4th AAPG/EAGE/MGS Myanmar Oil and Gas Conference, Myanmar: A Global Oil and Gas Hotspot: Unleashing the Petroleum Systems Potential, Yangon, Myanmar, November 13-15, 2018