Planning and Technology Utilization: A Holistic Approach to Marginal Field Development

Abstract

The Nong Yao Field in the G11/48 concession is operated by Mubadala Petroleum on behalf of the other concessionaires KrisEnergy and Palang Sophon Limited. Nong Yao recently commenced production following a successful development drilling campaign, which was extremely challenging due to subsurface uncertainties. The subsurface team adopted an innovative method of well sequencing and optimization of targets, such that every well drilled is used to de-risk other wells, in order to avoid costly additional appraisal drilling. The key methodology involved a deep understanding of the exploration and appraisal data gaps and as a result the uncertainties / limitations of the static and dynamic models. A field development plan was developed that could achieve additional appraisal objectives, and in doing so, de-risk other wells as the development was executed. Uncertainties that the team sought to mitigate included structural uncertainty (due to shallow gas effects), fluid contacts and fluid type uncertainty, sand distribution and connectivity uncertainty and also uncertainty in the aquifer extent and degree of pressure support expected. This information was gathered by planning deeper high deviation development wells with complex 3D trajectories, which could intersect multiple reservoir sands and provide the formation evaluation and well landing points for later horizontal development wells in shallower reservoirs. Achieving appraisal objectives while drilling both in the static and dynamic sense, helped in optimizing well locations and led to the cancellation of multiple water injection wells, which were not required as drilling indicated better aquifer and pressure support than initially expected. This led to substantial savings in well costs and enabled rig slots to be utilized for production wells rather than unnecessary injection wells. Key technologies were used to achieve appraisal objectives. A high build rate hybrid RSS tool was used to deliver complex 3D well profiles and land wells above oil-water contacts while maintaining high ROP and wellbore quality. The deep resistivity distance to boundary LWD tool ensured horizontal production wells stayed in the reservoir sands and also helped to map the top and extent of structures, improving reserves calculations and reservoir simulation. In key wells the use of the ultra-deep resistivity tool for reservoir mapping combined with the LWD near-bit triple combo, helped in mapping the reservoir prior to entering it, eliminating the requirement for separate pilot wells. The impact was that more marginal oil pools could be developed with a higher degree of confidence. The clear value of these innovations was a reduced overall development cost and wells better placed for recovery and production. With lower development costs, more reservoirs of this nature in the Gulf of Thailand can become viable to develop, which has a significant impact on the future of Thailand's oil and gas industry.