Maximizing Well Construction Strategy for Combined Appraisal and Development in Stacked Reservoirs –A Case Study

Abstract This paper highlights the value-driven development strategies deployed in designing and constructing a multi-reservoir appraisal and development well. The reference field is a shallow water offshore brown field in Nigeria and has been producing since 1997 with significant remaining hydrocarbon resource in place. These strategies were based on a cross-functional holistic view of the development objectives, which revolved around appraisal data acquisition needs, expected volumes, cost, execution complexity and optimal well sequencing. The approach influenced the planning of a multipurpose appraisal/producer well to optimize the re-development of several reservoirs in the field. A broad appraisal and development scope such as this, came with attendant complexities for which well design and execution strategy had to be optimized. This paper further describes the strategies deployed to manage the identified well construction risks: Well trajectory intersecting multiple hydrocarbon bearing reservoirs with depleted pressures Drilling across multiple faults with risk of lost circulationDeep well collision risksExtended openhole exposure due to logging requirements in the production section andComplex completion assembly installation–2-string completions at >15,000ft with multiple jewelries (downhole gauges, gas lift mandrels etc.) This strategy ultimately improved drill-well campaign economics by over 60%, saved the cost of drilling two heel pilots, and acquired critical data that helped optimize other wells on the rig schedule. Subsurface data gathered from this well, integrated with production data helped articulate different possible subsurface scenarios that impacted completions designs and optimal reservoir management plan. Data from this appraisal/producer well also aided the optimization of reservoir production and development strategies towards achieving incremental uplift from 3 streamed producer wells and additional potential for future development.