Bonga Field: A Phased Development to One Billion Barrels

Abstract

Abstract Bonga field is located 120 km offshore and lies in water more than 1,000 meters deep across an area of 60 square kilometers. The hydrocarbon-bearing reservoirs are at depths of 6000 – 1000 ftss. The field was discovered in 1993 and came onstream in November 2005 as the first deepwater development project in the Gulf of Guinea It was developed with subsea wells, production manifolds and water injection terminals connected to a Floating Production, Storage and Offloading (FPSO) facility through a series of subsea flowlines and risers. Over a period of 18 years, the field has achieved a cumulative oil production of over 1.0 billion barrels, 815 Bscf of gas export and 1.5 billion barrels of water injected through a total 39 oil producer and 36 water injector wells. This performance is grounded in extensive early exploration & appraisal efforts and a continuous revision of the field development plan (FDP) to accommodate new opportunities and optimizations of the existing facilities as more data became available. The field took final investment decision (FID) based on an Estimated Ultimate Recovery (EUR) of 579 MMbbls in 1999. By 2019 the EUR had increased to 1300 MMbbls due to an increased Stock Tank Oil Initially in Place (STOIIP) estimate, better reservoir connectivity than expected and the appraisal of additional hydrocarbon bearing intervals. Bonga has been developed in phases, with Phase-1 development consisting of 9 oil producers and 7 water injectors targeting five deeper and relatively better-quality reservoirs. Subsequent phases targeted shallower reservoirs and added further infill wells into the deeper reservoirs. In 2014 the Bonga North-West (BNW) near-field opportunity, identified in the early 2000s through exploration & appraisal drilling, was developed as a subsea tie-back to the Bonga Main hub. BNW added an additional 4 oil producers and 2 water injectors to the well stock and increased the field's daily production by ca. 60 kbopd. A key enabler of the exceptional value delivery from the Bonga field has been a robust Well, Reservoir and Facility Management Plan integrating a reservoir management strategy (water injection for pressure maintenance and sweep efficiency), surveillance and data acquisition including 4-yearly Ocean Bottom Node (OBN) 4D seismic data acquisition, vigorous well interventions, creative management of limited slots and drilling of infill wells to maximize oil production and ultimate recovery. This paper provides an overview of the Bonga field development journey to achieving one billion barrels of oil produced, highlighting the key role of exploration & appraisal and continuous update of field development and production strategies, enabled by the application of new data, new understanding, and new technologies.