Using High Fidelity OBN Seismic Data to Unlock Conventional Near Field Exploration Prospectivity in Nigeria's Shallow Water Offshore Depobelt
Obobi Ume Onwuka, Chudi Obinna, Ifekelunma Umeogu, Olalekan Balogun, Precious Alamina, Adelola Adesida, Akingbade Kolawale, Ibianga Sokubo, Jude Osimobi, Johnbosco Uche, Dave Mcpherson
Abstract
Abstract It is well-established that Nigeria's Shallow Water Offshore depobelt has large exploration potential and provides an upside for long term hydrocarbon production security. Long-standing imaging challenges associated with legacy streamer seismic data have led to safe and efficient acquisition of high-fidelity Ocean Bottom Node (OBN) seismic data covering three Oil Mining Leases’ (OML's) in the Depobelt. Multiple processed vintages of the data have resulted in better illumination of the subsurface structural and stratigraphic framework. This paper focuses on how the OBN data has helped improve our evaluation of the SOMA prospect. SOMA is an amplitude supported, 2-way fault bounded footwall closure bordered by key analogue wells to the north and south of the opportunity. The objective interval spans Pliocene to Messinian Upper plays with a depth range of 2,000 to 9,000ft (within the hydrostatic and amplitude domain). Compared to the legacy data, the new OBN data highlights a minor late-stage fault that compartmentalizes the prospective block separating it into two compartments – Block A & Block B. Eleven Reservoir Seal Pairs (RSP's) were interpreted and risked as gas. However, only three of the RSP's were considered commercially viable – contributing 56% of the entire prospect's Ultimate Recovery (UR). The reservoirs are expected to be mostly channels (single/multi-storey) and shorefaces deposited in the inner to outer shelf environment. Observed Direct Hydrocarbon Indicators (DHI's) show good calibration with offset wells where amplitudes conform to structure, are consistently higher in hydrocarbon filled sands and switches off in the brine leg. This paper aims to share key observations, results & learnings deduced from adopting an integrated subsurface approach, with strong subsurface collaboration geared towards delivering drill ready Near Field Exploration (NFE) volumes to support the business.