Impact of 3D Seismic Re-interpretation of OML 20: The Oguta North Prospect

Ralf Esedo and Berti Ozumba
Shell Petroleum Development Company of Nigeria, Port Harcourt, Nigeria

OML 20 is located within the northern part of the Niger Delta in the Northern Depobelt within SPDC acreage. Initial exploration activities were concentrated in this early part of the delta before large fields were discovered in the Central and Coastal Swamp Depobelts of the Niger Delta. Given the successes recorded in these southern depobelts, more activities were focused on them as they latter came to be known as the "Golden Belt" of the Niger Delta. The concentration of activities in the southern depobelts made justification for new seismic acquisition difficult outside the southern depobelts as only few fields were discovered in the northern depobelts. Following the change in seismic technology acquisition from 2D to 3D, most of the northern delta within the SPDC acreage was left with inadequate 3D seismic coverage. However, given the favourable crude oil prices in the international market, the increasing profile of gas demand and the reserves replacement ratio that drives new developments in Nigeria's fiscal regime, exploration activities have started to be re-intensified.

The major discovery in OML 20 was the Oguta field. It was discovered based on the interpretation of 2D seismic data. New drilling can as now only be justified on 3D seismic data as the big and obvious prospects may have been drilled based on the interpretation of 2D data set. Recently a 3D seismic acquisition campaign was carried out in the area. Following this acquisition and subsequent processing, the data has been re-interpreted. The product of this reinterpretation is the Oguta North prospect. The Oguta North prospect is a large fault bounded closure within a northwest to southeast trending fault block north of the Akri-Oguta field. The culmination of this prospect is against an oblique fault that could not be defined on 2D.