Integrating Lessons Learned from Development Drilling to Early Field Performance into the Construction of a New Geologic Model, Deepwater Offshore Nigeria

Taye S. Akewusola, Lisa A. McBee, Felix O. Obere, Jianhua Feng, Raymond H. Young, Don Ying, Edwin U. Nwaeri, I. Uka, S. Fadahunsi, and U. Oguamanam
Esso Exploration and Production Nigeria Ltd, Lagos, Nigeria

The subject field produces from middle Miocene confined deepwater channel reservoirs and represents one of the early exploration successes in deepwater West Africa. The production and injection wells are tied back to a Floating Production and Offloading vessel (FPSO) with a production capacity of 230 KBD oil, 90 KBD water and 360 MSCFD gas. The field is currently producing 165 KBD of oil from fifteen producers supported by three water injectors and four gas injectors.

Appraisal and early development drilling encountered multiple fluid contacts across the field highlighting the uncertainties associated with predicting reservoir connectivity. The multiple contacts were initially thought to be largely due to sealing faults and laterally extensive top seals. Although multiple geologic and reservoir simulation models were built to address the uncertainties, fundamental understanding of the structural and stratigraphic framework, as well as connectivity was lacking due to data limitations.

In order to mitigate the reservoir connectivity uncertainties and provide insights to the geologic model and reservoir simulation, interference well tests were conducted at field start-up. These data combined with production data show that the reservoirs are more laterally and vertically connected than originally predicted. Furthermore, a reservoir connectivity analysis (see Corona et al, this volume) confirmed that the hydrocarbons are in pressure communication and that the numerous oil-water contacts are controlled by internal spill-points and base-seal. The field has primarily a single gas-oil contact.

The connectivity learnings are being integrated into an ongoing reservoir characterization effort based on the interpretation of a high resolution 4D baseline survey. The interpretation has resulted in significant changes in the base structural and stratigraphic framework.

AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery