AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
The Dilemma of Fine-Grained, Very Thinly Bedded Reservoirs; Storage Versus Deliverability, Elon Reservoir Area, Okume Complex, Offshore Equatorial Guinea
(1) Americas Production, Hess Corp, Houston, TX.
(2) Exploration and Production Technology, Hess Corp, Houston, TX.
(3) Africa Production, Hess Corp, Houston, TX.
(4) Exploration, Hess Corp, London, United Kingdom.
Elon Reservoir Area, Okume Complex, offshore Equatorial Guinea, is comprised of high quality, Cretaceous reservoirs deposited in a submarine canyon setting. This canyon contains a variety of deposits including those associated with vertically stacked to laterally migrating leveed channel complexes. A spectrum of reservoir facies is observed in the Elon area. Among these are very thinly bedded to laminated, turbidite sands (<2 cm) with abundant mudstone (Facies 3). Based on analysis of >1600 ft of conventional core, Facies 3 is the most common of the reservoir facies by a factor of 2-3. Because of its relatively high abundance and average porosity of 24-25%, Facies 3 contributes significantly to the OOIP (“storage”) of the field. However, due the relatively low NTG and low permeability, Facies 3 is a very minor contributor to accessible or “effective” OOIP and permeability thickness of the reservoir system (“deliverability”). Hence, Facies 3 represents a dilemma to reservoir characterization and modeling. While important to hydrocarbon storage in the developed area, Facies 3 is minor contributor to well deliverability, and is very difficult to identify and model. Careful integration of seismic, electric logs, cores and production data reveals that not all Facies 3 reservoir intervals are the same. Facies 3 can be subdivided into intra-channel (3a) and inter-channel (3b) sub-facies. Sub-facies 3a occurs within the fills of channel complexes, while sub-facies 3b occur outside channel margins and are interpreted as levee/overbank strata. This presentation will review important distinctions between these different types of thin-bedded reservoirs in terms of reservoir architecture and performance.