Depositional environment and reservoir quality assessment of the \u201cBruks Field,\u201d Niger Delta

Ayonma W Mode,Solomon I John,Okwudiri A Anyiam

doi:10.1007/s13202-017-0346-y

Ayonma W Mode, Solomon I John + Show 1 more

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https://doi.org/10.1007/s13202-017-0346-y

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Abstract

This study is a contribution to the understanding of the depositional environment and reservoir architecture of the “Bruks Field,” Niger Delta, Nigeria. The objective is to use sequence stratigraphy and petrophysical evaluation in characterizing the reservoirs encountered in the study area. Well logs from six wells (B001, B002, B003, B009, B010 and B012-ST); biofacies data from wells B001 and B002; and a 3D seismic volume were analyzed to understand the spatial and temporal trends of reservoir sandstones, the environments of deposition, petrophysical properties of the F-sandstone and fault patterns on the structural map of the field. Log correlations show a considerable thickness of sands marked as fluvial. Results also show that the reservoirs are of foreshore, upper shoreface, lower shoreface, tidal channel and channel sands, which were deposited in a shallow marine setting. Two depositional sequences SEQ1 and SEQ2 were delineated with maximum flooding surfaces (MFS) 10.4 and 8.6 Ma, respectively. The depositional sequences are bounded with sequence boundaries (SB) dated 10.6, 10.36 and 7.4 Ma. The F-sand reservoir has an average net to gross thickness of 0.55, effective porosity of 0.29 v/v, permeability of 2506 mD and water saturation of 0.14 v/v. These values depict good reservoir quality, though the sand is deposited in tidal channels with the presence of heteroliths. The delineated faults composed of mainly growth faults, listric fault, antithetic and synthetic faults that formed the hydrocarbon traps for the F-sand.

Highlights

This study is a contribution to the understanding of the depositional environment and reservoir architecture of the ‘‘Bruks Field,’’ Niger Delta, Nigeria
This paper presents the results of the reservoir quality assessment carried out on the reservoir sands in the ‘‘Bruks Field,’’ Coastal Swamp, Niger Delta, using the integration of sequence stratigraphy and petrophysical studies
These reservoirs were interpreted as shoreface, tidal channel and distributary channel sands (Fig. 3a, b)

Summary

Introduction

This study is a contribution to the understanding of the depositional environment and reservoir architecture of the ‘‘Bruks Field,’’ Niger Delta, Nigeria. In the Niger Delta, three depositional settings indicate that deposition occurred during several regressive/transgressive episodes in overall progradational setting These depositional settings can be subdivided into the lower overpressured marine Akata Formation which underlies the delta and it is composed of thick shale successions (potential source rock), turbidite sands (potential reservoirs in deep water) and minor amounts of clay and silt. The paralic successions grade into an upper series of massive sands and gravels (Benin Formation), deposited under continental conditions (Evamy et al 1978; Weber 1986) It is a transitional series composed mainly of sand but with some shale

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