Depositional environment and reservoir quality appraisal of offshore 'K-Field', Niger Delta, Nigeria

Abstract

This study attempts to evaluate the hydrocarbon reservoir and depositional trend of ‘K- Field’ via suites of wireline logs.
This is to identify, correlate the sand bodies and evaluate their petrophysical attributes with a view of understanding their
variation as itaffects the reservoir, hydrocarbon prospect and productivity in the field, and to determine the
palaeoenvironment of the lithofacies. Six sand bodies were identified and correlated across three wells. Zones of sand
level with water saturation < 0.50 were the hydrocarbon bearing. The various hydrocarbon reservoirs determined are six
(W-7), four (W-2) and three (W-11) respectively. The average petrophysical properties of the reservoirs range from 19% to
25%, 54.84 md to 1159.90 md, 20% to 42% and 58% to 80% for porosity, permeability, water saturation and hydrocarbon
saturation respectively. The porosity and permeability range from good to excellent. The identified reservoirs show high
movable oil saturation (MOS), low residual oil saturation (ROS) and favourable values of movable hydrocarbon index (Sw/
Sxo< 0.7). The field has both oil and gas hydrocarbon with the Gas Oil Contact (GOC), Oil-Water-Contact (OWC), Oil-
Down-To (ODT) and Gas-Down-To (GDT) contact types. The cross plot of water saturation and porosity revealed that the
grain sizes of the sand bodies range from coarse to very fine. Bulk Volume Water (BVW) cross plot indicated that most of
the reservoirs are heterogeneous and not at irreducible water saturation. The log facies recognized suggest a palaeo-
depositional environment of basin plain, crevasse splay, prograding and transgressive marine shelves.