Multi-Well Reservoir Heterogeneity and Flow Unit Characterization Using Wireline Logs, RQI, and FZI in the Niger Delta Basin, Nigeria.

Abstract

Reservoir heterogeneity and hydraulic flow unit characterization constitute critical 
parameters in optimizing hydrocarbon recovery within structurally and stratigraphically 
complex depositional systems such as the Niger Delta Basin. This study investigates 
reservoir quality, compartmentalization, and flow unit architecture in the offshore 
QUAC Field, Niger Delta, Nigeria, through an integrated petrophysical evaluation of 
wireline log datasets acquired from three wells: QUAC-1, QUAC-2, and QUAC-3. The 
workflow incorporated gamma-ray, neutron–density, sonic, and resistivity logs to 
quantitatively estimate shale volume (Vsh), porosity, and permeability, while hydraulic 
flow units were delineated using the Reservoir Quality Index (RQI) and Flow Zone 
Indicator (FZI) techniques. Four principal reservoir zones were identified and classified 
on the basis of distinct lithological and petrophysical characteristics. Computed shale 
volume values range from 0.12 to 0.45, indicating moderate to high vertical heterogeneity 
across the reservoir succession. RQI and FZI values cluster between 0.09–0.18 and 0.90
1.12, respectively, suggesting the predominance of moderate-quality hydraulic flow units. 
Neutron–density crossplot analysis reveals the occurrence of multiple hydraulic flow 
units governed by depositional facies variability and post-depositional diagenetic 
modifications. Among the delineated intervals, Zone 2 across all wells represents the 
cleanest, most laterally extensive, and hydrocarbon-saturated reservoir unit with 
enhanced reservoir continuity and favorable petrophysical attributes. Conversely, Zone 
3 consistently exhibits poor reservoir quality, characterized by elevated shale volume 
values ranging from 0.38 to 0.45, thereby functioning as a potential flow barrier and non
reservoir interval. The integration of multi-log petrophysical analysis with hydraulic flow 
unit classification provides a robust framework for understanding reservoir 
heterogeneity and compartmentalization, thereby supporting efficient reservoir 
management and strategic hydrocarbon field development.