TITLE:
Estimating Volume of Shale in a Clastic Niger Delta Reservoir from Well Logs: A Comparative Study
AUTHORS:
Vianney M. Kamayou, Chukwuemeka N. Ehirim, Sunday S. Ikiensikimama
KEYWORDS:
Volume of Shale, GRI, GR Method, Neutron-Density Method
JOURNAL NAME:
International Journal of Geosciences,
Vol.12 No.10,
October
19,
2021
ABSTRACT: The volume of shale (Vsh) is a critical parameter in petrophysical analysis
that enables the accurate estimation of other petrophysical parameters like
effective porosity, saturation and Net-to-Gross. This is an important step in
characterization of reservoirs as well as valuation of hydrocarbon potentials.
GR (Gamma Ray), Neutron and Density as well as Potassium,
Uranium and Thorium logs were adopted to estimate and analyze Vsh for sand 4 reservoir
interval across five wells using the
empirical (GR-linear and non-linear) and Neutron-Density methods. Results show
that Vsh estimated by the
different methods varied from 0.24 - 0.39 for the GR linear method (highest), 0.12 - 0.24 for the Larionov method
(intermediate), and 0.04 - 0.28 for the Neutron-Density method (lowest). Although the
Neutron-Density method gives the lowest values of volume of shale, this does
not translate to the most accurate and reliable results. This may be attributed
to the non-singularity in measurements and varying sensitivities of the well
logs used in this method as well as the complexities of the wellbore condition.
The GR non-linear (Larionov) method provides consistent and comparable volume
of shale estimations with the neutron-density method than the linear GR method
and consequently, the non-linear GR method is recommended for estimation of Vsh in the studied field.