Отправлено: 24.10.12 05:19. Заголовок: Дельта Нигера (Наглубине в 4000 метров проницаемость выше 5000мД

Petrophysical evaluation of uzek well using well log and core data, Offshore
Depobelt, Niger Delta, Nigeria
Adaeze, I. Ulasi; Samuel, O. Onyekuru; and Cajetan, J. Iwuagwu.
Department of Geosciences, Federal University of Technology Owerri, Nigeria
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ABSTRACT
Petrophysical well log and core data were integrated in an analysis of the reservoir characteristics of Uzek Well,
Offshore Depobelt, Niger Delta Basin, Nigeria. The study essentially determined reservoir properties such as
lithology, depositional environments, shale volume porosity (Φ), permeability (K), fluid saturation, net pay
thickness, among others from well logs and cores, which are variables that determine reservoir quality. The original
hydrocarbon-in-place of each reservoir was also evaluated based on mean weighted averages of porosity, water
saturation, gross rock volumes and net-to-gross ratios. The analysis identified four (4) hydrocarbon-bearing
reservoirs (I, P, Q, and R). The Uzek Well sandstone reservoirs were generally coarsening upward sequences with
gradational/transitional basal and sharp upper contacts reflecting sedimentation in high energy environments,
possibly, the shoreface depositional environment. Average permeability values of the reservoirs is above 1000md,
while porosity values ranged between 20-30%, reflecting well sorted coarse grained sandstone reservoirs with
minimal cementation, indicating very excellent reservoir quality. Fluid types defined in the reservoirs on the basis of
neutron/density log signatures were basically water, oil and gas. Low water saturation (12-54) in the reservoirs of
the Uzek Well indicated that the proportion of void spaces occupied by water is low, thus, indicating high
hydrocarbon saturation. Quantitative porosity verification using Pearson Correlation Coefficient and Regression
Equations revealed significant similarity in the porosity values obtained from petrophysical well log and core data.
Plots on scatter diagrams using porosity values derived from petrophysical log and that from core analysis for the
four reservoirs obtained correlation coefficient (r) values of 0.7165, 0.8094, 0.5835, and 0.5025, respectively for
reservoirs I, P, Q, and R, indicating strong linear relationships. Plots of values of water saturation derived from
core analysis and that from petrophysical log for the reservoirs also showed linear trends. Plots of porosity values
against permeability values showed fairly strong linear relationships between the two variables in all the reservoirs
indicating that Uzek Well reservoirs are permeable and have pores that are in strong communication. The
petrophysical properties of the reservoirs in Uzek Well are enough to permit hydrocarbon production.
Key words: Niger Delta, Reservoirs, Characterization, Hydrocarbon and Saturation