Seismic and petrophysical evidence of abnormal pore pressure in western Niger delta
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Date
2015
Authors
Adeoti, L
Olatinsu, O.B
Ishola, K.S
Ogofa, M
Journal Title
Journal ISSN
Volume Title
Publisher
Arabian Journal of Geosciences
Abstract
A detailed pore pressure evaluation of Tango Field,
western Niger Delta, was carried out with the aim of ascertaining
depth to overpressure which enables proper well planning
and designing in order to reduce cost of exploration and
exploitation. The evaluation was carried out using both
petrophysical data consisting of sonic, density and resistivity
logs obtained in five wells drilled in the area and high
resolution-seismic reflection data from which the average
and interval velocities were computed. Crossplots were made
for well logs data which were fitted with regression curves,
and trend lines in order to establish overpressure patterns.
Plots of overburden, fracture and hydrostatic gradients with
leak off test (LOT), mud weights and modular dynamic tester
(MDT) were made to validate the trends established from the
crossplots. The results obtained show that normal compaction
trends (NCT) were established for all the data used in the
analysis and all the wells except well 5 which showed obvious
deviations from these trends. Well 5 encountered overpressure
at 8,000 ft which was considered earlier than anticipated,
hence, it was abandoned. Top of overpressures for wells 2
and 4 were estimated between 9,000 ft and 12, 000 ft respectively.
Porosity versus vertical effective stress from the plots
confirmed the above depth to overpressure which reveals that
the overpressures are primarily generated by disequilibrium
compaction.
Description
Keywords
Pore pressure , Porosity , Crossplot , Leak off Test , Petrophysics , Seismic
Citation
Adeoti, L., Olatinsu, O.B., Ishola, K.S., Ogofa,M.(2015). Seismic and petrophysical evidence of abnormal pore pressure in western Niger delta. Arabian Journal of Geosciences,) 8(2), 1003–1016