Detection and estimation of overpressure using borehole data from oil fields in the Niger Delta. – N. E. Umorem, J. O Ebeniro and C. N. Ehirim
Detection and estimation of overpressure using well data have been attempted. Suites of logs from three wells in the overpressured oil fields of the Niger Delta were used. Using the formation pressure information, the hydrostatic pressures of the three wells were derived. Working intervals were carefully selected from the same lithology (shale) within the depth of interest (6,000ft – 15,000ft) using gamma ray log. Overpressured formations display numerous properties when compared with a normally pressured zone at the same depth. The crossplots revealed the behavior of these properties with increasing depth. Comparison of these rock properties at different depth points showed changes in their trend behavior. Overpressure zones were significant with increasing depth (9,000ft).