Despite exploration and production success in Niger Delta, several failed wells have been encountered due to overpressures.Hence, it is very essential to understand the spatial distribution of pore pressure and the generating mechanism in order to mitigate the pitfalls that might arise during drilling. This research provides estimates of pore pressure along three offshore wells using the Eaton's transit time method. An accurate normal compaction trend was estimated using the Eaton's exponent (m=3). Our results show that there are three pressure magnitude regimes: normal pressure zone (hydrostatic pressure), Transition pressure zone (slightly above hydrostatic pressure), and over pressured zone (significantly above hydrostatic pressure). The top of the geopressured zone (2873 mbRT or 9425.853 ft) averagely marks the onset of overpressurization with the excess pore pressure ratios above hydrostatic pressure varying averagely along the three wells between P * = 1.06 -24.75 MPa and the lithostatic load range is λ = 0.46 -0.97 and λ * = 0.2 -0.9. The parametric study shows that the value of Eaton's exponent (m = 3-6) need to be applied with caution based on the dominant pore pressure generating mechanism in the Niger Delta. The generating mechanisms responsible for high pore pressure in the Offshore Niger Delta are disequilibrium compaction, unloading (fluid expansion) and shale diagenesis.
<p>The Nankai Trough is a locus of slow slip, low frequency earthquakes and M<sub>w</sub>>8 classical earthquakes. It is assumed that high pore pressure contributes substantially to earthquake dynamics. Hence, a full understanding of the hydraulic regime of the Nankai accretionary prism is needed to understand this diversity of behaviors. We contribute to this understanding by innovatively integrating the drilling and logging data of the NanTroSEIZE project. We focus on the toe of the accretionary prism by studying data from Hole C0024A drilled and intersected the d&#233;collement at 813 mbsf about 3km away from the trench.<br><br>Down Hole Annular Pressure was monitored during drilling. We perform a careful quantitative reanalysis of its variation and show localized fluid exchange between the formation and the borehole (excess of 0.05m<sup>3</sup>/s), especially in the damage zones at the footwall of the d&#233;collement.<br><br>Pore pressure was estimated using Eaton&#8217;s method on both drilling and sonic velocity data. The formation fluids are getting significantly over-pressurized only a few hundred meters from the toe of the accretionary prism near the d&#233;collement with excess pore-pressure (P*&#8776;0.04&#8211;4.79MPa) and lithostatic load (&#955;&#8776;88-0.96 & &#955;*&#8776;0.1-0.62 ) contributing to maximum 62% of the overburden stress.<br><br>The hydraulic profile suggests that the plate boundary acts as a barrier inhibiting upward fluid convection, as well as a lateral channel along the damage zone, favouring high pore pressure at the footwall. Such high pressure at the toe of the subsection zone makes high pressure probable further down in the locus of tremors and slow slip events.</p>
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.