Use of pore pressure data from the Norwegian Continental Shelf to characterize fluid-flow processes in geological timescales

Abstract

A dataset with pore pressures from more than 1000 exploration wells has been used to investigate the dynamics of aquifer systems in the Norwegian Continental Shelf (NCS). Variations in aquifer pressures reflect flow of porewater through permeable rocks over geological time. Strongly overpressured regimes are formed within confined aquifers in subsiding areas, where fluid flow out of the aquifer is controlled by vertical seepage. In transitional pressure regimes, fluid flows within permeable beds towards areas with hydrostatic pressures. In the hydrostatic regime, pressure differences result from density differences due to varying formation water salinity and by hydrocarbon columns. An underpressured regime has been encountered in confined aquifers in the platform areas of the Barents Sea, and is related to net uplift and erosion. In the case studies, pressure differences are interpreted in the context of the relevant pressure regime, and with a dynamic approach where segment boundaries and cap rocks are regarded as low-permeability restrictions rather than barriers. The present distribution of pressure regimes was developed over the last few million years due to rapid Pleistocene sedimentation and erosion processes.

Seal characterization and integrity in uplifted basins: Insights from the northern Barents Shelf

“…When comparing our study area with other parts of the Barents Sea (Riis and Wolff, 2020) Atlantis well initial leak-off pressure is also similar, however, subsequent cycles show much lower pressures.…”

Methods to Estimate Erosion in Sedimentary Basins

“…An overpressure of ~58 bars would be required to explain the 500 m shift to the minimum estimate obtained from VR data. However, this explanation is invalid as the Fingerdjupet wells are actually underpressured (Riis and Wolff, 2020). Alternatively, the fits obtained from VR data overpredict erosion as the average palaeo-thermal gradient was higher than the gradients predicted by the present-day temperature data.…”