Origin and generation mechanisms of geopressures in shale dominated settings world-wide: A review

Abstract

Geopressures are common in young Tertiary sedimentary basins where marine units underlie rocks of higher permeability. A low permeability environment and conditions that reduce available pore space or increase fluid volume are necessary for geopressures to occur and be maintained. In the Niger Delta, Gulf of Mexico, and indeed worldwide, the generation of geopressure is often related to the sedimentation rate, while its dissipation depends on the hydrological properties of the sediments(that is porosity, permeability, etc).Geopressures influences many fluid related aspects of petroleum geology including diagenesis, migration and accumulation of oil and gas ,and indeed reservoir quality. It also constitutes a hazard in drilling wells and directly impacts on drilling costs and the safety of petroleum exploration. The general overview of the different casual mechanisms and their relative contributions to the present day geopressure regime is indeed very important. The objective of this work is therefore to review the different mechanisms of geopressure and to assess the relative contributions of individual mechanisms to geopressure
development. A primary objective here is to critically evaluate the relative importance of each.