A Comparative Model Approach to Pore Pressure Prediction Applied to Central/Coastal Swamp Depobelt of the Niger Delta Basin

Résumé

Overpressured zones and porosity values in shale beds have been estimated for selected fields of the central/coastal swamp depo-belts of the Niger Delta. Pore pressure prediction (PPP), when done accurately can be used to avert disaster and helps in safe drilling. Eaton's sonic model, Bowers' model and Zhang's porosity-based model have been applied to predict overpressures using petrophysical log data from six 6 wells, each representing a field of the studied area. Predicted zones of hard overpressures (HOVP > 0.70 psi/ft) are generally below the depth of 10000ft. Top of geopressures (TOG) for the case study wells; WELL_A, WELL_B, WELL_D, WELL_G, WELL_H and WELL_K are 7000ft, 10500ft, 10000ft, 12500ft, 9000ft and 10400ft respectively. Eaton exponent '5.5' and Bowers model plotted with robust matches to measured pore pressures (MPP) everywhere except in one well. The porosity model equally yielded better matches to MPPs with higher values of fluid-transit-times typical of hydrocarbon fluid type (oil). These suggest, in combination with Vp-density analyses, a strong evidence of secondary mechanism causing overpressure in the basin. Very hard overpressures characterizes the deeper section of the basin (lower part of Agbada formation) at most of the well locations suggesting a strong evidence of fluid expansion mechanism which is also related to sediments unloading. The robust concordance between PPP and MPP profiles validates the results here and is a better guide for future drilling.

Citer ce document

Accès au document

Ce document est hébergé sur son dépôt institutionnel d'origine.

Auteur(s)

Statistiques

Consultations : 1

Téléchargements : 0