Relationships between fluid pressure and capillary pressure in permeability and wettability predictions

Abstract

In this work, the Bower’s and Gardner’s technique of velocity-to fluid pressure gradient methods were applied on seismic reflection data in order to predict fluid pressure of an X- oil field in Niger Delta Basin. Results show significant deflection common with fluid pressure zones . With average connate water saturation Swc computed to be 6%, capillary pressure and fluid pressure respectively 292-399 and 1212-1239 psi, the same relative permeability and wettability were predicted. The wavy signature of the curves suggest large pore throats, i.e increase in grain sizes of the particles as the depths of deposition increased, confirming the fining upward sequences that characterize proximal deltaic regions. More oil is therefore possible to occupy these larger pore throats. Well (1) indicates water-wet reservoir. With 54% Sw at kro equal to krw, well 1 is interpreted as a water-wet reservoir, while Well (2) indicates a mixed wettability, with 54% and 46% Sw at kro equal to krw. This suggests that well (2) will have some EOR implications during production. It is also possible that once oil is in place, the operation of temperature and pressure might have geochemically altered the properties of the mineral surfaces such that they become oil wet. Therefore mature reservoir might have a mixed wettability, with water-wet in small pores containing water and oil-wet in larger pores containing oil.

Keywords: Fluid, pressure, capillary, wettability, permeability