Patent ID: 6792354
Filing Date: 2004-09-14
Classification: G01V

Abstract:
A method for using petrophysical data from a plurality of wells, in a plurality of reservoir regions, containing a plurality of reservoir rock types, in the context of a three-dimensional geological model, for identifying dimensionless capillary pressure functions and using these dimensionless capillary pressure functions for determining reservoir fluid volumes, fluid contacts, J facies, the extent of reservoir compartmentalization, and an improved estimate of reservoir permeability, comprising:selecting a region of the world to be modeled; assembling well log measurements for the region to be modeled where measurements include porosity, water saturation, elevation permeability, shale volume, lithology, location, seismic impedance, and measurements that may be used to distinguish between various dimensionless capillary pressure functions; assembling pressure, temperature, and volume (PVT) relationships for fluids contained in the region to be modeled; estimating interfacial tension and contact angles for the reservoir fluids; estimating permeability as a function of porosity; estimating the properties and extent of equilibrium regions; calculating reservoir fluid pressures as a function of elevation for equilibrium regions from the assembled reservoir fluid PVT relationships and an estimate of the pressure for at least one elevation per region; calculating the dimensionless capillary pressure functions as a function of measured water saturation for well log data from measurements of porosity and elevation, and from estimates of interfacial tension, contact angle, and permeability as a function of porosity; identifying dimensionless canillary pressure functions from a plurality data points from the well log data by filtering plots of the dimensionless capillary pressure functions to highlight or accentuate characteristic dimensionless capillary pressure functions shapes; modifying or adding to equilibrium regions, to identify reservoir compartments and fluid contacts; defining J facies, a parameter to characterize the rock type according to unique combinations of dimensionless capillary pressure functions and porosity-permeability relationship; cataloging a limited number of dimensionless capillary pressure functions for the region of the world to be modeled; calculating for each log data point, for which there is porosity, water saturation, and elevation data, the J facies that most nearly describes the data point; calculating an improved estimate of the permeability for each log data point by determining the degree to which the permeability must be modified to bring the data point into exact conformance with the dimensionless capillary pressure functions of the J facies that most nearly describes the data point; interpolating porosity, permeability, and J facies into the inter-well region, for which there is no measured data; calculating the dimensionless capillary pressure functions from the porosity, permeability, elevation, and J facies, and equilibrium region for all points in the inter-well regions; calculating fluid saturations for all points in the inter-well region; calculating hydrocarbon volumes for all points in the region to be modeled.