In-Situ Determination Of Capillary Pressure, Pore Throat Size And Distribution, And Permeability From Wireline Data

The combination of wireline formation tester pressure measurements with conventional well log water saturation and porosity analysis permit the in-situ determination of a capillary pressure profile, a pore-size distribution profile, the mean effective pore radius, and the rock permeability. In this application of wireline data, multiple point measurements of fluid pressure recorded with the Repeat Formation Tester over the reservoir section define the fluid densities of the saturating fluids and the free water level and permit the calculation of the displacement pressure and the capillary pressure at any level of the reservoir. From these capillary pressure data, the water saturation versus depth profile obtained from the appropriate well log analysis can be transformed into a pore-size distribution profile and the mean effective pore radius can be defined. Variations in pore-size distribution over the vertical section of the reservoir can be recognized and quantified. Furthermore, permeability estimations can be made using the mean effective pore radius and the displacement pressure.