A New Method for Normalization of Capillary Pressure Curves

S E D M Desouky

doi:10.2516/ogst:2003038

Abstract

A new method for normalization of capillary pressure data of a reservoir was developed that incorporates the effects of pore geometry (pore size distribution index and flow zone indicator index), lithology index and irreducible water saturation. The hydraulic flow unit's approach was used to classify the reservoir formation into constant pore geometry units. The Leverett J-function was then correlated with the normalized water saturation for each reservoir unit to group the capillary pressure data of that unit into one curve. The method requires the measurements of capillary pressure, irreducible water saturation, and routine core data such as permeability and porosity. To check the validity of the proposed method, capillary pressure data, irreducible water saturations, and routine core data of a shaley-sandstone reservoir in the Gulf of Suez (Egypt) were obtained and were used in determining the accuracy of the developed equations. The calculations showed that the studied reservoir has four constant pore geometry units. An excellent agreement existed between the measured data and the calculated ones with average relative errors of - 5.8, - 4.3, 3.7 and 4.4% for flow unit-1, unit-2, unit-3 and unit-4, respectively.

Highlights

The capillary phenomenon occurs in porous media when two or more immiscible fluids are present in the pore space
Given the routine core data (k and Φ), capillary pressure data (Pc – Sw), and irreducible water saturation (Swr), the following steps are proposed for normalizing the capillary pressure curves. – Calculate the values of reservoir quality index (RQI) and Φn from core data using
By applying iterative multi-linear regression clustering [10] to the core data given in Figure 2, the optimum number of hydraulic flow units is four

Summary

Introduction

The capillary phenomenon occurs in porous media when two or more immiscible fluids are present in the pore space. Since the gravity forces are balanced by the capillary forces, capillary pressure at a point in the reservoir can be estimated from the height above the oil-water contact and the difference in fluid densities. Capillary pressure curves are usually determined in the laboratory by three methods: mercury injection, restored state cell (porous plate) and centrifuge. The description of these methods can be found in the reservoir text books [1, 2]. Leverett [3] was the first to introduce a dimensionless capillary pressure correlation function This function is defined as: J(Sw) = Pc √K/φ /(σ cos θ)

Methods

Results

Conclusion