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An Improved Correlation for Irreducible Water Saturation

Edge, David

Engineering Honours Degree, 2005

University of Adelaide


Irreducible water saturation is an important rock property that is used in many reservoir calculations, such as petrophysics and volumetrics, and fluid flow calculations.  Relative permeability end points and capillary pressure curves are also characterised by this property.  While there have been numerous correlations proposed in the literature, historically most tend to involve permeability and/or porosity.  More recently, the emphasis has been to incorporate features by using a Hydraulic Unit (HU) approach, utilizing the Carman-Kozeny equation.  In attempting to derive a correlation for irreducible water saturation, for both oil and gas reservoirs, a large data set of special core analysis data was utilised that is representative of several Australian onshore and offshore fields.

This report attempts to further the hypotheses that have been made previously regarding the direct relationship between irreducible water saturation (Swir) and Flow Zone Indicator (FZI). The FZI value can be equated from reliable porosity and permeability data.  This study is advantageous over prior studies due to the simple fact that such a high quantity of data has been provided for analysis.  This greater quantity of data has allowed the correlation to obtain a greater degree of reliability and therefore a representative formula can be defined.

Australian School of Petroleum



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