Irreducible Water Saturation Prediction: An Improved Methodology Based on Hydraulic Unit Parameters
Vu, Hai Hung
Engineering Honours Degree, 2006
University of Adelaide
Irreducible water saturation is one of the fundamental parameters in characterizing petroleum formations, playing a key role in volumetric and recovery calculations, petrophysical analysis and special core analysis. More recent research has shown that the Flow Zone Indicator (FZI), based on the Carman-Kozeny equation, is a promising correlation parameter. However, in reviewing such formulations, it is apparent that additional pore structure and rock mineralogy aspects should be included for improved predictability. Secondly, irreducible water saturation may be obtained by alternative measurement methods, involving different definitions, and this aspect accounts for a certain amount of noise in any relationship. Laboratory determined irreducible water saturation depends on the type of test and testing conditions, for example velocity or capillary number, particularly in case different fluids are involved. Furthermore, in obtaining irreducible water saturation from capillary pressure relationships, the maximum capillary pressure and corresponding irreducible water saturation may not be truly representative, particularly for low permeability plugs.
A new methodology based on Amaefule’s formulation (Amaefule et al., 1993) for predicting irreducible water saturation is described in this paper, addressing the above-mentioned shortcomings. The correlation is based on a large and diverse data set for Australian and overseas oil and gas fields, both onshore and offshore. It is believed that the correlation, or at least its form, is universally applicable. Results in predicting irreducible water saturation with the improved methodology is compared with those obtained with other relationships cited in the literature.