The Relation Between Rock and Fluid Properties
Authors: Garies Donald F. 
Published: December 2007

Introduction

The manner in which streamline flow is achieved in the Higgins and Leighton waterflood prediction procedure suggests that the prediction procedure suggests that the procedure might be simplified by planimetering procedure might be simplified by planimetering and mathematically applying streamline volumes in calculations. Early calculations along this line, using known methods of estimating water throughput and oil recovery, produced less than satisfactory results. Nevertheless, the idea seemed promising, provided more compatible throughput-recovery methods could be devised.

To devise these techniques, it was apparent that some method other than laboratory determination of Ko/Kw data was necessary. An early estimate of universal Ko/Kw data employed the Leverett-Lewis three-phase diagram for an estimate of Kro and a group of laboratory curves for corresponding estimates of Krw. Applied in the Buckley-Leverett procedure, these data produced surprising and unexpected constants in the produced surprising and unexpected constants in the derivative curves. Published Ko/Kw curves for specific reservoirs produced similar results. At that time it was observed that some unknown parameters dictated that the peak derivative parameters dictated that the peak derivative always occurred at 50 percent water cut and that at a given immobile fluid saturation the peak derivative was a constant value independent peak derivative was a constant value independent of the oil-water viscosity ratio.

It was reasoned that, if the peak derivative were independent of the viscosity ratio, it could hardly describe water throughput, which is most certainly dependent upon the viscosity ratio. Believing that perhaps this was the trouble with the irrational double-valued Buckley-Leverett curve, very basic flow relations were reconsidered to determine whether Ko/Kw could be calculated by logical reasoning.

The results of this study, reported in this article, formulate relations between rock and fluid properties. In turn, the rock-fluid relations build the foundation for simplified treatment of the streamline flow problem in waterflood calculations. The actual application of these relations to waterflood calculations is reserved for a subsequent article.

CONFLICTING CONCEPTS OF RELATIVE PERMEABILITY

A popular relative permeability concept states that the sum of relative permeabilities is always less than 1.0. Contradicting this view, we have the concept that any fluid may be used in determining absolute permeability, in which case the relative permeability to that fluid is equal to 1.0. Then we have the "Yoster effect", which essentially says that relative permeability may exceed 1.0 in certain cases. permeability may exceed 1.0 in certain cases. We also have the "Klinkenberg effect", in which case it is well known that higher absolute permeabilities result from using low pressure permeabilities result from using low pressure gaseous fluids. Finally, Darcy's law implies that a fluid cannot be injected into a pore volume that has no effective permeability to the injectal phase, though from practical experience we know that it can.