Chapter 7
Application of Saturation-height Functions in Integrated Reservoir Description

Paul F. Worthington
Gaffney, Cline & Associates
Alton, Hampshire, U.K.

ABSTRACT

In many integrated field studies, a single reservoir-zonation scheme is not meaningful for all deterministic interpretative applications. These cases require that the concept of reservoir partitioning should evolve to become fit for purpose. Thus, a stratigraphic zonation is used solely for correlation and volumetrics, whereas a petrophysical separation is applied exclusively in core and log analysis for reservoir properties, after which the petrophysical partitioning can be discarded. In such a case, in which the stratigraphic zonation and petrophysical separation do not naturally correspond, the adoption of fit-for-purpose reservoir-partitioning schemes allows saturation-height functions to be much more sharply defined because they are then related to units of fairly uniform physical character. The resulting values of water saturation are subsequently assigned to the stratigraphic zones, using a straightforward petrophysical combining algorithm in which a key parameter is bulk volume water. The nature of the combining equation therefore indicates that the optimum form of saturation-height function should include bulk volume water as predicted variable in reservoirs that require dual partitioning. Such an approach has general application in deterministic studies of water-wet siliciclastic reservoirs. The principal benefit is the controlled reduction of uncertainty in reservoir evaluation.