Abstract This paper examines the anomalous variations in the fluid properties across the Pembina Cardium Field in view of an extensive geological study of that area completed in 1975. Based on earlier geological concepts, it was impossible to generate a correlation between fluid properties and geology that had field-wide application. However, the recent geological study indicates that there are two separate and distinct producing zones. Further investigation showed that each zone had its own set of fluid properties. By relating the fluid properties to the appropriate producing zone, it is possible to derive a correlation which accounts for the variations in GOR's and other fluid property-related parameters in this field. A summary of the derivation and application of this correlation is discussed in this paper. Introduction The Pembina Cardium Field is an extensive oilfield approximately 113 km (70 miles) southwest of Edmonton, Alberta (Fig. 1). The under saturated reservoir was discovered in 1954 and was drilled out over the next several years. The pool, which covers an area of 283,000 ha (700,000 acres) and includes about 4,400 wells, is mostly under waterflood (Fig. 2). During the first few years of production from the pool, variations were found in the fluid properties. Properties such as gas-oil ratio, bubble point, viscosity and oil gravity varied significantly across the pool. Attempts had been made to explain these variations in the fluid properties, but there were no field-wide explanations. The purpose of this paper is to present a summary of the results of a study done on the variation of the fluid properties in the Pembina Cardium Pool in relation to a recent field-wide geological report. Geology of the Pembina Cardium Pool In the past, most geological studies on the Pembina Cardium Pool covered only certain areas of the field. However, in 1975, Rodgers, Klassen, Russum and Budrevics, of Amoco Canada. conducted a geological study of the whole field. Their work indicated that there were two main producing sandstone zones in the Cardium, and that these zones were not continuous across the field. Up to this time, it was generally assumed that there was only one major producing sandstone zone in the Cardium Pool. According to the geological study completed in 1975, the Cardium was broken up into the four geological zones described below:Zone 1-Conglomerate, a broad term covering all impermeable and permeable material at the top of the Cardium Zone, bearing pebbles.Zone 2-Permeable sandstone immediately underlying and usually in contact with the conglomerate when both are present.Zone 3-Impermeable zone consisting of bioturbated shale and siltstones with minor permeable sandstones.Zone 4-A regressive phase of permeable sandstone interbedded with bioturbated material. A diagrammatic cross-section illustrating these zones, as found in the Amoco-operated leases in the western part of the field, is shown in Figure 3.