Open File Report 2020-01

Author(s) Date 2020-02-11

A three-dimensional (3D) property model of sandiness/shaliness, porosity, and water saturation (AER/AGS Model 2020-01) was developed for the Upper Cretaceous Cardium Formation in west-central and southern Alberta. The Cardium Formation is represented by a terrigenous, muddy, sandy, and conglomeratic siliciclastic wedge that is encased in black mudstones deposited during the period of maximum inundation of the Mesozoic North American foreland basin, forming one of the largest conventional light to medium oil deposits in Canada. The shale volume in the Cardium Formation is inversely related to the sandstone abundance and was calculated from gamma-ray logs from oil and gas wells. The porosity was calculated from bulk density logs and the water saturation from a combination of the gamma-ray, bulk density, and deep resistivity logs. The 3D property model covers an area of about 90 000 km2 and represents an eastward-thinning wedge with a present-day maximum thickness of ~150 m in the foothills of the Canadian Rocky Mountains. This wedge thins out towards the Alberta Plains and grades into mudstone along its easternmost terminus. Several trends emerged from the 3D modelling including:

- The sandstone abundance generally decreases from northwest to southeast.

- In contrast to the sandstone abundance, the total porosity generally increases from northwest to southeast.

- The water saturation also generally increases from northwest to southeast.

- Sandstone and conglomerate are most abundant in the middle Cardium Formation. This interval can be clearly recognized in the cross-sections of the 3D property model for shale volume, density porosity, and water saturation.

The 3D property model illustrates the heterogeneity of shale volume, porosity, and water saturation in the Cardium Formation. It helps reveal depositional environments, history, and stacking patterns and provides insight into vertical and lateral connectivity of sandstone units. The resolution and accuracy of the 3D property model is constrained by the uncertainty and quality of the input logs and the methods used in modelling; as a result, the model is appropriate for regional-scale (1:100 000) assessments rather than site-specific investigations.

Mei, S.; Berhane, M. (2020): Three-dimensional property modelling of the Upper Cretaceous Cardium Formation in west-central and southern Alberta; Alberta Energy Regulator / Alberta Geological Survey, AER/AGS Open File Report 2020-01, 47 p.