Depositional and Diagenetic Controls on Reservoir Quality and Their Petrophysical Predictors in the Upper Cretaceous Doe Creek Member at Valhalla Field, Northwest Alberta
N. H. Ball and S. C. Atchley
Baylor University, Waco, TX
Valhalla Field, discovered in 1977 and located in northwest Alberta, Canada, produces from the Upper Cretaceous Doe Creek Member of the Kaskapau Formation. Original reserves in place are 279 million barrels of oil and 44.7 billion cubic feet of natural gas, of which 79 million barrels (29% recovery factor) and 32.1 billion cubic feet (72% recovery factor) are estimated to be recoverable by the Alberta Energy Resources Conservation Board. To date, almost 65 million barrels of oil (82% of recoverable reserves) have been produced by primary and secondary (waterflood) techniques.
This study evaluates the depositional and diagenetic controls on reservoir quality within the Doe Creek at Valhalla Field in order to identify reservoir-prone facies and predict the distribution of those facies in wells lacking core control. Analysis of core and well log data indicates that intervals of highest reservoir quality are preferentially associated with meter-scale sandbodies deposited in proximal lower shoreface and upper shoreface environments. Porosity and permeability data from calcite cemented zones are lower in value; however the majority occurs above the established cutoffs for Valhalla suggesting that cement may act as a baffle to fluid flow. Based upon the relationships of facies to deep resistivity, Vshale, and density-neutron porosity separation within cemented zones, a well log transform was created that successfully predicts the distribution of reservoir-prone facies and calcite cement in wells lacking core. These transforms may be used in the prediction of fluid flow pathways and hence, 3D numerical modeling of reservoir attributes.
AAPG Search and Discover Article #90087 © 2008 AAPG/SEG Student Expo, Houston, Texas