Devonian Duvernay Formation, East Shale Basin, Alberta
The East Shale Basin of Alberta is located geographically in the Three Hills and the Ponoka/Gull Lake area, with recent activity mainly found within the strike areas of Joffre, Morningside and Huxley.
The East Shale Basin (ESB) has seen a flurry of recent activity since 2016 following the published commercial success of Duvernay operators in the Kaybob, Alberta Region. The East Duvernay area has seen a rise in production from approximately 3000 BOE/d in late 2014 to over 12,0000 BOE/d in late 2017 with the number of East Duvernay area rig releases more than doubling from ~20 in 2016 to over 50 in 2017.
Productivity of the Duvernay Formation in the East Shale Basin is the key to profitability as Athabasca Oil Corporation estimates payout using $55/BBL at 17 months or 9 months shorter than the Kaybob Duvernay wells.
The Frasnian Duvernay Formation of the East Shale Basin lies conformably on the carbonates of the Cooking Lake Formation and represents the deeper portion of the basin of the prograding Ireton Formation. The Duvernay Formation was deposited in anoxic conditions due to restricted ocean current circulation as a result of the contemporaneously deposited Leduc Formation at the margins of the basin. Subsequently, the Duvernay Formation is composed of organic rich mudstone and mixed siliceous mudstone interbedded with bioturbated limestone.
The Duvernay Formation in the East Shale Basin offers higher liquid yields & lower GOR in the range of 0-1000 m3/m3 at shallow target depths less than 2500 metres, significantly shallower than the West Shale basin and Kaybob regions. The predicted liquid yield is related to thermal maturity and kerogen type and the core analysis data required to predict thermal maturity is made available through the Alberta Energy Regulator (AER).
The Devonian Duvernay Formation is a mainly organic rich shale representing a basin-fill sequence concurrent with Devonian Leduc reef growth at the margins of the basin. The mineral content of shale determines the mechanical properties of the rock. The Duvernay Formation is mainly quartz and carbonate rich with relatively low clay components resulting in a relatively high Brittleness Index. Formations with high clay components have a lower tendency to form natural fractures, therefore high clay content is considered to hinder fracture development.
The Duvernay of the East Shale Basin geologically differs subtly from the Duvernay Formation West of the Leduc Rimby-Woodbend trend with higher average porosities in the range of 10-15 % and generally a lower Ur, Th, K composition as displayed on the gamma ray petrophysical log profile.
As with the regional Duvernay Formation, determining net pay in the East Shale Basin is a combination of reservoir discriminators including porosity/permeability, nature fracture density, resistivity, total organic carbon, thermal maturity, hydrocarbon saturation and mineral composition.
Detailed formation top-picking suggests the elevation of the Devonian Duvernay Formation in the East Shale Basin ranges from -1100m in the north to -1900m Sub Sea in the south, with the approximate edge of the Big Valley Fenn Devonian Leduc reef trend bifurcating the East Shale Basin into two sub-regions.
Early seismic analysis suggests regions where the Duvernay Formation displays a large trough amplitude is an indicator of productivity and this study suggests Vesta Energy Ltd. is placing wells targeting the Duvernay Formation in regions with a strong trough amplitude seismic response.
3D seismic is beneficial to both geosteering & attribute analysis within the Duvernay Formation. The attribute analysis from the 3D combined with well log Information (dipole sonics) allow operators to build a geological/geophysical model targeting areas of higher productivity.
The East Duvernay Shale Basin has a thickness variation from approximately 25 metres to greater than 110 metres with the greatest frequency of Duvernay Formation thickness at 50-80 metres. A histogram of interpreted or mapped elements offers a rapid review for quality control.
In-house decline curve analysis (DCA) of the currently producing East Shale Basin Duvernay Formation area wells suggests an expected ultimate recovery ranging from 50 mbbls to more than 1 mmbbls. All elements of variability in production history are studied to provide the most accurate analysis.
Due to the limited producing Duvernay wells the sample set is low, however early analysis suggests a limited correlation between expected ultimate recovery (EUR) and Duvernay thickness within the East Shale Basin with Vesta Energy Ltd. and Artis Exploration Ltd. dominating early East Shale Basin Duvernay Formation production.
Chinook Consulting offers gathering, quality check, normalizing and interpretation of reservoir data and discriminators required to accurately quantify reservoirs. Chinook Consulting also offers reservoir multi-variable interval analysis and interpretations with the ability to compare and contrast to reservoir deliverability and productivity.
All information and interpretations provided in this summary was compiled using public sourced data unless otherwise specified and strictly the property of Chinook Consulting Services and may not be used without the written permission of Chinook Consulting Services.