GLJ’s Erfan Sarvar Amini, Ph.D., P.Eng. will present a paper entitled “Shale fracability in Kaybob-Duvernay: A new approach based on plasticity behavior” at the 55th American Rock Mechanics Association (ARMA) this June 18-25.
Kaybob Duvernay, one of the most prolific source rocks in the Western Canadian Sedimentary Basin, is the focus of this paper — providing new insights on optimization of multi-stage hydraulic frac jobs in the area.
The geomechanical behaviour of the Duvernay source rock is interesting and unusual. It has significant hydrocarbon storage with nano-Darcy scale permeability, and lacks any evidence of widespread micro fracturing when not proximal to a known fault lineament. The lack of micro fracturing, combined with extremely large pore pressures, variability in organic matter, and mineral composition, have resulted in complex mechanical rock-fracturing characteristics.
A novel universal fracability index is developed to quickly identify the best landing intervals for optimization of the frac jobs through creation of a maximum stimulated rock volume (SRV). This new index provides a high-resolution fracturing discriminator to separate the highest geomechanically competent intervals from the lowest, by integrating various parameters: Tectonic in-situ stresses, pore pressure, and geomechanical and petrophysical properties. This approach allows operators to improve the completion quality and well performance at almost no additional cost.
An example of this analysis is presented below for Duvernay Kaybob as a test case. Using the analysis, we show that, unlike commonly held beliefs among the Duvernay operators, the targeted pay (Upper Duvernay) is not geomechanically homogenous. In fact, the rocks become substantially geomechanically competent closer to the bottom of the pay. Currently, the majority of the wells in the Kaybob have landed in low-to-moderate fracable intervals. We determined the best landing interval to be closer to the bottom of the pay (as marked by the red circle). We also showed that highest fracable intervals tend to have higher pore pressure, lower net effective closure stress, higher organic matter, and lower initial frac toughness.