1D GEOMECHANICAL MODELING OF THE DEVONIAN DUVERNAY FORMATION AND OVERLYING SEDIMENTARY SUCCESSION IN THE FOX CREEK AREA, ALBERTA, CANADA

The Devonian Duvernay Formation is one of the foremost unconventional shale resource in the Alberta Basin. The Duvernay play is developed through the use of horizontal multistage fracturing technology. The Fox Creek area has experienced felt induced seismic events (up to Mw ~4). A 3D coupled reservoir-geomechanical modeling in the Bigstone study area is planned to infer the geomechanical properties of the intermediate zone that separates interval of hydraulic fracturing and shallow non-saline aquifers to better understand the system response to hydraulic fracturing.

1D mechanical earth modeling (MEM) was carried out to calibrate rock mechanical properties, pressure and stresses in three drilled vertical wells in the study area and in a neighboring calibration well. The log-derived mechanical properties of rocks were compared to available results of laboratory testing in the calibration well. Predicted pore pressure profile was validated by the measurements of pore pressure in neighboring wells. Profile of minimum horizontal stress was calibrated by the results of Diagnostic Fracture Injection Test available in closely located wells. Wellbore stability analysis was completed for the analyzed wells to validate 1D MEMs and compare wellbore failure (pore pressure, breakout and mud loss gradients, synthetic breakouts) to the observed drilling events (gas kicks, cavings, mud losses) and recorded caliper logs.

According to the obtained results of 1D MEM, more calcareous shales of the Duvernay and overlying Ireton Formation are characterized by higher values of static Young’s Modulus and rock strength than kerogen-rich shales. Pore pressure gradient in the Duvernay Formation ranges between 16 and 18 KPa/m; strike slip fault regime is inferred with SHmax oriented N43°E. No major drilling problems were reported in this interval that was drilled underbalanced in analyzed wells probably due to very low permeability of the shales. Most of the wellbore shear failure occur in the overlying Devonian carbonate beds and Cretaceous clastic rocks, in which numerous and large borehole breakouts occur.

We thank Schlumberger for consolidated license donation to the University of Alberta. This work was funded by NSERC through grants RGPIN 2019 04397 and DGECR 2019 00186 and the Environment Geoscience Program, Lands and Minerals Sector, Natural Resources Canada.