The Upper Devonian Duvernay Formation is a low-permeability unconventional resource play situated in the Western Canada Sedimentary Basin of Alberta, Canada. It is developed with horizontal wells and completed using hydraulic fractures that enhance the permeability and increase the hydrocarbon production.
Integration of wireline logs and seismic data can help in estimating dominant production factors such as: fluid properties (porosity, saturation, total organic carbon, etc.), pore pressure spatial variability, and geomechanical properties (Poisson's ratio and Young's modulus). Our focus was on estimating brittleness distribution within the reservoir because brittle rocks are easier to fracture and this is very important in achieving effective fracturing. Firstly, quantitative interpretation, a technology that integrates the wireline logs with prestack time migrated seismic data was performed to estimate the main elastic properties (compressional and shear wave velocities along with density). Then these elastic parameters were used to estimate the geomechanical properties: Poisson's ratio and Young's modulus. These dynamic geomechanical properties derived from seismic data are the equivalent to the one estimated from petrophysical analysis on logs as opposed to the static properties evaluated from core data. All geomechanical properties were analysed in close relation with three main facies characteristic for the Duvernay Formation of our study area: facies F1, carbonate or limestone massive to nodular, facies F2, organic rich shale or organic rich shale with carbonate inter-beds and the facies F3, clay rich shale or argillaceous shale with low organic content. Lastly, a seismic brittleness was estimated based on the dynamic geomechanical properties.
The estimated elastic properties allow for better mapping of the mid carbonate interval which is useful because these layers could be a fracking barrier and could pose problems for hydraulic fracture propagation. The brittleness volume along with the most probable seismic facies volume is very useful in differentiating the carbonate non-reservoir interval from the organic rich shale reservoir. A transition from high to low brittleness restricts fracture's ability to propagate across that boundary. The excellent subsurface imaging provided by these seismic cubes can help with better placement of the horizontal wells, allowing for a reduction in capital expenditure with less pilot wells required.
