Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Doctor of Philosophy

Program

Geology

Supervisor

Shcherbakov, Robert

2nd Supervisor

Hart, Bruce

Co-Supervisor

Abstract

In the last decade, with the development of horizontal drilling and multistage hydraulic fracturing technology, extraction of unconventional resources has significantly increased in western Canada. These industrial activities have been associated with the rise in the seismicity rate. This thesis aimed to improve the quality of the available geomechanical models of the injection-induced seismicity in the Western Canada Sedimentary Basin, by incorporating detailed geoscience characterization for two unconventional reservoirs of the Duvernay Formation in the Fox Creek area and the Cardium Formation in West Pembina. Hydraulic fracturing has induced seismicity in the first area, but no induced seismicity has been detected in the second. A 3D multi-layered geomechanical modeling coupled with fluid flow was applied in order to simulate fluid injection and obtaining the pore pressure and stress changes on the pre-exiting faults for both geological regions. Differences in geology including reservoir rock properties (i.e., elastic parameters and hydraulic properties), distance to the basement faults, presence of pre-exiting faults, stress field, and hydraulic properties of the underlying formations are shown to be primarily responsible for the differences in induced seismicity. In addition, a 2D one-layered geomechanical model coupled with fluid flow was constructed for analyzing the induced seismicity cluster that occurred in Dec 2014-Jan 2015 in the Fox Creek. To quantify the simulation results different scenarios for operational parameters, faults orientation, hydraulic properties of the reservoir and faults were investigated. The spatiotemporal distribution of pore pressure and Coulomb failure stress reveal that there is permeability heterogeneity in the reservoir in sections of pre-existing faults. Ultimately, the 2D geomechanical modeling approach was improved by defining the reservoir porosity and permeability as a function of pore pressure and stress field. The pressure-dependent model also suggests heterogeneity in reservoir permeability, as changes in seismicity rate is related to changes in porosity and permeability.

Summary for Lay Audience

In the last decade, with the development of horizontal drilling and multistage hydraulic fracturing technology, extraction of unconventional resources has significantly increased in western Canada. These industrial activities have been associated with the rise in occurrence rate of earthquakes. This thesis investigated physical mechanisms of fault reactivation during these operations by performing a numerical modelling approach. The modelling results suggest that mechanical and hydraulic rock properties, distance from the injection sites to the pre-exiting faults, and injection volume and duration are key factors controlling the fault reactivation mechanisms. In addition, the result of this thesis emphasizes the importance of detailed geoscience studies in creating more realistic models representing the regional geology.

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