Influence of natural fractures and stress path on brittle fracture propagation and hydraulic fracturing for improved rock mass preconditioning and enhanced permeability

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With ever-growing populations and rising living standards, global demand for mineral and energy resources are reaching unprecedented levels. This compels resource rich countries like Canada to shift towards developing deeper mines and unconventional gas reservoirs as near surface and conventional reserves are depleted. To do so, hydraulic fracturing is being proposed as a means to address key technical challenges being faced. Hydraulic fracturing is currently being used by mass mining operations to increase fragmentation and improve the mineability of stronger rocks being encountered at greater depths. It is also being explored as a means to mitigate high stresses and rock burst hazards in deep mines through modification of the stress field. Furthermore, shale gas producers are using hydraulic fracturing to enhance permeability and optimize well productivity. This new era of engineering challenges, will require a transition in the state-of-practice in hydraulic fracturing towards a more detailed accounting of geological complexity and its impact on safety, economics, and resource utilization in deep mining and unconventional gas extraction. Challenges currently persist in the frequent use of hydraulic fracture design tools that adopt simplifying assumptions regarding geology and the rock behaviour, namely treating it as a linear elastic intact material. In contrast, rock conditions are much more complex. Present are numerous natural fractures, including bedding planes, joints and faults. Recent progress has been made with my students applying innovative numerical modelling techniques that account for both shear along existing natural fractures and tensile fracture of intact rock in response to hydraulic fracturing. Building on the successes of my long-term research vision, planned research will continue to explore the integration of rock mass characterization, geotechnical monitoring and advanced numerical modelling to better understand the complex responses involved. The objectives will focus on the interactions that develop between a hydraulic fracture and the natural fractures present in the rock mass as a function of the superimposed stress conditions. The proposed research will explore linking characterization and “ground-truthing” of natural fracture systems with advanced numerical modelling tools and performance monitoring. This will be used to verify predictive models assessing the effectiveness of the hydraulic fracturing treatments performed. The scientific approach will include specially designed laboratory experiments that will be combined with field-based observations and state-of-the-art computer simulations. This will lead to both improved experimental design and more robust interpretation of results. Access to unique data sets, facilitated through my participation in a number of international field-scale experiments, will add to the novelty and expected significance of the research. The results are expected to significantly contribute to Canada’s body of knowledge on underground mass mining, unconventional shale gas extraction, and our internationally recognized expertise in deep mining. HQP will be provided with unique and practical learning experiences and skill sets that are in high demand in industry and are of strategic importance for Canada’s future natural resource development needs. Contributions will include both the advancement of the next generation of state-of-the-art engineering tools together with improved state-of-practice guidelines for geo-hazard assessment, performance assurance, and risk minimization in decision making.