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

随着人口的不断增长和生活水平的提高，全球对矿产和能源的需求达到了前所未有的水平。这迫使加拿大等资源丰富的国家转向开发更深的矿井和非常规天然气储层，因为近地表和常规储量已经耗尽。为此，水力压裂被提议作为解决所面临的关键技术挑战的一种手段。水力压裂法目前正用于大规模采矿作业，以增加破碎度，并改善在更深处遇到的更坚固岩石的采矿能力。目前还在探索通过改变应力场来减轻深井中的高应力和岩爆危险。此外，页岩气生产商正在使用水力压裂来提高渗透率并优化油井生产率。 这一工程挑战的新时代将要求水力压裂的实践状态向更详细地核算地质复杂性及其对安全性、经济性和资源利用的影响的转变。目前的挑战是经常使用水力压裂设计工具，这些工具采用关于地质和岩石行为的简化假设，即将其视为线性弹性完整材料。相比之下，岩石条件要复杂得多。存在许多天然裂缝，包括层面、节理和断层。最近的进展已经取得了与我的学生应用创新的数值模拟技术，占剪切沿着现有的天然裂缝和拉伸断裂的完整岩石在水力压裂。 在我长期研究愿景的成功基础上，计划的研究将继续探索岩体表征，岩土监测和先进数值建模的整合，以更好地了解所涉及的复杂反应。目标将集中在水力裂缝和岩体中存在的天然裂缝之间的相互作用，作为叠加应力条件的函数。拟议的研究将探索将天然裂缝系统的表征和“地面实况”与先进的数值建模工具和性能监测联系起来。这将用于验证评估所执行的水力压裂处理的有效性的预测模型。科学方法将包括专门设计的实验室实验，这些实验将与实地观察和最先进的计算机模拟相结合。这将导致改进的实验设计和更可靠的结果解释。 通过参与一些国际实地规模的实验，获得独特的数据集，将增加研究的新奇和预期意义。预计这些结果将大大有助于加拿大在地下大规模开采、非常规页岩气开采方面的知识体系，以及我们在深部开采方面的国际公认的专业知识。HQP将提供独特和实用的学习经验和技能，这些经验和技能在行业中具有很高的需求，对加拿大未来的自然资源开发需求具有战略重要性。贡献将包括下一代最先进的工程工具的进步，以及改进地质灾害评估、性能保证和决策风险最小化的实践指南。

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.