Impact of hydraulic fracturing in the overburden of shale resource plays: Process-based evaluation (SHAPE-UK)

近年来，英国在建立可再生能源方面取得了重大进展。在过去十年中，太阳能、风能、生物质能和水能的使用量稳步上升，从2004年的不到5%增长到2016年的近25% （DBEIS，“公爵”- 2017年第6章）。尽管如此，天然气仍将是向碳中和电力供应过渡的重要燃料。此外，天然气目前为英国大约80%的家庭供暖，并提供了重要的工业原料。随着北海天然气储量的减少，英国在十年内从自给自足的状态转变为进口超过50%的天然气。因此，出于能源安全、可负担性和环境影响的考虑，增加国内天然气供应是可取的，直到我们达到更好地建立碳中和能源（例如，核能）的程度。页岩气和页岩油改变了世界能源市场，促进了世界油价的下降，美国实现了天然气和石油的自给自足。此外，美国的二氧化碳排放量又回到了上世纪90年代初的水平，因为发电已经从燃煤发电站转向了燃气发电站。然而，转向页岩气并非没有争议。页岩气资源通常需要水力压裂或水力压裂才能以经济的速度生产。由于公众对一系列问题的担忧，包括地下水污染、诱发地震活动、大气排放和地面沉降，这种技术存在争议。2017年11月，英国将在北约克郡的皮克林河谷进行6年来的首次页岩气增产。英国对页岩气开采有严格的监管框架，要求密切监测与水力压裂相关的任何流体泄漏、裂缝生长和诱发地震活动。要做到这一点，需要详细了解当地的地质情况，以及在增产之前、期间和之后感知流体运动和应力变化的强大手段（例如，地球物理监测）。SHAPE-UK是一个项目，将建立一系列最佳实践建议，用于监测和减轻流体泄漏到上覆沉积物和靠近钻孔的地方。要做到这一点，至关重要的是我们要了解发生在地下的机械过程，这取决于岩石的组成、流体的化学性质以及它们遇到的结构（如断层）。通过一系列整合地质学、地球物理学、地球化学、石油工程和地质力学的相关工作包，我们将能够解决有关泄漏机制的基本科学问题，以及泄漏流体如何影响地下环境。来自6个机构不同学科的领先专家组成了一个团队，来解决“从储层到地表的耦合过程”——这是NERC在英国能源系统非常规碳氢化合物战略计划领域征求建议的挑战3。我们将利用柴郡桑顿附近的英国地球能源观测站新获得的数据。我们还非常幸运地获得了北约克郡一个新页岩气开发项目的地震、钻孔和地质数据，以及加拿大西部一个成熟页岩气资源的数据集。我们的项目合作伙伴包括在页岩气作业期间监测地下水和地震活动的监管机构。该团队可以访问几个全面的数据集，因此在回答与页岩气增产相关的基础科学问题方面处于非常有利的地位，这将为有效的监管政策提供坚实的基础。我们希望这个项目能够成为英国和国际未来发展的榜样研究。

In recent years, the UK has made significant progress in establishing renewable sources of energy. Solar, wind, biomass and hydro have seen a steady rise in use over the past decade, having gone from providing less than 5% of our electricity in 2004 to nearly 25% in 2016 (DBEIS, 'DUKES' - chapter 6, 2017). Nevertheless, natural gas will continue to be an important fuel in a transition to a carbon neutral supply of electricity. Furthermore, natural gas currently heats roughly 80% of our homes in the UK, and provides an important industrial feedstock. As North Sea gas reserves decline, the UK has in a decade gone from a position of self-sufficiency to importing over 50% of its natural gas. Therefore, for reasons of energy security, affordability and environmental impact, it is desirable to increase domestic gas supplies until we reach a point where carbon neutral energy sources are better established (e.g., nuclear). Shale gas and shale oil has transformed the World's energy market, contributing to the reduction of world oil prices and the USA becoming self-sufficient in both gas and oil. Furthermore, CO2 emissions in the USA are back to levels last seen in the early 1990s, because electricity generation has moved from coal- to gas-fired power stations. However, the move to shale gas has not been without controversy. Shale gas resources normally require hydraulic fracture stimulation - or fracking - in order to achieve production at economic rates. This technique is contentious due to public fears over a range of issues, including ground water contamination, induced seismicity, atmospheric emissions and ground subsidence. In November 2017 the UK will see its first shale gas stimulation in over 6 years, which will occur in the Vale of Pickering, North Yorkshire. The UK has a strict regulatory framework for shale gas exploitation, which requires close monitoring of any fluid leakage, fracture growth and induced seismicity associated with fracking. To achieve this requires a detailed understanding of local geology, and robust means of sensing fluid movement and stress changes before, during and after stimulation (e.g., geophysical monitoring). SHAPE-UK is a project that will establish a series of best practice recommendations for monitoring and mitigating fluid leakage into the overlying sediments and close to boreholes. To accomplish this, it is crucial that we understand the mechanical processes occurring in the subsurface, which are dependent on the composition of the rock, the chemistry of the fluids, and the structures they encounter (e.g., faults). Through a linked series of work packages that integrate geology, geophysics, geochemistry, petroleum engineering and geomechanics, we will be able to address fundamental scientific questions about the mechanisms for leakage, and how the leaking fluids might affect the sub-surface environment. A team of leading experts from a range of disciplines at 6 institutions has been assembled to address 'coupled processes from the reservoir to the surface' - Challenge 3 of the NERC call for proposals in the strategic programme area of Unconventional Hydrocarbons in the UK Energy System. We will exploit newly acquired data from the UK Geoenergy Observatory near Thornton in Cheshire. We are also very fortunate to have access to seismic, borehole and geologic data from a new shale gas development in North Yorkshire and a dataset from a mature shale gas resource in Western Canada. Our project partners include regulatory bodies who monitor ground water and seismicity during shale gas operations. The team has access to several comprehensive datasets and are thus in a very strong position to answer fundamental science questions associated with shale gas stimulation, which will provide a firm foundation for an effective regulatory policy. We expect this project to be a role model study for future developments in the UK and internationally.