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

Summary

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.

The potential for using HFS for the production of shale gas in the UK may lead to significant economic benefits, but it is also controversial. The overarching objective of the SHAPE-UK project is to provide a robust framework with which to assess, monitor and mitigate risks of leakage through the overburden of UK shale gas prospects - key issues in terms of public perception and robust regulation. The economic and regulatory importance of the project is significant and, given the generic nature of the work with respect to geological containment, there are many potential beneficiaries of the research.

Who would benefit from the proposed research?

Industry:
- Companies involved in production of hydrocarbons from unconventional reservoirs
- Companies involved in exploration and production of conventional hydrocarbons: risk assessment of petroleum seals and more effective and safer drilling of the overburden
- Companies involved in CO2 and gas storage, mining and geothermal exploitation, where rapid stress changes within the overburden can result in felt seismic activity and possible leakage through the overburden

Government and Regulatory Organisations:
- UK Policymakers & Regulators, including DBEIS and the UK & Scottish Environment Agency
- Oil & Gas Authority
- Nuclear Decommissioning Authority & similar European bodies (NAGRA, ANDRA)

Technology Organisers and Providers:
- UK: Energy Technologies Institute, Innovate UK, UKCCSRC, UKOOG, ITF
- Europe & Beyond: the European Environment Agency, EERA, IEA GHG

The general public:
- Via local councils, rotary clubs, etc., in areas of proposed shale gas exploration

How might the potential beneficiaries benefit?

We have worked closely with UK and overseas industry and regulators in all key areas of this proposal and are well placed to transfer results and knowledge. We also have a strong track record in public communication of science.

Financial beneficiaries: Companies applying for an onshore production licence, which is known as a Petroleum Exploration and Development Licence (PEDL), and, by association, UK PLC, require sound geologic risk assessment and will benefit from the framework resulting from this proposed work. On a more international scale, the issues faced with using hydraulic fracturing as a technique for developing hydrocarbon resources in proximity to substantial populations are not problems unique to the UK; potential shale gas provinces exist in other populated areas in North America (NY State has a fracking moratorium), Europe and beyond.

Regulators: will benefit from the project deliverables, including white papers and best-practice recommendations. Their involvement on the management boards of SHAPE-UK will ensure this. Examples include seismic network design, monitoring strategies, and a better understanding of envorinmental risks.

General public: local populations within the vicinity of proposed shale gas sites require clear and unbiased information about the safety of hydraulic fracturing. These communities will benefit from impartial and independent scientific information regarding potential leakage mechanisms and fracking in general.

Software development: A number of the investigators in the SHAPE-UK project have experience in producing commercially viable software, for example: fault seal analysis (Traptester, RDR Petrel Fault Analysis Pluggin); coupled flow geomechanical modelling (ELFENRS); seismic modelling (ATRAK); geomechanical prediction of microseismicity (ELFEN TGR); and pore pressure prediction (ShaleQuant). This will benefit UK PLC, as evinced by many of our 4* Impact Case Studies in REF2014.

Young scientists: Our students and young researchers have a strong track record of entering geological and environmental industries. Through annual meetings with industry representatives, they learn time management skills and are also obliged to see the relevance and potential impact of their research.