As the EU pushes ahead with its energy and climate agenda, it will need a broad range of cleaner energy sources including natural gas if it is to retain its leadership in emission reductions in a carbon-constrained world. Currently, about one-quarter of all the energy used in the EU is natural gas. The EU imports 54% of all the energy it consumes, at a cost of more than €1 billion per day. Energy also makes up more than 20% of total EU imports, which includes 69% of its natural gas. Energy security has been perplexing the whole of Europe for centuries, especially after the replacement of traditional high pollution energy, e.g. coal. So-called energy independence is also not helping with the current situation.
In reality, Europe still can draw upon significant domestic gas resources to meet part of its own demand in a lower-carbon future, while having one of the most successful rates of discoveries in the world and lower environmental impact. The latest investigation has demonstrated that with 5100 billion cubic meters (bcm) of known remaining natural gas resources, Europe has enough gas to meet around half of its own demand for another 25 years. The public concerns of geological disaster, underground pollution, contaminated water and ecosystem are the major obstacles to the shale gas revolution in Europe. Therefore, new environmental-friendly, high-efficient techniques as well as short- and long-term health monitoring for the related infrastructure are urgently needed for the natural gas exploitation in order to relieve the energy security stresses as well as related public and environmental concerns.
The current best practice for gas exploitation is the massive hydraulic fracturing technic. These controversies and protests never stop causing environmental and societal issues, e.g. seismicity disasters, underground pollution, freshwater consumption, gas leaks, etc. Because of all these potential hazards, many countries like Germany and France have legally prohibited hydraulic fracturing, and as a result, the shale gas revolution was nearly stifled in the cradle. For a single typical shale gas well, more than 30000 tons of fresh water, and around 150 tons of chemicals as well, will be injected into the target formation. The consumption of fresh water is unrecyclable. The injected chemicals are nondegradable including acid, heavy metal ion, high-molecular polymer, etc. Their underground pollution behaviour is still unknown in the short and long term. The influenced area is approximately 3 million sq. ft (600 ft fracture length multiply 5000 ft horizontal well) for a single well and will become larger and larger in long term along with the geological migration. Only new technics, especially which are environmentally friendly, are encouraged by the government and public so to promote shale gas exploitation. The pure CO2 fracturing technic is one of the most ideal and feasible technics replacing the traditional water-based technic. No water and chemicals are involved. Especially, this technic will be upgraded by integrating with Carbon Capture, Utilization, and Storage (CCUS) during this project, which benefits carbon emission reduction. This new technic will solve most of the pollution problems except the infrastructure degradation, causing gas leaking, which will aggravate global warming more seriously than CO2 does. The wellbore infrastructure issue is an unnoticeable but severe issue after fracturing operation, long-term production (leading to in-situ stress redistribution) and geological activities. Not enough attention is paid, fewer researches are carried out and no monitoring method is adopted. Fortunately, we are entering the time that sufficient data have been collected over the past few decades. Structural Health Monitoring (SHM) leverages proprietary sensors to infer knowledge on structural conditions that have been identified and shown to have several promising features, including the identification of critical zones. By using remote senescing data (Earth Observation), topological data (OpenStreetMap), crowd data (social media and mobile) as well as localized sensor data, with data mining techniques, in fact, regional scale geological conditions, as well as potentially affected areas, could be observed and monitored, timely intervention can be taken place to minimize the damages. Therefore, environmental-friendly technics and a monitoring system are urgently needed in order to explore shale gas and fully utilize it to its maximum potential. Several fundamental challenges exist in current research.
