Periodic Reporting for period 1 - CLEAN (Carbon fracturing and storage in shale with wellbore infrastructure monitoring)
Reporting period: 2019-08-05 to 2022-08-04
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.
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.
The specific works are carried out according to Annex 1 of the Grant Agreement. According to the objectives in WP-1, we performed experiments and numerical calculations to reveal mechanisms of CO2 and shale interactions regarding the absorbing, swelling, dehydration, etc. Then, the effects of the CO2-shale interactions on the permeability evolution in a propped shale fracture (a typical condition of CO2 fracturing) were analyzed under a formation condition (temperature and confining stresses). With sufficient fundamental research work, we also investigated the key techniques of CO2 fracturing at field engineering scales, and summarized and proposed the bottleneck points of the new fracturing technique. According to the objectives in WP-2, we built several machine learning workflows to monitor the injection process through the wellbore. For hydraulic fracturing, the major risk exists during the injections of proppant (small particles injected with fluid to prop up the fracked apertures). We, therefore, integrated the numerical models of particle-fluid two-phase flow in fractures with the typical machine learning algorithms, like SVM (Support Vector Machine), RF (Random Forest), ANN (Artificial Neural Networks), GRU (Gated Recurrent Units), etc. The interdisciplinary workflows were deployed for mining sensor data (hydraulic measurements, like pressure, pump rate, etc.), estimating the particle-fluid two-phase flow in underground fractures, and predicting the risks of hydraulic injection.
This fellowship will seek to conduct cross-disciplinary research that connects the supercritical fluid science, natural gas engineering, civil engineering to wellbore infrastructure health monitoring aid of the knowledge and tools from data mining, uncertainty quantification and machine learning. The fellowship has the ambitious vision to develop the underpinning technology for shale gas exploitation and Carbon Capture, Utilization, and Storage (CCUS) through the cross-fertilization of rock mechanics, hydromechanics and data science. We accomplished this by:1. Understand Carbon Fracturing and Storage in Shale (CFSS): Investigate CO2 storage behaviour in shale formation. Optimize CO2 storage efficiency and natural gas recovery. Develop special CFSS operation design, flow back and production schedule for CO2 storage, gas recovery and wellbore infrastructure monitoring. 2. Heterogeneous Data for Wellbore Infrastructure Monitoring and Maintenance: identifying relevant and representative wellbore structural health monitoring case studies, combining classical sensor data with social media, mobile phone, and video data, to better classify risk categories, understand the stressor contexts (e.g. fracture, environmental variations and climate changes), linking this with structural behaviour, to develop reliable machine-learning failure forecasting algorithms.