Smart Pulses for Subsurface Engineering

Lead Research Organisation: University of Strathclyde
Department Name: Civil and Environmental Engineering

Abstract

Geological engineering encompasses a range of applications from resource extraction (hydrocarbons, geothermal heat and power, water) to waste disposal (Carbon capture and storage, wastewater disposal) and energy storage (compressed air, hydrogen). All of these technologies rely on pumps to move fluid into or out of boreholes. This prosperity partnership brings together teams that have previously worked on pumps for well stimulation with new team members involved in geomechanics and monitoring systems. Our previous work has shown that the pumps used in well stimulation are often used in very simple ways to deliver a known pressure to the top of the wellbore, leading to inefficient processes that produce a lot of noise and waste. Our partnership aims to re-engineer such systems through three linked research themes. Firstly there is evidence that pulses in pressure or dynamic variations in mean pressure could be more effective in achieving the aims of geological engineering processes. To understand the potential of pulsed pumping we need a deeper understanding of the material response to dynamic variation of the system that is being pumped: the rock mass and the borehole (casing and cement). Secondly we need to understand how to control delivery of precise pressure variations into the borehole and how to monitor these as they travel down the bore and into the rock mass. This includes the need to monitor rock mass response to develop fully 'closed loop' control systems. Finally we want to integrate the systems understanding of the pumps, the pumped system and the control systems. We will trial our new pulse propagation and monitoring system in the UK (at a site where well stimulation will not take place) and test the new monitoring system at an active well stimulation site in N. America. A series of eight linked PhD projects will explore aspects of the problems, and investigate the application of smart pumping to other sectors such as water distribution systems or transport of mining slurry. Our overall goal is to reduce the cost and increase the efficiency of geological engineering through smart pumping, thereby reducing the environmental and social impact of such technologies.

We have brought together a partnership of two industry and two university partners. The Weir Group and University of Strathclyde have a long history of collaboration on well stimulation pumps and other applications. The University of Edinburgh bring unique, world-leading geomechanical experimental capability to the partnership, and have previously collaborated with Strathclyde on carbon storage and compressed air energy storage. Silixa are young company specialising in optical fibres for sensing. Together this partnership will conduct the research that will underpin the development of smarter technologies in pumping and geological engineering.

Planned Impact

A unique opportunity has risen to support an existing, strong partnership between the University of Strathclyde and the Weir Group with significant technical and scientific contribution from Silixa Ltd and the University of Edinburgh, to investigate the potential of smart pumping in subsurface engineering projects. Time dependent pressure loading could be key in optimum exploitation of subsurface energy resources but the understanding on the related physical processes and technological challenges prohibits its development to an engineering tool. The proposed research aims to provide detailed insights in the mechanical behaviour of rocks during fluid injection and highlight technological routes to make well stimulation a more efficient process, lower the recovery costs while maximizing environmental control. We will combine leading edge geomechanics technology with advanced monitoring, control and signal processing techniques for the optimisation of engineering design and risk control that could be integrated into other systems, e.g. in bioengineering. Weir are already engaged in a strategic collaboration with Strathclyde related to the engineering of high pressure pumps for well stimulation. Thus the companies have established a track record of collaborative product development that could serve as a template for future development of the technologies produced by this Prosperity Partnership project.

The beneficiaries of this study include:

1. Public Sector: This project will impact the nation's health and wealth; it will contribute to the economic competitiveness of the UK with the potential to adapt and apply the technology to optimize the process for gas storage, CO2 storage and deep geothermal exploitation. This is of major importance, specifically after the weak induced seismicity occurrence at Preese-Hall (Lancs, UK) in 2011. The reduction of the uncertainties involved in the injection of fluids at depth can positively influence the public attitude towards the use of shale gas/carbon capture as well as increase regulatory confidence, e.g. for safety case development and/or monitoring leakage in the case of CO2 storage.

2. Industry: The 'Smart pumping' proposition, as a world-leading technology, will contribute to the UK's successful progression to a low-carbon economy. The outcomes of this research will attract further funding in the form of R&D investment from international businesses and industries related to oil and gas, geothermal energy exploitation etc. The results will be used as foundation for the ability of the proposed methodology and technology to enhance the efficiency and performance of businesses, e.g., maximise the geothermal capacity of underground reservoirs by providing a better understanding of the sub-surface flow system and consequently contribute to environmental sustainability.

The facilities and knowledge gained during the project will put the UK at the cutting edge of predictive subsurface engineering analysis. The combination of machine intelligence and mechatronic control is an important driver for research and innovation, and supports our proposed integration of sensing, machine learning and analytical models in pump control systems - a deployment of technologies associated with Industry 4.0

3. Additional benefits: Material prepared throughout this project based on the knowledge gained about subsurface processes can be used at schools and local communities to contribute to engineering/geology/science related projects and enhance the learning process of the pupils and the engagement opportunities for local publics at future operational sites.

Publications

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Fraser-Harris A (2020) Sampling and preparation of c.200 mm diameter cylindrical rock samples for geomechanical experiments in International Journal of Rock Mechanics and Mining Sciences

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Jiang J (2023) Microseismic Event Classification With Time-, Frequency-, and Wavelet-Domain Convolutional Neural Networks in IEEE Transactions on Geoscience and Remote Sensing

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Kendrick J (2023) Rate-dependence of the compressive and tensile strength of granites in Advances in Geosciences

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Li J (2023) Domain Knowledge Informed Multitask Learning for Landslide-Induced Seismic Classification in IEEE Geoscience and Remote Sensing Letters

 
Description Experimental work in Theme 1 has focussed on adapting the experimental techniques used by Dr. J.Mouli-Castillo and Dr. J.Kendrick at ambient conditions for use at simulated in-situ conditions (mirroring conditions at depth) using the GREAT cell. Successful monotonic and pulse-pumping fluid injection experiments have involved interfacing two types of pump arrangement with the GREAT cell. The monotonic experiments demonstrated a linear increase in breakdown pressure with applied confining pressure which agrees with previous experimental results on samples over an order of magnitude smaller. The pulse-pumping experiments have demonstrated that a similar reduction in breakdown pressure is achievable by pulse-pumping at in-situ conditions as previously seen at ambient conditions. This is an important experimental verification that the reductions in breakdown pressure that have previously been measured are not an artifact of the unconfined conditions and are an important step in verifying that pulse pumping should be expected to influence breakdown under true subsurface conditions.
Notably, the sample breakdown during experiments in the GREAT cell occurred after much smaller number of pressure cycles than at ambient conditions. This was not expected, and experiments are ongoing to verify and investigate the cause of this effect.
Analysis of the pulsed pumping results in the framework of fatigue testing according to ASTM standards, finds that the reduction in rock breakdown pressure found is akin to the reduction in strength of materials subjected to fatigue in other stress fields.
Numerical modelling in Theme 1 has fully developed a new hydro-mechanical fatigue model for rock fracture propagation by incorporating the heterogeneous nature of rocks as well as the interaction between hydraulic fractures and natural fractures. Both linear and nonlinear fatigue models have been proposed and, for the first time, we have derived the analytical form of the first derivative of the fatigue damage. This innovative constitutive modelling work allows us to investigate the "softening" response of rock under different frequencies and amplitudes and hence provide guidance for pulse design. The work on the near-field hydraulic fracture inclination from the perforation as well as interaction between hydraulic fracture and natural fracture has been completed. Several journal papers have been published on the work of nonlinear fatigue model, the interaction of natural and hydraulic fractures, and the perforation and crack inclination. The work of the matched PhD student on in-situ XCT quantitative analysis of microcrack evolution in granite samples is on-going.
This work package so far has developed a suite of codes consisting of innovative fundamental constitutive models and finite element codes, to reliably simulate the rock fracture process caused by pulses. With the powerful numerical calculation capability, both near-field and far-field fracture problems can be resolved. Rock fatigue fracture under hydraulic pulses is a complex problem and further study is needed to address a number of research gaps, in particular, the shear property reduction under pulses, mix-mode degradation mechanism under pulses, etc. This fundamental science is currently missing, and we continue to work on this topic.
Numerical modelling and design of a lab-scale test rig for validation of the computational results in Theme 2 has established key concepts for pulse generation, development of a computational modelling tool for pressure wave dynamics, the application of the model to establish key operating conditions and design of a proof of concept experimental rig to demonstrate that pressure wave generation control is practicably possible. Through 2022 we have established the detailed hydraulic and electrical design of a 400 bar maximum operating pressure, 200 m length, 25 mm diameter pump-based hydraulic pipeline system to generate pressure pulses of the order of 100 bar and propagate them along the pipeline. Procurement was finalised, and manufacture and build progressed using outside contractors. The in-house software control and measurement system has been successfully developed and progressed. A structural analysis of the pipeline and supporting structure was undertaken to establish safe operating conditions. Rig construction and commissioning is underway in December 2022-January 2023.
Further work has investigated the scaling-up of the concept to a full scale well system with geothermal wells being used as the reference application. Here modelling and simulations were conducted to establish the operating characteristics of the pressure waves and allow the sizing of hydraulic components; pipe size, valves, pumps etc for prototype pulse generation. Engagement with component suppliers allowed us to evaluate the availability of existing components or the need for further development of components for pulse generation applications. This work is ongoing with a design evaluation and development requirement report as the outcome.
Seismic monitoring design in Theme 2 concluded this year and resulted in the development of a range of machine learning algorithms (semi-supervised and supervised) for automated detection and classification of seismic events. The semi-supervised approach based on graph-based learning is ideal when the amount of training data is relatively small, compared to the deep learning supervised approach. Both the graph-learning based semi-supervised and CNN-based supervised learning algorithms have demonstrated that they can be transferable to new unseen datasets, e.g., from the active SuperSauze landslide in the Alps to the geologically distinct Larissa earthquake sequence in Greece, with different seismometer network geometries. Unsupervised approach has been successfully deployed on seismic recordings from the Rest and Be Thankful active landslide site in the Scottish Highlands.
The key contributions have been
1. Surface monitoring network configuration for well stimulation sites for maximum detection with a minimum number of sensors
2. Quick and accurate detection and classification of microseimic events
3. Development of a workflow for the localisation of detected microseismicity in near real-time and minimum uncertainty:
a. Hybrid method to increase location accuracy
b. Computational time reduction of location algorithm to almost real time
Exploitation Route yes
Sectors Energy,Environment,Transport

 
Description Acoustic Equipment
Amount £7,948 (GBP)
Organisation University of Edinburgh 
Sector Academic/University
Country United Kingdom
Start 01/2021 
End 03/2022
 
Description GREAT cell II
Amount £130,000 (GBP)
Organisation University of Göttingen 
Sector Academic/University
Country Germany
Start 04/2021 
End 04/2024
 
Description RSE Saltire International Collaboration Awards
Amount £11,999 (GBP)
Funding ID 1913 
Organisation Royal Society of Edinburgh (RSE) 
Sector Charity/Non Profit
Country United Kingdom
Start 02/2022 
End 01/2024
 
Description Smart Pulses into Wells of Opportunity: deploying a world-first technology at an active site in the US.
Amount £16,190 (GBP)
Organisation University of Strathclyde 
Sector Academic/University
Country United Kingdom
Start 03/2022 
End 06/2022
 
Description StrathWide 2021
Amount £3,800 (GBP)
Organisation University of Strathclyde 
Sector Academic/University
Country United Kingdom
Start 09/2021 
End 05/2022
 
Title Experimental Investigation of Hydraulic Fracturing and Stress Sensitivity of Fracture Permeability under changing Polyaxial Stress Conditions 
Description This dataset comprises experimental data and associated analysis of hydraulic fracturing and fluid flow experiments conducted on synthetic and natural rock samples. 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? Yes  
URL https://data.4tu.nl/articles/Experimental_investigation_of_hydraulic_fracturing_and_stress_sensitivi...
 
Title Loading strategy for pulsed hydraulic fracturing 
Description The new strategy for pulsed hydraulic fracturing that we proposed can produce a steady and slow rock fracture with a reduced breaking stress. 
Type Of Material Computer model/algorithm 
Year Produced 2020 
Provided To Others? No  
Impact The model is able to consider the degradation of rock under fatigue and well simulate the fracture propagation in rock under hydraulic pulses. 
 
Title One Dimensional Algorithm 
Description One dimensional fluid dynamic model, for wave interaction. 
Type Of Material Computer model/algorithm 
Year Produced 2021 
Provided To Others? Yes  
Impact Compressibility and speed of sound variation due to pressure and second phase. 
 
Title Pulse Fracturing Data Sets 
Description Data being collected on the fracturing behaviour under cyclical pulse loading of granite samples and PMMA samples. Includes fluid pressures, cyclical loading, acoustic emmisions. 
Type Of Material Database/Collection of data 
Year Produced 2021 
Provided To Others? Yes  
Impact Information about cyclical stimulation 
 
Description Illumating slope instabilities 
Organisation National Center for Scientific Research (Centre National de la Recherche Scientifique CNRS)
Country France 
Sector Academic/University 
PI Contribution Provide AI tools to detect and analyse the events, benchmarking our results with their analyses
Collaborator Contribution EOST provide very large RESIF dataset with catalogue of landslide induced events,
Impact Project just started so no outputs or outcomes to report yet Multi-disciplinary. The Strasbourg team are geoscientists, Strathlcyde team are engineers
Start Year 2022
 
Description Illumating slope instabilities 
Organisation University of Strasbourg
Country France 
Sector Academic/University 
PI Contribution Provide AI tools to detect and analyse the events, benchmarking our results with their analyses
Collaborator Contribution EOST provide very large RESIF dataset with catalogue of landslide induced events,
Impact Project just started so no outputs or outcomes to report yet Multi-disciplinary. The Strasbourg team are geoscientists, Strathlcyde team are engineers
Start Year 2022
 
Description MC Lower-Saxony-Scotland Tandem fellowship 
Organisation University of Göttingen
Country Germany 
Sector Academic/University 
PI Contribution Mike Chandler was awarded a Lower-Saxony-Scotland Tandem fellowship from the European Centre for Advanced Studies, which involved a secondment during November and December 2022 at Georg-August Universitat Gottingen collaborating with Dr Marco Fazio. It will also involve Dr Fazio travelling to the University of Edinburgh for a similar period in summer 2023.
Collaborator Contribution Hosting the secondment, during which MC is helping to commission a new rig, which will result in extra data for Smart Pulses.
Impact n/a
Start Year 2022
 
Description Microseismic monitoring at a large infrastructure construction project 
Organisation Scottish and Southern Energy (SSE)
Country United Kingdom 
Sector Private 
PI Contribution Pilot study of microseismic imaging of structures at depth utilising construction noice as a signal source. Plus (more standard) microseismic monitoring for induced activity. Both using the new detection, classification and location codes developed under Smart Pulses.
Collaborator Contribution Provision of physical access to site for siting seismometers, site investigation and ground investigation data, construction noise data (e.g. timing of blasts).
Impact not yet
Start Year 2022
 
Description Microseismic monitoring at the Rest and Be Thankful 
Organisation BEAR Scotland
Country United Kingdom 
Sector Private 
PI Contribution Monitoring of the unstable slope, analysis of results, study the kinematics of the landslide will be carried out. A second tranche of monitoring is starting in spring 2023.
Collaborator Contribution Will provide access to the site and other monitoring and site investigation data
Impact None yet
Start Year 2021
 
Description Microseismic monitoring at the Rest and Be Thankful 
Organisation Jacobs Engineering Group
Country United States 
Sector Private 
PI Contribution Monitoring of the unstable slope, analysis of results, study the kinematics of the landslide will be carried out. A second tranche of monitoring is starting in spring 2023.
Collaborator Contribution Will provide access to the site and other monitoring and site investigation data
Impact None yet
Start Year 2021
 
Description Microseismic monitoring at the Rest and Be Thankful 
Organisation Transport Scotland
Country United Kingdom 
Sector Public 
PI Contribution Monitoring of the unstable slope, analysis of results, study the kinematics of the landslide will be carried out. A second tranche of monitoring is starting in spring 2023.
Collaborator Contribution Will provide access to the site and other monitoring and site investigation data
Impact None yet
Start Year 2021
 
Description OpenGeoSys, UFZ Leipzig 
Organisation University of Leipzig
Country Germany 
Sector Academic/University 
PI Contribution Using the GREAT cell experiments as a way of benchmarking their complex fracture-propagation models, and for testing predictions from their models. This is potentially very important for the GREAT cell as the equipment is unique around the world, and so it can be difficult to benchmark experimental results.
Collaborator Contribution The phase-field modelling technique they have developed is ideal for extending the results of our experiments to predict fracture propagation in more strongly anisotropic media such as may be important in shallow geothermal contexts.
Impact None as yet
Start Year 2022
 
Description Physical Characterisation and Mechanical Testing 
Organisation University of Liverpool
Department School of Environmental Sciences
Country United Kingdom 
Sector Academic/University 
PI Contribution Performed physical properties characterisation and mechanical testing of rocks and PMMA.
Collaborator Contribution JK was awarded Honorary Research Associate position within the school of Environmental Sciences. This has enabled access to their laboratories and equipment to conduct physical characterisation and mechanical testing of samples used in the SPPP project.
Impact Experimental datasets of physical properties
Start Year 2020
 
Description DECOVALEX Workshop 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Research from the GREAT cell was presented to teams of modellers from the DECOVALEX consortium. The data provide benchmarks for model development for the radioactive waste disposal community
Year(s) Of Engagement Activity 2020
URL https://decovalex.org/D-2023/task-g.html
 
Description Industry Engagement 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact talks with potential industry investors from the oil and gas, nuclear, pumps manufacturing and geothermal industries
Year(s) Of Engagement Activity 2020,2021