Monitoring Stored CO2
CO2 storage sites require ongoing monitoring and verification (M&V) to understand the behaviour of the CO2 plume stored
Surface-based seismic monitoring
CO2CRC delivered a broadly applicable procedure to predict, monitor and verify and assure CO2 migration and trapping in deep saline aquifers
Subsurface next generation monitoring
Aims to support the implementation of commercial carbon capture and storage projects by undertaking the validation of cost-effective subsurface monitoring technologies
Passive Seismic monitoring
Assessing the potential of passive seismic in plume detection for significant monitoring cost reductions
Shallow acoustic monitoring
The primary objective of this project is to investigate the feasibility of using shallow boreholes equipped with geophones/fibre optics to monitor the injected CO2 plume
Distributed Strain Sensing Technology
DSS technology can provide effective wellbore integrity surveillance that will ensure safer projects and reduce the cost of well remediations
Surface-based seismic monitoring
The Project delivered a broadly applicable procedure to predict, monitor and verify and assure CO2 migration and trapping in deep saline aquifers
Rationale
Seismic data can detect variations in the elastic properties of rocks, caused by changes in fluid saturations and pore pressure. Repetitive seismic (also known as time lapse seismic) is a powerful technology to monitor such variations.
Variations in the elastic properties of rocks, caused by changes in fluid saturations and pore pressure, can alter the acoustic resonance of geological features and travel times of seismic waves. These can be detected using repeated seismic surveys.
Objectives
The main objectives of the project were to detect the injected Buttress gas (~79% CO2 and ~21% CH4) in the low-lying saline aquifer:
- to ascertain minimum seismic detection limit,
- to observe the gas plume development using time-lapse seismic and
- to verify the plume stabilisation.
The research project
The injection occurred between December 2015 and April 2016. The injection and evolution of the plume was monitored by a comprehensive time-lapse seismic program. It used a 1 km2 array of 908 geophones buried at 4m in lines spaced at 100m with 15m between each receiver and 40km of fibre optic cable deployed below-ground at 80cm, together with well-based Distributed Acoustic Sensing (DAS) fibre optics and 4D Vertical Seismic Profiling (VSP) to monitor the injected CO2.
Mini vibroseis trucks were used as the source for each survey with approximately 3000 shot points in conjunction with two permanently deployed Surface Orbital Vibrators (SOV) for continuous monitoring.
This entire activity went on without disrupting the peaceful life of the cattle farm at the ground level.
Seismic surveys were undertaken before injection in February 2015 (base line), then after 5,000, 10,000 and 15,000 tonnes.
Two post injection surveys were also performed in 2017 and 2018.
The plume signature is also clearly visible on the 4D VSP images and agrees with the results of the 3D surface seismic.
An evidence-based conclusion therefore points to the stabilisation of the CO2 plume.
Other measurements acquired during the project have been in-zone and above-zone pressure monitoring during and post injection, interference well testing, Pulsed Neutron logging and downhole fluid sampling through U-tubes.
The data acquired, including plume images from time lapse seismic, were used to update static models and history match the dynamic models of the Otway site.
These models, were then used in combination with quantitative metrics to demonstrate the plume stabilisation over the long term.
Results & outcomes
CO2CRC demonstrated that the CO2 can be safely stored and monitored in reservoirs that previously contained hydrocarbons.
Established a workflow to evaluate long-term plume stabilisation using seismic data, simulation models and a set of quantitative metrics
Demonstrated that as little as 5,000 tonnes of CO2 can be detected using seismic monitoring at over 1,500m below the surface
Findings that a Distributed Acoustic Sensing (DAS) array has potential for imaging the plume
An observation that 4D data quality, using a buried geophone array, is sufficient to observe time lapse evolution of the gas plume from as little as a 5,000 tonne injection with post stack repeatability of 10 – 20%
A finding that burying geophones and cables underground can reduce seismic acquisition time and decrease the footprint of a seismic survey. Higher data quality and 10% repeatable acquisition geometry also reduces the time for fast track processing
An observation that with good levels of repeatability, offset VSP can be used to monitor the injection
A finding that data obtained using SOV single sweep data is of similar quality to that obtained by conventional vibroseis trucks, has higher repeatability and significantly lower costs, while minimising impact on landholders
Detection of a 15,000 tonne plume of injected CO2 as it grew and stabilised deep in the subsurface using a range of seismic technologies
Publications
Latest
Advanced Analysis of Time-lapse Seismic Data for CO2
Geosequestration Monitoring
4D surface seismic tracks small supercritical CO2 injection into the subsurface: Otway Project
Stage 2C of the CO2CRC Otway Project: Seismic Monitoring Operations and Preliminary Results
Parameter estimation and dynamic plume modelling using injection data: Otway Stage 2C Project
Modelling-driven workflow for 3D seismic inversion for Stage 2C of the Otway Project
Stage 2C of CO2CRC Otway project – Fast track 4D surface seismic processing results
Time-lapse Offset VSP data analysis – CO2CRC Stage 2C 2015-2016 data
Subsurface imaging using buried DAS and geophone array: initial results from CO2CRC Otway Project
Monitoring of the small-scale CO2 injection using 4D VSP
Time-lapse 3D VSP data analysis
Conformance of dynamic models to seismic images during and post-injection: Otway Stage 2C Project
Time-lapse processing of surface seismic data acquired in Stage 2C of CO2CRC Otway Project
Advanced Analysis of Time-lapse Seismic Data for CO2 Geosequestration Monitoring
Subsurface next generation monitoring
This Project aims to support the implementation of commercial carbon capture and storage projects by undertaking the validation of cost-effective subsurface monitoring technologies
Rationale
Conventional repeat surface-based monitoring and verification (M&V) surveys are expensive, complex to undertake in certain terrains, potentially unpopular with land-owners and local communities, and crucially they do not provide the social or regulatory assurances of immediacy of response that on-demand monitoring can provide.
High footprint, surface-based M&V operations are costly, running into the tens of millions of dollars onshore (hundreds of millions offshore) over the life of a project, and impinge significantly on social license, with frequent surface operations being potentially antagonistic to land owners, the public and the surface environment.
Permanent subsurface monitoring of plume encroachment to a targeted higher-risk area or zone (i.e. lease boundaries, therefore validating containment), promises to become a very effective monitoring solution.
In addition, a continuous subsurface monitoring system could also be designed to raise an early warning flag and prompt a high-speed response to a specific event.
The techniques to be tested in this project present a solution, currently untested for CO2 storage, that addresses the challenges above.
Objectives
- To develop and demonstrate a high-resolution, on demand monitoring system in the field that will provide an early warning solution for industry and regulators;
- To develop and demonstrate non-invasive monitoring techniques that will be acceptable for the community and regulators;
- To provide a prospectus of technologies and workflows that can be used to substantially lower costs in commercial monitoring projects;
- To evolve technologies from benchtop application to field validation, being driven by current and prospective operator need.
Publications
Cook P. J Geologically Storing Carbon, Learning from the Otway Project Experience, CSIRO Publishing 2014.
Ashworth P, Rodriguez S and Miller A, Jenkins C, Case study of the CO2CRC Otway National Project, Energy Transformed Flagship, CSIRO, 2011.
Sandrine Vidal-Gilbert, S, Tenthorey E, Dewhurst, D, Ennis-King J, Hilli R, Geomechanical analysis of the Naylor Field, Otway Basin, Australia: Implications for CO2 injection and storage 2010, International Journal of Greenhouse Gas Control, Volume 4, Issue 5, 827-839
Underschultz, J., Boreham, C., Dance, T., Stalker, L., Freifeld, B., Kirste, D., Ennis-King, J., 2011. CO2 storage in a depleted gas field: An overview of the CO2CRC Otway Project and initial results. International Journal of Greenhouse Gas Control 5, 922-932.
Jenkins C, 2013, Statistical aspects of monitoring and verification, International Journal of Greenhouse Gas Control 13, 215- 229
Boreham, C., Underschultz, J., Stalker, L., Kirste, D., Freifeld, B., Jenkins, C., Ennis-King, J., 2011. Monitoring of CO2 storage in a depleted natural gas reservoir: Gas geochemistry from the CO2CRC Otway Project, Australia. International Journal of Greenhouse Gas Control 5, 1039-1054.
Dance T, Spencer L, and Xu J 2018 Geological characterisation of the CO2CRC Otway Project Site – What a difference a well makes. Link to poster.
Noble, R, Stalker, L, Wakelin S, Pejcic B, Leybourne M, Hortle A, Michal K; 2012, Biological monitoring of carbon capture and storage –’ A review and potential future developments. International Journal of Greenhouse Gas Control 10, 520 – 535
The Research Project
The Project will evaluate the following monitoring methodologies:
Pressure monitoring
Using high resolution pressure gauges, two distinct modalities of pressure monitoring will be investigated:
Pressure inversion: locates a pressure source by way of triangulation from pressure measurements in the monitoring wells during and post CO2 injection. The acquired pressure data will be inverted to identify the compressible pressure boundary as the CO2 enters and migrates through the formation.
Pressure tomography: denotes a cluster of techniques that rely on interpreting the pressure changes resulting from perturbing the reservoir with water injections at one monitoring well and monitoring pressure at other wells.
In a world first, pressure tomography will be demonstrated on a CO2 plume to test the range and sensitivity of the technique to image a plume’s distribution.
With downhole pressure gauges set to acquire data continuously, the pressure data obtained for each survey performed will be inverted to produce an image of the CO2 plume in the subsurface.
Downhole seismic
The demonstration of downhole seismic monitoring involves using an array of permanent SOV to create a seismic signal which will be received by the DAS in the monitoring wells and detecting the plume as it grows and migrates during injection.
The development of ancillary monitoring methods such as using the analysis of earth tides and passive seismic will enable future geo-mechanical research to be conducted
Passive Seismic monitoring
Assessing the potential of passive seismic in plume detection for significant monitoring cost reductions
Rationale
Currently, it is necessary to create an anthropogenic seismic event to create the energy to enable seismic data to be acquired to image the subsurface. For instance, surface orbital vibrators are used as the seismic source/event.
Deriving as much information as possible from ambient noise through the continuous acquisition of data from the fibre optic cables in a passive environment (i.e. acquired without the generation of an external seismic event and relying on natural seismicity) offers the possibility to extend the applicability of seismic monitoring and offers industry a low cost data acquisition system for long-range monitoring without the invasiveness of conventional seismic monitoring.
CO2CRC completed a feasibility study in 2018 by recording data using the buried geophone array and the wellbore Distributed Acoustic Sensing (DAS) in detecting signals from a wide range of sources. The feasibility study demonstrated that there is adequate detectable passive signal that can be recorded by DAS equipment.
Objectives
The project will:
- Field test passive seismic monitoring during an injection period.
- Record passive seismic data over an extended and uninterrupted time period.
- Develop an algorithm to isolate and associate the observed events to meaningful subsurface changes.
- Utilise the wellbore and if required surface-deployed DAS data.
Shallow acoustic monitoring
The primary objective of this project is to investigate the feasibility of using shallow boreholes equipped with geophones/fibre optics to monitor the injected CO2 plume.
Rationale
A range of geophysical techniques and technologies have been tested at the CO2CRC’s Otway International Test Centre (OITC) since 2005 to monitor the stored CO2.
The implementation of permanent sources in combination with the Fibre Optics, using leading-edge technology, is being tested at the OITC and downhole seismic and 4D Vertical Seismic profiling (VSP) have been tested to monitor injected CO2.
The project requires deep bores (~1500m) to reach its objectives. Drilling is a major contributor to the overall cost of the monitoring phase. The cost of drilling reservoir-deep wells to implement Fibre Optics can be prohibitive.
The current proposal intends to investigate whether shallow wells 100-150m deep (rather than 1500m) armed with fibre optics sensors in combination with surface fibre optics receivers could be acceptable alternatives in monitoring the injected CO2 plume.
Objectives
The primary objective of this project is to investigate the feasibility of using shallow boreholes equipped with geophones/fibre optics to monitor the injected CO2 plume.
The key parameters to be examined are:
- Depth of investigation (injected plume): How deep a CO2 plume can be, to be visible by a series of shallow bores
- Depth of the monitoring boreholes
- Completion of the bore holes (e.g., vertical vs horizontal)
- The minimum size of the plume (detection limit)
Distributed Strain Sensing Technology
This project’s data outputs will form an internationally relevant dataset for calibrating and improving modelling of CO2 migration predictions in faults, increasing confidence in the modelled predictions, and help inform geological storage risk assessments.
Rationale
CO2CRC are collaborating with the Research Institute of Innovation Technologies for Earth (RITE), Japan and Curtin University to reduce the cost of reservoir and well surveillance and improve the monitoring of CO2 migration.
A key challenge for the CCS industry is effective well diagnostics for new and legacy wells. DSS technology can provide effective wellbore integrity surveillance that will ensure safer projects and reduce the cost of well remediations.
DSS can also be used to measure pressure changes along the wellbore. Previously restricted to single point gauges, distributed pressure measurements along a well perforation would help to understand the distribution of CO2 in the injection formation and improve plume imaging of the injected CO2.
RITE has recently successfully shown DSS performance at lab-scale, and now field testing is required.
In addition to well diagnosis, this project will provide insights to industry on CO2 fault flow characterisation and reduce CO2 storage project uncertainty.
Objectives
This project is a field trial of Distributed Strain Sensing (DSS) technology together with 4D reverse Vertical Seismic Profile (VSP) to monitor CO2 flow in a shallow fault at the OITC.
This project enables a concurrent, cost-effective trial of innovative monitoring technologies during a controlled CO2 injection operation to enable CO2 migration along the shallow fault. CO2CRC has existing shallow infrastructure at the OITC which is designed to perform this injection.
The objective of the project is to access RITE’s advanced sensing and real-time monitoring technology tool – DSS, along with CO2CRC and Curtin’s new 4D reverse VSP innovation to:
- Address well integrity issues and reduce the cost of well monitoring and remediations
- Monitor and characterise CO2 migration along the faults
- Reduce the uncertainty of CO2 storage into faulted structures
- Monitor CO2 plume movement around wells
- Measure pressure profile along the wellbore
- Transfer learnings from shallow to deeper faults, including improved conceptualisation, physics, and modelling of CO2 migration in faults.