The importance of studying regional geology before site selection and of establishing baselines; seeing monitoring technologies working in combination; use of fibre optic tools; the performance of cemented wells in different environments; and legacy well issues – these were among the many measuring, monitoring and verification (MMV) learnings from SECURe’s fruitful 10-day trip to North America.
A group of senior scientists from the EU-funded project undertook the fact-finding tour to gather examples of best practice in geoenergy projects, such as geological CO2 storage and shale gas extraction.
The trip took in research facilities including the National Energy Technology Laboratory (NETL) in Pittsburgh and the Illinois State Geological Survey’s Illinois Basin-Decatur Project (IBDP); government bodies, such as the Alberta Energy Regulator in Canada; and commercial operations such as Shell Quest and Enhance Energy.
It also included field orientation in Canada’s Banff National Park, which highlighted the need for geological surveys to inform site selection.
“The trip through Banff showed me the extent of natural variability of geological formations and how important it is for site appraisal to be carried out,” says Michael Kupoluyi, a project engineer at the UK’s Risktec Solutions. Risktec’s work on SECURe includes risk assessment and establishing a risk framework.
At Shell’s Quest, one of the world’s biggest carbon capture and storage (CCS) projects, the team could see first-hand the value of selecting a strong site, adds Jan ter Heege, an induced seismicity specialist and coordinator of the Geomechanics group at TNO, the Dutch organisation for applied research. TNO is also working on risk assessment for SECURe as well as on monitoring, mitigation, sharing best practice and stakeholder involvement.
“They had searched for a storage reservoir that was so perfect in terms of geology - notably the presence of multiple top seals above it - that by choosing such a site you already reduce a lot of risks,” he says.
Quest has exceeded expectations, capturing more than 1m tonnes of CO2 a year since its start-up in late 2015. Its MMV has been adapted during the project life, being both scaled back and refocused. In some cases, for example, the operators had acquired data but had not begun processing it until it was needed.
Similarly, at Decatur in Illinois, ISGS has employed an adaptive monitoring strategy, enabling the monitoring equipment for the project’s next phases to be reduced and targeted at regulatory requirements and managing overall project risk.
As expected, the amount of monitoring done at these commercial-scale projects was much lower than at the research projects the team visited, notes Jonathan Pearce, head of the Carbon Dioxide Storage team and a principal geochemist at the British Geological Survey. BGS is SECURe’s coordinator.
“At the CO2 research facilities, you are always going to get a portfolio of different monitoring techniques. That’s the nature of the research – the aim is to compare and contrast and optimise those different techniques,” he says. “That’s quite different to a commercial project, where you are establishing that the project is operating in a safe manner. That is absolutely fundamental, but what you are aiming for is to keep costs down to make the project as efficient as possible, so you want to reduce the amount of monitoring to a safe level.”
At Quest, storage monitoring costs were about C$5 a tonne but there was scope for them to fall as low as C$1, the team was told.
Another key MMV takeaway from the trip was the importance of establishing a baseline at the outset.
“Several of the sites we visited saw establishing baseline conditions as an absolute prerequisite,” says Jonathan. “I was expecting perhaps more discussion around the need for environmental baselines but many people in those commercial operations could see their value and they were a key part of the permitting approach.”
For Jan ter Heege, seeing different monitoring technologies working in combination, including at CMC’s Field Research Station (FRS) in Alberta, was “really powerful”. FRS is testing and developing fibre optic, geophone and dual comb laser arrays, vertical and horizontal seismic tools, and distributed acoustic and temperature sensors (DAS and DTS).
“It is very helpful to cross-compare results. You can really zoom in on what you are measuring and on what’s happening with the earth,” he says.
He also appreciated seeing some techniques in operation for the first time: “There’s always a next step to go from theoretical, scientific concepts to actually performing them at a site and determining the added value of the different approaches. That was really valuable.”
An area of particular interest was the use of fibre optic cables, on top of geophones, to measure seismicity. The cables are easily deployed and offer continuous monitoring over a large area whereas geophones are more isolated measuring points.
“They are two completely different ways of measuring seismicity,” he says. “At TNO we are looking into fibre optics but mostly at a theoretical level whereas in North American they are already installing these monitoring systems at sites.”
In terms of risks, several of the projects identified wells, and especially abandoned wells, as the main leakage threats for storage.
“Enhance put a lot of effort in looking at the status of abandoned wells. They initially thought of reusing some of them but decided it was better to drill new wells and avoid the problems of leakage later,” says Jan.
“The most important monitoring should be in and around the wells,” adds Karen Kirk, a geologist at BGS. “Any triggers observed here should initiate further monitoring techniques to constrain what is failing, followed by mitigation activities.”
Enhance, which monitors all production wells at the site continuously, stressed the need to make monitoring site specific. Its project uses techniques, such as laser monitoring of CO2 and hydrogen sulfide with monitoring split between geosphere (coalbed methane monitoring), hydrosphere (soil gas baselines; shallow water and water chemistry) and atmosphere (Supervisory Control and Data Acquisition and sour gas monitoring).
The team also took away valuable learnings on well bore integrity from its visit to Pittsburgh’s NETL. The laboratory’s analysis of cement, how it responds in different geologies and under harsh conditions, and monitoring and remediating loss of its integrity were of considerable interest; there could be opportunities for sensors developed by NETL to be tested in Europe.
NETL has done novel research on downhole chemical sensors (optical and wireless/passive), also applied to borehole cements including new sensors for in situ passive and active measurements in cements. This includes Laser Induced Breakdown Spectroscopy (LIBS), a new technique which, due to laser miniaturisation, can allow consistently high accuracy elemental analyses in fluids in borehole environments where optical connection is available.
The team also saw examples of MMV innovation at Decatur, the use of DTA sensors on the outside of injection tubing, for example. Downhole geophones had proved critical in detecting micro seismicity at this site, which captures CO2 from a large bioethanol plant.
For BGS’s Jonathan Pearce, Decatur is an inspiring example of a once small pilot project that is successfully upscaling into a purely commercial operation.
“The scale of operations in both the US and Canada in both shale gas and CCS is so far ahead of what we’re doing in Europe. The trip really brought that home,” he says.
“When you see it for real, when you talk to the people, it’s clear they have a level of ambition and understanding that will convert those projects into longer-term CO2 storage projects.”
Photos: Top, the SECURe fact-finding group at Banff National Park, Alberta, Canada; below, David Hills, Senior Geoscientist for Enhance Energy, describes a monitoring approach to the SECURe team. Credits sought.