Many consider fracking to be a dangerous process, fearing it releases gasses that pollute the water table and upper soil layers. Shale developers are using cutting-edge gas monitoring equipment to ease those fears.
In his 2010 documentary Gaslands, filmmaker Josh Fox recorded images of American homeowners setting fire to the water running from their taps. These images have become embedded in the public consciousness in the debate over the safety of shale gas development, and in particular the hydraulic fracturing process used to release the gas.
This process, commonly known as fracking, involves the drilling of a well that is used to pump a combination of water and chemicals that fracture the shale rock and allow the embedded gas to escape.
Fox’s film claimed that water supplies had been contaminated by both chemicals used in the fracking process and the gas that was released.
By doing regular sampling and laboratory tests we can demonstrate that nothing has changed at this well site, or if something has changed we can alert our client
GGS managing director Simon Talbot
Subsequent scientific research in the US has added further weight to Gasland’s claims: earlier this summer a study by Duke University analysed 141 drinking water samples from private water wells across Pennsylvania’s Marcellus shale basin.
Their findings concluded both higher methane concentrations in local drinking water within a kilometre of the drilling site and higher ethane and propane concentrations. There is no biological source of ethane and propane in
the region and Marcellus gas is high in both.
Cuadrilla’s shale gas exploration operations near Blackpool
A frequently expressed concern is that fracking operations will open up fractures that extend up to and contaminate the freshwater aquifers with gas, fracking fluids and formation waters. However, the shale formation is often several kilometres deep and the risk of this occurring is extremely small. Typically fractures propagate around 200m away from the production casing. What can occur is that incorrectly sealed and abandoned wells present in a shale gas development area and provide a vertical pathway through which contaminating fluids and gas could migrate. In the US, some ground-water contamination has been investigated by the US Environmental Protection Agency in Pavillion, Wyoming in a shale gas production area where hydraulic fracturing occurred at depths as shallow as 372m. Another risk is that the well casing ruptures to allow gas and fluid to escape. While many US wells only have a single casing layer, UK wells are required to have a cemented triple casing through aquifers to ensure there is a very low risk of rupture.
Fears that fracking may contaminate the UK’s water supply have been voiced by everyone from the protestors outside Cuadrilla’s site in Balcombe, West Sussex to the trade body for UK water companies, Water UK.
However, those working on UK shale gas sites believe that a combination of tougher environmental regulations and the benefit of hindsight means this country is unlikely to repeat the mistakes made at what they say are a handful of US projects.
Cuadrilla has hired environmental consultant Ground Gas Solutions (GGS) to monitor the gas regime at all of its UK sites and the firm is using a combination of cutting-edge technology and best practice techniques largely ignored in the US to ensure that an accurate picture of the true effect of fracking on gas migration can emerge.
One of the key failures made by US projects, says GGS managing director Simon Talbot, is the complete lack of baseline monitoring of each site’s gas regime before any drilling commenced.
“Ground gasses like methane are present in the natural environment,” says Talbot. “To effectively monitor a site you must establish a baseline to characterise the gas regime at the site before any works occur. There
is then an evidence base before any further monitoring occurs.”
At the Cuadrilla sites it is working on, GGS has carried out a pre-drilling baseline desk study of the near-surface geology, site history and land-use to identify possible sources of methane and other contaminants that may be present at each of the drilling pads.
At Cuadrilla’s site near Blackpool existing potential hazards include biogenic methane arising from local organic silts and peats as well as from made-ground and landfills. The desk study is followed by the installation of purpose-designed monitoring wells at each drilling pad and a programme of baseline monitoring, sampling and laboratory testing.
GasClams (see box below) are installed in each monitoring well where they collect continuous data on both ground-gas concentrations and the environmental parameters that affect the gas such as atmospheric pressure, temperature and groundwater level.
Any loss of integrity of the well casing or cemented annulus around the casing would result in shale gas escaping into the near surface soils and aquifers where it would be detected by the GasClams in the monitoring wells.
“Ground gasses are highly mobile and respond to a number of pressures,” says Talbot. “They flow up gradient, down gradient: you name it. The only way you can capture the ground gas regime effectively is by continuous monitoring.”
However, current gas monitoring equipment generally falls into one of two categories: permanent systems used for safety purposes where if gas concentrations exceed a certain level then an alarm is sounded; and hand-held devices for spot-monitoring.
However, neither type of technology provides an accurate picture of the movement of gasses over a period of time which is why Talbot, along with Dr Stephen Boult of Manchester University spin-out company Salamander and Professor Peter Morris of Ion Science, developed GasClam.
“What GasClam has done is bring those two existing modes of gas monitoring technology together into a device that will fit inside a monitoring well,” says Talbot.
Regular samples for laboratory testing
“It has an onboard datalogger that will monitor the concentration of gasses over time and also measure a number of the environmental parameters including: atmospheric pressure, borehole pressure, temperature and ground water level changes.”
In addition to the continuous monitoring provided by GasClam, GGS takes regular samples for laboratory testing. The samples are analysed for their carbon 12 to carbon 13 isotope ratio and detailed chemical composition.
This “fingerprinting” exercise reveals each different type of gas present and its likely origin. For example, ground gasses naturally occurring near the surface will have lower ethane concentrations than the methane that could be released by the fracking process.
“By doing regular sampling and laboratory tests we can demonstrate that nothing has changed at this well site, or if something has changed we can alert our client and there will be a range of actions the operator
could take,” adds Talbot.
These actions, he says, could range from stopping drilling to allow further investigation, to sealing up a well and abandoning a site. In addition to its work with Cuadrilla, GGS is also working with rival developer IGas and deploying GasClam on its unconventional sites in the UK, while Morris’ Ion Science is now marketing GasClam around the globe.
So while protestors might hope that GasClam’s data forces developers to abandon their sites, it seems more likely the technology could giving fracking operations the environmental legitimacy they so desperately need.
Continuous monitoring – how GasClam works
GasClam is the world’s first in-situ borehole gas monitor that can collect data continuously. It measures methane, carbon dioxide and oxygen concentrations as well as atmospheric pressure and temperature, with a samplingfrequency that can be set at anything between every two minutes to just once daily. Data is downloaded to a PC or viewed remotely using the optional GPRS telemetry system. Manufactured from stainless steel and batteryoperated, GasClam can be powered for up to one month based on hourly sampling.