A British research project to recreate fracking in the lab could help determine if the controversial drilling practice could produce chemicals besides natural gas.
A team from the British Geological Society (BGS) has designed equipment to study what substances might be extracted from UK shale deposits by simulating the hydraulic fracturing process already used to obtain methane from the rock.
The work being carried out in partnership with Leicester University, which has already begun examining the content released from UK shale, could also help fracking operators optimise the process.
‘When you look at the literature, nobody’s ever just taken a [UK shale] rock, fracked it and looked at it,’ said Prof Paul Monks, who is leading the research for Leicester University.
Some operators in the US, where fracking is already widespread, extract hydrocarbons besides methane from shale that are then used as feedstock for the petrochemical industry, he said. ‘People are discovering that there’s a double economic benefit.’
If a similar range of hydrocarbons could be extracted from British shale it would likely increase the economic justification for fracking, which has struggled to take off in the UK due to widespread environmental concerns about the process.
The first stage of the research saw samples smashed open with a press and the emitted gases identified in real time as they emerged, using a very fast mass spectrometer that can simultaneously measure thousands of samples to produce a “fingerprint” of the rock’s composition.
Initial results showed Bowland shale samples taken from several hundred metres below the surface in Lancashire (far from the multi-kilometre depths drilled to by fracking operations) were composed of around 3.8 per cent organic chemicals including so-called aromatics such as benzene and toluene.
The BGS researchers have now designed equipment to more accurately recreate the gigapascales’ worth of pressure that occur during fracking, which is performed by injecting water and chemicals into a borehole.
To do this, they plan to inject fracking fluid into a simulated borehole within a cylindrical shale sample 80mm by 50mm in size, which would normally be held in a sheath and surrounded by hydraulic fluid to simulate external pressure.
‘The problem we have with fracking is what happens when the fracture hits sample,’ said Dr Robert Cuss, who has led the design work with colleague Dr Jon Harrington (and whose team includes one Humphrey Wallis, who happens to be the grandson of the wartime engineer Barnes Wallis).
‘With traditional apparatus this is likely to break the sheath, or the fluid outside will influence the experiment. Our sample will sit within a rigid steel body so when the fracture reaches the steel it won’t propagate through that.’
A partially porous filter will be placed between the sample and the steel case, through which nitrogen will be pumped in order to flush out the emitted hydrocarbons while limiting the impact on the experiment’s mechanics.
Because the BGS team want to study the physics of fracking as well as the chemistry, acoustic sensors will be used to detect exactly when a fracture starts to form in the sample, which will then be examined using a CT scanner.
This work should help the researchers produce data to answer several questions that would help optimise the fracking process. ‘Can we predict what pressures are necessary to start fracking?’ said Cuss.
‘If it’s pressurised very rapidly or much slower, does that change the network of fractures you get and does that influence the amount of gas you get back as a return? … Can we better predict and reduce the fracture going outside shale?’
Having a better understanding of the composition of the shale should also enable operators to optimise the efficiency of their operations, selecting the best target rocks and using the exact amount of energy necessary to frack them.