The 7 stages in the lifecycle of a fracking pad

There are a number of distinct stages in the development of a shale gas exploration site, many of which most people probably won't even know about. We thought it might be useful to have a quick look at them.

 

They are:

Site selection 

Planning and Permitting 

Site Preparation 

Drilling 

Fracking 

Flowtesting

Decommissioning and Restoration 

 

Site Selection

The first thing that fracking companies need to do is choose their sites carefully. There will be a number of things that they specifically look for: good road access; not in a groundwater Source Protection Zone 1 (SPZ1) area; limited residential dwellings nearby; not in a National Park or Area of Outstanding Natural Beauty (AONB); away from underground faults; and above rock with good "prospectivity" (i.e. likely to contain a sizeable quantity of gas) to name a few.

They search Ordnance Survey maps, publicly available environmental registers and the record from earlier geological survey work and any previous drilling activity. They will also obtain 3D images of the sub-surface to identify the thickest bands of shale rock and to avoid faults.

Planning and Permitting 

Once they've selected a site location, they'll first negotiate access rights with the landowner before applying for planning permission and environmental permits. 

As anyone that's paid attention to the UK shale gas debate in recent years will know, this is a lengthy and detailed process. In Cuadrilla's case, for instance,  it submitted 4,000 pages of environmental statements to support its planning application at Preston New Road covering everything from site ecology to local traffic impacts. 

The planning and permit applications are publicly consulted on, often more than once, giving all relevant stakeholders an opportunity to comment. 

A decision is then taken by the relevant planning authority and the environmental regulator. 

Site Preparation

Up until now, there's been no visible activity at the proposed site. 

Armed with planning permission and the necessary environmental permits, fracking companies can get on with building their sites.

This will see groundwork contractors strip off the top soil and form the shape of the "pad". Access roads will be built, security fencing erected, and an impermeable membrane installed to capture any surface spills before compacted stone is laid on top to form a stable base for the drilling equipment. 

During this phase of work, a shale gas site will resemble a typical construction or civil engineering site, with diggers and tipper trucks. 

Drilling

With the site built, the drilling rig and associated equipment will be delivered and erected. This will include drill pipe, steel well casing, and ancillary equipment used to deal with the rock "cuttings" that return to the surface as the drill bit rotates and cuts through the various layers of rock. 

The drill bit is attached to hollow drill pipe which turns slowly. Fluids are pumped down through the drill pipe and around the bit to keep it cool and help flush the rock fragment to the surface. Length after length of drill pipe are attached together as the drilling gets deeper and deeper, and then removed while special tools are inserted into the hole to measure things like rock density and porosity at each stage. This is known as "wireline logging" and uses a special, sealed radioactive source lowered into the wellbore.

The surface casing is installed, and drilling continues progressively in the same manner to the required depth. The drill bit gets smaller and successively smaller diameter casing is fitted, all with cement in between to form a good seal and multiple leak barriers between the inside of the well and the outer environment. 

All the while, geologists are collecting core samples of the rock that the drill passes through. 

It is during the drilling activity that the site will be most visible to people because of the 30-50 metre height of the drilling rig. But it's a short-term affair and the rig is soon demobilised and removed.

During the drilling of the well, safety mechanisms called a Blow Out Preventer (BOP) and the "Christmas Tree" wellhead are installed.

Fracking

Once the well is built, and the drilling equipment has been removed, fracking can start. 

Fracking involves pumping a mixture of mostly water and sand (99.95%) and chemical additives that are non-hazardous to groundwater (0.05%) into the shale rock to create a network of tiny hairline cracks. The sand is used to prop them open so that the gas can flow out.

First, a device called a "perforating gun" is lowered into the well,  manoeuvred into position and used to punch holes in the steel production casing where the well reaches the target shale rock. These holes allow fracking fluid to exit the well and returning fluid and gas to enter it.

Fracking is carried out in discreet stages. You'll hear opponents refer to "High Volume Hydraulic Fracturing" or "HVHF" and how it might use over 18,000 cubic metres of water per well, but that isn't all pumped underground at once - it's done in segments, each using anything from around 300 m3 to 800 m3. 

After each frack stage, pumping pressure at the surface is removed allowing gas and fracking fluid to flow into and up the well. You'll hear this called "flowing the well" and it's where the name "flowback fluid" comes from. 

The gas is separated from the liquid and any sand that returns. 

Flowtesting

As well as gaining a better understanding of the geology and "rock mechanics" (which is what determines how much fracking fluid is used and at what pumping pressure), the fracking companies want to know how much gas they can get to flow to the surface and so they test it.

The "Initial Well Test" takes around 90 days during which they will attempt to maintain a constant flow of gas from the well. 

Another goal of the well testing is to measure the quality and composition of the gas, to determine its suitability for delivery into the gas distribution grid should shale gas development and production follow the exploration phase.

In this 90 day testing period per exploration well, any gas that's found will probably be burnt in a flare.

Decommissioning and Restoration

As the term implies, after all the exploratory work has been completed, the site gets returned back to its original condition.

The well is sealed with special cement and mechanical "plugs" and capped off below the surface. All the other equipment is removed, and you're soon left with a farmer's field that looks no different than before.

Of course, it's possible that an exploratory site could be repurposed to become a production site at some later date, which would delay the final stage of the lifecycle - but that would require the fracking company to go right back to the start and make a new application for planning permission as a production site. 

 

What you'll see from this brief overview is that the appearance of a fracking pad will differ at different times in its lifecycle. Sometimes it will resemble a construction site, at other times you probably won't even notice it's there. 

There are essentially three traffic peaks: (1) during the site preparation when hardcore is being delivered to create the pad surface; (2) during the delivery of the drilling rig; and (3) during the fracking operations when flowback wastewater is being removed from site in road tankers. But these are spread out, and take place consecutively not concurrently, and in between, localised traffic levels will be similar to the background norm.

Any noise is most likely to be associated with the drilling and fracking stages - although, as we've seen at Cuadrilla's Preston New Road site, drilling is actually a lot quieter than people had been expecting and it's likely that fracking will be the same when that starts.

So there you have it - the seven stages of a shale gas pad's lifecycle and an idea of what to expect during each one.

 


Showing 3 reactions

Please check your e-mail for a link to activate your account.
  • Dale Green
    So, basically Frack Free Eqs was talking nonsense then… Every point they made, with such assertion, melts away when looked at with any regard for reality.
  • Agent Orange
    Hi FFEQS, thanks for posting – even if we don’t agree with each other!

    You’re right that 300m3 – 800m3 is below the IA2015 stage threshold of 1,000m3 but because they’re talking about 45 stages at Preston New Road, for example, even at just 300m3 each that’s still 13,500m3 and therefore meets the legal definition of Associated Hydraulic Fracturing. So there won’t be any leapfrogging of regulation.

    You say “pah” to public consultation but that’s just because it hasn’t given you the result you want. At least you’re consulted – in a good chunk of the US where fracking takes place, the public has no say whatsoever.

    That’s not true about changing the status of land to brownfield – there are hundreds of abandoned wells in farmers fields dating back to the late 1930’s but none are designated as brownfield.

    Yes, in theory, a fracking company looking to improve well performance could seek to use more additives – but all that would change is the percentage concentration, they’d still have to be declared to and agreed by the Environment Agency as non-hazardous to groundwater.

    That’s 90 days of flaring per EXPLORATION WELL. In a production scenario, there won’t be any routine flaring – they want to sell us the gas, not spend millions extracting it just to burn it all on site.

    We don’t need an arbitrary minimum set-back distance, proximity to homes etc is decided via planning law.

    You’re right, we haven’t mentioned the wastewater in his post but then it was just an overview of the various process steps in a fracking pad’s lifecycle – check out our Fracking Facts and Fracking FAQ pages for more.
  • Frack Free Eqs
    Best piece of satire I’ve read in a while.

    300m3-800m3 ? According to the Infrastructure Act, as amended, this does not even meet the government’s definition of fracking which has to involve, or is expected to involve, the injection of—
    (i)more than 1,000 cubic metres of fluid at each stage, or expected stage, of the hydraulic fracturing, or
    (ii)more than 10,000 cubic metres of fluid in total. Please could you explain which planning and regulatory processes are are leapfrogged by such a definition?

    ‘Public consultation’ Ha!

    ‘Farmers field’ = now a brownfield designated site, ripe for development.

    0.05 % non toxic chemicals! And no chance that a cash-strapped operator of a non productive well will apply to the EA to change the permit and add to the mixture to increase productivity. In fact why even apply – they are ‘self regulating and reporting’

    90 days of 24/7 flaring per well. How many wells will we have with a mature shale gas industry? Has the cumulative impact on health, enviromment and climate been independently assessed? Are we talking out dated metrics used in PHE report to justify that this can be done safely?

    Minimum set back distance? No – not in the UK.

    No mention of produced water treatment and NORMs – off site but possibly a conentious issue?