The Risk Management Tool Box Blog

How Can a Fracked Well Fail?

Graham Marshall - Monday, December 08, 2014

Opponents of the drive to create energy self-sufficiency and energy-security in Britain will often call on the alleged threat to drinking water as a reason not to develop British gas resources through the process known as hydraulic fracture stimulation.

Here is a typical example of the frightening propaganda used by opponents of unconventional gas; in this case from the "Frac-free Ryedale" website: "Our drinking water would become contaminated if one of the wells leaks, as they are likely to do over time. It is estimated that one in four wells will leak within five years, and 50% of all wells will leak within 15 years."

Now before we get too far ahead of ourselves, I'd like the folks at Frac-free Ryedale answer two simple questions:

Firstly, how, does one in four wells leak within five years?

Secondly, how do 50% of all wells leak within 15-years?

You see, the problem I have with these claims, is that they are simply nonsense: let me show you how a gas well is constructed to prevent any risk of failure and you can work it out for yourself.

When the drill-rig drills the hole into the ground - anywhere up to a depth of 9,000 - 12,000 feet below the surface, and a further 9,000 - 12,000 feet "lateral" (horizontal), an outermost "conductor casing" is inserted.  This conductor casing is a steel tube which fits into the drill hole.  Surrounding the conductor casing and filling the space between the steel tube and the wall of the drill hole is a cement liner. So this provides the outermost barrier between the inside of the well-bore and the outside rock.

Inside of the conductor casing, another steel liner is then inserted into the bore-hole - called the "surface casing".  The gap between the surface casing and the conductor casing is then filled with another layer of solid cement.  So this provides a second barrier inside the well-bore to help prevent any hydrocarbons escaping from inside the well; and prevent any contaminants from migrating  from the outside rocks.

If that wasn't enough protection, there is then a third steel liner - the intermediate casing - inserted into the well-bore inside of the surface casing.  The gap between the intermediate casing and the surface casing is, once again, filled with hard-setting cement.

So, that is now three layers of steel tubing, and three layers of solid cement between the outside rocks and the inside well bore.

But we're not done with protecting the aquifers just yet; inside those three steel rings and three cement walls, the well completions folks then insert a penultimate barrier - called the Production Casing. Outside the Production Casing is another layer of cement.  Inside of the Production Casing is a gap (called the annulus) and inside the annulus is the final protective barrier inside the well.  This is the Production Tubing.

The Production Tubing is a steel pipe that allows gas to flow from the bottom of the well all the way to the surface. The gas (or oil) stays inside the Production Tubing at all times.

So, as you can see, it is practically impossible for any hydrocarbons to escape through five layers of steel tubing and four layers of reinforcing cement and contaminate groundwater aquifers.

Put quite simply, the claim that 25% of wells will fail within 5 years and 50% will fail within 15 years is nonsense.

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