11. Produced water and flowback fluid: re-injection and reuse

When you can re-inject produced water and reuse flowback fluid in onshore oil and gas operations or transfer produced water to another operator.

11.1 Re-inject produced water

Produced water is any water that is produced by exploring and extracting hydrocarbons from a well with oil and gas. This does not include flowback fluid.

You can re-inject produced water into geological formations from which hydrocarbons have been extracted to encourage the further production of hydrocarbons.

You can also re-inject produced water into geological formations that for natural reasons the Environment Agency has determined as ‘permanently unsuitable for other uses’. See the Groundwater protection technical guidance for more information about this.

You must have a groundwater activity permit to re-inject produced water. You may also need a radioactive substances activity permit.

Re-inject produced water at the same site

You do not need a radioactive substances activity permit if you generate and re-inject produced water at the same site to encourage further hydrocarbon production. This applies even if the produced water contains naturally occurring radioactive material (NORM) at a concentration above the out of scope values.

This is because the produced water is supporting production so is not classed as waste.

You will need a radioactive substances activity permit for some other re-injection activities.

Re-inject produced water at a different site

You must have a radioactive substances activity permit if you want to re-inject produced water to encourage production and the following apply:

  • it is at a different site for which you are also the operator
  • the concentration of NORM in the produced water is above the out of scope values

This is because the produced water is an unwanted surplus at the original site and is therefore a radioactive waste, even if you are using it at a different site.

Transfer produced water to another operator

Both you and the operator you transfer produced water to must have radioactive substances activity permits if both of the following apply:

  • you transfer the produced water to another operator for re-injection to encourage production at a different site
  • the produced water contains a concentration of NORM above the out of scope values

This is because you’re transferring radioactive waste between operators, even if it is meant for use (rather than for disposal) at the different site by the other operator.

Re-inject produced water for disposal

If you want to dispose of produced water by re-injection, and it has a NORM concentration above the out of scope values, you will need both a:

  • groundwater activity permit
  • radioactive substances activity permit

If the NORM concentration is below the out of scope values, you can re-inject produced water for disposal under a groundwater activity permit. This is because it is not radioactive waste.

In both cases, the re-injection for disposal can only take place at:

  • the original site
  • a different site, into geological formation from which hydrocarbons have been extracted
  • a different site which the Environment Agency determines as permanently unsuitable for natural reasons

Waste produced waters are extractive waste and you must have a mining waste permit to cover their overall management.

If you cannot comply with this guidance on disposing of produced water by re-injection, you must take the waste water to a permitted waste facility for disposal.

Re-inject surface water mixed with produced water

You must not re-inject surface water run-off mixed with produced water for disposal purposes.

Surface water run-off mixed with produced water can be re-injected to encourage the production of hydrocarbons. This can be done at the same site or a different site if the surface water is clean (not contaminated by activities on your site). You must treat surface water before you can use it for re-injection, for example, using an oil separator.

11.2 Re-inject reused flowback fluid for hydraulic fracturing

Flowback fluid is hydraulic fracturing fluid which returns to the surface after high-volume hydraulic fracturing. This may include mobilised natural gas and formation water.

You can reuse flowback fluid as fresh injection fluid for the purpose of hydraulic fracturing. You must reuse flowback fluid where you can so you are meeting the Mining Waste Directive obligation to minimise waste.

If you have flowback that cannot be reused it is waste. It is likely to also be classed as radioactive. You must send this waste to an appropriate permitted waste facility for treatment or disposal.

Re-inject flowback fluid for disposal

The Environment Agency will not allow you to re-inject flowback fluid into any geological formation for disposal, whatever its NORM concentration is.

Whilst the re-injection of flowback fluid for disposal is not strictly prohibited, the Environment Agency is currently taking a precautionary approach to protect water bodies and groundwater. Re-injection for disposal is not a proven best available technique (BAT). Other disposal techniques are better environmental options. For example:

  • disposal at a waste facility with the appropriate permit
  • treatment using on-site waste water treatment facilities