7. Managing extractive waste
Classifying and coding extractive waste for onshore oil and gas activities and best available techniques (BAT) for managing extractive waste.
Extractive waste, more commonly known as mining waste, is waste directly resulting from land-based prospecting, extraction, treatment and storage of mineral resources.
The oil and gas activities that produce extractive waste include, but are not limited to:
- drilling boreholes or laterals to access the resource formation
- well completions
- well workovers
- well bore treatment including acid washes to remove formation binding
- formation testing activities such as leak off tests
- well stimulation including hydraulic fracturing
- production of oil and gas to the surface
- suspension or decommissioning of a well
- well abandonment
The extractive wastes generated by these activities include, but are not limited to:
- drilling muds
- drill cuttings
- well completion fluids
- flowback fluid mixed with formation minerals and salts
- produced and formation waters
- proppants such as sand removed from flowback fluid
- waste suspension and spacer fluids
- any condensates that are discarded
- testing or well stimulation fluids
- waste gases, including fugitive emissions
You must classify the waste generated by your operations into one of these categories:
- inert
- non-hazardous non-inert
- hazardous
Classifying your waste will help you:
- decide how to handle it
- complete the paperwork you must give waste contractors so they can help you manage your waste in accordance with the Duty of Care regulations
The guidance document How to comply with your environmental permit: additional guidance for mining waste operations has more information on classifying extractive waste (pages 19 to 21).
You must classify your waste using the correct code from Technical guidance WM3: waste classification.
Waste water-based drilling muds are classified on the basis of their type and composition. Related wastes are those resulting from the drilling activity, including:
- processed drill cuttings
- acid wash returns
- spacer and suspension fluid
Drilling mud wastes are typically contaminated by the drilling fluid used. Drilling muds that contain barite or chlorides (such as salt-saturated and potassium chloride) are potentially hazardous waste.
You must assess waste for hazardous properties and persistent organic pollutants before assigning a classification code. If these are present, you must use the classification code 01 05 06*.
An asterisk at the end of the code means the waste is hazardous.
The document Technical guidance WM3: waste classification explains how to assess if waste is hazardous and how to classify it.
Water-based drilling mud wastes containing barite
Use the following waste codes:
- drilling muds and other drilling wastes containing hazardous substances: waste code 01 05 06*
- barite-containing drilling muds and wastes other than those mentioned in 01 05 05 and 01 05 06: waste code 01 05 07
Water-based drilling mud wastes containing chlorides
These are water-based drilling fluids that contain significant levels of chlorides such as salt-saturated and potassium chloride drilling fluids. Use the following waste codes:
- drilling muds and other drilling wastes containing hazardous substances: waste code 01 05 06*
- chloride-containing drilling muds and wastes other than those mentioned in 01 05 05 and 01 05 06: waste code 01 05 08
Water-based drilling muds that do not contain barite or chlorides
Use the following waste code:
- freshwater drilling muds and wastes: waste code 01 05 04
Use the following waste code:
- waste from mineral non-metalliferous excavation: waste code 01 01 02
Pipe scale is likely to exceed the out of scope values for naturally occurring radioactive material (NORM). You will need to classify it as radioactive waste.
NORM is usually present, but if it is not use waste code:
- drilling muds and other drilling wastes containing hazardous substances: waste code 01 05 06*
Any oil-based drilling muds you return to the supplier are not classified as waste. Any oil-based muds you spoil, or lose in the formation, will be waste and will always be hazardous.
You must treat oil-based muds lost as part of the drilling process as a fugitive (unplanned) emission. You must take remedial action to stop the losses, for example switching off the drilling operation.
You must report these losses to the Environment Agency in writing providing details of:
- quantities of oil-based mud lost
- where in the geological sequence you lost them
- how you controlled the losses
Related wastes include:
- processed drill cuttings
- acid wash returns
- spacer and suspension fluid
These wastes are typically contaminated with oil-based drilling fluid making them hazardous.
You must screen drill cuttings on site as part of the drilling operation to reduce:
- surface contamination by oil-based drilling muds and fluids
- the amount of waste generated
The processed drill cuttings will be hazardous waste.
Waste oil-based drilling muds and related wastes
Use the following waste code:
- oil containing drilling muds and wastes: waste code 01 05 05*
Natural gas may arise during appraisal, drilling or production activities. It is classified as highly flammable and therefore hazardous under Annex 3 of the Waste Framework Directive. Waste oil is also classified as hazardous.
Use the following waste codes:
-
gases in pressure containers (including halons) containing dangerous substances (this is the right code to use even though the description may not appear to be applicable, the code is determined by the activity that creates the waste): waste code 16 05 04*
-
oil-containing drilling muds and wastes: waste code 01 05 05*
Wastes from derived oil include:
- crude oil that you pump to the surface as a product, but then spill, becomes a waste when you clean up the site
- grit collected in the 3-phase separator that has been in contact with crude oil
- very small quantities of waste crude oil from oil or water separators that is not economically viable to treat as a product
- waste oily water from oil or water separators that you will not reuse for re-injection
Use the following waste codes:
- oil spills: waste code 13 08 99*
- solids from grit chambers and oil or water separators: waste code 13 05 01*
- oil from oil or water separators: waste code 13 05 06*
- oily water from oil or water separators: waste code 13 05 07*
These BAT are indicative – they set out the best techniques you could use when you manage different types of extractive waste. You can propose using alternative techniques if you can demonstrate that they provide the same (or better) level of environmental protection.
BAT are likely to include a mix of technologies and management methods.
Planning and design
These are the indicative BAT:
- assess the wastes you will generate on site before operations have started
- apply the waste hierarchy to all wastes
- design and build the well in a way that reduces the volume of drilling mud used and drill cuttings produced, but still provides well control and integrity
- evaluate whether you will generate any solid wastes with elevated levels of naturally occurring radioactive substances and if so, develop plans for how you will identify and manage it in accordance with RSR guidance
- for waste gases, use the methodology in the report Waste gas management at onshore oil and gas sites: framework for technique selection (or an equivalent approach) to demonstrate that BAT have been chosen to prevent (or where not practicable, to reduce) emissions and impact on the environment
Fluid selection and management
These are the indicative BAT:
- design drilling muds in a way that minimises the amount of mud lost or fluid gained - taking into account the filter cake design, inclusion of non-hazardous lost-circulation materials, and appropriate mud weights
- displace oil-based mud from the well and return all recovered mud to the supplier after you have completed each well – mud you return is not classed as waste
- use a closed loop system for oil-based drilling mud, with mud passing through the solids control equipment and recirculated in the well
- use a partially closed loop system for water-based mud which allows continuous fluid level management - spent water-based mud which cannot be used again is classed as extractive waste
- monitor the mud management system to assess for any losses or gains
- use mud pit volume totaliser to identify drilling mud lost to the formation or any gain in fluid
Well cellar construction
These are the indicative BAT for the well pad and associated surface infrastructure:
- construct water tight well cellars that can control any wellhead spills
- test, install and operate a blow-out preventer on the well
- check well cellar integrity before you start drilling
- make sure all casings and tubing are appropriate for the pressures and conditions under which you will use them
- make watertight anything that penetrates the well pad or lining systems (such as a rat hole) to prevent site surface water being lost, or wellhead spills entering the underlying land and groundwater
Containment measures
These are the indicative BAT:
- install an impermeable liner across all areas of the site before you start drilling – the modelled lifespan of the membrane should exceed the anticipated life of the well
- use appropriate construction quality assurance standards for the materials being installed as part of the impermeable liner
- check the integrity of seals in all areas of the impermeable liner - particularly areas used by traffic, or to temporarily store extractive wastes, or with built structures
- build areas for the temporary storage of extractive wastes following the standards in Containment systems for the prevention of pollution (C736)
- bund all storage tanks on site following the standards in Containment systems for the prevention of pollution (C736)
Drill cuttings: general management
These are the indicative BAT:
- separate drill cuttings from the drilling mud as far as reasonably practicable - you must do this at the surface using suitable solids control equipment
- the solids control equipment should use a mechanical separator (for example a shaker) that can separate drill cuttings from drilling fluid
- the solids control system should use mud cleaners (such as de-sanders and de-silters) and centrifuges, to remove finer fraction cuttings from the drilling fluid
- keep drill cuttings that are hazardous waste separate from any non-hazardous waste - you must supervise cuttings skips at all times when active mud management is taking place
- separate cuttings from water-based mud, and cuttings from oil-based mud, and transfer into different temporary containers or skips (according to type) for collection
- cover drill cutting skips or temporary containers to prevent water getting into them
- make sure waste cuttings are characterised according to waste type
- remove waste cuttings from site as soon as reasonably practicable using an authorised waste contractor who will take them to a waste management facility that has the correct permit
You may use on-site secondary treatment of cuttings to:
- dewater
- reduce the hydrocarbon concentration or remaining on cuttings
You should use relevant sector-specific BAT for your proposed treatment. This could include cuttings dryers or thermal desorption. You should carry out a site-specific cost-benefit analysis to select your treatment. The Environment Agency can assess your proposals for on-site treatment as part of your permit application.
Spacer and other fluids management
You must manage these types of fluids when you are extracting waste in oil and gas activities:
- spacer fluids
- suspension fluids
- kill fluids
- workover fluids
- completion fluids
- interfacial mixtures or slops
Here are the indicative BAT for managing these fluids:
- you must have a material safety data sheet for all substances used available on site
- clearly mark and bund chemical storage areas using the standards in Containment systems for the prevention of pollution (C736)
- do not store chemicals on site longer than is needed for your operations
Waste cement management
These are the indicative BAT:
- pump enough cement to seal off the formations when you install casing and during well abandonment
- calculate how much cement you will need and measure volumes to avoid ordering or mixing too much and generating waste cement
- temporarily store excess, returned cement you cannot use on site as concrete in lined skips - as soon as reasonably practicable, use an authorised waste carrier to take them to a waste management facility with the correct permit
Waste hydrocarbons management
These are the indicative BAT:
- separate waste oil from other wastes and put in a tank in a bunded area
- carry out regular maintenance inspections on tanks and bunds
- have emergency spill response equipment, expertise and procedures available on site
- take waste oil off-site for recycling at a centre with the correct permit
- comply with Environment Agency guidance on incinerating or flaring waste gases, see section 8
- comply with the guidance for managing vent emissions from storing and handling crude oil, see section 9.6
- manage waste gases from flowback fluid and produced water appropriately using the methodology in Waste gas management at onshore oil and gas sites: framework for technique selection or an equivalent approach
Waste proppants management
These are the indicative BAT:
- separate on-site returned proppant into an enclosed container – this must be located on the site well pad membrane
- consider opportunities for reuse or recycling - where reasonably practicable
- remove spent proppant off site for recycling or disposal at a permitted facility
Waste flowback fluid management
If you cannot reuse the flowback fluid for further hydraulic fracturing, these are the indicative BAT for managing waste flowback fluid:
- store in sealed tanks in a bunded area pending removal off-site
- treat off-site at a permitted waste water treatment facility
Waste produced water management
If you cannot reuse the produced water these are the indicative BAT:
- store on site in sealed tanks in a bunded area
- re-inject for disposal
- treat off-site at a permitted waste water treatment facility
Spill management plan
You must have a spill management plan which ensures that any material spilt on site will be contained and removed. Your plan must include:
- training all staff supervising, loading or transferring wastes on site to use spill kits
- having spill kits available on site at all times, and in all areas where you’re transferring or temporarily storing extractive wastes
- carrying out daily inspections for leaks and any damage to the pipework and the associated storage tanks of the drilling mud system
- repairing or removing any leaking or damaged equipment immediately
- recording and cleaning up all spills
You must notify the Environment Agency of all uncontained spills or breaches of containment in line with the requirements set out in your permit. You must also take the measures needed to:
- limit the environmental consequences of such an incident
- prevent further possible incidents or accidents
Waste removal
These are the indicative BAT:
- using a risk-based approach, sample consignments of waste and characterise before removing from site - keep a reference sample
- record the quantities and characterisation of drill cuttings and keep these records for at least 2 years
- record all waste transfers from your site and keep these records for at least 2 years – you must make these records available for inspection by the Environment Agency when requested