Research

Emissions from gas flares could be higher than industry estimates – new study

pnr 181102 Cuadrilla Resources

Photo: Cuadrilla Resources

Emissions from flares – including climate-damaging methane – could be underestimated, according to new research published today.

The Environment Agency has assumed that flaring waste gas on onshore hydrocarbon sites was the best practice for protecting the environment.

But the regulator has conceded that evidence to support this conclusion was limited.

It said there were few measurements of how much unburnt gas was emitted that could harm the environment and may contribute to global warming.

A study for the EA by the National Physical Laboratory concluded:

“unburnt hydrocarbons from flares can be elevated, implying that combustion can be inefficient. This means that if flare emissions are estimated by assuming efficient combustion of hydrocarbons, then actual emissions may be underestimated – including methane.”

The study, one of six research projects on the onshore industry released today, found that combustion efficiency at four case study sites varied from about 85%-99%, depending on the flare and stage of operation.

It found a “tendency for higher emissions of unburnt hydrocarbons to occur under conditions of low [gas] flow”. Hydrocarbons could also be released during non-operational periods from leaking gas valves, the study concluded.

The authors recommended that site operators should keep full records of relevant flare types, flows, inlet gas compositions and operating conditions.

Predicting fractures

Another study found short-comings in software used by fracking companies to predict fractures in shale rock.

Computer models are a key part of hydraulic fracture plans, which are used to regulate operations.

But the study author, the British Geological Survey (BGS), concluded that different software and modelling approaches produced different results using the same inputs.

Relying on hydraulic fracture simulators alone as proof of compliance – particularly in new shale gas areas – was not feasible, the study said.

The authors found that hydraulic fracture stimulation software was now more capable and accurate than a few decades ago.

But they said the sophistication of the software varied. Most was limited to modelling simple fractures, despite growing evidence that induced fractures were more complex.

The research also showed that very few commercially-available simulators were capable of coupling hydraulic fractures with the existing natural fracture network. But the study said this was essential to accurately assess the connectivity of the hydraulic fracture network.

The study recommended that regulators should consider whether the input parameters used in hydraulic fracturing proposals were reasonable for the expected formations, fluids and  stress conditions.

It also said hydraulic fracturing activities should be monitored as they progressed, and the models refined to improve their accuracy and as proof of compliance with permits.

A more comprehensive review should be carried out and key issues, such as stress and rock properties, should be quantified.

Other studies released today looked at:

  • impact of leaks from abandoned wells on groundwater quality
  • methods for analysing air quality and groundwater data near oil and gas sites
  • identifying fracking-induced earth tremors

Key points from studies

Flare emissions

Title: Review of differential absorption using LiDAR flare emission and performance data

Purpose: Review data on how well waste gas is burned in flares

Method: Light Detection and Ranging (LiDar) remote sensing technique, known as DIAL (differential absorption). The EA said this technique shines a laser into the flare and records the wavelengths, intensities and timings of the reflected light which indicate the composition, concentration and position of the gas. This can be used to evaluate the combustion efficiency, and the amount of unburnt methane and other air pollutants released to atmosphere. The technique measured emissions of hydrocarbons, sulphur dioxide and NOx.

Key findings: The four case studies, which included what was described as “a conventional onshore oil extraction site”, did not provide enough examples for a comprehensive analysis of flare emissions performance covering different types of flares, flows, hydrocarbon compositions and operating conditions.

But the project concluded:

  • Emissions and combustion efficiency can vary from about 85%-99% depending on the flare and stage of operation
  • Tendency for higher emissions of unburnt hydrocarbons under conditions of low flow
  • Gas valves may leak so hydrocarbons are released during non-operational periods
  • Frequent gaps in supporting data on flaring provided by operators
  • DIAL can quantify emissions of gases but operators should also keep full records of relevant flare types, flows, inlet gas compositions and operating conditions

Authors: National Physical Laboratory

Links: Summary and report


Simulating fractures

Title: Review of software used by the oil and gas industry to model hydraulic fracturing

Purpose: Review computer models used by oil and gas industry to understand how fractures extend underground. The Environment Agency said it needed to know what the models do, how they operate and how they help to assess environmental risk at individual sites.

Method: Literature review of commercially available software for hydraulic fracturing and catalogue of main features.

Key findings: Seven modelling packages identified had different levels of sophistication and provide different results.

  • Some models did not simulate the effects of induced fractures on the existing fracture network.
  • Regulators should consider whether input parameters used in hydraulic fracturing proposals are reasonable in the conditions and operations expected
  • Hydraulic fracturing activities should be monitored and models refined to improve accuracy
  • More comprehensive review should be carried out
  • Stress and rock properties expected in shale gas fields should be quantified

Author: British Geological Survey

Links: Summary and report


Abandoned wells and groundwater

Title: Impacts on groundwater quality from abandoned hydrocarbon wells

Purpose: Evidence from the USA shows hydrocarbon wells have had an impact on some shallow groundwater, mainly because of well integrity or poorly constructed wells. Previous studies have showed evidence of limited methane emissions to air from abandoned UK oil and gas wells. The project aimed to better understand whether abandoned deep wells have leaked and what would be the impact on groundwater quality.

Method: Reviewed records of 2,000 UK onshore oil and gas wells to identify those most likely to impact on groundwater. Selected two former gas wells (Nooks Farm, Staffordshire and Ashdown, Sussex) and two former oil wells (Hemswell, Lincolnshire and Lomer, Hampshire) for field investigation. Two rounds of sampling collected a total of 48 groundwater samples. The study used existing groundwater boreholes and no dedicated monitoring boreholes were installed near the study sites.

Key findings:

  • Low concentrations of hydrocarbons were found in groundwater.
  • High maximum dissolved methane concentration of 407 ug per litre was found in the first sampling round but not repeated in the second.
  • Volatile organic compounds, polyaromatic hydrocarbons, pesticides, herbicides, fungicides, surfactants, analgeisics and veterinary compounds were found in some samples at low concentrations. None could be linked unequivocally to abandoned wells.
  • Soil gas survey at Ashdown and a new study location (Bolney, Sussex) produced ambiguous results with elevated concentrations of carbon dioxide and methane.

Authors: British Geological Survey and Environment Agency

Links: Report


Risks to deep groundwater

Title: 3D groundwater vulnerability

Purpose: Examine sources of groundwater deep below surface and assess its vulnerability to pollution.

Methodology: Assessment of the risks of subsurface oil and gas activities to groundwater at different depths in five case study sites across England.

Key findings: Most of the aquifers studied were found to be at low risk of contamination. Some were medium-low or medium-high risk. None were found to be at high risk.

Author: British Geological Survey

Link: Summary 


 

Monitoring air and groundwater quality

Title: Onshore Oil and Gas monitoring: assessing the statistical significance of changes

Purpose: Identify methods for analysing air quality and groundwater monitoring data near onshore oil and gas sites. This will help define baselines and show how changes from the baseline may be detected.

Key findings: Advice on procedures for monitoring survey design and data analysis, with appropriate statistical tests.

Author: Environment Agency

Links: Summary and report


Identifying fracking-induced earth tremors

Title: Guidance on seismic cluster definition and identification

Purpose: Investigate a statistical approach known as clustering to distinguish seismic events induced by fracking from background everyday seismicity. Real time analysis of clustering of seismic events could help to indicate the onset of fault reactivation and allow early intervention.

Key findings:

  • The approach could be used to detect and cluster unusual seismic activity as long as the events were more than about 450m from the main seismic cluster.
  • The method is promising and may be worth further work to develop bespoke software.
  • It could also be used to test the effectiveness of clustering methods as early indicators of problems in fracking operations.

Author: Professor Peter Styles, Calculus Geoscience Consultants Ltd

Links: Report

Updated 23/10/2019 to include details of sixth report

10 replies »

  1. All in all it would appear that the guinea pigs of the Fylde will, as planned by the Establishment, be providing invaluable data to be crunched in the form of damaged properties from earthquakes, contaminated land and groundwater from flooding and worst of all ill health from all the airborne toxins liberated over our heads!
    Thanks you Cuadrilla et al. You have all been put on notice of Liability for any and all harm caused by your actions!

  2. Good to see the EA working on the issue of flaring. However I do not see from their report that they have reached any other conclusion, other than it is still the right thing to do, as the alternative is to vent the gas ( despite the comment in the summary saying they have insufficient information to support the conclusion that it was the best thing to do )

    So, vent climate damaging methane or burn it and produce climate damaging CO2 ( if pure climate damaging methane of course ). The issue seems to be flare efficiency across the range of operating conditions. If the popped offshore to many an older Southern North Sea platform, they could measure the venting, of course, as there are no flares.

    Re the onshore conventional oil and gas site I guess there is only one large enough to fit the description in the report.

    By the by, is there any other type of methane other than ‘climate damaging methane’?

  3. Hewes62,

    Sorry but I don’t get your point?

    Flaring and venting has been carried by Cuadrilla at PNR regularly, both following fracking Well1 last Winter and fracking Well2 this Summer.

    Just fact reports from Gate Camp indicate both Flaring and Cold venting has occurred in the last few days!

    • Peter K R

      You say that fylde fracking, as planned by the establishment, will provide invaluable data to be crunched in relation to

      1. Damage to properties from earthquakes
      2. Contaminated land and groundwater from flooding
      3. I’ll health from the airborne toxins liberated over our heads

      As the DOD post relates to flaring I commented on that point ( no 3 ). There are plenty of flares in the UK that run 350 or so days a year ( petrochemical sites, refineries, gas terminals and a couple of onshore oil and gas fields ). Plus tens of thousands across the globe.

      The affects of these on the surrounding populations has been studied. Hence there would be no need for anyone to crunch data on the health effects of flaring. It is already available.

      So, in that respect, I doubt there that anyone ( or any establishment ) awaits the Cuadrilla flaring ( either the brief flaring in the past or the likely brief flaring to come).

      Re earthquakes, I would also doubt that an establishment awaits data to determine the damage to properties from earthquakes. That data exists based on global data ( no need to wait for it ) and closer to home from mining induced seismicity.

      However, you would be right in terms of crunching data re seismic vents caused by fracking, which is now available due to the seismic monitoring installed for the fracking. That was curtailed when an event, classed as the worst case even ( given the geology ) happened ( as per past comments here on DOD re expected max of 1.6 with the traffic light system and risk reduction measures, vs 3.0 without those measures).

      Why fracking started off in the fylde, I am not sure, but someone on here knows I guess ( ie why it kicked off under Gordon Brown and a Labour gov ).

      Re contaminated land and groundwater from flooding, I am not sure how that differs from the data available from existing oil and gas sites ( such as TE in the vale of Pickering, WYF, any gas terminal or Grangemouth..say or the local chicken farm ). Unless the site is storing it’s frack fluid in ponds or allowing fuel tanks to leak into the bunds, then flooding should not have a major impact on land or the local streams.

      But, I think that this will all be immaterial for the fylde as I doubt ( given the issues re seismic activity ) that it will be allowed to restart, ban or no ban ( moratorium or no moratorium ).

      Maybe the companies prefer a ban, as a moratorium is not a ban, and having no force in law ( see past DOD reports ) does not give rise to compensation claims against the gov for PEDLs paid for and costs to date on working the issue ( including legal fees for planning issues ).

  4. Hewes62,
    Can’t post much just now but for some reason the Establishment said a couple of years ago they needed emissions from actual UK onshore fracking operations to be analysed. Evidence from overseas wasn’t considered appropriate for the UK because our emissions might be different. Cuadrilla also said they wouldn’t cause earthquakes here unlike elsewhere because our ground conditions are different. The appointed Regulators said fracking in the UK wouldn’t contaminate groundwater and drinking water.
    Well the Earthquake assumption has been proved totally false.
    The other two issues regarding public health and water/ground contamination will take longer to be finalised.
    Obviously large nett employment increases were a fabrication because of the permanent loss of jobs in farming and tourism.
    Oh and viable recovery rates of commercial gas reserves were seriously overstated apparently.
    I’m off now.

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