Last month, Croner reported on two aspects of the controversial process of fracking for shale gas exploration, which has recommenced in Lancashire. One growing concern is that the fugitive emissions or leaks of methane from both conventional and unconventional natural gas extraction, transport and storage could be as high as 8% for unconventional gas and 6% for conventional gas. Rick Gould reports.

Fracking was back in the news again at the beginning of February when the chief executive of UK shale gas company Cuadrilla stated, during a discussion held on BBC Radio Lancashire, that the shale gas reserves in Lancashire could have a market value of £136 billion. He added that he thought this valuation was not too optimistic and that the company believed that it could extract 10% of the 200 trillion cubic feet of shale gas, which has been discovered in the Bowland.

At the same time, environmental pressure groups have reaffirmed their total opposition to fracking, with continued action aiming to halt its progress; for example, during February, Friends of the Earth arranged a free training day, which described how the planning system can be used to oppose fracking. Greenpeace, meanwhile, began its own Battle of Britain campaign, urging the UK to put an end to fracking, among other environmental concerns.

Across the pond

In the United States, where fracking for shale gas is now well established, two pro-environmental non-governmental organisations appear to be taking a different approach. Neither group is in favour of fracking for shale gas, or the continued use of fossil fuels for that matter. However, both groups accept that the process will occur, so they are acting to minimise the environmental impacts of fracking through campaigning, action and by disseminating information on how the process can be better controlled.

The Environmental Defence Fund (EDF) describes five areas of high concern about fracking and campaigns on these areas. It includes, for example, a strong concern that the growth in shale gas exploration could easily thwart the development of renewable sources of energy, and the move away from fossil fuels. Moreover, the EDF is fiercely campaigning to ensure that fracking is controlled as far as possible, in order to reduce or eliminate emissions to air and to prevent fracking fluids from contaminating surface water and groundwater. The EDF’s position is that natural gas has a role as a transition fuel, since it is better than coal, but only if the releases to water and leaks of methane are limited. The EDF points out that reducing the leakage and venting rate for methane to 1% could have the same benefit over 20 years as closing a third of US coal power stations.

The Natural Resources Defense Council (NRDC) in the US shares many of the same views, concerns and aims as the EDF, especially regarding fracking for shale gas. So in 2012, several months before the US Environmental Protection Agency introduced a new law to significantly reduce fugitive emissions of gases from the oil and gas sector, the NRDC had already published a report describing 10 techniques and technologies that can dramatically reduce the emissions of natural gas from processes such as fracking, conventional gas extraction, and the storage and transportation of natural gas.

While these 10 techniques and technologies fall under a category known as the maximum achievable control technology, the NRDC is eager to point out (in its view) that all the techniques and technologies are available today, proven and are accompanied by evidence of their economic viability. Table 1 shows the techniques and technologies, which are reproduced from the report.

It is notable that half of the measures could account for just fewer than 80% of the potential reductions in emissions. The payback times quoted by the NRDC are all relatively low and while the methodology for calculating payback times does appear a little simplistic based on the figures quoted, even the financial benefits could be significant when applying traditional methods of investment appraisals, such as net present values and internal rates of return.

BATs

At the time of writing, the exploration for shale gas within Europe is in its infancy when compared to the US. However, a quick survey of the EC’s reference documents on best available techniques (BATs) showed that many of the techniques and technologies do feature in the guidance, albeit in a fragmented and disparate fashion. However, if unconventional gas exploration and extraction does expand to US levels, it is likely that the EC and national regulators will produce specific guidance for the process, with the types of techniques and technologies described in the NRDC report being promoted as BATs.

Table 1: techniques and technologies to reduce fugitive emissions from the gas sector

Type of technology or technique

Description

Estimated payback time

Percentage of leaks that the technology can reduce

1

Green completions

Temporary equipment installed at a well site separates fluids and gases, when the wells are drilled, repaired or stimulated during fracking.

<0.5–1 year

39% (with plunger lift systems)

2

Plunger lift systems

This type of equipment is used to remove liquids from a well and keep the gas flowing without having to vent methane. These systems do not need separate sources of power.

<1 year

3

Tri-ethylene glycol (TEG) dehydration with emissions-controls

Retrofitting TEG Dehydrating systems with emission controls, combined with optimising the dehydration processes.

<0.5 year

1% (with desiccant dehydrators)

4

Desiccant dehydrators

This removes moisture in the gas without venting methane. These systems work by passing the gas through a bed of moisture-absorbing salts.

<3 years

5

Dry seal systems

Fitting centrifugal compressors with dry seals. These use gas to create high-pressure barriers that prevent leaks.

0.5–1.5 years

3%

6

Improved compressor maintenance

Simply replacing the worn rod-packing on compressors more often can significantly reduce methane leaks.

0.5 years

9%

7

Low-bleed or no-bleed pneumatic controllers

Some pneumatic controllers leak methane, even when operating normally in a process known as bleeding. However, high-bleed controllers can be replaced with low-bleed ones, fitted with bleed reduction kits, or gas-based pneumatics can be changed to air-based pneumatics.

Pneumatic controllers low-bleed <0.5 years

Pneumatic controllers no-bleed <2 years

13%

8

Pipeline maintenance and repair

Connecting a new pipe to the pipeline-system, compressors and depressurising the pipeline, to flow gas to a nearby low-pressure fuel system can stop methane being released when pipes are being repaired or replaced.

<1 year

2%

9

Vapor recovery units (VRUs)

Methane can escape from tanks containing crude oil and natural gas. VRUs can capture 95% of the methane that would otherwise be vented.

0.5–3 years

3%

10

Leak monitoring and repair

Methane leaks from gas facilities often go unnoticed as the gas is colourless and odourless. A highly systematic, well-planned and implemented program of regular monitoring and leak repairs can significantly reduce fugitive emissions.

<0.5 years

18%

From Leaking Profits — The U.S. Oil and Gas Industry Can Reduce Pollution, Conserve Resources, and Make Money by Preventing Methane Waste, NRDC, 2012.

Last reviewed 12 March 2013