Official Report: Minutes of Evidence

The Chairperson (Dr Archibald): I welcome Dr Rob Raine, an energy geologist from the Geological Survey of NI. I will hand over to Dr Raine to make an opening statement, and then we will invite members in for questions.

Dr Rob Raine (Geological Survey Northern Ireland): Thank you, Chair and members, for allowing me to present to you. I intend to give a short presentation covering the technical aspects of hydraulic fracturing.

I have a degree and PhD in geology, followed by five years' experience in the oil and gas sectors, working on a range of reservoir types across the world. For the past nine years, I have worked as the energy geologist at the Geological Survey of Northern Ireland, where I am an expert on reservoir properties. I have an in-depth knowledge of Northern Ireland's petroleum geology and exploration history. Although I am not a reservoir engineer, and I do not have direct work experience in the shale gas industry, I have experience in assessing petroleum licence applications, which requires a good understanding of production methods such as hydraulic fracturing.

Before we cover the specific topic of hydraulic fracturing, it would be beneficial to start with a summary of the different types of hydrocarbon reservoirs, their properties and the parts of Northern Ireland that are considered prospective for each type of hydrocarbon.

Oil and gas can accumulate within rocks, and these reservoirs and their hydrocarbons can be divided into two categories, termed conventional and unconventional. Conventional hydrocarbons are those where migration has occurred from an organic-rich sediment into a reservoir rock, and the hydrocarbons are trapped by an overlying impermeable rock called a seal. Unconventional hydrocarbons, on the other hand, are found in reservoirs that do not fit that pattern. Types of unconventional hydrocarbon reservoirs include coal bed methane, tight gas sandstone, shale gas, tar sands etc.

The large difference between conventional and unconventional hydrocarbon reservoirs lies in the two reservoir properties of those reservoirs: porosity and permeability. Porosity is, essentially, the pore space between the grains of sediment, and the permeability is the connectedness of that pore space and its ability to flow hydrocarbons from the reservoir into the wellbore. In that respect, shale is a very different reservoir to sandstone because the pore space is so much smaller than that within a sandstone.

Unconventional reservoirs have hydrocarbon molecules that are too large or too viscous to move unaided or the pores are too small to allow the free flow of the hydrocarbons. Therefore, these reservoirs require additional technologies during testing and production, such as hydraulic fracturing.

The geological history of Northern Ireland has led to several areas of thickly buried sediment, which have been buried to a suitable depth to make them prospective for oil and gas. Almost all the prospective areas for shale are concentrated in the north-west carboniferous basin, which is located largely in County Fermanagh. The darker blue areas on the slide show the most prospective areas, and the lighter blue areas have rocks —

The Committee Clerk: Dr Raine, can I just interrupt? We are still on your first slide.

Dr Raine: You are?

The Committee Clerk: Yes. I have not been moving them. You need to move them. Thank you.

Dr Raine: OK. I am sorry about that.

The Committee Clerk: No problem.

Dr Raine: I just showed the slide of different types of conventional and unconventional hydrocarbons. The second slide shows the reservoir properties of those different reservoirs and how conventional reservoirs differ from unconventional reservoirs.

Moving on to the prospectivity of Northern Ireland, unconventional reservoirs are located particularly in the County Fermanagh area, in what is called the north-west carboniferous basin. The orange areas are principally prospective for conventional hydrocarbons.

If we focus on unconventional reservoirs such as shale, additional techniques are required for extraction and fracturing. Fracturing is one such method that is used in the production. Hydraulic fracturing — or fracking — is a combination of two techniques: the drilling of long, horizontal, lateral extensions of the wellbore, which has been made possible by the technology of directional drilling, and hydraulic fracturing at high volumes, which is why it is usually given the term high-volume hydraulic fracturing or HVHF to distinguish it from other types of fracturing, which I will come to later.

The two individual techniques were developed in the early 20th century but were first used together commercially in the 1980s. There have been many technological steps in the journey of those two processes, and they continue to be modified as they are used and new technologies become available.

The production of gas from shale involves deep drilling to reach the target shale horizon, which is usually in the vicinity of around 2 kilometres in depth, and directional drilling of horizontal laterals, which can be around 1.5 kilometres in length. A steel tubing called production casing is set in the wellbore and holes are punched in that to create a connection with the reservoir. The fracking fluid is mixed at the surface and injected into the well under high pressure to create fractures in the shale. Within the fluid, a proppant such as sand keeps the fractures open following the fluids return from the rock, and that provides a pathway for gas to flow into the well. The process is repeated from a single well pad to drill a number of wells.

The choice of the frack fluid is dependent on the reservoir properties, the cost and its availability. However, the fluid mostly is mostly comprised of water, between 90% and 95%, but other fluids such as liquid carbon dioxide or liquid nitrogen are being explored, especially in water-scarce regions. A proportion of proppant is added to the fluid, which can consist of silica sand, resin-coated sand or ceramic beads, and that is mixed with around 1% of chemical additives. The common chemical additives change the performance of the fluid through the fracking process to protect either the reservoir or the equipment. The most typical additives used are friction reducers, clay stabilisers or chemicals that act as a biocide. The added chemicals each have a specific purpose, and although there is a very long list of chemicals that can be used, often they are just selected for the specific purposes needed.

The volume of fluids required for high-volume hydraulic fracturing in a shale gas well varies between different sedimentary basins across the world. It depends on the pressure that is required, the thickness of the shale formation and the required fracture length. In the United States, typically between 2·6 and 9·7 million gallons of water are used per well, which is roughly the equivalent of 3·8 million litres. One million US gallons is equivalent to 3·8 million litres. Between 60% and 85% of that fluid does not return to the surface. What is returned comprises a mixture of fluid that has been released from the rock, called produced water, and some return of the frack fluid, called flow back.

There are a number of other techniques used in production. High-volume hydraulic fracturing is just one technique. There are lower-volume fracturing techniques, which are termed stimulation and can be used in both unconventional and conventional reservoirs. Often, if you have damage to the reservoir around the wellbore, it is used to create porosity within that to enable the hydrocarbons to flow in. There are other forms of process that are used to sweep the oil or gas through the reservoir, and steam, water or polymer can be pumped into the well. In general, it does not create fractures because of the difference in the pressure, but it is a similar process and uses many similar techniques.

Finally, it is not only the shale gas industry that uses hydraulic fracturing. In some forms, low-volume hydraulic fracturing can be used in water boreholes, in exploration for coal bed methane or tight gas sandstone. There are cases where it has potential to be used with geothermal systems that do not have the natural porosity, although there are no working examples of that, and it is currently at concept stage. That is my last slide.

The Chairperson (Dr Archibald): Thank you for that overview. The slides are in our packs as well. Those are really useful to give us the background to fracking and the different types of fracking.

Some queries were raised around the definition of fracking in the Bill. As I understand it, that was taken from the Petroleum Act 1964 that the Bill seeks to amend. Will you comment on whether you think the definition needs to be widened?

Dr Raine: The Petroleum Act 1998 in Great Britain, which was amended by the Infrastructure Act in 2015, has the definition of hydraulic fracturing in terms of the quantity of the water. So it is any process that involves more than 1,000 cubic metres in any one stage of the process or more than 10,000 cubic metres in the entire process. That is what they use as a definition of high-volume hydraulic fracturing. That distinguishes it from the other types used in other industries or in other reservoirs.

The Chairperson (Dr Archibald): Thanks for that. That is useful to know about the water quantities. I was referring to the rock types. I do not have the Bill in front of me at the minute as I am doing things online this morning, but it think that the Bill refers to shale and not sandstone. Will that need to be widened?

Dr Raine: Low-volume and high-volume hydraulic fracturing can be used for sandstone, shale or even limestone. It is wherever you have a reservoir that is low permeability and the pore spaces are not connected up. It is generally used to connect the pore space.

Mr Weir: Thank you for your presentation. To follow on from the Chair's question, you obviously have a level of expertise that is way beyond any of us. We need to get our heads around the definition. You mentioned that it can be used in shale gas and water boreholes. If we are looking at water extraction or whatever is done around that, is the impact the same as that of the operation for shale gas?

Allied to that, if the actions that are carried out depend on what is being sought, could those be differentiated in any potential legislation?

Dr Raine: As far as I am aware, the volume of water involved in hydrogeology boreholes is a lot less. In fracturing for shale gas, the quantity is almost an order of magnitude different to that of any other type of hydraulic fracturing that is used in other industries.

Mr Weir: We are in a slightly unusual position in that the draft legislation will not proceed in this Assembly term, but we are trying to scope out where things could lie in the future. In your expert opinion, would legislation be able to reflect the differential in quantities or define a dividing line, if you like, between shale gas extraction, targeting it specifically, and actions involving boreholes or other aspects?

Dr Raine: It is certainly possible to define fracturing for shale gas. Originally, the definition was set up to define the volume as being the volume of proppant or quantity of sand that was added to the water. Since then, different legislation has focused on the amount of water that is involved, because that is a distinctive part of the process that distinguishes it from other types. The pressure is also very different in shale gas exploration. A number of things could be used to define it.

Mr Weir: I have a final question, which, again, I ask so that we can get our minds round this and contextualise it. One concern that is raised about fracking is the risk of tremors arising from it. What is the typical range of tremors and level of efficacy? What impact would there be on a resident who is relatively close? What would they notice from a tremor? Would it be equivalent to, say, a large lorry going past your front door? What is the typical impact of tremors that people would feel? Maybe there is a spectrum of variability.

Dr Raine: It is probably not appropriate for me to talk about that. I am not a seismologist and do not have expertise in that.

Mr Weir: No; that is fair enough.

Dr Raine: A report on the potential for induced seismicity has been carried out and is available from the British Geological Survey.

Mr Weir: I appreciate that entirely. It is right that you do not want to get drawn into that area. To be fair, you are probably closer to being a seismologist than the rest of us. By the same token, I appreciate that you do not want to venture an opinion on something on which you do not have absolute expertise. Thank you.

Mr Dickson: Thank you very much for your presentation. Slide 6 of the presentation shows the composition of fracking fluid. I am somewhat disappointed that you would use oilandgasinfo.ca as the source of that information. The little infographic that is with it shows what the chemicals are and gives a benign household use for virtually all of them. The reality is that many of those chemicals are lethal, depending on the quantities in which they are used.

Of course, the great fear is that any one of those chemicals could get into the public water supply and agricultural land. Those are the areas of severe concern for members of the public. I am quite disappointed that the Geological Survey of Northern Ireland is describing those chemicals in that way. For example, if you had used Greenpeace as your source, you would not have given such a benign description and infographic of the chemicals that are used. Can you give the Committee your analysis of the chemicals that are used in fracking processes?

Dr Raine: I take your point on board. It certainly was not my intention to suggest that those chemicals are benign. The US has a very well established shale gas industry, and almost 1·7 million wells have been fractured in that area. You can contrast that to the UK, which has seen relatively limited exploration for shale gas. There is no knowledge of what will be involved in the frack fluid for those reservoirs. It will depend on what is needed during that process. Cuadrilla's site in England used only three chemicals in the fracturing process. Although there is a very long list of potential chemicals, many of those may not be used.

Mr Dickson: I understand that the use of those chemicals depends on the geology and type of mining and drilling that is being done. Do you know what three chemicals Cuadrilla used in England?

Dr Raine: I do. Sorry, it was four chemicals. Cuadrilla obtained permission from the Environment Agency to use polyacrylamide, sodium salt, dilute hydrochloric acid and glutaraldehyde biocide. Cuadrilla only used the polyacrylamide friction reducer and sodium salt tracer in the first Preese Hall well.

Mr Dickson: Polyacrylamide is a human poison.

Dr Raine: That is not my area of expertise.

Mr Dickson: No; I understand that.

Dr Raine: I am not a chemist or a health professional. I believe that the health effects were covered in the Hatch report, which was commissioned by the Department.

Mr Dickson: It is not an argument with you, but I want to express concern that your organisation is displaying those chemicals in a rather benign way. It might be useful if you gave much more information. I do not have difficulty with you describing the household use of those chemicals, but household use is in tiny quantities compared to the large volumes that are used in hydraulic fracking. The public need to be made aware, through government information, about the serious danger that those chemicals pose.

Dr Raine: I agree. Although the proportion of chemicals in the frack fluid is a small percentage, the actual volume of chemicals can be between 180 and 580 cubic metres per well. I understand your point.

Mr Dickson: Yes. It is the high volume of the carrier fluid, which is water, that has the ability to dissipate widely in the area where the fracking is undertaken. Thank you very much.

The Chairperson (Dr Archibald): Does any other member have a question? OK. Rob, thank you for the briefing. The detail is really useful to us. As has been indicated, the Bill will not proceed in this mandate, but a future Committee will return to it in the next mandate. Thanks for providing that detail.

Dr Raine: You are welcome.