It has finally happened. I have been threatening to write this blog for some time. Over the years I have visited and worked on a number of land-based rig sites across five continents. I have also been on a total of three fracking jobs, two on land. I think we can ignore the marine survey as neither the Tories of southern England nor Greenpeace / FOE are likely to superglue themselves to Dyce heliport. What happens over the horizon, out of sight of land, is out of mind as far as most of the population is concerned.
I have decided to do this blog in two parts with this, the first part, being based upon my actual experiences of land-based well sites. In the second blog I intend to look at the pros and cons of drilling in the UK, fracking, and where, if at all it fits into the nation’s long term energy and economic needs.
What follows in this first part will be broken down into easy-to-swallow segments. We will first address what the average well site consists of; the amount of disturbance is created in terms of land use, noise and traffic, and also the benefits of being near a well site for communities and local businesses (yes there really are some!). We shall also examine what goes into the creation of a borehole and how it is fracked.
Now I cannot claim expertise in all the fields as each are specialised. In fact that is what few really appreciate about working the oil patch: we are a collection of experts with very few able to perform all the tasks involved. In order to know our own job though, it is necessary to know what the other folks are doing. In the process of making an oil well (technically it is called a bore hole or well bore because most drilled do not contain oil!) there are many variables so those readers who know me professionally, please understand you are not the target audience. Generalisations will be made, processes simplified and technical terms exiled.
The first question that springs to mine is how on earth does a company decide to drill in Location A and not Location B? Especially since Location A maybe in the South East, be in rich farm land near to several quaint villages (with accompanying astronomic property prices) while Location B is some blasted heath in the far-flung corner of the North East, which seems to be the Conservatives preferred location for such industrial activity. Of course, the answer is geology and a technique known as seismic is the most usual method for surveying the sub-surface of the Earth. Now the planet is 1000s of kilometres thick but as prospectors we are only interested in the top five kilometres or so. The reason for this is that as we go deeper into the planet, the hotter it gets; too hot and any oil and gas is literally baked away. Picture the different rocks as layers in a cake; sometimes though the cake layers have been tilted and even bend or broken. These layers can be mapped across the country and linked to where they break the surface. In fact, when it comes to England, the layers are angled so in general they come to the surface in chronological order, with the youngest rocks coming to the surface in the East and oldest in the West of the country. So it is quite possible that in economically poor areas, there simply isn’t the right layer present while those in the South East are once again sitting upon a fortune. Geology doesn’t have a social conscience.
It is possible to target a given layer but until somebody drills into it, it is simply unknowable what it contains. In most cases the contents turns out to be water; sedimentary rocks are saturated with the stuff. On occasion though, oil and / or gas does accumulate and are trapped in certain layers. These are the juicy targets that petroleum geologists are seeking for. Now some people (in fact a surprising number of people) think as an oil accumulation forming in a vast cave underground and that that drilling into it is like pushing a straw into a drinks carton. I’m sorry but it ain’t so. The top layers of the Earth are more like a sponge with the water, oil and gas in the microscopic holes between the solid bits of rock. It is important that these tiny holes are interconnected though; more on this later.
So the oil company have decided where to drill, have paid the lease rights to both government and landowner. This is a problem for companies for the last thing they want to deal with is a host of small-holders each holding out for a fortune. They much rather deal with a few large-scale estates. One well I working upon in the North West of England was leased from a Duke, as the family holdings were extensive and the negotiating process simplified as a result. So the first practical point is that if you are waiting for an oil company to show up and pay you a fortune for drilling in your back garden, you can forget it.
One benefit though of drilling on large estates though is that well sites are often surprisingly discrete. Unless they are positioned right on the side of a road (or somewhere are flat as the Lincolnshire Fens), most people will just notice the occasional obscure sign with an arrow giving directions. Of course, I am the first to agree that if you are in plain view of a rig site, it does nothing to enhance the landscape. There is a lot of traffic movement related to the setting up and running of a well site but drivers, especially those with heavy loads, are given strict routes to follow in order in minimalise disturbance to local communities. It is strange but well sites can be the deuce to find for the first time. Which is all to the good as they are not pleasant places to be. A drill site location has to be levelled and since the average site is the size of two football pitches (roughly 3.5 acres / 1.4 ha) it is no small feat. The site has to be recorded for the intention is to return it to its original condition, including contours, once the drilling is over. But in the meantime activity is twenty-four-seven; the site brightly illuminated at night and generators constantly running. On such a site will be the drilling derrick (the rig), its power supply, a large area of shallow pools for the storage of drilling mud and other fluids, storage areas for drill pipe and casing (more of which later), a narrow elevated platform called a cat walk, reserved zones for specialist vehicles such as cement and wireline trucks, a container park, portable cabin offices, catering (sometimes), some crew quarters and a car park. The zone will be serviced by a heavy-duty forklift and will have a mobile crane either permanently on site or on hire and thus a frequent visitor. The work area will be surrounded by a fence (with emergency access gates) and with have a single entrance in order to keep animals, the unwary and the innocent out. It is an industrial site and strict safety rules are enforced for the protection of all.
A basic drill string consists of a drill bit, a set of weights known as the collars and the drill pipe, which is stacked in sections upright in the derrick. The borehole is actually drilled by rotating the drill string from the derrick. As you will know, dig a hole deep enough and it will start to fill with water. The deeper the hole and the water will fill up the hole with greater force. This is prevented in a wellbore by the use of drilling mud, which stabilises the pressure and keeps the hole from collapsing. Drilling mud is actually clever stuff; it has to be heavy enough to keep the fluids from the Earth coming in but not so heavy that it actually starts to break the rock down. This stuff is pumped through the hollow drill string and returns to surface where it is constantly monitored for contamination by water, oil or gas. If the volume of the mud has found to increase more that would be due to thermal expansion (remember, it’s hot down there) then this could indicate fluid from the well coming into the mud. Known as a kick, this could be the precursor to a full blowout.
Now, I am sure most of you remember the old movies where the old drillers strike oil which gushes up in a fountain, all us rig-monkeys dance around singing “We’ve struck oil! Yeehah!” and the oriental clients shout up to Bruce Willis “You No.1 driller Harry!” Well, if oil starts shooting out of the derrick anywhere near me, you can be sure I would be legging it. That is known as a blowout and is A Very Bad Thing. The drilling mud is the primary defence against a blowout but in case that is not enough, the well can be closed (shut in) by the BOPs – blow out preventers. In the worst case scenario, the whole string can be severed and the well closed in by what is effectively a massive pair of sharpened gates – the shear rams. At this point most readers are going to think of images of the Deep Water Horizon and you would be right. But Horizon was a failure of not just the BOPs but also the cement as well, which we will discuss next.
The well is drilled in sections. A “typical” well may be first opened using a 30” diameter bit, then the next section a 20” bit, deeper still 12.25” then 8.5” and for a really deep or high pressure well (usually deeper than 4.5km), down to a 6” bit. As a gross generalisation, an average well is in the order of two-and-a-half to three-and-a-half kilometres deep. As each section is completed, it is lined with steel casing and this is secured with cement to prevent any fluids returning up the outside of the casing. In the case of Deep Water Horizon, not only did the controls to the BOPs fail but the oil was able to come up the outside of the casing; it was a disastrous triple failure of mud, BOPs and cement.
Before the final bit of casing is run into the hole to secure it though, the well has to be surveyed. Despite what most drillers think, it isn’t all about “makin’ hole!” The geologists are rather keen to know what said hole is being made in. The most certain way to find out is to take a core sample but this is slow and expensive. The well can also be “logged” with a variety of electronic tools that, using electricity, sound, radioactivity and magnetic resonance (same technology as the MRI scanners in a hospital), building up a picture of what the rock properties are, the ratio of solid rock to space, how the spaces are connected and what fluids they contain. Fluid samples and pressures can also be taken. All this information goes into making up a picture of what is actually down there.
We have the geological picture, some oil and gas has been found (if they are not found then the well is cemented back and abandoned), the well has been cased and cemented firmly, so what happens next? The well has to perforated and tested. Perforation means holes are blown through the steel and cement over target zones. The fluids released are then allowed to flow.
You know these pictures of oil wells burning off gas in a big flare? During exploration this most usually happen during the well-test phase. The company has to know the rate of flow and at this stage there isn’t the infrastructure in place to keep any of the hydrocarbons produced so that is why they are flared off.
I just want to pause for a moment and reflect upon some of the information mentioned. As can be gathered, a well site is not a safe place. There is heavy machinery, crane lifts, stacked equipment, radioactive materials, explosives, and fluids under extremely high pressure around. All personnel have to undergo a large amount of safety training. Jobs have to be carefully planned and co-ordinated in order to avoid disasters occurring. The most effect way to stay safe is not to be somewhere you don’t have to be.
I also mentioned some advantages about having a well drilled nearby. The most obvious would be if one was an owner of a small business. While some workers would have accommodation on site, many would not. Hotels, guest houses and owners of property available for rental would definitely benefit, as would local shops, cafés, restaurants, bars and taxi services. Those who would suffer most would be those unfortunate to be on the main trucking routes. The disruption would last in the order of months.
With a standard oil-filled reservoir, that would be the end for that well until in required a work-over. A wellhead would be fitted and the rig would move on to the next location, which may be nearby or far away. But with fracking, that isn’t the end of it. The well is perforated but the difference between a rock that requires fracking and one that does not is the microscopic connections between the voids. In a traditional reservoir, those pathways exist; in a fracked well they have to be created. The primary ingredients of a frack solution are water and sand but, depending on the constituents of target rock, other chemicals such as acids may be added. This solution is forced through the perforated casing, into the rock and breaks up the formation, thus releasing the oil and gas. This is fracking. If the rig pumps are not used (perhaps the rig has moved on to a new location) fracking requires truck-based pumps and there can be a lot of them on site. The site I worked in Quebec had nearly thirty of them. But again, the operation is temporary; both land operations I took part in lasted less than one month.
Finally, a pipeline would have to be laid in order to bring the produced gas from the wellhead to storage and processing. Burial increases the cost of the pipeline but if I was an energy company in the UK (which, by the way, I am not, nor do I represent one) I wouldn’t even consider laying one across the surface. It is important that the countryside is returned to as near to its original state as possible.
This has been a long blog and I appreciate you making it this far. In Fracking for Beginners Part Two, I will be having a closer look at fracking, what can really go wrong, what are the choices we face and recommendations as to what can be done to ensure that the UK has the energy we and our children will need for the century ahead.
Click here to read Part Two
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