Tech Talk - of longer wells and drawdown pressure

There are, simply, three major parts to the coming global economic mess that will be created as we enter into the period of Peak Oil. The first of these comes from the current rising demand for oil, particularly emphasized by those countries, such as China and India, where demand is rising fastest. The second part is the declining production from existing fields as their reserves are drawn down. (Though it should be remembered that even when “exhausted” the fields will still contain vast quantities of oil, but oil which is at present not economically recoverable). And finally there is the oil in the undeveloped, and undiscovered wells and fields that can be added to the existing reserve to help ameliorate the imbalance between demand and supply from existing wells.

The high decline rates from long horizontal wells drilled into, and along the shale deposits in the United States, most particularly the Bakken and the Eagle Ford, mean that there is a constant need to drill new wells to sustain existing production. The EIA has taken note of this and calculated based on some assumptions, the number of rigs that must be operating in these fields, so that they will drill enough new wells to sustain current production.

Figure 1. The number of rigs required in the Bakken and Eagle Ford formations to sustain production at the level of the previous month (EIA).

Should the need be to increase production (which is the current assumption by most prognosticators of future equilibrium between demand and supply) then these numbers need to be significantly higher, perhaps by as many as 50 additional rigs. At present the Bakken rig count is running at around 176 rigs while there are around 270 rigs drilling in the Eagle Ford.

One of the ways in which production is anticipated to expand above earlier estimates for the wells drilled in both fields comes from the ability to drill longer horizontal wells and to increase the fracture density along these wells.

However, as the Kingdom of Saudi Arabia discovered some years ago, longer wells can only be viably effective out to a certain distance, beyond which there is no gain in productivity. As a result they have changed their drilling patterns so that the wells are shorter, with multiple laterals spreading from the original wells to more thoroughly cover the rock within the formation. Initially wells were drilled out to distances of up to 12 km, but over time the KSA found that this was too long.

Since there is a somewhat similar argument to be made for the wells in the United States, as they move to longer distances, I thought I would go over the explanation as to why this is not a very productive idea a second time.

To begin consider that regardless of whether I put a tiny glass of water or a huge glass of soda in front of you, if I glue it to the table then the amount that you can drink at one time becomes limited by the size of the straw that I give you to drink the liquid, rather than the amount in the container. And to get that liquid into the straw and up into your mouth requires that you suck on the straw.

What you are doing is reducing the pressure at the bottom of the straw, while the pressure from the atmosphere on the top of the liquid remains the same. By creating this differential pressure there is now a force to move the liquid into the straw and thence up into your mouth.

But, as Fishbuch et al showed, as the horizontal well bore gets longer the pressure at the back of the hole declines as then does the difference in pressure between the oil in the rock and the well (the drawdown pressure), and while the longer hole gives an overall increase in production to a certain point this seems to maximize at a length of around 6,000 ft. Beyond that distance the differential pressure between the formation and the well falls to a point where there is less benefit to the additional cost of drilling to that distance.

Figure 2. Drop in well pressure with increased well length, while increasing overall oil flow (Simulation by Fishbuch et al )

The answer which Aramco came up with to get around this problem was to use a main lateral from which a number of shorter laterals could then be drilled out into the formation, providing higher drawdown pressures within the wells and making it also easier to isolate any well section where the underlying water broke through into the well.

Figure 3. Schematic of a Maximum Reservoir Contact well as used in Saudi Arabia (Aramco).

The optimum length at which a well can produce is a function of the rock type and structure as well as the nature of the oil/natural gas that it contains and the water content (to name by a few of the parameters). Thus there are limits to the analogy, nevertheless it does show, even in the much more productive rocks of the fields in KSA that there are limits to how far a well can be productively driven, and these limits will also exist in the shales of the United States, although the oil locations and the optimal ways of extracting it are somewhat different.

The extraction of oil and natural gas in these shales is more sensitive to the levels of drawdown pressure, since much of the oil and gas is found in natural fractures that are not that wide (although they may be spread further apart by the fracking process itself). With exposure to the lower well pressure thus being restricted to a relatively small volume, significant reduction in the pressure because of the location relative to the heel of the well can have significant effects on lowering the overall well production.

Further as a general rule the complex valve systems used in KSA are not installed in the shale wells of the United States, making it less practical to focus the relative pressure differentials at different points along the well bore as a means of increasing production sequentially along the well.

Waterjettting 23a - Injecting abrasive into a waterjet

In an earlier part of this series I wrote about the introduction of abrasive into waterjets, and the loss in energy that occurs when the abrasive and the air that transports it are accelerated into the waterjet stream in the mixing chamber of a conventional abrasive waterjet nozzle assembly.

Figure 1. Conventional mixing of abrasive into a waterjet cutting stream.

Because air is conventionally used to carry the abrasive into the mixing chamber, and due to the relatively high volumes that are entrained it is often the case, as Tabitz* and others have shown, that the abrasive velocity exiting the jet is reduced as air volume increases.

Figure 1. Simulation of the effect of increasing air volume and abrasive feed rate on the particle velocity issuing from a conventional abrasive waterjet nozzle. (Tabitz et al*)

Using a higher density fluid to carry the particles into the mixing chamber is a self-defeating exercise, since the heavier fluids also will have to be accelerated to the final velocity, so that if a carrier fluid is to be used, then air is a logical choice. But it can make up some 90% of the jet leaving the nozzle, the water comprises roughly 9% of the remainder, so that only 1% of the jet may be abrasive, and this is the component that does the cutting in harder materials.

There should be a different way of approaching this, and in the early 1980’s Mark Fairhurst, at the time a graduate student in the UK, came up with an answer, which was presented at the BHRA Conference held in Durham in 1986. The initial system was relatively simple, but demonstrated the principles of the approach which was initially known as the Direct Injection of Abrasive Jet (or DIAjet for short).

Figure 3. Initial flow circuit from which the DIAjet system evolved. (after Fairhurst-1**)

The concept of the DIAjet circuit is that the abrasive particles are first loaded into a pressure vessel, which is then closed. When the pump is turned on part of the water flow from the pump feeds into this vessel through two control valves. The first is at the top of the tank, while the second was directed to feed at the bottom of the Tank, making it easier to feed abrasive into the underlying ejector, which mixed it with the main water flow from the pump, and thence carried it to the nozzle. This approach has a number of advantages over that of the conventional mixing chamber. The immediately obvious one is that there is no air added to the system, and the energy imparted to the water by the pump is only shared with the abrasive particles, without the system losses that occur where air is added to the mixture.

As a result the abrasive particles acquire a higher percentage of the water energy, and achieve particle velocities that allow cutting at 3,500 psi and 5,000 psi, whereas otherwise with a conventional system the jets would be at pressures ten times this high (although we will get into some of the caveats to that statement as this segment of the series continues).

In the earliest version of the system (and in some stand-alone versions that developed later, as I will discuss later in the series) the abrasive was added by simply unscrewing the lid, adding the abrasive to the tank, and then resealing the lid. Part of the problem that this causes is that, if the feed is not properly controlled abrasive can be caught in the threads of the cap piece, and this will then gall the threads and rapidly wear out the connection.

BHR, who first developed the machine, overcame this problem initially by using a secondary circuit to feed the abrasive into the pressure vessel, and this could be arranged so that there were two pressure vessels (which rapidly transitioned into pressure cylinders modified from other applications) one of which could be charging, while the second was in use. The basic circuit then became:

Figure 4. Schematic flow for the first commercial DIAjet system (after Fairhurst-2***)

It is perhaps illustrative to show one of the modifications to the design that was made in Missouri, where we used a small pressure-washer pump to feed the water to the pressure vessels, while the abrasive storage (the hopper shown in figure 4) was made from the pressure tank used in high-pressure painting applications. Because the lid of that pressure vessel was not threaded it was quite easy to refill, and the two cylinders were operated alternately. The entire system was designed to fit into the bed of a pick-up truck.

Figure 5. A small portable cutting system based on the DIAjet system. The assembly is mounted on a metal platform, and includes a water reservoir so that it is largely self-contained, and simple to use.

This new way of adding the abrasive to the waterjet feed has been developed for a number of different applications, although, because of the problems that arose in operating valves which control flow that contains abrasive, there have been some problems that have persisted in finding circuit designs that can operate on a consistent basis for the steady cutting applications where long cutting times are needed. But this approach has a number of applications where the abrasive need only cut for a relatively short period of time, during which the valves can function effectively, and where the jets can perform a cutting operation that is difficult for other cutting applications to achieve. It is, for example, possible to use a DIAjet type of system (if controlled properly) to cut through a live explosive detonator, without causing the explosive to go off. But I will talk about some of these developments, and some of the other capabilities of the system in later pieces.

*Tabitz, Schmidtt, Parsy Abriak, and Thery “Effect of Air on accceleration process in AWJ entrainment system, 12th ISJCT, Rouen, 1994 p 47 - 58.
** Fairhurst, R.M., Abrasive Water Jet Cutting, MSc Thesis, Cranfield Institute of Technology, January, 1982.
***Fairhurst, R.M., Heron, R.A., and Saunders, D.H., "Diajet" -- A New Abrasive Waterjet Cutting Technique," 8th International Symposium on Jet Cutting Technology, Durham, UK, September, 1986, pp. 395 - 402.

Tech Talk - the numbers keep going down

One problem with defining a peak in global oil production is that it is only really evident some time after the event, when one can look in the rearview mirror and see the transition from a growing oil supply to one that is now declining. Before that relatively absolute point, there will likely come a time when global supply can no longer match the global demand for oil that exists at that price. We are beginning to approach the latter of these two conditions, with the former being increasingly probable in the non-too distant future. Rising prices continually change this latter condition, and may initially disguise the arrival of the peak, but it is becoming inevitable.

Over the past two years there has been a steady growth in demand, which OPEC expects to continue at around the 1 mbd range, as has been the recent pattern. The challenge, on a global scale, has been to identify where the matching growth in supply will come from, given the declining production from older oilfields and the decline rate of most of the horizontal fracked wells in shale.

Figure 1. Growth in global demand for oil (OPEC MOMR )

At present the United States is sitting with folk being relatively complacent, anticipating that global oil supplies will remain sufficient, and that the availability of enough oil in the global market to supply that reducing volume of oil that the US cannot produce for itself will continue to exist.

Increasingly over the next couple of years this is going to turn out to have created a false sense of security, and led to decisions on energy that will not easily be reversed. Consider that the Canadians have now decided to built their Pipeline to the Pacific. The Northern Gateway pipeline that Enbridge will build from the oil sands to the port of Kitimat.

Figure 2. Route for the Northern Gateway pipeline (Northern Gateway )

The 731 mile long pipeline will carry 525 kbd to the port, and a twin pipe will carry some 193 kbd of condensate back to Bruderheim to help in the processing of the initial crude. It will, sensibly, move the oil that was to have come down through the Keystone pipeline to American refineries instead to tankers out to the Canadian coast, where it will be shipped to Asia to meet their growing demands. Given the investment in the pipe, infrastructure etc once this oil is committed to that market and the US will not be able to gain that supply back when it is needed in a few years.

There is a secondary impact to the opening of that market that may not be evident for a little time, but it something that the Russians discovered after the gas pipeline connected Turkmenistan to China. Suddenly there is a second market for the product, and producers are no longer tied to having to accept the price that the sole purchaser is willing to pay. At the moment, when there is a sufficiency of oil, that is an incidental, with significant impact only in improving the economics of the oil sand operations, but since it now ties the American refineries that would have received this oil more closely to the Venezuelan production it now receives (a somewhat less reliable supplier) this change remains as something of a future concern. It is not likely, in itself, to initially change the price of oil much ( a minor increase) but it will change the names and nationalities of those that profit from the trade.

The problems that the Keystone pipeline had are, to a degree, a function of the lack of concern over the supply of oil to the American market. As long as oil production continues to increase, from the Bakken and Three Forks in North Dakota, and the Eagle Ford in Texas, then there is no clear evidence for concern. But those wells are cumulatively starting to reach peak production, and the next shales on the list (the Spearfish and the Tyler) don’t hold the potential to match the gains that have been achieved to date. Particularly this is when, as the North Dakota DMR notes, the wells see an average decline of 65% in the first year.

Figure 3. Typical Oil production from a well in the Bakken:Three Forks region of North Dakota (ND DMR Oil and Gas Division )

The projections that gains in production continue thus rely on a continued high level of drilling and production with a defined rig count required having been estimated, and an assumed sustained level of production even beyond the time that the “sweet spots” start to disappear.

Figure 4. Projected production from the Bakken:Three Forks formations, assuming well productions are sustained and that the rigs are available. (ND DMR Oil and Gas Division )

At the end of June, 2014 the rig count in North Dakota is less than 190 (DNR says 189, but Kirk Eggleston notes that some 15 of these are moving, so that the real number is 173, a bit less than 225. That suggests that peak production may be delayed, and lowered from 1.75 mbd down to around 1.4 mbd. This reduction in short-term supply will have less impact in the US than elsewhere since it will be used to release oil that the US would otherwise have bought to the world market, but less than anticipated, and at a slower rate than expected. (Note that Eagle Ford production growth rate is also slowing and that this also affects OPEC projections which anticipates that US oil production will grow some 950 kbd this year).

At the same time, as I have noted in an earlier piece the reliance of many models of future oil supply have focused on Iraq as the next major supplier to sustain growth in production, even as other suppliers decline. But those projections are increasingly obsolete. It is unrealistic to expect the oil export business from Iraq to be sustained and continue to grow in the face of the developing civil war. The nature of the conflict makes it difficult to see how it can be easily resolved, and particularly if the country becomes divided, then the oil pipelines become a target of opportunity to attack the financial underpinnings of the different sectors. It is likely that the pipeline from Kurdistan into Turkey will carry increasing volumes up to Ceyhan and thence to the world market, under better security, given that does not now venture into Sunni territory, but the vulnerabilities likely remain.

The result of these declines in anticipated production (not to mention Libya, the Sudan’s etc) is likely to become evident within a year, while demand continues to grow. The balance need change only a small amount however, for the consequences to be dire. As Mr. Micawber said in “David Copperfield”:

Annual income twenty pounds, annual expenditure nineteen [pounds] nineteen [shillings] and six [pence], result happiness. Annual income twenty pounds, annual expenditure twenty pounds ought and six, result misery.

Waterjetting 22d - more on shrouds

The use of a shroud to capture the water and debris from waterjet use, feeding it to an exhaust hose, that will then carry it away from the site, has become more universally applied over the last ten years.

There are, however, different ways in which this new combination (which has been given different names depending on the usage) can be applied, and how the components can be best combined for most effective application.

At the low end of the pressure range, feeding a 2,000 psi waterjet at 2 gpm into the soil at the entrance to a suction hose has created a powerful new tool for deep soil excavation. The technique, known as hydro-excavation, has a variety of different applications – one of the simpler demonstrations was shown by Hydro Spy here on Youtube.

The demonstration lasts some five minutes, and helps show why there is still improvement needed in equipment design, since the vacuum intake is not extracting material at a constant rate, but is only being fed by a hand-held lance that it often not cutting very efficiently, while at the same time the head is either buried in debris or being held too high off the surface to effectively capture the loose material effectively.

Figure 1. Components of a hydro-excavation system, the jet is breaking the soil into pieces that are they removed from the hole with the water, through the suction line. (Hydro Spy )

Because the two actions (jet fragmentation and vacuum removal) are separate they are both working at much less efficiency than if the situation were modified. For example, in the video, the lance is used to pry pieces of soil from the wall and too much time is spent with the lance away from the suction line or with the intake to the line buried and not removing material.

Figure 2. Frame from video showing lance being used to pry soil block from the solid – the suction line is not getting any water or soil at this time.

It is often forgotten that, in soils, the jet penetrates to maximum depth in about one hundredth of a second. Thus, to be effective it has to be moved over the surface relatively fast ( as it is in parts of the video) in order to be most efficient. This is, however, most often best achieved by driving the head mechanically, rather than relying on an operator to move the nozzle as fast as it should be moved. In a simple situation such as this it may be, for example, much more effective to use a dual-jet self-rotating nozzle assembly (which can be obtained from one of several equipment manufacturers) since these designs spin the jets over the surface more rapidly and consistently, so that the material is more effectively broken into relatively small pieces.

However in this section we have been discussing the use of shrouds and intakes to the suction line, and this design becomes of equal importance in ensuring that the system works at its most efficient. If the entry to the suction line in blocked because it has been run up against the bottom of the hole, or into a tight cluster of large pieces of material, then there is no production, until the head is lifted away from that seal. (Or if a short rod is attached to the bottom of the inlet to ensure that there is always a gap between the lip of the line and the bottom of the hole).

On the other hand if the inlet is lifted too far away from the surface, say more than half-an-inch, then the suction force pulling the pieces into the line becomes significantly less effective and production will again suffer. This is made worse where the floor of the opening is very uneven, since this makes it more difficult to maintain the gap at which the suction is most effective.

It becomes more effective – whether removing soil in this way or removing paint from a ship hull at much higher pressures – to integrate the jet action with the design of the shroud/inlet to the suction line. The two cases are otherwise different in that in the softer material the jets are cutting quite deeply (though hopefully no more than about half-an-inch at a time) into the soil, which causes the jet to rebound back up into the shroud body and makes water and debris collection relatively easy.

This is not the case with the removal of paint and coatings, where the layers are often relatively thin, and the jet will rebound, often parallel with the underlying steel that it does not have the power to penetrate. (Nor is this desirable, other than for the jet to penetrate into any corrosion pits in the surface and clean them).

With thin coating removal, since the surface is otherwise relatively smooth, the shroud can be mounted on wheels that allow the operator to set the gap thickness between the shroud and the surface. (The closer the shroud lip to the surface, the higher the force that holds the shroud to that surface, but also the higher the force that the motors must apply to move the shroud against the friction forces that are created). The suction force in this case will hold the shroud against vertical walls and even against the underside of ships hulls, bridge decks, etc. provided that the geometry of the head is optimized to provide that balance of enough suction to hold the head, without it getting too high for the trouble the traversing motors).

There is one other, final thought, in those cases where the jets are cutting into and along paint and other coatings. In some cases the coating can be best removed where the jet is attacking along the surface, rather than almost perpendicular to it, as is quite often the case in head designs. This can give a better and more efficient surface cleaning, but if the jets are at too great an angle to the surface, the operator runs the risk of seeing the jets carry the debris out past the edge of the shroud, making it much more difficult to capture and remove.

One way of getting around this problem is to incline the jet path within the shroud, so that at the distant end of the jet path within the shroud it intersects the path of the next jet around the design, which has sufficient force to stop the jet moving further out. We have successfully demonstrated that this does work in an application, where the jet was cutting relatively shallow grooves in the surface, and with greater penetration the jet will rebound upwards out of the slot, and more easily captured by the overlying shroud.

Figure 3. Showing how, by aiming the jet path into that of the next stream around the shroud the energy of the jets can be contained within the shroud envelope and the splashing outside of that envelope is much reduced.

Tech Talk - More on Iraq

A single picture is sufficient to tell the story of the fate of the Baiji Refinery in Iraq. Recently reached by the ISIS forces, it has been the largest refinery in Iraq, with a capacity of 310 kbd, and has been used to provide products for domestic use. Since it would provide fuel for both sides in the conflict it had been left largely intact, but that “understanding” seems to have fallen apart.

Figure 1. View from space of the fire at the Baiji Refinery in Iraq (Slate)

The remaining significant refineries in Iraq are at Daura near Baghdad which can produce 210 kbd, although promised at 280 kbd and Basra in the south, which can produce 140 kbd. There are an additional 11 very small refineries located around the country.

The conflict has already led to a drop in Iraqi exports of around 300 kbd and while this will not immediately impact the United States, given that imports have been declining in the face of growing domestic production, it will affect the overall global market, with longer term impacts on price and availability. India, for example, is already worried. It is quite possible that Iraq will partition, with the northern tier ending up Kurdish.

Figure 2. The Kurdish part of Iraq (Talking Points Memo)

This region has already run a separate pipeline through its own territory up into Turkey and thence to Ceyhan. From there it is tankered, and the Kurds have just sold a shipment to Israel, which arrived at Ashkelon on Friday and unloaded that night. The report has, however, been denied by the Kurdish Ministry. Three more tanker-loads destined for other customers are now in process at Ceyhan. The tanker was one which has, until recently, been unable to find a market.

In May, the Kurds took a further step by leasing two tankers, loading them in Jihan and looking for buyers. Attempts to sell oil to Morocco and other countries were rebuffed, out of solidarity with Iraq and concerns over legal action. It now seems that the Kurds have re-discovered their old ally Israel, which agreed to purchase the oil. To avoid a direct sale, the Kurdish tanker unloaded its oil onto another tanker. It’s unclear if the purchase is a one-off deal or the start of a permanent arrangement.

But the Kurdish pipeline is currently limited to a capacity of 100 kbd, whereas the main pipeline running up the center of the country (and through ISIS territory and control) can handle 600 kbd. The potential for a continued drop in Iraqi exports flowing north to Turkey of over 500 kbd is thus now quite possible. However the oilfields in the Kurdish territory are only, at present, producing around 120 kbd. Yet, by the end of the year it is projected that the pipeline can be expanded to handle flows of up to 400 kbd, with that capacity being reached as additional oilfields around Kirkuk are connected into the system and production raised. In the meantime additional oil is being trucked up to Turkey.

The impact of the conflict has already caused bidding on the Nassiriya oilfield and refinery to be postponed indefinitely.

Figure 3. Location of Nassiriya (Red point) (Google Maps)

Bidding on development of the 4 billion barrel oilfield, and associated 300 kbd refinery, was scheduled to have taken place on Thursday, but after being postponed in December and January has now been put off indefinitely.

At the same time Lukoil remains optimistic about expanding the West Qurna 2 field over the next year. The field has started production, and reached 200 kbd and Lukoil is hoping to start filling tankers in the third quarter of this year. The project was shared with Statoil, but they dropped out in 2012. West Qurna is in the South of Iraq, and at present a considerable distance from conflict.

Figure 4. The location of the West Qurna 2 field. (Statoil)

The field is anticipated to ultimately be capable of yielding 1.8 mbd of oil. In order to handle higher flow rates a new agreement has just been signed in which Lukoil will build two new pipelines from the field down to the off-shore terminal at Fao.

As long as the conflict remains north of Baghdad, and the oilfields in the South are not threatened then the major restriction on plans to grow exports from the south to 6 mbd may continue to lie with the Iraqi bureaucracy and the delays in installing the necessary infrastructure needed to support both production and also transport of the oil to the offshore terminals. There has also been some reduction in targets, for example Zubair which had been producing at 200 kbd was originally scheduled to produce at 1.2 mbd a target that was dropped to 850 kbd last year. A 200 kbd gas and oil separation plant (GOSP) has just been contracted, with completion in 2016.

This does not discount, however, that sabotage and terrorist attacks will not have some impact. The main pipeline to Turkey has been closed for months due to such attacks, but while that pipeline runs through Sunni territory, the lines from the Southern fields are all within Shia controlled land, and those in the north are now controlled by the Kurds. Oil companies have, however, as a precaution, begun repatriating some of their employees. Gazprom has just begun production from the Badra field. Originally projected to begin, at 15 kbd, in 2013. Production has now begun, although it is now anticipated that it will be another couple of months before the field reaches that initial 15 kbd target, and 2017 before it peaks at 170 kbd. Gazprom have, at least publically, “no problems” at the site.

Waterjetting 22c - More on shroud design

Lowering the pressure in a hose connected to a cutting head, by connecting it to a vacuum pump, will pull a certain amount of the water and debris released from a cutting/cleaning event into that hose. However to ensure that all of this material is captured, rather than just a fraction, requires a little more care and effort in the system design.

At the end of the last post on this subject, I began discussion of the use of shrouds to help to contain the ejecta and to direct it towards the suction line.

Figure 1. Schematic section through a shroud of a device, designed to mine high-level radioactive waste.

There are a number of different lessons that we learned as we developed this tool, and this piece will discuss a number of them. During the development and demonstration of the device we had to use a simulant, and a relatively weak cement was chosen, which would allow us to design the tool to operate it where we could see it, and easily interact with it.

Figure 2. Cutting test under way (no shrouds were used in this early test series)

The easiest way to drive the nozzle system was to run the high pressure tubing through a fixture that contained a hollow shaft electrical motor. This saved a lot of space, and allowed the high pressure tubing to feed into a distribution manifold under the motor, which fed the high-pressure water to a set of rotating nozzles.

Figure 3. Test rig without jets to show the design of the test head.

In figure 2 the jets issue from two self-rotating nozzle sets, themselves fed through a rotating feed tube, itself rotating around a central axis, and driven through a belt drive and gearing.

Various different patterns were cut into the simulant, as the different heads were moved over the surface, with the pattern controlled by the different rotation speeds relative to the overall head speed over the surface.

Figure 4. Computer image of the jet paths over the surface, in one combination of parameters for a head similar to that shown in Figure 3.

The design of the head was aimed at producing a set of jet passes (given that each jet was slightly inclined to the surface) which would produce pieces of simulant that were never larger than half-an-inch in size. Yet at the same time the goal was to remove 4 cu. ft. of waste each minute. The larger we could break out the particles, the less cutting we would have to make into the waste itself, saving energy and time, while at the same time increasing the overall volume we could release in that time.

Figure 5. Deeper cut into the simulant.

At the same time if the cut depth was too great, then several new problems would arise, apart from the initially obvious one of producing particles that would be bigger than the suction hose could easily handle. (Though we overcame that hurdle by running the particles through a high-pressure jet pump that effectively cut any oversize particles down to an acceptable size as part of its design).

The suction line needed more than just the water from the cut, to be able to pick up all the debris from the cutting operation. Air had to be drawn in around the sides of the shroud, yet at the same time the walls of the shroud had to come down to restrict the amount of that air and keep the suction strong enough at the surface to remove all loose material. This is done by fitting a rim of bristles (such as form the head of a paint brush) around the edge of the shroud that come down to brush over the outer edge of the cut, stopping a lot of the material from escaping out from the edge, while limiting the amount of air that feeds into the shroud, and in this way holding the suction pressure inside the shroud.

Figure 6. Early test showing a square shroud with bristles around the edge as it cuts into the waste. (Part of a previous pass has been filled with clay as part of the test). The shroud was larger to ensure that all ejecta was captured – as shown.

During the tests we found that the metal rim should, optimally, be no more than half-an inch from the surface of the material, after it had been cut, to pull all the material from the bottom of the crevices. But the edge of the head has also to pass over the surface in successive passes. So that high points left by deep cutting (Figure 5) will catch on the head, and can interfere with the rotation of the head on the next pass.

The aim of the cutting head design was, therefore, to leave a relatively smooth surface (of the sort shown in figure 3) over the waste after each pass, so that the head could be fed automatically down a fixed amount without any risk of it catching on large peaks left by the previous cut. This risk could also be lowered a little by slightly tilting the head backwards as it moves over the surface, since this allows slightly larger points to enter the head, where they are attacked by the jets before the driving mechanism has to pass over them. This tilting also makes it easier for the head to clean right up to the walls of the tank, where otherwise the edge of the shroud would hit the wall and stop the jets from removing that last rind of material from the edge. (Though it could be cleaned by a subsequent pass with the head turned up parallel to the wall and moved over it in that way – though this wouldn’t capture all the material as easily, due to wall curvature.)

Tilting the jets at a high angle so as to cut material at the edge of the shroud was also a possible problem, since it made it easier for the water to escape from the edge of the shroud, and out into the main body of the tank, which was undesirable. But I’ll talk about that in a later piece. Let me just note that, when these factors were all combined no material escaped from the edge of the shroud.

Figure 7. Test late in development, where a head similar to that shown in figure 1 is cutting over waste, without any material being ejected from around the shroud edges.

Tech Talk - Thatcher, Putin, Coal and Gas

Back some forty years odd years ago when Edward Heath was Prime Minister of the United Kingdom, and the coal industry was still nationalized, the miner’s union went on strike, just after the Christmas Season. This followed an overtime ban that had started the previous November. The strike began on January 9, 1972 and lasted 7 weeks. Tellingly, just after it began some 17 schools had to close, as they had no heat in their buildings, without coal. Within a month the Government had to declare a state of emergency, and factories began to close due to a lack of power. Sensibly the Government of the day gave in to miners’ demands and they went back to work at the end of February.

Two years later there was a relatively similar series of events, with an overtime ban, followed by a three-day workweek as power cuts and blackouts developed, but this time Edward Heath also called a General Election, assuming he had the national sympathy. He was wrong, he lost.

These lessons were not lost on Margaret Thatcher, who had noted that it was not smart to offend the miners when the nation still relied on coal for much of its power, and when, in the winter, there was not a lot of coal in reserve at the power stations (because of the preceding overtime bans leading into winter). Thus, in 1984 when she, in turn, had to face the wrath of the National Union of Mineworkers (NUM), she had made sure that the situation was much different. Prior to the strike she had arranged for coal stockpiles to be built up over a period of three years. In addition the strike began on March 5th. It started because of the Coal Board decision to close 20 mines (since the earlier strike the number of miners had already fallen from 250,000 to 187,000 and the closures would cut another 20,000 from that number). It crumbled a year later, with a vote to return to work on March 3, 1985. The mining industry never recovered, and by the turn of the century the NUM was down to around 5,000 members.

I was reminded of those days by the latest clash between Gazprom and the Ukrainian government. In the past, when the Russians demanded that Ukraine pay its gas bill, the timing usually took place at the beginning or in the heart of winter. The problem that this gave the Russians was that they were supplying Western Europe through Ukraine, and any shut-off in the supply of natural gas to Ukraine had immediate consequences in Europe, which has become increasingly dependant on that gas. The result of the timing of the disputes was, therefore, generation of considerable diplomatic pressure leading to a relatively rapid resolution, without Russia getting all the deals that it wanted.

This time, however, it may be that Russia has learned, as Margaret Thatcher did, that timing is critical in this type of situation. Instead of waiting to November to call in the bill, Gazprom has presented it in June, when European demand for natural gas is lower. In addition the Nord-Stream gas pipeline is in place. This carries roughly 2 trillion cu. ft. a year of natural gas 760 miles into Germany, without passing through Ukraine. The twin pipes were completed and on line by October 2012.

Figure 1. Nord-Stream (Baltic Sea pipeline) bypassing Ukraine with 55 billion cu m of natural gas a year, (Daily Mail), out of a total sale of 262 billion cu m.(Spiegel)Note a second major pipeline from Yamal goes through Poland.

And while there has been talk about bringing in natural gas through Nabucco, that has slowly faded in the face of reality. Gazprom (as Brenda Shaffer has noted) has done remarkably well in gaining control of the different feeds and pipelines that come out of the East and head west into Europe. For example:

Moscow has taken steps to block the entrance of Iran into European gas markets; in 2006, the Russian company Gazprom bought a pipeline from Iran to Armenia and limited its size to ensure that it could be not be used to carry Iranian gas into Europe.

Consistently supplies have been confined to pipes that are under Russian control. It has a percentage of the Interconnector that carries natural gas into the UK and there has been little regard paid as it stepped in and took interests in other national pipeline companies across Europe.

So Gazprom can now wait while Ukraine exhausts its own reserves. It is reported to have some 13.5 billion cu m on hand, but it needs to have 18-20 billion at the start of the winter, if it is to get through. By stopping the flow now, Russia is having Ukraine burn those reserves between now and winter, while keeping the nations further west supplied. This means that the pressure will become that much more intense on Ukraine as winter starts to approach, and there is no alternate source of supply.

Gazprom has not hesitated to profit from this in the past, and is already in a position to demand whatever price it sees fit.

Ukrainian and Russian officials have been fighting about gas pricing since Yanukovych was ousted. After Russia annexed the Crimean Peninsula, it hiked gas prices for Ukraine 81 percent, from $269 per 1,000 cubic meters of gas to $485. That price was the highest in Europe, and Ukrainian officials refused to pay, calling it politically-motivated retaliation.

Gazprom has since lowered its price demand to $385, broadly in line with prices for other European countries. Ukrainian officials have sought to pay less and have said the way Russia was structuring the deal meant they would remain vulnerable to price hikes if they did anything to displease the Kremlin.

“Any price they offer is in the form of a discount that can be undone at any time,” said Pierre Noel, an energy security expert at the International Institute for Strategic Studies.

Don’t hold your breath waiting for this to be resolved.