Saturday, July 31, 2010

Traveller's Rest

Because of a minor technical problem, posting will resume after the weekend with the normal weekend posts going up during next week.

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Thursday, July 29, 2010

Deepwater Oil Spill - windows can be short, and a digression

The windows that allow significant work on the oil spill in the Gulf are likely to become rarer and more valuable opportunities as the hurricane season, forecast to be stronger than average, moves towards its mid-point. While the starting signals for a hurricane don’t begin by looking that ominous, and those initial signals don’t always grow into a significant threat, as Bonnie just demonstrated, the last thing that can be afforded in this disaster is complacency. And so, as plans are laid out for a methodical approach to sealing the Deepwater well, so we see two more possible threats appear on the horizon.

At the moment the casing is being run for the relief well, there is some curiosity on where all the supposedly spilled oil went (some of which might be explained by the ramp up in flow as the BOP eroded so that in the earlier stages of the disaster there might have been significantly less oil escaping into the Gulf than the flow levels seen at the time of the capping), but there is not a lot of new information. And so, with your indulgence, a little digression.

One of the reasons that I write is to help explain why things are being done the way that they are, and how technical processes now being used to produce fossil fuels came to happen. Early in my experience of doing this I discovered that you can really help ease a descriptive explanation by using the right illustration. As a result my classroom type lectures are now made up with many more illustrations than they are with word-intensive Power Point slides. Yet, to be honest, that knowledge came, in part, from the memories of my childhood, and my still fond recollections of reading historical fiction where, if I was lucky, the story would be illustrated with four or five illustrations of the action. (And it was the presence of those illustrations that often drove the selection of the books that I borrowed from the local library).

Many of these early stories were illustrated by N.C. Wyeth and it was his teacher, Howard Pyle, who noted that “Pictures are highly important for children, well worth a thousand words, especially if they don’t understand 800 of them. First graders know 6,000 words, adults 30,000 or more.” This remains true with older audiences where the technologies being discussed are a little arcane, where the artisans of this new era use words that are not in the common lexicon.

And so, having the chance at the end of the family vacation, today we dropped by the Brandywine River Museum, where for the second time in the last month we spent almost from opening to closing time, wandering around the galleries. (The other was the Peabody Essex in Salem, a more conventional museum and thus a totally different experience).

The Wyeths are a legend in American art, with the major focus being on Andrew and Jamie, and indeed the tour we lucked into joining and given by Andrew’s grand-daughter Victoria focused very much on those two with wonderful, and unique insights. (We went out to the Kuerner Farm that Andrew painted, and also up to the House and Studio that N.C. built; both of which were well worthwhile, and seeing the “backset” with some of the props held a fascination that could have used a lot more time than we had available).

Having stayed across the street in the Brandywine River Hotel, and eaten dinners at the two immediately local restaurants, we have had a really enjoyable break, and one that I would really recommend.

The art of illustration has, to a large extent, been lost over the last half-century even though there are with programs such as Poser, Bryce and Vue; tools that folks such as I (who needs two rulers, a computer and a drawing table to create a straight line) can use to make our less mechanical ideas visual. (I use Strata for my mine models.)

It is no less critical now than it was in Howard Pyle and N.C.’s days that folk understand what the words are trying to say. Witness that Kent Wells uses illustrations and animations to help explain the complexities of the processes being planned at the Gulf.

Our family argue about ranking the members of the Wyeth family and their work, but the legacy of illustration that Howard Pyle and his students grew, and which N.C. Wyeth came to be a master of, brought his work and the pleasure of viewing it to more folk than I suspect have been influenced by his later family. Wyeth and the critics of his time downplayed the role of the illustrator, but it is an honorable and indeed vital need that we, who communicate information, have and make use of.

Sadly I don’t think that nearly enough technical teams across the board of technical application take the trouble to phrase their talks with illustrations, so that those outside of the “select few” that are masters of the technical terms can follow the discussion. And yet I should admit, on the other side there are also those who can present, with a suitably generated illustration a promise of a technical future that is not really born out by the technical details of the technology that is being sold.

But illustration can be a great help to imagination, and so I take my hat off to the masters who made it so, and if you’re in the neighborhood . . . . .

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Wednesday, July 28, 2010

Deepwater Oil Spill - the hundredth day

Admiral Allen held a press conference in the Gulf region (rather than recent ones held in Washington), in which he noted that the news of the rapid disappearance of the oil already emitted by the Deepwater well is raising questions as to how long to retain the different parts of the fleet assembled to deal with it. Well pressure continues to slowly build, and there are no signs that the well integrity has been breached. The problem of the skimmer fleet, and the distributed lengths of boom are non-trivial. Should a hurricane appear then the oil-contaminated boom segments can become polluting sources themselves if they are carried inland. And so they must be collected, cleaned and stored, if there is no longer a need. (Or if they are too contaminated they may need to be disposed of as hazardous waste).

The Admiral also discussed the continuing developments with both the top static kill, (waiting on the cementing of the relief well) and the progress of the relief well itself. The packer sealing the well has been released and recovered, and the well is now being cleaned, before operations restart.
They removed the subsea containment device—which they call a packer—that was put in to protect the well while they evacuated the site before of the severe weather.

After that (was) done, they will run another drill string clear to the bottom of the relief well, and then they're going to flush the entire wellbore out to make sure there's no particles or anything—sediment from the formation. When that is done, they will be ready then to put the casing pipe in. The casing pipe is the last structural member that will go into the relief well and cement that in place.

Once that is done, that will be the cue to start the static or the top kill we've talked about, which will happen next week. Following that—then we'll be in a position, once the cement dries, to go ahead and drill into the annulus and begin the bottom kill sequence of events as I've briefed before.
Note that once the RW is cased and cemented then it is not necessary to have the cement harden before doing the static kill, though it will be necessary for the relief well operation to complete.

In the latter case, since the cemented casing will act as a springboard to allow the drill to advance the last one hundred feet to meet the 7-inch casing of the original well, accuracy in positioning is still critical to success. The RW is planned to run alongside the original well, slowly chewing through the original cement annulus and finding out whether that is the source of the oil, or whether its integrity is still sound. (And with lots of opinions there is yet little real data on which to give a definitive answer.)

In regard to the static kill, he answered a question on the chances of success by noting
One of the things that, as you know, has been a subject of a lot of controversy or discussion, I would say—maybe not controversy, but discussion, spirited discussion among the science team, BP engineers, and so forth—is why the pressure was so low when we capped the well itself, down in the 6,000 range.

The competing theories from that are we have depletion in the reservoir that caused the pressure to be lower or there could potentially be a leak down there.

One of the things we're going to find out when we start to put the mud in for the static kill—if there's a precipitous drop in pressure, we'll know we have a well integrity issue at that point. If there is not, and we fill that well with mud right away, and it holds pressure, I think we'll know a lot more about the condition of the well.
One of the big concerns with injecting fluid into the well lies with the strength of the rocks in the bottom of the existing well. There is some concern that if the mud injected into the well is too heavy, then it can raise the pressure in the bottom of the hole to the point that the surrounding rock fractures. At this point the build-up of pressure in the well is relieved, as the fluid can now flow into the crack generated (and there is the precipitate drop in pressure that the Admiral refers to). That (because the rest of the well is lined with a cement and steel jacket or casing) is most likely to occur in the lowest section of the well, where it was not lined with both steel and cement, but rather a full-well-length steel tube (the production casing) was cemented into place, with cement only at the bottom of the well. Further the oil bearing rock tends to be weaker than the rest.

It is thus down around the zone of the producing rock that this fracture and leakage – the loss in well integrity – is likely to occur. And it is that zone that will be penetrated by the relief well. Thus if there are problems that arise during the static kill from the top of the well, then they will likely be remediated by the following arrival of the relief well in the critical region.

Now I think there may be another complexity (and in reality there are many in this process) and that relates to the possible injection of cement at the end of the static kill as a way of sealing the well. My concern is that while the static kill will displace oil and gas in the well by pushing them back into the formation, from which they earlier escaped, that is not true with the mud. The oil and gas, having flowed out of the rock with the differential pressure having the well pressure lower, can flow back, when the well pressure is higher. Mud on the other hand, bear in mind, is designed in part to line the well and provide an impermeable liner to the well during drilling. Thus to inject cement with the intent of driving some of the mud that the cement displaces into the formation may require higher pressures that with the oil and gas. This may, in turn, bring the well pressure above that at which the formation fractures. It is for reasons such as this that I expect the process to be carried out somewhat slowly, and in stages, rather than as a sudden “magical” flourish to end the crisis.

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Tuesday, July 27, 2010

Deepwater Oil Spill - Clearing the Relief Well to restart

The work in the Gulf that is moving toward a more permanent solution to the leaking well beyond the current cap on the well is moving forward at a slow and cautionary pace. In his briefing at 2 pm this afternoon, Admiral Allen noted that the riser has now been connected between the Development Driller III and the BOP on the relief well. When that pipe is put into place it is full of seawater, and for a variety of reasons it is best that this is replaced with drilling mud of the required density before proceeding any further. (You may remember that it was the reverse of this process that led, in part, to the Deepwater Horizon disaster). Once this process was completed, then the pressure holding the packer in the well so that it sealed against the walls of the well, has been released. This allows flow down the drill pipe in the well, and then back up through the gap between the drill pipe and the steel and concrete casing of the well that is known as the liner. This gap that the mud will flow through is known as the annulus, and mud will be pumped down the pipe and up the annulus in a process known as circulation, which, because the mud will leave the drill pipe at the bottom of the well is known as “bottoms up.” According to Mr Wells in his later brief once everyone is sure that the well is in good condition, they will pull the packer. This will likely occur tomorrow, and once that is out of the way and the well recleaned, the final length of casing for the relief well will be run down to the bottom of the well and cemented in place.

Normally this is a job for which Halliburton would be subcontracted (as they would have been for the earlier cementing of the casings higher in the well bore. However, in the brief Admiral Allen became a little coy in regard to who would actually be doing the work.
You know I don’t know off ha(n)d but we can find that out and get it to you. You know a lot of these things are done by subcontractors and there are a lot of them that are out there. And they aggregate together to do what their specialty is and we will get that and pass it to you. I just don’t know off hand.

The casing should be in place and cemented by the weekend, at which time the preparations for the static kill will move into performance, with Mr. Wells anticipating that the process could even start late on Sunday night.

Going back to the animation that was used the first time that the top kill was tried, the flow will, this time, include a vessel holding the mud, as well as a vessel with the high pressure mud pumps needed to inject the mud into the well through the choke and kill lines. Here is the initial animation from BP:

I expect that this operation will follow much along the same lines, only the relative locations of the choke and kill lines may be relatively displaced by the changes in circuitry that happened during the oil collection phase of the effort.

There is increasingly less concern over the likelihood of there being an additional leak of oil from this well, into the Gulf, though that does not preclude other accidents from happening elsewhere. As Admiral Allen noted:
the Coast Guard received a report that the uninspected towing vessel, Pere Ana C pushing the barge Captain Beauford collided with an oil and natural gas rig in the northern part of Barataria Bay south of Lafitte.

The structure itself is called C117 and that is a state owned well. We have about 6,000 feet of boom around the facility right now, there’s an over flight in progress with Admiral Paul Zukunft and Governor Jindal right now and they are assessing the issues on scene, and will be available to report updates on that later today and out of the JIC and so forth.
Subsequently the well was reported to be spouting a mixture of fluids into the air from the unplugged well. Fortunately there are enough resources in the area to deal with the developing problem.

With the time since oil was flowing into the Gulf getting longer, the amount of oil that can be collected from the Deepwater Horizon well is significantly reduced, and so some of the fleet could more easily be made available if needed. The dispersal of the oil does seem to be justifying the decisions of both BP and the various agencies to rely on the dispersant at the beginning of the spill. The longer term effects of the process will not, however, be available for some time.

And in the meanwhile, BP, having agreed to pony up the $20 billion for compensation payments, is making a business charge of $32 billion for the spill, so that, it appears that it will not have to pay taxes on those funds, which will thus cost the taxpayer somewhere around $10 billion. It is, after all, a business cost. But there are also going to be questions raised about how long the funds should pay for damage, if the oil is dissipating, the sands are clearing and the fishing is returning. Obviously, for example, the sand islands being raised along the coast will not be installed in time to be of much benefit for the current problem, given the speed with which the oil is dispersing so does the $0.36 billion being spent on that project reflect the best use of funds? These issues are likely to remain very contentious as we move into the election cycle.

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Monday, July 26, 2010

Deepwater Oil Spill - Restarting Progress

BP does not seem to have gone back to the daily briefings, let alone the twice-a-day ones that were being issued just a couple of weeks ago. Admiral Allen has given permission for the top and bottom kill (through the relief well) activities to continue. The Admiral also noted that the riser for the RW has been reattached, and the reconnection, removal of the plugging packer, and cleaning of the well is in process. It is estimated that the intersection with the original well will now occur on the 7th August, with the final set of casing being run into the hole this week, and then, after cement injection, the well will WOC (wait on cement) while the cement hardens, and is then checked. In the meanwhile the undersea valve system is being modified to carry out the static kill that I discussed earlier. (And the leak monitoring has transferred to the BOA ROV 2, which is now showing four leaks.)

Once the flow channel to the well is restored, and the casing set and cemented in the relief well, then the Q4000 will carry mud from the HOS Centerline, driven by pumps on the Blue Dolphin into the riser, and down to the BOP to carry out the static kill. The Admiral currently expects that this will begin on August 2nd. He did note that the plan is still to inject cement into the top of the well, after the mud has killed any pressure differential between the bottom of the well and the reservoir, and thus also stabilized the well.

As the more immediate and visible problems reduce, with this path toward the final sealing of the well, and with future flows from it into the Gulf becoming less likely, the oil on the surface, and that migrating towards the shore is getting less. This will allow the Admiral to redeploy assets. For example it now appears that the risk of oil East of the Mississipi is declining, and that commercial fishing there may reopen before the end of the week, given that
"We're 90 days into this, and I think the data speaks for itself," said Randy Pausina, assistant secretary for fisheries at the Department of Wildlife and Fisheries. "There's been no indication that any seafood is even remotely close to being at any level of concern. Find me the concern and prove it to me."
Sport fishing has already been restarted.

We are now in the most intense driving season of the year, and this is evident, with traffic noticeably heavier on the roads in New England in recent days. SeaCoast Sunday noted in their paper edition on Sunday that occupancy rates in the York area of Southern Maine are over 90% during the week and at 100% on weekends. It is therefore not surprising that gas prices are on the rise, being on average 25 cents higher than this time last year.

We have been fortunate that the weather in the Gulf has not generated that much damage to the rigs and platforms yet this year, and those that were affected by Bonnie are now back in business. But the season is still young, and may yet remind us of our vulnerable dependence on oil.

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Sunday, July 25, 2010

Deepwater Oil Spill - After the storm

The “Bonnie” storm has passed, and the different vessels are not only returned to the site, but are already making progress in returning to operations. As Admiral Allen noted on Sunday
DDIII is now running the riser pipe down. They have 67 joints to complete, they've done 39 of those as of about 10:30 Central Daylight time this morning, need about five more hours to do that. They are planning to latch on to the well around midnight tonight. Development Driller II which was – had drill – was involved in drilling the backup well is returning to site and will start running their riser today.

Q4000 is inspecting the yellow pad, that is the control device that's placed subsea to operate the hydraulics. They replaced the valve on that and they plan to install it later on today and then they will begin preparations for the static kill operations.
He also noted that the pressure in the well has now risen to just over 6,900 psi, while the temperature at the BOP remains at 40 deg – suggesting no flow and that well integrity is apparent. The storm has, however, dispersed and moved the oil, and they are resurveying to find where the threats now lie.

He then gave the current anticipated time line for the kill of the well.

The time line is roughly over the next week. We'll return the Development Driller III, run the riser pipe, latch in, pull that undersea containment device, which they call a packer.

They're going to need to circulate conditioning fluids through that pipe line to make sure it's ready what they call conditioning a hole and then some time in the next week they'll be in a position to be able to run that (nine and seven-eighths inch) liner which is the critical path right now to moving – to move ahead.

Once that liner is laid, they're going to put cement in and around it. And at that point the two vessels that were supporting the liner operation, one call the Blue Dolphin, the other is called the Center Line will redeploy and hook up with the Q4000.

This is sometime – this will be sometime during the week of 1 August. And they will set up for that to be able to inject the static kill and during that week of August subject to the (inaudible) I'm sorry the containment pipe being installed and cemented in then we will go to the static kill with the Q4000.

Kent Wells has also now released the animation showing how the different kill methods will take place, and interestingly also showed the section at the bottom of the well that shows the different layers of oil bearing rock in the reservoir.

The animation follows along the process in much the way that I described in an earlier post on the bottom kill, which is now scheduled in two parts. As the Admiral noted, the first part is to case the relief well. Once that is in place, and the cement run, then the top kill will start.

Because the well is shut-in, the plan is that the flow to the surface will be reversed. the flow lines are now passing oil and gas to the surface, the circuits will be reversed to return them to their original condition, and then mud will be fed into the well. Because this can be done a little at a time, it will be, and the pressures will be monitored to ensure that, as the well fills with mud, that there are no integrity problems.

Once the well is full of mud, they may try pumping cement into the well from the top (this is shown in the animation), though, because of concerns over flow control, I would suspect that they will not put the cement in until they connect through the relief well, and they will then do a two stage (annulus and then inside the casing) final kill.

And I should note that, contrary to my concern, the leaks that are being shown again now by the HOV ROV1 are no worse than they were before the storm, so perhaps that is not going to be much of a problem going forward.

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Pre-mechanized longwall mining

In the last post on this subject, I wrote about how miners were able to remove almost all the coal from a section, either by leaving small remnant pillars or building packs to hold the roof in place, while that coal was removed. By retreating the face back towards the shafts the overlying roof rock was then allowed to collapse into the void left by the coal removal. However, as this process began to evolve the miners noticed a couple of significant things that helped in the understanding of how the roof was responding, and helped to make longwall a safer and more effective method of mining. The first was that at the roof broke behind them, so the rocks would bulk up (they gain about 60% volume as they break and pile). Within a distance of about 2 seam heights, as the roof was converging, without underlying support, it would then meet the broken pile of rock, and thus get some support from this. As a result any support that the miner installed would not need to carry the full weight of the overlying roof to the surface, but only that of a few feet, which needed much less strength.

Thus by about 1870, and possibly in the Lancashire coalfield in the UK, they had modified the process further, and were only supporting the roof around the actual mining operation. How could they get away with this?

There was one other fact that helped make it possible. In some of the earliest tech talks I mentioned that the weight of the overlying ground can be simplified to being around 144 lb./sq ft for every foot of depth – based on the simplifying assumption that a cubic foot of rock weighs 144 lb. Thus converting this to a pressure in lbs/sq inch. (of which there 144 sq ins to a sq ft) this means simplistically that for every foot of depth one goes into the ground, the pressure increases by 1 psi.

Now when you make a hole in the ground, that load, or equivalent rock pressure, has to move somewhere. And it moves just a little so that the weight of the ground over the hole is carried by the rock on either side. However, what happens if this additional load is too high for the rock and it fails?

Well if the rock were just a thin column it would collapse, but if it were thicker, then the weight would just move further into the coal. Now if we came along and moved the coal that had failed, then the hole would just continue to get bigger. But if we leave the coal in place, then the broken coal acts to confine the coal further into the solid. And this confinement gets higher, as the failing pressure continues to move into the wall. And what happens is that this confinement builds up the strength of the coal, so that at some distance into the wall (or face) the coal strength reaches a point that it can carry the weight of the ground above the working area.(For a simple analogy think of a deck of cards, which individually cannot bear weight, but when held together by a rubber band, or a carton, can support quite a bit of weight). (And for those who prefer a more scientific description – the lateral confinement moves the failure from two-dimensions into three, with the minimum principal stress building as one moves into the solid material, and raising the overall failure stress behind it).

This works not only for the coal in pillars, or ahead of the working face of the longwall, but also for the rock that has fallen into the waste and is confined by the rock around each piece allows it to regain some strength, and so collectively the broken rock behind the working face (called the goaf or waste) will continue to compress as the full load comes on it, but will carry the weight of the ground from about twice the seam height, all the way to the surface, and with the other end of the "bridge" as it were resting on the confined coal ahead of the working face.(While the width of this bridge varies with depth, coal and rock strength etc, for an initial estimate you can imagine it as being around 500 ft).

Simplified side view of the coal as the miners removed the coal along the face, moving to the left. They put up wooden supports (three wooden props and a top bar) and let the roof behind the working face that these protected, collapse.

Thus the miner, working at the face, needed only to support only the rock that is up about twice the seam height he was working (in those days women did not do the actual mining). And this could be done with relatively small tree limbs, called props. However, because the rock could break into pieces, the prop support would be distributed, by having a plank, or half split timber, as a bar on top of the prop. Putting one prop at each end thus gave a sort of "goal post" support. Thus, along the face, there would be, at about 4-5 ft intervals, these prop supports holding the roof up.(The coal is made slightly blue in the pictures to give a better contrast - sorry!)

View looking down on the working area from the top of the fallen rock pile. I have erased a small section of the coal to show the position of the cutter bar of the coal-cutter as it is either dragged, or self propels itself along a cable stretched down the working face.

In the initial working of the longwall panel, the coal was undercut by a team of holers, who each cut a slot at the bottom of the seam, to a depth of about 3-ft, and collectively undercut the face over the course of a shift. As the faces grew longer there was a search for a machine that would make that undercut without the intensive manpower. One such tried to mechanize the simple swinging action of the pick.

Early coal cutting machine used at Garth Colliery in Wales in 1863. (National Museum Wales )

The development of the machine, the coal-cutter, dates from around 1876 when a compressed air machine was developed by Francis Lechner, in which picks mounted on a chain, did the cutting of the coal. (The more modern versions of this look like a chain saw on its side). It took a number of years for the machine to evolve into something that was widely accepted, and by that time the company had been taken over by Joseph Jeffrey (a banker) and became Jeffrey Manufacturing Company. (By the time my dad worked for them they had become British Jeffrey Diamond, and they later became part of the Dresser Group). They had spread to Europe by 1905.

And electrically driven machines were developed, which have not changed that much in the intervening years.

Early Coal Cutter (Iron Miners )

With these machines pulled along the face, undercutting the coal, to give a cut depth that was more typically 7-ft deep, the next step was to break down the overlying coal. Sprags (small wooden wedges) were slipped into the slot at intervals, as the cutter passed up the face – usually run by three men. At the same time holes were being drilled along the face, about 6 ft apart, with a stick of dynamite placed in each one.

After the face had been undercut the coal was blasted down between shifts (7.5 hours) then the collier shift would come in and each man would have about 10 yards of face to load the coal from, and to re-support. To get the coal from the face, a rubber conveyor belt was run along the back end of the supports that were in place before the blast, and the coal would normally not break that far from the face. As the miner shoveled he would also put in a new set of timbers, overlapping the old, and supporting the new working area. Typically this would take another seven hours, with an ideal seam height being about 4.5 ft. Above that the coal volume to move was much greater, and below that it got a bit awkward. For example, below 2 ft thick you lie on your back, with a prop under your shoulder and shovel over your head - how would I know? Yes, there was a reason to go to college).

View of the face, after the coal has been loaded out. The rubber coal conveyor between the last two rows of props must now be broken into strips, and moved forward a row, ready for the next cycle. Then the back props and bars are removed. (Saving the front two props and chopping out the back one).

In the third shift, the men would come in and break down and move over the conveyor belt, and then remove the last row of wooden supports, bringing the roof down, beyond the new line of supports.(Smart folk would use a come-along and a chain to pull down the props, young idiots (guess who) would go in with an axe to chop them first). For this was the state of the industry when I went to work in it in 1961. There have been many changes since.

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Saturday, July 24, 2010

Colorado temperatures using TOBS

Back in March I first looked at the temperature data for Colorado, comparing the GIS station data with that generated with the homogenized data from the USHCN. (Incidentally their process is described on that site, explaining in part how they were able to generate data from sites that did not have full sets of information. The immediate concern that I have with that, for the purposes of the present discussion, was that as I went through the data tables for the sites in Coloradolooking at the data corrected only for time of observation (TOBS) I was struck by how few stations were providing data in the early years. Averaging has some problems, that I will likely discuss in a future post, but when there are less than half the stations reporting, then using them to estimate the values for the unknowns becomes a little more questionable.

OK, so let me go back and insert the TOBS data in the spreadsheet of the form that I used for the original post: I note, while doing so that there are 24 stations in the USHCN group, while there is only one for the GISS network. Yet of those 24 only 6 have temperatures given for 1895, when the series starts (and for which there were a full set of values for the homogenized data I had originally used – for that set the only value missing was an 1896 value for Telluride – ah, well.) There was also only one GISS station at Grand Junction.

Running the averaged values and comparing the difference between that station and the USHCN TOBS values gives an average temperature difference of 6.15 deg. While that is still high, it is less that the 6.65 deg warmer that the homogenized data suggest. As to how it played out over the years:

And there has been a clear increase in the recorded GISS temp, relative to the USHCN over the decades. The correlation has a lower correlation than there was with the homogenized data, but that data plot (in the original post) showed that the difference was getting less over the years not greater.

Now as for the average state temperature itself, and this is a bit of a surprise, since the first time I ran this, there was a clear increase in temperature over the years. Using the TOBS data (but including the GISS value) that is no longer the case.

There is that curious blip upwards after 1984, but looking at the overall not any remarkable changes. In regard to the change in the Standard Deviation with time, the shortage of data points in the earlier years skews this value beyond where it might completely valid, though the decline in recent years might be more credible.

Moving on to the effect of population, Colorado has a smaller population in larger cities, and without the homogenization to remove the effect of UHI there is a correlation to the log relationship that I have noted before (and which has previously been suggested by others).

The correlation coefficient is slightly lower, in fact, with the TOBS data, which isn’t supposed to be the way that it correlates, since the homogenization was supposed to remove those effects.

Looking at the effects of Latitude, there was no correlation with the homogenized data, and that also holds true with the TOBS data. (This, from the other states reviewed is relatively inconsistent).

Because, to a great extent, the mountains get higher going toward the west, there is a correlation with longitude:

However, when checked, the correlation is better with elevation, explaining the apparent result.

And that correlation has held true for both sets of data.

Interestingly, since my first post, there has been some interest in Colorado climate, with there being a paper out by Noah Diffenbaugh of Stanford, which apparently claims that the increase in global temperatures will be emphasized in higher states such as Colorado.

Given that there has been a CO2 increase Dr. Alan Keen refuted that prediction based on an examination of the trends in temperature data, which included the USHCN homogenized values, though after they had been used to give a value for the “Colorado” grid – a value that I will get to in future posts, when I have some more state data completed. Dr Keen provided the following plot:

Well let’s press on and get some more data.

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Friday, July 23, 2010

Deepwater Oil Spill - Tropical Storm Bonnie -1a

I have not been over to the ROV sites for a while, since the rigs are preparing to close, but (h/t to JamesRWhite) I have to say that if I were running a pressurized line that had the leak that is now evident in the Hos ROV 1 feed, I would be seriously thinking about doing something to alleviate the problem. (Such as pumping in mud to alleviate the driving pressure).

Leaks on the fittings around the wellhead

And if I didn't do something there were two members of my staff who would have bent my ear until I did.

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Thursday, July 22, 2010

Deepwater Oil Spill - Tropical Storm Bonnie -1

With all activities shutting down around the Deepwater well due to the projected path of Tropical Storm Bonnie, as it has now become, it is appropriate to quote the Press release from Admiral Allen today.
Due to the risk that Tropical Storm Bonnie poses to the safety of the nearly 2,000 people responding to the BP oil spill at the well site, many of the vessels and rigs will be preparing to move out of harm's way beginning tonight. This includes the rig drilling the relief well that will ultimately kill the well, as well as other vessels needed for containment. Some of the vessels may be able to remain on site, but we will err on the side of safety.

As I stated earlier today, I have directed BP to continue with the well shut in procedure while the work to kill the well is temporarily suspended. I have also directed BP to take measures to ensure the vessels operating the ROV's are the last to leave, and the first to return in order to maximize monitoring of the well. Monitoring of the site during the well integrity test remains one of the government's highest priorities.

While these actions may delay the effort to kill the well for several days, the safety of the individuals at the well site is our highest concern. We are staging our skimming vessels and other assets in a manner that will allow us to promptly re-start oil mitigation efforts as soon as the storm passes and we can ensure the safety of our personnel.
Kent Wells briefing on Thursday had little to add to this, though there was a little emphasis on noting that the Admiral had given permission for the well to be kept shut in.

And just to remind us that there are other things that the natural cycle of the Earth can bring to our attention, there is a little more earthquake activity north of Iceland today, that we have seen in a while. But is remains relatively deep, at the moment.
UPDATE: While this is offshore Northern Iceland there have been 3 subsequent earthquakes of 3.0 or more magnitude in the area (where the yellow star is) since I posted this. Stars are for 3.0 or larger, dots are for smaller ones and quite common along the rift line.

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Wednesday, July 21, 2010

Deepwater Oil Spill - There will now be a slight intermission (pause)

The approaching tropic system that has been mentioned in earlier posts has now not only caught the attention of the folks at the Deepwater well, but has moved them to action. Because of the length of time that it takes to disconnect the systems and then move the vessels out of harms way, BP decided to insert a storm packer, or plug into the relief well and has gone ahead and put it into place. (From Kent Wells briefing on Wednesday afternoon). This will allow them to disconnect the drilling platform from the well and to move it out from the site if necessary. Before the rig could set the packer it had to withdraw all the drill pipe from the well, though it would use some of it to set the packer, which was put into the well 300 ft below the seabed.

The sequence of events that Mr Wells had defined, and which appears to have won the approval of the review panel and Admiral Allen, was that the relief well would have to be cased, before the static kill of the well was attempted. There is a concern that, with the relief well only about 4 ft from the original well, in a condition where the relief well has only rock walls without a liner, the risk of possible wall failure in the relief well was too great. This is not a judgment that it is easy to argue with without much more information on the actual geology at the current bottom of the relief well. If the rock is intact, and relatively competent, given that the well is still above the zone where the leak has likely damaged the rock, then this may be somewhat overcautious, but if there is any risk of weak rock, and of communication between the two wells then it may be a valid precaution. Although it should be noted that the original well is supposed to be still sealed with casing and a liner at this level in the well – since the RW was supposed to run the last casing while some 50 ft above the end of that liner.

But with the static kill now on hold until after the “weather” storm has passed, and the drillship brought back on site (if it has to move), the well re-established, and the plug removed, and then, after checking the well, taking time to run the casing, cement it in place, and check the cement quality after insertion (something that will be a priority into the foreseeable future) it may be some time before the static kill is implemented.

There are a number of different ways the well can be temporarily plugged, but in general a packer is used. This is a device that contains a section with a flexible rubber sleeve (see below). The packer is lowered into place, and the packer inflated (you might think of it as similar to blowing up a bicycle tire) so that the packer section fills the well bore, and stops fluid from leaking. (The full procedure for installing one version of such a packer is given here).

Diagram of the parts of a storm packer(From Packers and Service Tools Inc )

There is an alternate system made by Weatherford described here. This has three sealing sections rather than the one shown above.

After the storm, and with the rig relocated, the drill string can re-attach to the top of the packer, deflate the rubber section, unsealing the well. The packer is removed and the well can restart. The removal of the packer is not without risk, and accidents can happen. But with that packer in place, the relief well operation is on hold, and so is implementation of the static kill, in BP’s eyes. Given that it will take 3 -4 days to re-establish the well and run the casing, the end of the operation is now moving inexorably into August.

There is one additional worry however, and that is that the current seal on the well is being allowed as a test condition. It is possible, and Admiral Allen alluded to this in his press conference today, that the well will need to be re-opened before the vessels disperse ahead of the storm. With all the connections to the floating risers, and the dispersant tanks not having been connected up and tested, this may lead back to a spillage of the full flood of the oil into the Gulf, until such time as the vessels return and re-establish control after the storm has passed. (The weather one, not the political storm this decision is likely to raise). That action will come down, as other things have, to the judgment and decision of just one or two individuals who will decide whether to leave the well shut-in or to re-open it.

The leaks in the system are, at the moment, very slow, though not insignificant, since they are pointing out points of weakness in the system. Can they be left for a week to ten days, without deterioration? – That is a judgment call. And it requires an assessment of what the consequences of a failure would be, relative to the oil invasion that will come with opening the valves.

The storm will affect other activities associated with the spill. Crews that were skimming the oil have been laid off, and some of the boom may also be moved. It will be interesting to see how the newly dredged islands hold up in this weather.

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Tuesday, July 20, 2010

Deepwater Oil Spill - time is not our friend

There is a certain frustration in hearing some of the officials who act as spokesmen for the management team handling the spill from the Deepwater well in the Gulf of Mexico. Their evaluation of the situation is bound around a full collection and compilation of the existing evidence, a comprehensive and contemplative understanding through a scientific explanation of the causes of whatever anomalies and other behavior that is not following the model anticipated, and subsequently then working out the best steps forward and determining the potential benefits relative to alternative approaches. Such an attitude works well in a scientific laboratory, where whether the results are available tomorrow or next week only really matters if there is another lab in the world that is working closely along the same lines as you are. (And if the work is relatively topical that is often the case). Unfortunately this relatively leisurely approach to making progress is not nearly as compatible with a situation where a high-pressure piece of equipment is showing signs of leakage, and where there is the possibility that, within the week, equipment is going to have to be withdrawn from the site because of the imminence of a hurricane.

The imposition of an ultimately superior layer or more (depending on how much the White House is actually involved in decision making) of evaluation and decision making can do little beyond stretching the time over which decisions are made, eating up the time that is available for action, before the current gentle weather window closes. Now it may be that the current tropical depression will not solidify into a problem (I’ll let wiser heads in those topics answer that question), but even if this one does not, there will come a time when one will, and the working interval is shrinking.

Some of the worries about seeps in the vicinity have now been put to rest, in his brief yesterday Admiral Allen noted:
The first one was to see pitch about three nautical miles (Ed. Note amended to kilometers) from the wellhead itself. We do not believe that is associated with this particular well integrity test or the Macando well.
Similarly the bubbling from the sediments around the well have not been seen as something to worry about, although the material ejected is being tested. (It proves very difficult to get a meaningful picture of this). There is, however, one leak that is due to the well, and that is in the equipment that is sitting on the well itself.
Let me just tell you right away, because this happened overnight, as you know, we had a – a connector piece of equipment that we established in to allow us to put the capping stack on. These are the three rams that are associated with the capping stack. This is a schematic of those three rams. The leakage is occurring in a flange just located right about here, and there is hydrate formation appearing on this side of the capping stack as we move forward.

We do not know, but we do not believe this is consequential at this time, nor is – doesn't appear that the hydrate formation is inhibiting any operation of the capping stack. This is something we will continue to monitor as we move forward.
He noted that
it is the collective opinion of the folks that are talking about this that the – the small seepages we are finding right now do not present, at least at this point, any indication that there is a threat to the wellbore. . . . . . . There is a – there's actually a metal gasket in the flange, rather than a rubber (one). It's actually a metal – metal seal in there. And that appears to be the source of (the leak). But we don't know if it's consequential to the operations of it. It's not a huge leak, but it is causing the formation of hydrates.
(Ed note I corrected some transcription errors). The lack of concern seems to focus on the possible stratification of the fluid in the wellbore, and the concentration of any sand, which could cause problems if rapidly released.

Now that in itself is somewhat revealing, since one of the things that I have discussed in the past is the concentration of sand in the fluid flow, and that, when the fluid gets to a pressure differential of 2,500 psi or more that sand will erode metal and anything else in its way, as it flows out. With the sensible admission of the presence of that sand, what BP intend, apparently and if necessary, is to bleed the pressure down sufficiently slowly that the current segregation within the well, with the lighter gas-related hydrocarbons rising to the top, can be maintained until the pressure differential is low enough that the sand would no longer cause much erosion if caught up in the fluid. (Whether this would need to take the “several days” that Admiral Allen suggests is, perhaps, debatable.

There are a couple of problems with that. The first is that the sand is not in a single size range, but likely goes all the way down to sub-micron in size. The smaller particles don’t settle out that easily and thus are likely to be present to some concentration in the fluid throughout the well. Which raises the second problem which is that particles do cause erosion if they are moving over a surface at relatively high speed (caused by the pressure differential). In a much earlier post I discussed this and the effects that it might cause.

In my other life we have dealt with the problems of having abrasive get into high pressure fittings, and the leaks that result. Leaks tend not to fix themselves, and get bigger over time. Expecting that they might not change over the next month, while the odd hurricane might pass by, and the relief well completion gets postponed, is not a reassuring path to take.

In Kent Wells review on Tuesday he was, similarly to Admiral Allen, complacent about the leaks.
And then in terms of the couple of gas leaks that you probably observed on the BLP and capping stack. Those are just coming from places where we have what we call (metal) seals. Those are small leaks that are as a result of gas. Those connections have been tested to very high pressures in the case of the capping stack we actually tested it to 15,000 PSI with water and with no leaks, and it’s just when we – we probably got a gas bubble that’s formed up there and that’s why we have that very slow leak. It’s nothing that we’re concerned about.
At those pressures and temperatures, the gas is still liquid and still capable of carrying sand with it.

The potential for injecting mud to kill the well, which is getting more of a hearing at the moment, could be the way forward. Once mud in any significant volume is introduced into the well, through existing lines initially designed just to do this very thing, then the pressure at the top of the well will decline. This lowers the differential pressure across any leaks, lowering the flow and extending the time period before they may fail.

But, in regard to doing this “top kill”, Admiral Allen noted
We now have a closed system, so there's back pressure. And so the question is is there enough back pressure there where you could do basically more of a static rather than a dynamic top kill, where you could put mud in. That might suppress the hydrocarbons.

There's been some discussion about whether or not that might be possible. We're looking for BP to give us an idea of whether or not that it's possible, how they would do it. And we'll react to that when we receive it.
And BP themselves does not have a sense of urgency about moving forward with the process. From Kent Wells:
And then in terms of the static kill – and once again, I want to reinforce, no decisions have been made yet on proceeding forward with that. But we are continuing with preparation and planning. We continue to get equipment lined out, what we would want to do, making sure that we will have the right equipment out there to do it, writing procedures, starting to get procedures approved.

At the same time, we’re doing testes (sic) with scientists, challenging the way we’re thinking about this, what we’re doing, so we’ve got parallel paths going on that’s leading towards somewhere ideally in the next day or two that we’d be in position through unified command to make a decision whether we’d go forward with that.
He may take a couple of days to make an animation showing how it will work. Essentially however it involves reversing the flow down one of the kill lines (originally set up to allow mud flow into the well) which are now being used to allow oil to flow out of the well and up to a service vessel. From Kent Wells:
Now, one of the things we do need to do is we need to make some changes on the Q4000 to change it from its ability to contain oil and turn it back around into the pumping facility. But that does not take us very long to make that change and of course we’ll always have the ability to change back if at some point we need to do that.
It will, likely, take much longer for management to decide whether or not it should proceed. And the weather window continues to shrink.

Oh, and from the Admiral’s brief, in case you missed it.
The Discoverer Enterprise is no longer on station.

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Monday, July 19, 2010

Deepwater Oil Spill - bubble, bubble oil and trouble

UPDATE on this post. Although there has been some additional discussion, and the test has been allowed to run another 24-hours, not much else has changed over the past 24 hours, apart from knowing that the anomaly on the BOP is a slight leak on the flexible joint. I am going, therefore, just to add to the earlier post, to give an update on the overall situation.

I rather suspect that we will know a lot more about the behavior of the sediments and matter at the bottom of the Gulf within the next year or so than we have learned in the past hundred years. I am looking at the view from the Skandi ROV 2 at 10 am on Monday, and it is looking at a patch of mud that is bubbling a little, though over a relatively significant area (that of the camera illumination). There is no trace of oil venting and flowing upwards (and a fish just swam by) so there will be, no doubt, some samples taken, and, over time, we will learn what is the cause.

There were other views, from different ROVs that seemed to show clouds of something, but the definition was poor and it was not clear that this was not mud that the ROV itself has stirred up. This has been the case several times today, in watching the video, though there were, in the seep area, shots of small drops of oil heading up to the sea surface.

Given the debate that is developing between BP and the panel that advises Secretary Chu and Admiral Allen, the redirection of the thought process to include another attempt at a top kill, brings in a whole pile of new matter to be used in those discussions

As the day continued there has been clarification of the remarks that both Admiral Allen and Kent Wells have made in the past, as well as an update on the relief well progress, and the resurrection of the idea of possibly doing a top kill. Looking at the Kent Wells conference at 5 pm he began by reporting on the status of the relief well:
Our first relief well, the total depth is at 17862, that’s our casing point. We’re four feet horizontally from the Macondo well at 2.8 degrees and we’re looking directly at the Macondo well. So we’re absolutely perfectly positioned. The team is feeling very good about how they’ve set this well up.

They’re now in the process of what we call opening the hole. So they’re drilling the hole a little bit bigger diameter and then on Wednesday, Thursday we’ll run casing and cement is in place and there’s some testing to do followed by the drill out and ranging runs

The pressure in the well itself has rise to over 6810 psi and is rising at about 1 psi per hour. This lower pressure than the pressures originally estimated makes it possible to reconsider the top kill option. This is where, by feeding mud into the top of the well through the kill line, while the well is shut-in, the mud fills up the well. (The oil and gas are pushed back into the formation). Then should they be able to fill the well up with this mud, the weight of the full column of it, down the well, would be high enough to balance the pressure of the oil in the formation. At this point, rather than the well being shut in, by the cap, it becomes killed by the mud pressure on the flow. There is no longer any concern about pumping the mud in at any high rate of pressure, since the flow is already stopped. Instead the mud flow and pressure can be set to a slightly higher pressure than currently is in the well, and then slowly increase the flow to fill the well, without bringing the pressure to such a high level as to further compromise the well integrity. The injection would be followed with cement, to seal the well at the top of the underground part. This would later be followed by the well intersection by the relief well, and an injection of cement at the bottom of the well.

There are three areas where concern has been raised over the possibility of oil escaping the well below the sea bed and migrating back up to the surface. This is why the ROVs are located around the well monitoring the sea bed itself. There are, as noted earlier, patches where the sea bed is evidently bubbling (in that you can see where the bubbles pop out of the mud). But there is no sign of gas or oil then slowly rising to the sea surface from the bubble action. It may, therefore be something like a field of clams sitting below the surface and aspirating and then spitting out some of the sea water. This action is not at the moment of concern, BP has checked the fluid coming out of the sediment and it is running at around 15% methane, which could just arise (according to Mr Wells) from biodegradation in the mud below the sea bed.

There is a natural seep some 3 miles from the site, this hydrocarbon flow has been tested and is not related to the Deepwater Spill. And so the only other area of concern is a very small leak coming out from the seal in the flexible joint (which, if you remember was straightened before the new cap was installed). The leak, at the moment is very small, and not of that much concern. However if the leak starts to get bigger, and then turn into a stream, it may pick up some of the sand that is reported as being a concern from being in the BOP assembly. This will then, at the pressures anticipated, be enough to erode out the leak to an unacceptable size within a couple of hours. For now, however, it is very small, and not continuous flow, and so can be viewed with less concern, relative to other issues.
The leak was detected in a flange between the top of the well and the rams that regulate flow up the main bore.

Video footage is showing some hydrate build up on the outside of the stack and scientists believe a small amount of oil and natural gas is leaking out.

Allen said the leak is not expected to hurt performance of the device and is not seen as a threat to its structural integrity.

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Sunday, July 18, 2010

Deepwater Oil Spill - should oil flow restart?

At the end of last week BP began the testing of the Deepwater well cap, closing all the valves and stopping the flow of oil and natural gas into the Gulf waters. With this cut-off in flow, the volumes to be collected at the surface are rapidly diminishing around the well, and the use, albeit controversial, of the dipersant at the same time as more of the oil was collected, means that the amount making it to the shore has also already diminished. So now the question becomes, does BP restart the collection process by re-opening valves to the surface vessels? It also opens the questions as to how much of the preventative work now being brought up to speed, is actually going to be needed?

The debate as to whether or not to re-open the well is illustrated by the comments by two of the main characters. In his Sunday brief Doug Suttles noted the success of the new cap, and the fact that there is no evidence of leakage from it. He had noted that the oil in the reservoir is hot, but by monitoring the temperature at the new cap, they had seen, over time, internal temperatures fall to those of the surrounding sea. This would indicate that hot oil is not still reaching the cap, and that fluid flow in the upper sections of the well has ceased.

At the same time the slow but steady increase in pressure within the well indicates that it has integrity, and is able to withstand the build-up in pressure as fluid accumulates around the well down at the level of the initial reservoir. Nevertheless BP are continuing to monitor and run seismic surveys to make sure that there are no surprises.

On the other hand Admiral Allen sent a letter to BP on Sunday, that raises some new issues.
My letter to you on July 16, 2010 extended the Well Integrity Test period contingent upon the completion of seismic surveys, robust monitoring for indications of leakage, and acoustic testing by the NOAA vessel PISCES in the immediate vicinity of the well head. Given the current observations from the test, including the detected seep a distance from the well and undetermined anomalies at the well head, monitoring of the seabed is of paramount importance during the test period. As a continued condition of the test, you are required to provide as a top priority access and coordination for the monitoring systems, which include seismic and sonar surface ships and subsea ROV and acoustic systems.

When seeps are detected, you are directed to marshal resources, quickly investigate, and report findings to the government in no more than four hours. I direct you to provide me a written procedure for opening the choke valve as quickly as possible without damaging the well should hydrocarbon seepage near the well head be confirmed.

It seems that those who argue that there are possible leaks from the well into the surrounding sediment have found at least one politically powerful ally.

The phrasing of the letter is, however, a little odd – the “the detected seep a distance from the well and undetermined anomalies at the well head” section raise questions as to – what seep, at what distance? And what about “undetermined anomalies” if they aren’t determined are these the “unknown unknowns” we have been warned about in the past? And as comments have noted, there is the question of the legality of re-opening a well, and deliberately restarting to pollute the Gulf.

The press release that the Admiral also issued today expresses concern over the possibility of a sub-surface leak.
Work must continue to better understand the lower than expected pressure readings. This work centers on two plausible scenarios, depletion of oil from the reservoir and potential leakage caused by damage to the well bore or casing.

While we are pleased that no oil is currently being released into the Gulf of Mexico and want to take all appropriate action to keep it that way, it is important that all decisions are driven by the science. Ultimately, we must ensure no irreversible damage is done which could cause uncontrolled leakage from numerous points on the sea floor.
Do I detect the hidden hand of Dr Chu in that penultimate sentence? I notice that the option of cross-flow is not specifically mentioned as one of the alternatives, particularly near the reservoir, and I get the impression that it is only in the near surface that there is concern about leaks.

There is a second concern with the decision to re-open the well which makes this issue a bit of a hot potato. Whoever makes that decision, and BP seem to have made sure that it is the Admiral who must visibly make it, will be the individual that starts the oil flow back into the Gulf – and that won’t be popular.

Admiral Allen recognized that the flow would be restarted in his press release on Saturday
When this test is eventually stopped, we will immediately return to containment, using the new, tighter sealing cap with both the Helix Producer and the Q4000. Additional collection capacity of up to 80,000 barrels per day is also being added in the coming days.
Kent Wells, in his brief the same day noted that
if we do decide at any point either during the remainder of the test or following the test, that we want to open the well back up initially we will have to blow it back into the Gulf for some period of time, relevantly short period of time to bring the pressure down on the well so that we can then go in to our collection systems namely the (Q port) valves and the Helix Producer.

While I am not totally sure of the reason for the longer term period of oil release, there have been rumors of a three-day period, there is a relatively simple explanation as to why the pressure in the well has to be released before flow can start back up the riser lines to the vessels on the surface. If the valves between the well and the risers are opened with the well at pressure, then that pressure is immediately transferred to the fluid in the line, and a hydraulic shock, similar to that known as “water hammer,” will propagate down the fluid line. Although water hammer is usually seen when a valve suddenly shuts in a pressure line, the same sort of effect can occur when a sudden pressure pulse is applied to the fluid in a line of pipe.

The most dramatic example of that which I have personally encountered was when we were first removing explosive from a casing using a high-pressure waterjet lance, and the flow channel blocked. The resulting bang initially caused us to think that the explosive had reacted. But the round was still there and it was only when we looked at the hose, which had split in several places, and had both end fittings fail, that we realized what had happened. Having a similar failure in a hose carrying oil from the seabed to the surface would create a much greater problem and one much more difficult to fix than ours, which was working in the same sort of pressure range as the fluid contained in the well.

But the pressure can be lowered relatively rapidly over the course of time (a matter of minutes not days, in the same way that the flow was cut-off to the Gulf) so there may be some other issues that are not yet being made public. After all with the cap holding some intermediate pressure, it is not necessary to vent fluid into the Gulf, as flow is allowed to the surface collection vessels, in a condition that would lower the well pressure from the current levels without putting oil into the water.

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The Earliest Longwall - coal mining before the 1830's

Earlier I have written about the large amount of coal that was often left to hold the roof up while miners excavated the coal from rooms offset from main tunnels, with the rooms themselves being extended to create an intersecting set of passages. But even where the pillars left between the original tunnels are later removed as the mine retreats the working faces back towards the main shafts and exits, a significant amount of coal can be left.

About 250 years ago this was a clear problem in the Shropshire coalfields of the United Kingdom. At that time underground mining was usually carried out by crews of men and boys, where the coal was first removed by undercutting the coal seam manually with a pick, to a depth of about 3 ft. The bulk of the coal was then broken down to this slot and the fragments (ideally about 4-inches in size) were shoveled and hand-loaded into pit tubs, to be hauled away. A good day's work was about 20 tubs, and I have described this method and how it evolved, in earlier posts.

However, even as early as the 17th century (Economic Development of the Coal Industry 1800 – 1914 Brian R. Mitchell p 71) a different method of mining began. At first it was known as Shropshire mining because of where it started, but it later became known as “longwall mining”. The advantages, even then, of the technique were obvious. They included a greater percentage of larger coal (easier to sell), simplicity of working and ventilation, better roof control and a greater production of coal from the workforce, perhaps as much as 30% higher. In particular it was a cheaper method of mining and it allowed a much higher level of production from an area by concentrating the activities of the miners, and focusing the transport.

I just came across the book that appears to have been the first proposal for the more modern version of its use. (The Miners Guide – being a description and illustration of the principal mines of coal and ironstone in the counties of Stafford, Salop, Warrick and Durham”, by Thomas Smith 1836. And so I thought I would begin this short sequence on longwall mining with a description of how the technology first evolved, from that book.

The method was one that gradually evolved from initial headings that were mined by two separate working teams, the first being the holers and the second the brushers..

When the coal was of good quality, and high, then the process was to undercut the coal to a depth of 3-ft, with a man being able to undercut a length of about 22.5 ft a day. He would then cut vertical cuts to the same depth along the edge of the heading, which in the illustration below would be about 30 ft wide – depending on coal and roof quality. There were a group of these men who initially worked the face, and then moved on. They were followed by the brushers, whose job would be to break out the bulk of the coal from the face, and load it into tubs. They would also support the roof with timber props, as this was needed and the coal was removed. This was conventional room and pillar. But it left a lot of coal in the pillars.

Plan view of room and pillar or "on the square" mining.

Initially it was in thinner coal seams that “the long way” was developed as a way of getting almost all the coal out.

First, as with conventional mining, gate roads are dug out to the edge of the property (back in those days this was about 300 to 600 feet) with the direction going down the dip of the seam from the shafts at A and B, which are about 20 ft apart and some 7 ft in diameter. These roads were 6 - 9 ft wide and full seam height. Air passages or thirls were driven between the gate roads to help ventilate them as they were driven (the “a” passages). Cross-connecting tunnels between the gateroads were then driven, near the edge of the property.

In those days it cost around 0.35 to 0.4 English pounds (Ep) per yard, with workers being paid 0.225 Ep per day including candles and drink. The thirl would cost around 0.15 to 0.2 Ep per yard to drive. (An area up to 60-ft in diameter would be left unmined around the shaft area to hold it up).

Once the edge of the property had been reached then a section of the mine, some 90 ft long, would be mined with six miners each taking some 15 ft and holeing the coal. This was undercutting the face, to a depth of 3 ft, over each stint, and it would take a day, with the each miner also cutting a vertical slot at the edge of his section, so that it was held only by the coal at the back of the panel. The sections were mined on either side of the gate roads, moving towards the common middle of the “panels” being mined.

The holers were then finished in that section and moved to a different section, and a second set of miners mined out the rest of the coal, known as brushing the coal to the 3-ft depth. At the same time, since they were removing all the roof support they would put in timber props to hold the roof up, and would also construct small pillars or cogs, that were made from stone, fine coal, and other refuse, when they felt they were needed. In this way the white strip shown in the diagram below, at the back of the mine was extracted first, with the sections progressing first laterally out to the adjacent gate roads, and then back towards the shaft. While it takes 6 men to hole the 90 ft face, it would take only 3 men to brush and cog it. (And they would use small charges of gunpowder to help if the coal was not easily broken out). The difference from conventional room and pillar can be seen in the small size of the cog pillars that were left, as mining progressed. In this case, from one gate road to the next, with the mining face parallel to the gateroads and retreating from one to the next.

Plan view of Shropshire mining, the mining faces were parallel to the gate roads, and the dotted lines show the way that the tracks would be laid to get the tubs in and out.

Wooden tracks were laid along the gate roads, and then bent to pass along behind the face, to allow a horse and boy to collect the tubs as they were loaded, and then to replenish the men with empties. The costs for this method of mining, which was known as broaching, was given as:

(note that there are 12 pennies (d) in a shilling (s) and 20 shillings to an English pound of the period. And an English pound is now worth roughly $1.50). At that time the market for coal was such, that the mine owner would expect to get the following for the coal (with the price based on size).

A profit, at best, of just under 0.10 Ep per day, per working section.

The technique, was still quite dangerous, since the expanse of roof that the miners worked under got larger as the excavation moved away from the gate roads, and the cost of moving rock and dirt into the workings to build the cog pillars would have been significant (as would the time taken to assemble them).

Thus a new method was proposed, and the initial description is as follows:
For getting out the coal by long work, the pits A and B are sunk, as in the other case, at a distance of six or seven yards from each other; and the main gate roads driven to the boundary of the work at C and D, properly thirled with the openings for temporary use. From the ends of the main gate roads branches are cut, at right angles, to E and F, along the boundary line of the proposed area to be cleared, so that the mine may be said to be headed in the form of a Roman T, the roads E C, and D, F presenting the faces of the coal, which are to be worked homewards, or towards the pits. Simultaneously with the traverse gate roads, an air head ef is driven at a distance of three or four yards, with its thirls, which are closed in succession as the work proceeds. . . . . .The necessary roads and heads being completed, the work of getting commences; in order to which, the miners hole one yard under along the entire faces of work EC and DF which may be each from 50 to 100 yards in length according to the extent of the area to be cleared. Cuttings are then made at proper distances, to the height of five or six feet, or to a convenient parting, and the coals are brought down, turned out and drawn away along the gate roads. Cogs or pillars are then constructed of the waste and slack, to support the upper measures.

The holeing and cutting then proceed another yard in width, and then another; still clearing away the coal and supporting the roof with cogs, till the lower measures are drawn out, to the width, along the under face of 8 or 10 yards. By this time the over-hanging measure have, by their gravitating force (sic), sunk and bedded themselves on the cogs, pressing them down to a sort of continuous floor of what is called gob, or compressed and compacted slack. This is assisted by the use, as experience may dictate, of timber, which is taken away when the working of the stage above commences.

This is the first description I have found for what we now call longwall mining. By turning the mining face so that it advanced into the solid and away from the opening left, the overlying roof was able to bridge over the working area. This considerably improved roof control, and made it a much safer method of mining. In presenting the method the author notes that the cost of large coal, using room and pillar mining, which is the top method described, worked out to be around 0.118 Ep per ton mined. When the costs were worked out for the long way, the mined cost was found to be 0.105 Ep per ton, giving 0.013 Ep (3.25d) benefit.

However the increase in the volume of coal produced (and thus the royalty yield per acre) doubled to 2,046 EP per acre.

At the time that the book was written, it was a method just beginning to be developed, and the presentation was as much a proposal as a description of something in place. How it turned into the most productive of underground mining methods, in the course of the following 180 years will take another post or two to describe.

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