Monday, August 30, 2010

Deepwater Oil Spill - another weather pause

The weather is currently holding up the proceedings at the Deepwater Horizon well site. The seas are some six to eight feet, which is apparently the height of the top 1/3 of all waves. (There is a table that shows how it is affected by wind speed, duration and fetch, which last is the surface area that is being affected by that wind). There is a site with a post on wind basics that explains). So the underwater effort is likely to be put off for another two to three days (depending on how Earl behaves, though it's not supposed to get close, but it might. The current problems are more local to the Mississippi Delta). So there will be a delay for at least a couple of days until the water settles down a little more. The problem is caused by the considerable length of the risers and cables on which the large steel structures sitting at the sea bed will ride as they are moved about. With the waves lifting and the swells rocking the vessels there are risks both from the changes in dynamic loading, and also in generating a pendulum effect as the weights sway. Much better to pause a little longer.
At his press conference today the Admiral described the plans for the next step in the process:
the Discoverer Enterprise (will) remove the capping stack and then back off. (At) that point (the) Q4000 will come in and lift the blowout preventer (BOP) which will also (hold) the transition spool which was put in to accommodate the capping stack. And a third step will be (for the) Development Driller II, which is drilling a second relief well, (and which) will move in with the new blowout preventer, and put the blowout preventer on.

Once that blowout preventer is in place, the well will be in a position to withstand the pressures expected on the intercepts of the analysts by Development Driller III and the drilling mud that will be forced in there when that happens. All is in readiness, and at this point we are just standing by for a weather window.
In discussing the current thoughts on why there are three pieces of pipe in the BOP, the Admiral also explained where his concept of the the pipe being fragile was generated.
When we first were looking at the riser pipe, if you remember, there was a kink. And then we were looking to cut the riser pipe, and we made a shear cut. And then we actually unbolted the stub that was bolted to the flanges before we put the capping stack on. At one point, we actually saw two pieces of pipe.

The original presumption at that point, and this is a long time ago now, was that a part of the pipe had fallen down into the Lower Marine Riser Package, and it was alongside a pipe that was extending through the centerline down into the BOP. As we have gotten into the blowout preventer itself and taken a good look at it, we found out that that pipe is fragile, is broken into three pieces, and we no longer have a pipe that's suspended in the centerline.

So our assumption is, our original assumptions on the pipe – and at that time they actually might have been. These pipes are being subjected to a lot of different forces in there. If you remember, we've had the dynamic kill and the static kill. There have been a lot of different fluids that have been forced through the blowout preventer or the capping stack, Lower Marine Riser Package.

In general, we have concluded that the pipe is of extreme fragility. And while we could try and recover it, the pipe that we can get to right now is not connected to any pipe that is on the (center) line. It could extend out into the BOP. So for that reason we just foregone any more fishing experiments, and have gone directly to remove the blowout preventer.
If I understand this correctly the current thinking is that none of the pieces of pipe above the shear ram are being held by it, and that they are less consequential as a result. Whether that also means that the DP was actually sheared in half by the ram is a different question, but apparently not one that the current investigation is going to look at further at the moment.

It does, peripherally suggest that there may not be any pipe now below the rams. Because if the different treatments that have caused the pipe to break into these bits did so across the shear ram plane, then there may not be enough holding the pipe below the BOP and it may be long gone. The gamma scan that showed the DP was there was, after all taken very early in this process, and much has happened to the well since.

The Admiral also noted that the drop in pressure (from the anticipated perhaps 9,000 psi) when the well was finally shut in is now believed to be due to reservoir depletion.

Oh, and for those of you admiring the ability of those on the platform to fish, the Admiral noted that the team involved in those operations included BP, Schlumberger, Transocean, Cameron and Baker Hughes personnel.

Incidentally I also think there was another transcription error (I tried to smooth some earlier ones by interpreting the words transcribed with my own (in paren, within the quotes). In dealing with the question of whether the DP is still there, and if it is held in place with either hydrates or cement he said:
The answer is I don't think we know. You know we think there may be a chance the pipe might have adhered to cement during the static kill process. We don't know that to a virtual certainty. But we don't want to try and pull the blowout preventer without having a contingency ready to deal with that eventuality.

So what we're doing is, we're going to life the blowout preventer. If it doesn't come off easily, we’re going to apply 80,000 pounds of lift. And maybe somewhat of a mis—we'll calling that the gentle pull. If for some reason that does not free the pipe then we will go in and mechanically open the rams and lift the blowout preventer out over the pipe, and then we'll share the pipe with the wellhead.
I believe that last ‘share” should be “shear” and will, actually, more likely be a saw cut.

And the small flow of bubbles from the stack, which the Admiral feels inconsequential, as earlier such flows proved to be, is still going on.

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Deepwater Oil Spill - a slight pause while we wait

With Hurricane Danielle disappearing into the North Atlantic, and Earl trying to decide where to go next, we have Fiona waiting in the wings as a threat to longer term activities in the Gulf. Those are moving forward slowly. The current infrastructure over the well has been largely disconnected in preparation for switching the BOP and upper assembly for that which was on the second relief well.

The equipment is all waiting, and usually starts to do functional things after midnight, but that is not happening at the moment, so perhaps we will have to wait for something to occur later on Monday morning, at which time I will upgrade this post.

11:30 am UPDATE:
Bubbles coming out of the stack at 11:15 am.

While there is a steady small stream of bubbles coming out of the stack, of unknown origin, and being monitored by the Oly - ROV2, the rest of the operation has been temporarily put on hold by the rough seas on site. Work will restart when it gets a bit calmer.

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Sunday, August 29, 2010

Supporting underground tunnels

With thoughts of the miners in Chile, and suggestions that a rescue tunnel will also be started to try and drive down through the broken rock, I thought I would write a little today about holding rock together. For those of a slightly cynical nature, I recently used the example of the Forth Road Bridge, in comparison with one of the bridges that the Romans built in France. The latter is over 2,000 years old and still standing, the former was built in 1964 and is now being scheduled for replacement, since the cables in the old one are corroding and snapping. The point of the comparison being that if you know what you are doing with rock, you can build a structure that can carry load for a long time. (And if you think about it, the rock that the Romans built with is bits of broken rock, rather than the solid structure that a tunnel starts out drilling through).

The Roman Bridge at Chaves (James Martin )

When man first started digging into rock, whether to get flints, create shelter or extract some coal that would burn, it was a relatively slow process. The miner relatively slowly dug out the rock, giving the loads around the hole some time to redistribute, and small holes could be made that would be stable for a long time. That is only a generalized statement and not always true, there are several factors that limit its validity. The first is water. Of the underground hazards water is one of the worst. In its most visible form it can fill the hole, and drown all those in it. There have been many disasters where water has invaded a mine, either from the surface, or from nearby underground workings. (For example Quecreek).

But water has a more insidious role underground, travelling into the mine with the air that the miners must breathe. Underground the ground temperature stays quite constant, and for many mines nearer the surface, the temperature can be quite cool (one I was in recently was at 58 F). So in the days of high humidity of the summer, the moist air moves into the mine, meets the cooler rock, and the moisture condenses onto the rock. It soaks into the rock, and usually weakens it – some shales (the more common rock in coal mine roof) will lose 60% of their strength when they get wet. And it is often why there are more accidents from roof falls in the summer – while in the winter it is more the time for gas explosions – another story).

The second problem that affects the rock relates to the number of cracks in it. If you drive along a road and pass through a road cut where you can see the cracks that develop around individual lumps of rock. Some, the bedding planes, are formed when the rock was first laid down as a sediment, some were formed as the rock was twisted and distorted over geologic time, or during the time that it changed from the sediment into the rock structure encountered today. And some cracks are made as the opening in the tunnel is made. We want to break the rock in the tunnel face into small pieces that we can pick up and carry away, and so we place explosive in known patterns of drilled holes in the face that will break the rock into bits, when the explosive is set off. Generally the charged holes are set off in a sequence, so that after breaking out the middle of the face, successive rounds (they are set off with timed detonators) will blast successive layers of rock into the opening until the desired shape has been removed. In the process some cracks from the outer ring of blast holes will extend out beyond the intended wall of the tunnel and into the final wall. (Seems to happen more on Mondays and Fridays for different reasons).

So there are several concerns that face an engineer that is going to try and drill a tunnel through rock, whether it is solid or already broken into boulders and smaller pieces. The first is to get some idea of the general strength of the rock – designs that work in something like a granite won’t work in a very weak shale, for example. Once the rock strength is known, then the amount of cracking, either natural or man induced needs to be found. There is a very simple way of doing this that a group at Urbana/Champaign developed called the Rock Quality Designation (RQD), under Don Deere to simplify how it is measured, you drill a core through the rock layers that you want to drive the tunnel under. You recover the core and measure the core lengths that are more than 4-inches long. That total value, divided as a percentage over the length of core recovered gives you the RQD. Over time (it is now 40-years old) it has been shown to give a very good first estimate as to how badly broken the rock is, and it is used in many design programs to decide how best to hold the roof up.

When working out how to hold the roof of the tunnel up, the engineer knows that he is not trying to hold the weight of all the rock between the tunnel and the surface. The work that most of us used to refer to as the basis for the support of the tunnel was written by Karl Terzaghi . Again, to simplify a relatively complex subject, he came up with a simple method of classifying rocks so that, the designer of the support would know how much rock load from above the tunnel, the supports would have to carry. And very often it was only a small additional amount above the height equaling the width of the tunnel. (The presence and actions of water being the main factor that would make it a lot worse).

Karl was starting the knowledge base that now allows engineers to classify rock and thus design the tunnel supports before the tunnel gets started. It was only a start, however, because back in those days (beginning in 1925) most of the tunnels were supported with large steel arch girders. Because those had to be ordered and delivered before the tunnel was started, getting that size wrong could be very expensive, and there have been many lawsuits as to whose fault that was. (Very awkward, for example, if the tunnel is half-way under a harbor when you discover the steel beams aren’t big enough).

Possible heights of overbreak that have to be supported over the tunnel

Since then a new method of support, which works more on helping the rock to support itself, along the lines of the Roman arch bridges, has been shown to often be more effective. Although it has been generally more effective, and more flexible, it has become more popular, but I will write about it, and the change from steel arches to sprayed on concrete (shotcrete) and rock bolts, next time.

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Saturday, August 28, 2010

California temperatures, the TOBS data

Back in April I first commented on the historic California temperature changes, using the homogenized data then available from the USHCN. Since then they have posted both the raw data and that corrected for Time of Observation (TOBS), as well as the data that has been adjusted to apply other perceived corrections. At the moment I am going back and seeing how the TOBS data is changed by those corrections. So this will examine that data, using the same form as originally. (Note that following the comment by Kinuachdrach the evaluation of Death Valley at the bottom of the piece has been UPDATED).

So first I go to the US Historical Climatology Network and download the 54 station set of data (there will be a short pause while I do this). And then there are the four GISS stations whose data we got the first time around (we aren’t going into those adjustments at this time). Looking at the difference between the few GISS stations and the average for the USHCN set it is interesting to note that while the GISS stations got successively warmer than the state average, in the raw data the reverse was the case, although the decline was very small.

The average difference between the two sets is 1.63 deg, which is the same as for the homogenized data. For the state as a whole, over the past 115 years there has been a steady warming trend, though the raw data suggests an average increase of 2 deg F per century, while the homogenized data suggests only 1.3 deg.

Looking at the effects of geography, there is the correlation with latitude:

There is virtually no change in the relationship of temperature with latitude, though there is sensibly no correlation with longitude, similar to the result with the homogenized data.

Given that California goes all the way to the sea, the effects of elevation should be significant, and in both cases they are.

The regression is a little higher than with the homogenized data (r^2 0.4) but otherwise they are much the same. Which speaks for having a significant number of stations in the state, since there were a significant number of years where there were dropped data from several of the stations. This becomes obvious as the standard deviation shows that scatter getting worse as the collective number of stations reporting peaked. Interesting with the raw data it is leveling off, whereas it was getting worse when the data was homogenized.

And even having to make some assumptions about the number of inhabitants of some of the more remote stations there is still a logarithmic correlation with population.

The correlation is slightly worse however (it was 0.10).

And just for grins, this is what has been happening in Death Valley, and it looks as though that has been getting hotter too.

California was the first state that I have looked at that was on the coast, and so it will be interesting to see if there is a coastal effect and define what it is, and how far inland it stretches. But for that we need more data.

Kinuachdrach made a comment on the Death Valley data (see below) and so I went to see what the condition of the weather station was, and discovered something that I thought readers might find of as much interest as I did. The full story is at the reference by John Daly.

There are, actually, two weather stations now in Death Valley, where the all-time highest temperature in the United States was recorded on July 10th, 1913, at 57 degC. Using the GISS data for California, the plot that is given is this:

And the site has a plaque that says:
"During the summer of 1998 - the warmest year on record - we recorded the hottest air temperature anywhere in the world of 53.06°C ±0.1°C (128°F) on 17 July 1998 at 3:15 pm local standard time."
Since the GISS plot stops before that, I am, being curious, just going to go to the GISS Site and download the latest version of the graph:

Note that since the high temperatures were single days, and the data plotted is the average for the year the records aren't evident. However the station was apparently changed in the 1990's to give the record at Badwater, rather than the earlier data that was recorded at Furnace Creek, according to John Daly. The differences are, among others, that Badwater (as documented) is more of a sun trap than the old station, 20 miles away out in the open, at Furnace Creek.

But it is worth commenting that over at Watts Up With That, Steve Goddard has noted that there seems to be some work on re-adjusting the data back to 1998 that removes the overall high temperature that they showed then (and which agreed with other records) in favor of lowering that temperature so that the overall graph now shows a steady increase in temperature over the last three decades (which does not agree with other records). So when I show you the GISS record (which as with the USHCN data is modified from the original raw data) until I have worked out (or more likely someone else has) what was done with that data before it was plotted, all I can give you is what is on the record. And in this case, I suspect it is only a part of a continuing story.

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Deepwater Oil Spill - stopping the fish

The attempts to recover pipe from within the blowout preventer (BOP) on the Deepwater well have now halted, without being able to recover any of the pipe. Instead attention is now being given to the removal of the BOP itself and its replacement with the BOP from the second relief well. In his remarks on Friday Admiral Allen gave, as his explanation:
What we have found is we have gone down there, the pipes have settled against the side of the BOP and we can't successfully put the overshot devices over them. We've come to the conclusion that any more attempts at fishing are probably not going to result in success.

And at a meeting this morning between our science team and the BP engineers it was decided to recommend to the principals, the cabinet secretaries we go ahead with the removal of the blowout preventer and the replacement of the blowout preventer with the one that's on Development Driller 2.

This is due to the one whose apparent fragility of the pipe that keeps breaking and falling off to the side and also the unknown condition of the BOP below that and I can talk about that in a little bit.

So the plans are right now to replace the BOP. The approximate timeline going ahead is as follows, starting today and through Saturday and Sunday we will make preparations to remove the BOP and replace it.

This did not agree with what I saw occurring during the time that I watched both the recovery attempts over the last two nights, and from the videos that others posted on Youtube, and which I referred to in those posts. However, not being a part of the team running this operation there may have been some things happening that I and others are not aware of.

I still remain concerned about the condition of the lower section of the BOP and the presence of either hydrates or cement, both in the area of the BOP rams, and around the drill pipe as it extends down into the well. To explain the concern in perhaps a little more detail, let me first talk a little about the casing hanger that the Admiral referred to as one of the limiting well conditions today.

The casing hanger is the device at the top of the well that holds the production casing in place. In the extended transcript of his press conference on Friday, he referred to the company that made the hanger (Dril-Quip) and gave a link to the drawing of the hanger, this one, which I have labeled, because I am going to try and explain, using this and other diagrams, what the Admiral meant with some of his remarks, as I interpret them, and some of the concerns I continue to have.

Labelled section showing the parts of the casing hanger (note that there is an animation at the source site)

In essence, at the top of the production casing, the long continuous tube that was placed from the sea bed down to the bottom of the well, there is a hanger that holds the top of the casing against the surrounding liner and well head assembly. To show that in more detail I am going to use a different source, to highlight the hanger section.)

Casing hanger.

The casing comes up through the center and connects to the top element. The weight of the casing now pulls the upper section down, seating the conic surface, and also spreading the elastomeric packer (the black layer) which pushes out against the sides of the surrounding wellhead wall, providing the seal. This seal is between the liners around the top of the well, and the production casing, it is, in other words, the seal at the top of the annulus between the production casing and the wall of the well.

I have put this in to explain what the Admiral meant when he was talking about trying to lift the BOP off the well head, which means unlatching it from the top of the well head assembly. The BOP latches around the top of the assembly shown in the top figure.

To remove the assembly, the Admiral has approved the following process:
Commencing on Monday and through Tuesday the Discoverer Enterprise will latch on and remove the capping stack. And the capping stack will be temporarily stored nearby on the ocean floor. Once that has been completed the Q4000 will move in and connect to the BOP and will unlatch it.

And then there'll be a series of two decision points will occur. We will attempt to pull it free and we are prepared to apply up to 80,000 of force in addition to the weight of the blowout preventer to lift it. We call this the gentle tug.

If the blowout preventer comes free we will then use the (Boa Sub-C) and the ROV's to attach a line to it and cut it (the drill pipe) just above the well and at that point we can bring the BOP to the surface on the Q4000.

If for some reason the blowout preventer does not come free with a gentle pull, our intention then is to manually open the ram sequentially down through the blowout preventer and then raise the blowout preventer and cut the pipe at the well head.
He later explains why there is this limit of 80,000 lb in the “gentle pull.”
What they’re concerned about is somehow potentially dislodging the hanger and the casing hanger that is at the top of the well. That is also the – as you know that is a device that contains the seal between the annulus and the well and the blow out preventer. So the threshold for the pull has more to do with the potential to unseat the casing hanger and the seals that seal off in the annulus.
So that if you go back to the second illustration, the seal is maintained by the weight of the production casing, pulling the head of the hanger down so that the elastomeric seal spreads. If the upward lift on the BOP is transferred through the drill pipe to the top of the casing, they are concerned that if the DP is held within the casing hanger, that pulling it too hard may take the weight of the seal, so that it contracts back from the wall, and opens up the annulus.

Now to explain why that might happen, and why there might be all sorts of other concerns, let me move away from the hanger itself, and go to a modified frame from the Dril-Quip video. (For those looking at the video I have changed the picture to show the center as though it were the drill pipe).

To make life easier for me I am just showing the lower end of the BOP, below the rams, the central drill pipe and the upper end of the well head (without the hanger detailed).

Now in a normal situation the drill pipe would be held by the three rams at the bottom end of the BOP, and slightly above the picture. In an ideal world there would be nothing else in the gap around the drill pipe (i.e. the annulus).

But we know that above the rams, that there is either hydrate or cement around the DP.

View from the fishing camera showing the top of the drill pipe above the BOP rams, surrounded by what may be either a hydrate or cement fill.

And the pipes are held and seem unable to be moved
What we know is, the pipes that we can see are in pieces, sitting inside the lower marine riser package and we are having trouble lifting them out with the fishing devices. We have no further information and cannot tell the condition of the pipe below the blowout preventer.
If the material holding the pipes extends down into the rams of the BOP and below it could fill the upper annulus down through the casing hanger. Thus pulling on the BOP would exert a pull, through the DP and this fill, on the hanger and could unseat it.

Should the BOP not move, the plan is to open the rams on the BOP, so that it no longer holds the pipe. But if the rams are cemented in place by the fill, this may be very difficult to do, since trying to flush out that fill on Thursday evening didn’t work. And even if it did work, the fill may occupy the annulus between the BOP and the DP below the rams and above the latch, so that the DP is still held by the cement. (At which point if the chemicals don’t release it they might try the jetting again, since that works both on cement and hydrate). It is only by freeing the BOP from the drill pipe, and hoping that the pipe remains held by the underlying fill within the hanger, that the BOP can be released, removed and replaced.

The problem is that if, when the rams are opened, the cement/hydrate holding it is not strong enough, then the pipe may fall to the bottom of the well, carrying with it the evidence on what actually happened to it within the BOP. (Opening the rams will also drop out the other two pieces of pipe currently above the rams). Tough decisions.

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Thursday, August 26, 2010

Deepwater Oil Spill and San Jose Mine concerns

There has not been much apparently said about the fishing for pipe within the blowout preventer (BOP) at the Deepwater well today. The project seemed to come to a studious pause with the discovery of a considerable volume of hydrates around the shear valves in the Deepwater BOP, as opposed to the lesser quantities of hydrates in the 3-ram stack that was placed on top of the well, as part of the shut-in procedure.

The interlocking crystals appear to be filling the empty spaces just above the rams in the BOP, and holding the pipes in that space with sufficient tenacity to make them difficult to remove. If that is indeed the case, and the crystal growth extends down through the BOP and into the spaces at the top of the well then it poses a potentially significant problem to the extraction of the drill pipe, and the removal of the existing BOP. The current BOP needs to be replaced so that a functional BOP can be placed in its stead, and the well can be conventionally plugged and sealed and then abandoned.

However, if the hydrates have extended down through the mechanism and space of the BOP, then, as with the upper set of rams, the moving parts of the BOP may no longer be functional, meaning that the drill pipe cannot be released. This then raises a further complication, since if the drill pipe continues to extend below the BOP (and it is believed to extend some 3,000 ft) it too may be held within a hydrate plug that fills the space between it and the steel and cement rings that form the upper lining of the well. I will probably explain how we use that principle in bolts that hold the mine roof up around the world that are often called full-column resin anchors, in a Sunday tech talk fairly soon, but the net result is that the BOP and drill pipe may be locked in place.

This makes the next step in the process somewhat difficult to predict, since the intent in removing the BOP was both to allow the well to be plugged, but also to provide a backup protection for the top of the well, at the time that the relief well drilled into the lower part of the well, and where the changing pressure condition at the bottom of the well might cause the seals at the top of the well to rupture and, with inadequate protection at the bottom of the well potentially allow the well to start leaking again.

While this consequence is somewhat unlikely, it depends on the condition in pieces of the well that are not available for inspection. Hydrates above the shear ram suggests that it is likely that they extend below the rams, but there is no way of knowing without clearing the passage. And the extent, or even the possibility of the drill pipe being held within a plug of hydrates is not that much different to it being held in a cement collar that adhered as the cement was pumped to the bottom of the well.

The hydrates above the ram could be removed (either with the high-pressure jetting or chemical/thermal soaking) but it may be more difficult to get through the BOP to release the underlying catch holding it within the sea-floor mount, and to release the drill pipe, or even to section the drill pipe to release the assembly. And just before midnight (as I did a last check after writing this post) they started flushing the BOP with some fluid.

Moving down to Chile, the machine that will be used to drill the relief well is a variant on a raise drilling machine, that is used more commonly for boring holes upwards from the underground space, rather than reaming them down. It is a Strata 950, made by Murray and Roberts through RUC Cementation. The unit, was, apparently, only built last year.
RUC Cementation has established the capability to design and manufacture specialist large diameter raise borers in its Kalgoorlie workshop. During the year (2009), three Strata 950 raise borers (the most powerful underground raise drill rig in the world) were completed, one for its own use and the other two for group operations in South Africa, Canada and Chile.
Raise borers normally work by drilling a small hole (13-inch diameter) down from the surface to an existing underground space. Then a reaming head is attached to the drill steel at the bottom of the hole, and the head rotated and pulled back up the hole, allowing the debris to fall into the larger hole below it. It is a relatively fast and effective method of creating shafts, and is increasingly used at the surface and in underground mining.

Normal use of a raise borer .

In some cases, such as the present one in Chile, it is not possible to get the larger reaming head down to the bottom of the shaft. In that case, once the initial central bore has been completed, then a second reaming head is mounted and will drill down along the same line, with the debris still falling down the central hole, and being disposed of underground.
This alternate way of drilling is not as fast, since the operation has to be careful not to block the borehole with the cuttings from the reamer, and it is a little more difficult to keep going straight. The following two pictures are of a competing model but serve to illustrate the principle of the Down Reaming process:

In contrast to up-reaming the drill shaft is in compression which might help on longer bores. One of the drilling requirements is to watch the torque that develops in the drill rods, since this can build-up to sufficient levels that, if suddenly released (as in drilling broken rock) it can whip the head around sufficiently fast as to break the string.

The actual teeth on the bit are specially designed for the rock that the bit will be expected to penetrate, but they are conventionally bit or button teeth, similar in shape to those used in the smaller cones of a conventional oilwell bit.

Reaming head being loaded into place.

The drill will operate from a concrete pad, which is, I gather, now poured, but must set before operations can commence tomorrow, and the hole is not planned to be lined, which may also cause problems, since there is no easy way to deal with rock that falls behind the head. However this particular one is called “David” so let us hope it can meet all challenges.

The Strata 950.

I do have a couple of other concerns. One is that the miners were apparently getting water from an underground stream, and one worries as to whether this water leaves the mine though an existing natural channel, or if it has been flowing to the bottom of the mine, where it might have been earlier collected and pumped out. If the sump pump no longer has power, this could imply that the mine is slowly flooding. And in that regard, the decision not to send power down into the mine, means that they could not send down and power small pumps that the miners could then use to keep their current location dry.

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Deepwater Oil Spill - Recovering pipe

The problem with not watching the video feeds from the ROVs at the Deepwater site on a very regular schedule is that it becomes hard to define if anything has changed since the last time you looked. At 11 pm Central tonight, for example, the feed has switched back from the downhole camera to the ROV camera on the Boa Sub C ROV1, and the borehole feed shows that the pipe containing the camera seems to be dangling in the water, as it has been some time ago. So it was not clear from the suggested cameras as to the current status of the fishing attempts to remove the different length of drill pipe (DP) which are still within the BOP and the stack above it.

However, switching to the Enterprise ROV1, suddenly there is a piece of pipe being examined. It is difficult to tell exactly which piece it is, though it is apparently marked in what may be foot intervals, but the examination at the moment is focusing on the end of the pipe, which is the male end of a pipe section, and it is hard to determine whether the threads have been damaged or not. (This is being written as this occurs). MoonofA has an explanation (this was part of the fishing string) and I will add that comment below the fold and the current pictures.

Close-up of the lower end of the pipe

Earlier the pipe had rotated so that an identification number could be seen:

The pipe has a number of spaced marks on it, with five marks higher getting to 70
(suggesting the other side of the joint might have carried a 5).

The mark just below the point where the pipe section goes into the end of the fishing tool that caught it reads 90, and then there are three individual marks and the fishing tool holding the upper end of the pipe section.

Hmm! That’s interesting they have just apparently driven the open end down into the mud:

So that they could release the top and go and look at it.

And it appears, at first, that this was the piece of the pipe that was cut through by the diamond saw that the Admiral referred to in his press briefing.But then they do a close-up of the top and it is the female section of the joint at the other end of the drill pipe.

Upper end of the drill pipe

And this too gets a close examination of the threads.

MoonofA's explanation of this is:
That part of the drill string fell off from one of the two fishing strings the Discoverer Enterprise had brought down. Pretty embarrassing for the crew to lose some 30-60 lower feet of the drillstring with a fishing tool on it only to have to fish for it later on ...

Here is a video by RockyP showing the lost part standing vertically in the mud.

But the Discoverer Enterprise has two derricks and the other derrick had another pipe down with a fishing tool and with a cam inside it. That pipe went down and looked for "fish" inside the stack: Video by Naula.

The first fish found at a depth of 5015 feet was the longer piece of broken drillpipe with a squeezed end and they actually tried successfully to get it inside the overshot tool. But when they yanked the tool up the fish escaped: video in double speed by me.

The camera then went further down and at the height of the flex joint at 5026 feet depth found this:

We are seeing the inside of the flex joint from the camera in the fishing tool. There is in the center-right an open piece of pipe. Next to it is some rough space open where fluids come through from below pumped by the Q-4000 through the choke line of the BOP. At the top of the picture another pipe can be seen which extends above. Both pieces are probably held back by what appear to be hydrates (though this could be just loose "beehives" of hydrates or something else).
Hard hydrates would explains why the first attempt to yank the longer caught fish did not work. It is probably held back by hydrates on its lower end.

The fishing trip has ended for now.

The big question to us at #theoildrum is: How did hydrates form so deep inside of the stack? When was there seawater as well as methane, both needed to form these hydrates, in the BOP and stack at the same time? Or do we see something different than we think?

Heading Out comment - they did remove some of the hydrates using a high-pressure jet earlier in the work, and this should still be down there, so they may go in with a lance to clean out the hydrates, but if they exist throughout the lower BOP then the entire assembly may be frozen in place, and if this extends down into the casing of the well, then as I mentioned in an earlier post, trying to pull up the drill pipe, and even recover the BOP may be halted because they will snap the drill pipe before they will be able to break it loose. Alternately they could try flooding the area with chemicals again.

Earlier in the day Admiral Allen explained some of the events that I discussed in yesterday’s post, noting that the rams in the stack had become jammed because of the formation of hydrates within the mechanism, that then led to them freezing as the hydrates were disturbed. BP then chose to flush the system again, using an antifreeze solution.
Question: What chemicals were used in the recent flush to remove hydrates?

A. BP used a methanol soak as the predominant medium for melting the hydrates. They also circulated MEG water - methyl ethylene glycol (antifreeze) - to help improve visibility conditions.

Q. Will there be ROV feeds available to observe the pipe removal?

A. BP will have the regular suite of ROV's on scene for the operation and the pipe extraction should be visible through the Enterprise ROV camera.
With the problem of the ram movement in the capping stack having been resolved, the plan for the day was to go down inside the stack to recover the pieces of pipe that had been found. One of these is relatively short (about 18-inches long) the second (and here the Admiral corrected a length given earlier) is some 13-ft long, and then there is the section of the DP itself.

Now the segment that appears to have just been removed would be 30-ft long if it were a standard length of DP, so I am wondering if this was a transcription error in the relevant paragraph of the teleconference?

The other issue dealt with by the Admiral dealt with the possibility that when the cement was pumped down the well it might have adhered to part of the drill pipe, and filled a gap between it and the production casing, so that over some unknown interval the DP might be effectively glued to the casing. His comment
We believe we can easily remove two of those pieces of pipe because they're standing free inside lower marine riser package. After that, we will have to determine the condition of the pipe extending down into the blowout preventer, if it goes below that down into the well, if the pipe somehow might have been cut and is suspended there and it was cut below the blowout preventer, there's no pipe we do not know any of that right now because we cannot see down there.

We are creating alternatives that will allow us to either remove the pipe if it's removable. And if it is not, plans to how we were remove the blowout preventer with the pipe attached and bring that to the surface and cut the pipe at some point. Our science team and BP engineers continue to work with all those alternatives as we move forward. We are hoping however to remove the two pieces of pipe and have a better idea today or tomorrow about the remaining piece of pipe.

Unfortunately, not having watched earlier this evening I missed the section of pipe falling off, and what led to the sequence of events i described above, where the two ends of the pipe being examined were, in fact, at one time joined together, rather than being the one section of drill pipe that I had initially thought that they were.

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Wednesday, August 25, 2010

Deepwater Oil Spill - More questions than answers

Hmm! So what is going on at the well? On Tuesday evening there were a couple of posts in the comments at TOD, one of which showed oil leaking past the shear rams in a BOP, as a Youtube segment, (H/t TOB ) while the second was a short clip showing the shear opening (H/t Chuck Schick ) . Because of the bandwidths involved I am just going to take a couple of frames from them to show the situation. This is from the Youtube segment:

This is a different shot from the one shown in a loop by Chuck which includes this frame:

And then there was the ejection of what appeared to be mud from the stack at about 12:41 pm that (H/t MoonofA) is also on Youtube.

Which leaves one wondering what is going on? Did the DP fall and rupture the casing and this is flow from the annulus? Has the seal at the top of the annulus lost its integrity? Is this oil, gas or some combination – since mud alone would be denser than seawater and should sit in the well without a problem, given the testing that was done at the end of last week. Is this perhaps some residual fluid in one of the lines that was being flushed out, and if so which one?

There are (and I am writing this around 10 pm Central) it seems two borehole cameras. The official one, which is swinging in free water it appears at the moment, and that from the BOA Sub C ROV1, which is the feed that is showing the ram blades and the flow. Unfortunately (unlike the main ROV cameras) this is not date stamped, so that when I just went back for a check the view is relatively quiet with no flow and the valve open – so this may have been another unwarranted alarm. But it would be nice if, perhaps, the Admiral could explain this. (At the moment the listing of the Transcript of the press conference for Aug 24th reverts through a link to the Transcript from the 23rd).

In regard to the events in Chile, now is not the time to talk much about the rising price of metals and other minerals that come from underground – their depletion and the problems they cause are more the subject of the more conventional posts that we write at this site – but I did note the comment on the price rise of copper which has gone from $1.835 to $3.234 per pound in the last year.

More small diameter drill shafts are being sunk, so that there is communication down one, supplies down a second and a third, soon to be completed, will be for ventilation. The large drill that will drill the rescue shaft is now on site and is being set-up to start the hole.

For those who have not seen the layout, ( H/t Ericy this shows the relative position of the refuge and the slope that was the main access to the underground.

You will notice that there are a few more turns than the simple spiral that some of the networks have been showing.

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Monday, August 23, 2010

Deepwater Oil Spill - Fishing and Quecreek equipment

There has not been a lot of visible progress at the Deepwater site today. As might be anticipated when BP are trying to extract the three segments of pipe that Admiral Allen commented had been found above the Blowout Preventer (BOP) and in the rams.
To tell you what we found there, there are basically three sections of pipe. There was a section of pipe that is suspended in the middle on the center line that we believe goes down below the blowout preventer into the well some distance. There is a shorter piece of pipe that is sitting beside that pipe in the blowout preventer that was broken or cut about the length of the blowout preventer itself. And then there's a very small piece of pipe laying crosswise.

We believe these pipes are where they're at as a result of the diamond wire cut that we attempted on the riser pipe and then the final shear cut that we did. And we know which cuts were where, because one pipe has a very clean cut, indicating that – that was cut by the diamond wire saw. And the other one is compressed and cut, which would indicate that was cut by the shears that we used.

So we have a good idea of where the pipes are at and where they're located. We're now conducting diagnostics inside the BOP and the capping stack to ascertain the best way to remove the pipes.
Given the need for the procedures to be conceived, written up, approved and then followed, it may be a little time before the pipe segments get removed. This is particularly true if the ram closures that I noted in the last post have yet to be fixed.

The Admiral does not seem concerned with the possibility that if they get hold of the long length of drill pipe that is held in the grip of the rams in the BOP that it will shear when the holding rams are released. This suggests perhaps that they may know (from the scans made of the BOP back near the beginning of this episode) what the pipe looks like, and do not expect that it has been materially cut by the shear blades. (Since it is that cut that would be needed as a starting crack, to help initiate separation of the pipe at the cut, and since it has not failed yet, they may assume that it has sufficient integrity to hold up during the removal process).

Nevertheless he is not concerned that if the pipe were to fall down the well, that it would do much damage to the cement plug at the bottom of the well. He was asked that specific question at the press conference, and replied:
I don't believe so. (It'll fall down) into the well to the extent that it could, and as long as it wasn't protruding above the wellhead, would actually not become an obstacle to removing the blowout preventer. But I think, for forensic purposes, they would like to have that pipe so they can examine it.
He does not, thus, anticipate that it would do much damage to the bottom of the well, even if it fell and hit the top of the cement plug, given its length and that it is surrounded by the production casing and, over an unknown length, by an external cement liner filling the annulus to the surrounding rock.

At present the down-hole camera is not working, the stack seems to have been left open with the BOA Sub C Rov1 monitoring it to see if there are any returns, and the drill rod is swinging freely in the water.

Screen capture from ROV1

In regard to the situation of the Chilean miners, a special drill is being brought to the site from elsewhere in Chile, and in fact may be there by now. The drill that will be used is likely of this size:

Drill bit used at Quecreek

The picture is from the Quecreek rescue operation. However that was a relatively shallow coal mine, with softer rock, and so they are apparently going to use a bit with polycrystalline diamond compact teeth which will allow them to cut through the harder rock. The penetration rate is expected to be about 65 ft a day, though some of the rock from the video shown of the existing borehole passage, seemed to be broken, and that will make drilling that much more difficult.

The refuge is on the side of a spiral tunnel or slope, that rotated around the ore body as it traversed lower, and in the higher regions of the mine, this was closed by a rock collapse. It appears to have been the only access to the deeper parts of the mine. In many countries there has to be a second way out, brought about after the Hartley Mining Disaster in the UK in 1862, when 199 miners died because the only shaft into the mine was blocked. (The first school I went to was at New Hartley, when my Dad was manager there).

Once the shaft has been sunk, then a small cage will be lowered to bring the miners to the surface, one at a time. The cage is obviously of small diameter:

The rescue cage at Quecreek.

Small as it is it held each of the miners and brought them to safety.

Rescued miner being brought out of the Quecreek Mine.

Let us hope that the miners in Chile are similarly all safely recovered.

Meanwhile, looking at other natural hazards, there have been about half-a-dozen 3.0 or greater earthquakes in the Loki area of Iceland in the last few days, and just when it appears that we will dodge the Hurricane bullet of Danielle, the next one seems to be forming behind it.

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Sunday, August 22, 2010

Deepwater Oil Spill - TV cameras and Chilean Miners

The fishing expedition to recover the drill pipe (DP) from the Blowout Preventer (BOP) at the top of the Deepwater well is moving somewhat slower than initially was suggested would occur. BP have provided a feed from the camera that was lowered into the stack.

It is not clear, since I wasn’t following this all day, what has been going on, though it has been suggested (H/t Unconformity) that the obstruction that appears in the video was one of the rams in the stack that was in the wrong position. This was followed by an adjustment of the stack, but apparently the camera has been returned to the surface. It may have malfunctioned, since the screen went blank just after this shot.

Note the time id.

UPDATE: Thanks to Acornus and MoonofA in comments at TOD, the object in front of the camera is apparently one of the two shear blades from the Ram in the stack which has failed to open. MoonofA has posted a better shot of the situation at about 6 am CDT. I have dotted in the rim of the hole further down, so that you can see that the extent that the rams still protrude, though they are higher up so the protrusion is greater.

The two blades blocking the hole

In the meanwhile it appears that it is being fed into the stack without a riser in place, though we could be getting the various BOP/stacks mixed up, since once the BP is out of the way, the intent is to move the DP11 BOP over the well, to replace the old one.

View from Enterprise ROV1

It looked as though, also just before the loss in signal, that the ROV1 grabbed hold of the DP to help steer it down the center of the stack assembly:

Enterprise ROV1 grabs pipe

ROV1 guiding pipe in stack

The pipe is now (11:40 pm) back out of the stack.

For those who have just heard about the 33 trapped Chilean miners, apparently they were working in the 2,250 ft level of the mine when, seventeen days ago, there was a massive roof collapse in the area that included the access shaft. After two weeks of exploratory drilling, a drill broke through in the area of the refuge where all the miners have been trapped. They are all still alive, one sent out a message to his wife attached to the drill, but it is impossible to reach them through the existing workings.

As a result a special rescue shaft will be drilled down, large enough to lower a cage into which, one at a time they can be extracted. (The technique was used to rescue the miners at Quecreek mine in the USA). The shaft will be 27-inches in diameter, but it is going to take up to four months to reach that level, and so the current shaft will be used to send down water, food and oxygen to sustain them until then. They have been able to run some equipment and generate electricity and have apparently some considerable room at the refuge site. It apparently takes a couple of days at a time to drill one of the smaller access holes.

Our prayers will remain with them and their families.

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Working thin coal - the coal plow and Hydrominer

In the last couple of years there has been a growing concern about the amount of coal that remains in the productive reserve for the world. At the same time the incoming British Government, which had been somewhat antagonistic to coal while in opposition, may be giving large coal-fired power plants a reprieve. Questions might therefore arise as to how long this fuel source is going to last, if use increases more than projected. While I am not going to answer that specific question today, I will address a part of the issue. Namely what do you use to mine coal when the seams get too thin for modern equipment?

The lowest coal which I personally have mined was about 1 ft 8 inches high. The low coal was caused by a roll in the middle of the face (the floor got closer to the roof) which was normally about 3 ft high (The Beaumont seam at Seghill Colliery in the spring of 1962). In that height you lie on your back, put a pit prop under your shoulder to give you some leverage, and shovel across your chest. In more advanced mining countries it is unlikely that we will return to such manual labor, which is not very productive. So what do you use?

The most productive machine in most longwall operations is the shearer, which I described in the last tech post. The problem is that it most effectively runs on top of the armored face conveyor (AFC) and the power pack that drives the cutting head and haulage unit takes up quite a bit of space. One idea was to take the shearer off the conveyor and have it slide along the ground on special shoes, with the cutting head mounted ahead of it on the longwall. My father had rather strong opinions on this, since two of the mines he worked with had such machines. Remember that the coal conveyor must snake over behind the machine in order to allow the supports to also advance.

To hold the machine together, the gear boxes at each end and the power pack in the middle, there are through-bolts down the machine. Now it breaks down in low coal. The roof is say 2 ft 6 inches above the floor, the machine is 22 ft long, and the conveyor is 7 inches high. How are you going to take the machine apart to fix it? (The answer involves explosives, and is not a “quick fix.”)*

So if the shearer is not an ideal machine, what is? The answer is known as a coal plow (or Hobel in Germany where they were developed by a company then called Westfalia Lunen.) Very simply in some coal types, particularly those that are brittle, the coal at the front of the face is weakened and cracked by the pressure of the overlying ground. Thus if you take a narrow pick and drag it across the coal it will peel off some coal. Put a number of these picks together and the coal between them will also chip off – perhaps to a depth of a couple of inches. Make the machine move down the face rapidly, with the rams pushing through the AFC to keep the plow pressed against the coal, and you have a simple but effective mining machine.

Plow on face – note the picks in the different elements that can be removed to adjust for varying seam heights. (Shield parts removed to show the plow)

The coal in which this is most effective does not necessarily have to be mined over its full height, since often, when undercut, it will fall under its own weight. Depending on the coal strength, the depth of cut of the machine can be adjusted. As a result the coal produced can be quite large, sometimes bigger than the average size of the fragment coming from a longwall shearer face. It is, however, an "interesting" experience, to see one working under a sandstone roof, where the face rolls a bit.

There were a variety of plows built, depending on coal height, coal type, and the speed at which the plow could be moved down the face. It is a fast moving operation, but one that is not that popular at the moment, since, in most higher coal a shearer may be more effective and produce more coal. However in the years to come the plow may make a comeback.

By then, however, it is possible that the picks on the machine, that generate dust, will be replaced by high pressure (10,000 psi) water jets which cut into the coal perhaps a foot ahead of the machine, and allow mining without the generation of the dust and sparks that make current operations so dangerous. It has been done before, and is a relatively simple technology to adapt to future conditions.

Waterjet plow operating underground in Germany (from Gluckauf)

We called it the Hydrominer, and as I learn how, I’ll put up some video on Youtube of it operating. There are better ways of using the jets than those shown, so that the plow can actually mine coal to a web depth of over 3 ft 9 inches (we have) at shearer speeds.

Incidentally longwall mining was not a part of the Modern Marvels review of Coal Mining, though in Part 3 they do show the development of the continuous miner, and shuttle car. (H/t to Pasttense who gives a list of some Youtube films), though there are a number more than I had thought there would be.

* At least in those days they excavated a chamber ahead of the machine by blasting it out with explosive and removing the coal by hand. This allowed them space to pull off the head, remove the bolts, fix the machine, and put it back together again.

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