Joined: Jun 2003 Gender: Male Posts: 938 Location: PERTH WESTERN AUSTRALIA
Re: Oil, Gas Leak on Seadrill West Atlas Jackup - « Reply #50 on Sept 14, 2009, 12:25pm »
Hi Pupjoint, Both you and Leonard have hit the nail on the head. We are in armchairs and not at the coal face. I have no preference for one rig versus another on the basis of rig type. I asked the question of you regarding why it was said that a Jack-up is preferred over the semi. You answered me with the clipping from the Herald Sun. The diagram regarding a vertical well was shown at a press conference with Mike Alcorn of Alert. Do not know where to obtain a copy. Regarding the steps forward, In spite of a vertical well being planned a DD will be used. That is a certainty. As Len says the formation feeding the gas/condy to surface can only be killed if we can get sufficient hydrostatic overbalance into the first well. The column of gas in the vertical section of the first well will need to be bled off. And a 'U' tube created. The success of this shall depend on the permeability of the contributing formation. If it is hungry a lot of mud and LCM will be required. This is a big job and not one that needs to be rushed. Two weeks waiting for the 'right' equipment is insignificant in the scheme of things.
Re: Oil, Gas Leak on Seadrill West Atlas Jackup - « Reply #51 on Sept 14, 2009, 1:07pm »
No worries Holdril, your question re: why not use a semi ? got me thinking. The DD will probably ensure its a dead straight hole with no flicks from vertical in surveys which I guess would be gyro surveys to eliminate interference from metallic objects and ferrous ore bodies.
The terminology though in media releases has been a bit cryptic albeit we don't share the same psyche as journalist when it comes to translating oilwell techno jargon presented at press conferences. A common term that sets them off in a spin is "tight hole" literally or figuratively. This though is the first time I've heard of a relief well drilled to plug a leak. Perhaps the engineering definition of what constitutes a blowout or a leak; spill; fracture; fissure does not always tally with insurance or other definitions for the same terms. For example terms like fissure conjures up related stuff like casing burst resistance, SSSV or wellhead seals. While phrases like "very very rare incident", " cause yet to be ascertained " (although remedy is underway) and "fracture" conjures stuff like "total losses", "underground blowout", even perhaps " umderground earth tremor" seeing the surrounding area is fault ridden especially with a major fault line running much further away between "sunrise" and E.Timor.
Information or opinions are solely provided for educational and/or discussion purposes on an informal public forum and should not be interpreted as a recommendation for a specific treatment plan, course of action or product/ service. Use of any of this information does not replace consultations with qualified individuals in these respective fields.
Joined: Jan 2009 Gender: Male Posts: 134 Location: A snowy place with hills
Re: Oil, Gas Leak on Seadrill West Atlas Jackup - « Reply #52 on Sept 14, 2009, 8:02pm »
FWIW on the Semi vs Jack up debate, the jack up is preferable from a borehole accuracy point of view due to reduced errors in the survey in position. One component of borehole positional accuracy based on surveys is a the accuracy of the measured depth of the surveys. The error associated with measured depth in the standard ISCWSA model (H Williamsons model) is different for a Semi and a land (or jack up/platform) The Land rig has a 0.35m random error associated with each survey where as a semi is 2.2m, there is a 0m systematic error for a jack up and 1m systematic error in MD for a jack up.
In a vertical well these errors are not really an issue for a regular appraisal/production well, however for a intercept well you would probably try to get as much as you can where ever you can. That and cost of the rig.
The DD will be there as I suspect they will run motor or an RSS system to keep vertical and obviously an MWD system, vertical wells are not always vertical despite the best of intentions. Not sure if a gyro would help much, with modern in field referencing/geomagnetic referencing the survey accuracies are probably comparable.
One area I am not sure about is the surveyed in position of the well center on a jack up vs semi sub. Can a jack up well center be positioned and surveyed in any more accurately than a semi sub?
Well back to the armchair, good luck out there guys n gals.
Joined: Jun 2003 Gender: Male Posts: 938 Location: PERTH WESTERN AUSTRALIA
Re: Oil, Gas Leak on Seadrill West Atlas Jackup - « Reply #53 on Sept 14, 2009, 11:13pm »
Once again from the arm chair. In spite of the comparative comfort a surveyor may have regarding the position of the rotary table; Jack-up versus Semi, the survey on a semi is tied to the well head at seabed. This provides a less mobile reference than the Well Head on a jack-up that is swaying due to ocean currents. Pup Joints comments regarding the printed word filtered through inexperienced Journalists love of the dramatic is valid. I would like to know what happened and what is happening. Guess I'll have to wait. One of my theories is that the older wells drilled before the jacket was installed was suspended with SOBM as control fluid. During the long period between suspending and staring the new campaign 'Barite Sag' stole the hydrostatic control and gas entered the well bore and percolated to the surface charging a higher permeable zone with pressure equal to the gas pressure at 2,600 m. Just a guess from the arm chair.
Re: Oil, Gas Leak on Seadrill West Atlas Jackup - « Reply #54 on Sept 15, 2009, 1:20am »
Holdril, no doubt tie-in point for surveys to wellhead at seabed provides provides a better fixed point of reference, but I believe Wired's post alludes to error from survey "measured depth" if using a semi that will contribute to borehole trajectory error "prior to tie'ing" surveys to the wellhead fixed point, similar to what I posted in addition to Laurie Oake's article in response to your question.
I share 100% with you the same hunch regarding "Barite Sag", however if this is the case then suspended weighting agents in mud would have settled to the bottom of the hole making mud heavier at the bottom possibly fracturing formation even though static thereby lowering wellbore fluid column height reducing hydrostatic cap thus allowing gas in the upper section to invade the well bore- assuming barefoot section.
What I don't know is if they drilled vertically through the pay zone cemented back up, or stopped just short of it, before RIH Csg and P & S with view of kicking off horizontally for the 8.5" OH, at a later date, in which case the question of plug type and quality instead of mud solids settling out of solution crops up.
With P & S wells like these, does anyone know what measured are taken to prevent such occurrences ? example perhaps- special gel suspension ingredients ? Robin what d'ya reckon?
The intention I suggest is not to second guess anyone at the scene from our arm chairs or grandstand from a judgmental perspective but more so to be of one mind with them as they tackle this problem and most of all learn as much as we can as information filters through, and it don't matter if your theory turns out incorrect, either way we all get to learn from it.
Information or opinions are solely provided for educational and/or discussion purposes on an informal public forum and should not be interpreted as a recommendation for a specific treatment plan, course of action or product/ service. Use of any of this information does not replace consultations with qualified individuals in these respective fields.
Joined: Jun 2003 Gender: Male Posts: 938 Location: PERTH WESTERN AUSTRALIA
Re: Oil, Gas Leak on Seadrill West Atlas Jackup - « Reply #55 on Sept 15, 2009, 4:43am »
My current role is on similar project more extreme HP and HT but similar. We address the potential of settling weight materials with Brine, currently we use Ca Br.
To achieve depth control on a semi we have a Motion Compensator and tide Gage. We conduct a 'Long Baseline Survey' to establish an accurate position.
This is not to say one is more accurate than the other. Rather I am trying to say it is of no consequence.
Re: Oil, Gas Leak on Seadrill West Atlas Jackup - « Reply #56 on Sept 15, 2009, 11:40am »
Semi or jackup should not matter, so long as the water depth is sufficient to accommodate the semi's taller BOP assembly and the mooring system can hold position within the ball joint's range or motion. It's harder to do that in shallow waters, but I have used a semi in as little as 200 ft. The advantage of the semi would be the ability to get off location quickly in the event of a well control problem. In fact, sometimes semi's are used for that reason, where shallow gas uncertainty precludes a jackup's usage.
The exact positioning of the wellbore should not be an issue for either rig. The required survey accuracy for the location and for the trajectory are well within reach with current technology to place the well's borehole within a few feet of the blowing well. If the well is still flowing, they may use acoustic or magnetic vector technology to steer an intersecting path - the technology is there to steer to the problem rather than depending on survey accuracy to hunt it. Once they are close enough to kill the well, they will pump kill mud and frac across to the blowing well bore, then perform a high-rate dynamic kill from the bottom up.
It sounds as if the well flow has been tapering off over time? If this is a producing well that is leaking, then it may still become possible to kill the well from surface.
If the well is still flowing, they may use acoustic or magnetic vector technology to steer an intersecting path - the technology is there to steer to the problem rather than depending on survey accuracy to hunt it.
Hi Tadwell. Quick couple of questions with hope you will oblige. Could both acoustics and magnetic vectors be used from the onset ie: top hole section of the relief well ? I imagine sound traveling through rock would, compared to magnetic flux, have a longer range but got no idea of the effective range either method of sniffing out the live well has ?
Or do both require some minimum proximity to the live blowing well to take effect over surveys for direction?
Information or opinions are solely provided for educational and/or discussion purposes on an informal public forum and should not be interpreted as a recommendation for a specific treatment plan, course of action or product/ service. Use of any of this information does not replace consultations with qualified individuals in these respective fields.
Joined: May 2003 Gender: Male Posts: 2,132 Location: Sarawak Malaysia
Re: Oil, Gas Leak on Seadrill West Atlas Jackup - « Reply #58 on Sept 15, 2009, 7:57pm »
With technology available today or even years ago, getting to a precise location below the surface is not difficult. Whether on a platform, jackup, drillship or semi, it is the same. Maybe exploration it is not so vital to 'hit the nail on the head'. BUT what happens with Subsea completions that are done from a floating situation, in thousands of feet of water, NOT a 'fixed' seabed location these guys are talking about. Do they think the well is any different when the wellhead and BOP are on the seabed rather than where it can be seen on the surface. Compensated systems on floaters are just as accurate as 'pushing' the stick is done on 'fixed' systems. Controlled drilling will get you wherever you want.
I was directional drilling on a platform before the term DD appeared. The drillers did it.
You can drill any which way you want, even DD's screw up, as was shown not so long ago when an operation started losing mud, over the 'hill' with the drill bit above ground.
I was present when Mike Alcorn supervised the drilling of a relief well in Indonesia, when directional drilling was in its infancy. The well was located, mud pumped, the well was controlled. From a jackup where a semi would have had difficulty due to water depth except for some of the older types that could sit on the bottom. NO thrusters or props.
More technical details ; 2 excerpts same article in "The Australian" ______________________________________________________ Early on August 21, as the West Atlas entered the final stages of pre-production, a crack developed in the temporary system sealing one of its five wellheads.
With vast amounts of oil and gas spewing out and no idea exactly what had happened, those on board the rig knew they had to get off quickly.
In an emergency evacuation, all 69 workers on the jack-up rig were airlifted to Dili and more than 60 workers on a nearby pipe-laying barge were also evacuated, as divers who surfaced found themselves surrounded by the oily substance. The damaged well is sunk to a depth of 2.6km, then curves into the oil and gas reservoir for a total length of 3.6km. A concrete and rubber plug was meant to hold the oil and gas until it was ready to be pumped.
PTTEP Australasia director and chief financial officer Jose Martins admits he is unsure what had happened.
"There's a pipe that's gone down 3.5km," Martins says.
"That pipe is sitting in a reservoir and, because it's a development well, it's not in production, because of that it's plugged. So it has quite a sophisticated system of plugs and about 20 odd metres of concrete, or cement, pumped into the well bore.
"And that is designed to keep it from flowing. And on top of that is always a whole lot of seawater in the pipe as well. That's what stops it from flowing. However, there must be some fracture in the system somewhere which we can't detect, which is causing the leakage." ______________________________________________________
The ALERT team is providing technical and other advice on the drilling effort, including the use of electromagnetic equipment that will guide the drill down to the original well and flood it with heavy mud to block the leak. ______________________________________________________
Information or opinions are solely provided for educational and/or discussion purposes on an informal public forum and should not be interpreted as a recommendation for a specific treatment plan, course of action or product/ service. Use of any of this information does not replace consultations with qualified individuals in these respective fields.
Joined: Jun 2003 Gender: Male Posts: 938 Location: PERTH WESTERN AUSTRALIA
Re: Oil, Gas Leak on Seadrill West Atlas Jackup - « Reply #60 on Sept 15, 2009, 11:37pm »
Thanks for the link. You notice he said sea water on top of plug. If so that is an engineering oversight. Leaving sea water in the well is usually a cheaper method than brine so that's what the 'Accountant' driven Oil Patch does. It is up to the engineer to fight for the safest barrier, at least two between pressure and atmosphere. Here we have the fallacious concept that a cement plug will contain gas. So the plugs let go, the cement is considered to be a plug, which it isn't. Seawater does not provide a barrier and The Well head is not made up properly. A rupture or a crack is highly unlikely.
Re: Oil, Gas Leak on Seadrill West Atlas Jackup - « Reply #61 on Sept 16, 2009, 12:13am »
Could it also be that the percolated or "leaked" gas reached such volumes and height to achieve pressures large enough to exceed MAASP or wellhead seal limits ? In which case this would have occurred by itself sooner or later even with total absence of the drilling rig.
The article states that the commentator is the chief financial officer so I reckon there's always possibility for technical detail lost in the translation between him and his engineers. However the area is known to be low pressure but not under pressured. If it is literally like he says - a development well- plain old seawater at 0.465 psi /ft alone won't overbalance things if the cmt plug gives way but pending more details, may have been good enough to act as a water cushion during testing .
On a separate note: It pays to ensure that right amounts and timing is used during cement jobs with regard to the adding and mixing of important additives. A slack cmt service hand can sometimes plonk all additives required for the job in one go into the last batch or two when by right it should have been trickled throughout the various stages whilst pumping cmt. No doubt though some additives are meant for the last bit of the tail end. Pre cement jobs recipes only stipulate type and amount of additives to be used albeit supervisors and DEs should be aware which additive is used for what purpose and when or at what stage they should be added. A proper cement-job-events-list should also be furnished to the client. Perhaps one of our members, well clued up on these matter might wish to comment ?
Information or opinions are solely provided for educational and/or discussion purposes on an informal public forum and should not be interpreted as a recommendation for a specific treatment plan, course of action or product/ service. Use of any of this information does not replace consultations with qualified individuals in these respective fields.
Information or opinions are solely provided for educational and/or discussion purposes on an informal public forum and should not be interpreted as a recommendation for a specific treatment plan, course of action or product/ service. Use of any of this information does not replace consultations with qualified individuals in these respective fields.
Re: Oil, Gas Leak on Seadrill West Atlas Jackup - « Reply #63 on Sept 19, 2009, 5:43pm »
Montara platform seen from the air on September 12, 2009. Oil slicks around platform are clearly visible; the white haze is a spray of water vapor, natural gas, and natural gas condensate from the uncontrolled well. The West Triton rig in the background has begun to drill a relief well to intercept the damaged Montara well a few thousand feet below the seafloor. This operation is expected to take at least 3-4 weeks. Photo courtesy of Environs Kimberley.
Information or opinions are solely provided for educational and/or discussion purposes on an informal public forum and should not be interpreted as a recommendation for a specific treatment plan, course of action or product/ service. Use of any of this information does not replace consultations with qualified individuals in these respective fields.
Joined: Apr 2008 Gender: Male Posts: 35 Location: Houston, TX
Re: Oil, Gas Leak on Seadrill West Atlas Jackup - « Reply #66 on Sept 21, 2009, 11:37am »
pupjoint,
Generally, floaters are used to drill relief wells, but it has little to do with survey accuracy. Shallow zone charging and the probability of a secondary blowout event while drilling the relief well usually means that the rapid escape capability of a floater is better than using a bottom-founded rig which can (and, sadly, has) resulted in foundation failure below the spud cans with a consequential rig turnover.
Here, the blowout well is cased, so shallow charging is remote and the use of a bottom-founded rig is appropriate. Personally, I would rather be on a floater in case the relief well blows out for some reason before kill operations begin. Again, a rapid riser release and drive off would be possible without having to deal with jacking down, releasing the spud cans and being towed off the site. But that's just me.
Re: Oil, Gas Leak on Seadrill West Atlas Jackup - « Reply #67 on Sept 21, 2009, 5:20pm »
lskinner,
thanks for sharing that information. PETTEP stated they chose a rig which could fix itself on to the seabed to maximize chance of relief well success.This led me to think "survey accuracy". However they might have other reasons.
If however in a separate or hypothetical incident where a cased well has been shut in too late after taking in too large an influx and surface pressures exceed MAASP and shoe-cmt integrity breached with gas bubbles seen at the seabed emanating around or outside of the wellhead, would the threat of shallow zone charging apply ? that is if we both have similar definitions for "shallow zone charging" ? Thanks in advance. My view of shallow charging is basically underground blowout where a shut in influx or kick is allowed to expand to the point pressures exceed formation pressure at a weaker or thief zone, enters such a zone and charges it with much higher pressure than it originally had.
Information or opinions are solely provided for educational and/or discussion purposes on an informal public forum and should not be interpreted as a recommendation for a specific treatment plan, course of action or product/ service. Use of any of this information does not replace consultations with qualified individuals in these respective fields.
Re: Oil, Gas Leak on Seadrill West Atlas Jackup - « Reply #68 on Sept 22, 2009, 1:10pm »
Progress report (42) as relief well drilling to stop flow passes halfway mark
Drilling on a relief well to stop the flow of oil, gas and water from the Montara well head platform in the Timor Sea remains on track, having passed the drill depth halfway mark and is continuing today.
The total operation — to drill to a depth of 2.6km to intersect the existing well and allow for the injection of heavy mud to stop the flow — commenced on 14 September 2009. It is expected to take about three and half weeks from that date to complete the initial relief well operation. This will be followed some 24 hours later by a specialist crew boarding the West Atlas rig and well head platform to further secure the situation by plugging the well bore. This operation is expected to take about another week.
The first phase of the relief well drilling operation saw the initial 26 inch diameter hole drilled to a depth of 149m and a 20 inch conductor pipe was then run through and cemented into position. This was completed on 15 September. This was followed by the drilling of a 17½ inch diameter hole to a depth of 1,622m.
This was achieved early yesterday morning (21 September). Work to insert a 13 3/8 inch casing into the well was completed this morning (22 September). The casing is scheduled to be cemented into position today. The next phase of the relief well operation will see the drilling of a 12¼ inch diameter hole Read full report and photos here
Re: Oil, Gas Leak on Seadrill West Atlas Jackup - « Reply #69 on Sept 26, 2009, 11:05am »
Date: 26 September 2009
Work to drill a 12 1/4 inch hole to reach a depth of 2300m in the latest stage of the relief well, the drilling operation is continuing and is expected to be completed over the next few days.
The previous phase of the drilling to a depth of 1622m was completed on 21 September. The final phase of drilling the relief well will see a 9 5/8 Inch liner inserted into the well before drilling an 8½" hole from 2,300m to the final depth of 2.6k. This is currently scheduled to start early next week
The drilling operation remains on track to take a total of three-and-a-half weeks (from the start date of 14 September) to stop the leak.
Information or opinions are solely provided for educational and/or discussion purposes on an informal public forum and should not be interpreted as a recommendation for a specific treatment plan, course of action or product/ service. Use of any of this information does not replace consultations with qualified individuals in these respective fields.
Joined: Jun 2003 Gender: Male Posts: 938 Location: PERTH WESTERN AUSTRALIA
Re: Oil, Gas Leak on Seadrill West Atlas Jackup - « Reply #71 on Oct 6, 2009, 4:42am »
It appears that the objective is to pentrate the casing. Then fill the old hole from the bottom up. That will not work if they can't bleed the trapped pressure that is in the casing.
It appears that the objective is to pentrate the casing. Then fill the old hole from the bottom up. That will not work if they can't bleed the trapped pressure that is in the casing.
with respect, looks like they have not intercepted the casing yet or missed it first time round. Presentation diagrams to the media show the the intercept trajectory coming downwards parallel and horizontally above, perhaps allowing them to meander or snake forward in line if they miss things first time round, if they don't run out of "runway length".
Literally seeing from pictures of the incident that wellhead seals have been breached, could the kill pump rate be adjusted to cope with the displacement of influx fluids bottom to top ?? ie: bleed through the leak... if seals are not totally buggered.
Assuming of course that:-
its not a barefoot completion section that's the source but a cased completion ( they are using a casing sniffer as per PTTEP daily reports ). This also means no frac job possible and they'll have to to hit the casing spot on ( much harder) preferably below the kicking zone, pump heavies, bleed gas out through the existing leaks in plugs or/and wellhead and wait till heavies reach and displace the vertical section to take any counteracting hydrostatic effect ? Also means they must know where the well was perforated and analysis of oil samples from the sea might be able to confirm this and perhaps hit it below this section.
Information or opinions are solely provided for educational and/or discussion purposes on an informal public forum and should not be interpreted as a recommendation for a specific treatment plan, course of action or product/ service. Use of any of this information does not replace consultations with qualified individuals in these respective fields.
Joined: Jun 2003 Gender: Male Posts: 938 Location: PERTH WESTERN AUSTRALIA
Re: Oil, Gas Leak on Seadrill West Atlas Jackup - « Reply #74 on Oct 7, 2009, 3:17am »
If they had not penetrated the casing, why would they try to pump heavy mud. And If the relief well is not kicking, surely the drilling fluid is heavy enough. Of course the Original Hole is full of light fluid and gas. It is like a big compressor receiver. It appears that somebody is anxious. I hope they do not create a new problem due to impatience.
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