This aliilaali guy is improving fast, so I wanted to share his opinions about what the flow rates probably are, and also shelburns (under the fold), and what they could max out as, as well as what he thinks the causes are. He puts this in a nice theoretical congressional investigation context, but it’s just his opinion. Ie, he’s using this as a writing device. That is, please don’t take this as actual testimony. I’m saying this clearly because sometimes people just don’t get humor and mistake it for fact.

But I think this is a fair overview from a guy who does this for a living in deep water, and almost, ideally, might help serve as a basic reality check for some of the wilder ideas that are probably starting to float around the internet right about now. Source is theOildrum.com BP Deepwater Oil Spill – The Oil in the Water, Seeps, and an Open Thread thread.

aliilaali on June 8, 2010 – 1:53pm Permalink | Subthread | Comments top

idle thoughts on flow rates…..seems like folks putting out numbers high as 200,000 BOPD …other are crunching 100,000 BOPD ……these are very high numbers and all I can say is IMHO we are not lucky like the Saudi’s…..these numbers are what we wish we could get form a well in the GOM… producers have been searching for wells that can put out such numbers for 30 odd yrs and it just hasn’t happened yet …if a BP engineer is called to testify under oath today to congress…..IMHO the conversation would be roughly similar to

Congress: do you beleive the rate is 5,000 BOPD
BP ENgg: i hope not….if its 5000 i’ll crack some balls in the geology and reservoir dept…and I wont be getting any yearly bonus drilling such wells this far out in the sea

Congress: do you believe its 20,000 BOPD
BP Engg: congressman you’re not as stupid as you look …and my bonus will come in good this year then

COngress: do you beleive its more than 30,000 BOPD
BP Engg: if you want me to sign something …i will need you to put 30,000 as the flow rate …that’ll cover my ass good and proper

Congress: do you believe its 40,000 BOPD
BP Engg: theoretically its possible…but I can only hope for such good luck in the Mississippi delta

Congress: do you believe its 50,000 BOPD
BP Engg: congressman it only 1 well and its not in the middle east

Congress: do you believe its more than 75,000 BOPD
BP Engg: come now congressman …..i have better things to do than answer such stupid questions.

Congress: was this a particularly dangerous well to drill or did they drill too deep and extend their engineering resources beyond limit
BP Engg: ahahahha…congressman these depths are not extreme…in fact this is a very shallow well compared to what I have been drilling for the past 15 yrs

Congress: so not a difficult well to drill…not particularly deep …hmmmmm..didnt exceed engineering tolerances on the equipment ……i don’t understand what happened then
BP Engg: drilling best practices were not followed ….and drilling DW doesn’t excuse such lax approach to work …

Congress: I have heard some disturbing rumors about this well in march and April ….loss of well control and stuck pipe
BP Engg: congressman you lose control of wells all the time….stuck pipe happens all the time..infact I am drilling two wells right now ….one has stuck pipe as we speak ….the second one we lost a lot of mud….we are trying to pump in heavy right now to get things back on track …so sue me

Congress: what about these disturbing rumors of leaky pipes in the BOP
BP Engg: definitely disturbing this ….would’ve cost tops one lost day …most likely around 15 hrs to have gotten things ship shape with the BOP ..can’t imagine why they would risk failing hydraulics on an exploratory well….

Congress: so that it …its the BOP that is at fault (thinking hes nailed it)
BP Engg: congressman …a BOP under best practices should never be considered a line of defense….if you need a BOP then you have already screwed up ….drilling mud is primary and best means of well control…a BOP is a hail mary pass during the last 3 seconds of the 4th quarter when you need a touchdown ..things should not come to that …..ask any football coach

So again, the opinion here is that poor drilling practices, unsafe practices, failure to engage in proper safety procedures and tests etc, are the real problem.

Next we have shelburn’s views of flow rates from the same comment thread, roughly the same conclusions only with a bit more fine grained analysis:

shelburn on June 8, 2010 – 4:46pm Permalink | Subthread | Comments top

Summary – My best estimates is that the current leak rate is about 25,000 bpd in a range between 20,000 and 35,000 bpd.

But the total spilled oil is not the 1,200,000 barrels (900,000 to 1,800,000 barrel range) that the media would get by multiplying the rate times the number of days. It is probably considerably less, maybe about 620,000 barrels (300,000 and 1,000,000 barrel range). This is allowing for about 50,000 barrels recovered and at least 90% of the oil prior to the DWH sinking being burned off.

Why the difference? And my convoluted way of getting there.

One of the things that most people seem to miss is that the leak through the BOP has been growing with time.

The original estimate by the government a couple days after the DWH sank was 1,000 bpd based on the size of the oil slick. At this time the slick was small and they weren’t using subsea dispersants.

About 4 days later (Apr 28) they increased that to 5,000 bpd also based on the size of the slick.

I have no reason to believe these estimates weren’t reasonable at the time although there was probably oil being absorbed into the water column that wasn’t being accounted for.

Estimating from oil spills gets more difficult as the spill get larger, the oil breaks into separated strands and dispersants are added. Oil slicks, like mixed phase, turbulent flow is very difficult to gauge accurately. Error rates in the range of +/- 50% are common.

The next estimate was based on a May 11 video of the end of the broken riser released by BP. Professor Wereley of Purdue who estimate 72,179 bpd from the riser and threw in 25,000 from the kink in the riser for a total of over 97,000 bpd. He presented this to the media and on May 19 to a Congressional committee. They made his work public and it was full of errors. I won’t keep beating that dead horse but I wrote some previous comments about his errors. But using his particle velocity measurements (that is his field of expertise) I came up with a range of 8,000 to 24,000 bpd – 16,000 bpd (+/-50%)..

The task force has estimate 12,000 to 19,000 bpd, but they also had one group saying up to 25,000 bpd. We don’t know the date of the spill information or video clips they used. I’m not comfortable with the 12,000 to 19,000 range as that is inside the error range I think is reasonable considering the quality of the data. I’ll go with the 12,000 to 25,000 range.

When BP cut off the riser they estimated an increase of 20%.

Those are the data points we have to work from – very poor and lots of unknowns.

We know from the pressure readings at the BOP that there was a restriction through the BOP that dropped the pressure by 5,000 to 6,000 psi. There was also a pressure drop across the kink.

It was visually apparent that the leak at the kink dramatically increased from nothing in early pictures to a couple small leaks a few days later to about 4 or 5 sizable leaks before BP cut off the riser so we know there is a considerable increase due to erosion.

I tried to make a rough graph of the increase of flow rate over time with this very poor data but it suggests a logarithmic curve with a very high rate of increase in the beginning which decreases with time. This would seem to support some common sense factors. Erosion of the leaks will drop as the volume of the leak gets larger in relation “circumference” of the holes, the driving pressure will drop as the volume increases and there might be a drop in formation pressure.

Taking a wild guess it appears that the increase from the task force report until the date of cutting the riser could be in the order of 10%.

If we try to compile this we get a time line like this:

April 23 – 1,000 bpd (+/-50%) – US government from spill
April 28 – 5,000 bpd (+/-50%) – US government from spill
May 11 – 16,000 bpd (+/-50%) – Wereley modified by me
May 20? – 18,500 bpd (+/- 35%) – task force (date of data unknown)
June 5 – 21,000 bpd (+/-40%) – before risers cut based on log curve growth
June 5 – 25,000 bpd (+/-40%) – after riser cut based on BP’s 20% increase

Because BP is recovering 15,000 bpd and there is still flow through 2 or 3 relief valves that appear to be about 4” dia plus some leakage at the bottom of the cap I feel safe in putting the bottom limit at 20,000 bpd.

And I think the flow rate is probably close to or at its maximum barring any additional damage to the plumbing. Further erosion will probably be offset by decreases in formation pressure.

By the way, BP has never made a public estimate of the flow, every time the media attributed a flow rate to BP it was actually from NOAA or the USCG. That was confirmed by Admiral Allen on Monday.

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