DeepWater Horizon-- Digging for Facts

Various --- Oil Drum initially ^ | June 21, 2010 | Ernest at the Beach

[Ernest_at_the_Beach]

An attempt to look thru various sources and answer some basic questions .

1. Can we get a handle on a basic Fact ...What was the pressure at the bottom of the drilled hole in the formation ?

From the Oil Drum:

BP's Deepwater Oil Spill - Matt Simmons on Dylan Ratigan Today, Closing the Relief Ports, and Open Thread 2
Comment by avonaltendorf on June 8, 2010 - 12:06am

Thread Posted by Prof. Goose on June 7, 2010 - 9:00am

***************************EXCERPT*************************************

Comment by avonaltendorf on June 8, 2010 - 12:06am

I received a personal note, which I acknowledge gratefully.

Down to business. I agree with Matt Simmons and posted as much evidence as I could garner from publically available ROV feeds. We aren't being shown the IR or sonar images. Low res video is crap compared to what the ROV pilots and BP folks are looking at. Obviously USCG is in the dark or has been ordered to follow the White House playbook until they get a handle on how big a problem they have. In my view, it is a medium-sized problem, not quite as gigantic as Simmons suggested to Ratigan.

**********************************snip***********************************

Let's roll the movie back to the events of April 20. Simmons thinks that the reservoir pressure is 30,000 psi judging by the force of the blowout. This is clearly impossible. If true, it would have blown out immediately on penetration April 17. The scout ticket tells us that the pressure at the top of the reservoir was no greater than ~13,000 psi based on mud weight to control lost circulation:

LWD (RLL, BATSON, PWD) @17173, M 14.1, NO SWC, 9 7/8 LNR @14759-17168, LOT 15.9, LWD (RLL, BATSON, GEOTAP, PWD) @18260, LOST CIRC W/14.4 MUD, C&C SPTTD LCM

LWD=Logging While Drilling
RLL=Recorded Lithology Log with gamma ray and resistivity
NO SWC=No Side Wall Cores

PWD=Pressure While Drilling
LOT=Leak Off Test to measure strength of wellbore wall

At 18260 ft, Lost Circulation with 14.4 lb/gal mud, then Circulated and Conditioned the mud and Spotted a Lost Circulation Material pill to cure the losses. They had drilled into the top of the reservoir (gas cap) and mud started leaking away into the reservoir, because 14.4 mud weight was greater than the reservoir pressure. Assuming a vertical well, reservoir pressure was less than 14.4 x .052 x 18260 = 13768 psi, or mud would not have been lost.

It was a slow process of gas reaching bubble point plus a nonsense negative test ordered by Kaluza that sandbagged the drillers into displacing to seawater without watching mud returns or understanding what was happening. When a gas bubble formed it expanded rapidly as it travelled up the riser unopposed, blowing out the seawater and mud. It was followed by very light liquid and more gas. The BOP did not fire on EDS from the bridge because hydraulics were gone or malfunctioned, but there was mux control to one or both of the pods. Only when the rig sank and riser collapsed did the BOP see a "deadman" condition and attempt to shear the drill pipe -- except by then it was clogged with debris and couldn't shear or close fully.

Thus we have gas and light oil at low pressure spewing from the riser swivel. Below the BOP should be ~8,000 psi, which is sufficient to find paths of opportunity to nearby vents. However we have to keep in mind that collapsed casing and broken cement gives the reservoir a path to salt welds (thin mostly vertical remnants of salt withdrawl) and fractured slump faults. It is therefore possible that light oil at 13,000 psi could migrate updip miles away.

I posted such evidence as I found. It is not enough to prove anything, but convinced me that Simmons knows the deepwater GoM geology.

[Wonder Warthog]

":1)Hydrogen Sulfide (toxic, flammable) safe levels: 5-10 ppb tested: 1200 ppb 2)Benzene (toxic, carcinogen) safe levels:0-4 ppb tested: 3000 ppb 3)Methaline Chloride (toxic, flammable) safe levels:61 ppb tested: 3000-3400 ppb"

This is ALL bullshit. 1.2 ppm of H2S is NOT harmful by any mechanism. Its one characteristic at the level is that it smells bad. Benzene is "slightly" carcinogenic. To develop the very rare cancer involved takes years-long exposure. And "methaline chloride" (correct spelling is "methylene chloride") is not found in oil at all. So if anyone says it is, they are lying in their eye teeth.

[a real Sheila]

does anyone know the inside diameter of the relief well pipe at the bottom where it is to intersect the current well?

[Ernest_at_the_Beach]

Man, system is still very slow this morning...

Thanks for that link...

13,000 psi is looking very credible.

[Ernest_at_the_Beach]

Thanks.....

This system is so slow,...I think I will turn to other things....

I am sure John is working hard to get the weekend troubles behind us.

[Ernest_at_the_Beach]

I do not know....I'll look later today on the Oil Drum after I get back from a dental appt.

Somebody may answer earlier.

[Gondring]

Someone is pulling your leg in a major way, as both CharlesWayneCT and Wonder Warthog have pointed out.

For example, look at the EPA's air monitoring page:
http://www.epa.gov/bpspill/air.html

The results of sampling for Florida are at http://www.epa.gov/bpspill/data/air_sampling_update.pdf
I think someone might not understand the units in use, too. These are in micrograms per cubic meter.
Funny aside: note that someone tried to copy ug/m3 down, and it made ug/m4, ug/m5, etc. :-) With all the money they spend, it's sad they are entering data by hand and have such a clunky interface.

And check out the USGS earthquakes: http://earthquake.usgs.gov/earthquakes/recenteqsww/Maps/10/275_30.php

Clean as a whistle when I look.

[Marine_Uncle]

One hardly knows what to believe is the true condition at this well bore site. To many wide variance in pressure numbers and barrels per minute/hour/day being leaked at any given orifice or from the seabed, to know what to think at this point.
And as for the supposed huge oil plumes. What would keep the oil from rising to the surface based on the specific gravity of salt water verse oil.
To much does not seem to be accurate reporting.

[Smokin' Joe]

The initial mud weight I recall was 16.8 lbs/gal. Doing the math, the hydrostatic from that mud weight before the riser was displaced is: 16.8*.052*18000=15724 psi at 18000 ft.

Displacing the riser would have dropped that hydrostatic (at full displacement with seawater) by (16.8-8.5)*.062*5000=2158 psi. which leaves 15724-2158=13566 psi of hydrostatic pressure at 18000, and the formation flowing. Formation pressure is somewhere between the two, because the riser was not yet fully displaced when the formation began flowing.

Pressure at the wellhead would be the difference between formation pressure and the hydrostatic pressure from the fluid column in the wellbore, and the question there remains one of how severely gas cut that column is. If the oil/gas mix has a weight of 5 lbs/gallon, the pressure at the wellhead would be from 13566-(5*.052*13000) to at the high end 15724-(5*.052*13000), or from 10186 psi to 12344 psi. It all depends on the gas cut in the fluid column and the density of the oil.

Keep in mind, there are a lot of dynamic factors ignored here, (sidehole friction, ECD, and any constrictions in the wellbore) this is just an offhand calculation of a range of static pressures, and not solid as fluid mechanics go.

[SunkenCiv]

:’) Thanks Ernest_at_the_Beach. And happy belated birthday (hope I didn’t let any cats out of any bags).

[Ernest_at_the_Beach]

LOL...thanks.

[dixiechick2000]

You are amazing! Thank you for generating the replies...

and happy birthday. ;o)

[Ernest_at_the_Beach]

Well,...thanks...not sure what I did.

Around here you just post something .... ping a few people.... and experts join in and supply info...

This "community" is amazing.

[Ernest_at_the_Beach]

Today's Dialogue at the Oil Drum really gets into why 100,000psi is not the psi in the formation...

well's borehole pressure

*************************************EXCERPT*************************************

I have spent the past 30 min looking for a good ref for over burden the source of the well's borehole pressure and haven't located one.

A good rule of thumb is .45 psi per foot of depth for sea water column and .75 psi per foot for rock formation.

The oil/gas zone is permeable, that means there can be no differential pressure between 2 points in the permeable zone except for the differential depth. So yes it's like a tire, except when it's flowing, pore size changes flow rates within the formation but not greater than the initial pressure.

Believe rock he has good explanation.

We need to put this 100,000 psi nonsense to rest. It makes TOD look less than reliable for facts.

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ROCKMAN on July 3, 2010 - 1:02pm Permalink | Subthread | Parent | Parent subthread | Comments top

Chip -- Dig thru the doc and you'll find a pressure plot. From the log data they estimate the OBG (overburden gradient) to be around 16 - 16.3 ppg. They probably used the wire line density log to come up with a site specific OBG. You'll also notice the frac gradient is in the upper 15’s. I suspect the low FG is why they’re setting csg just above the intersect: cut down the possibility of lost circulation.

ppg.http://energycommerce.house.gov/documents/20100614/BP-Production.Casing.TA.Options-Liner.Preferred.Long.Version.pdf

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geek7 on July 3, 2010 - 1:29pm Permalink | Subthread | Parent | Parent subthread | Comments top

I think one doesn't need a good reference to come to a conclusion that 100,000 psi is VERY suspect. Here is what I did:

To have a high pressure there must be a great weight of overburden. I convert psi to lb per cubic foot. I know that 5000 ft of column is H2O and that the remaining 13000 ft are something else. I propose a two layer model x feet of shale (because shale is a very common geologic deposit in places where people drill for oil, density 167 lb/cuft) and y feet of gold (because its density is high, 1204 lb/cuft). I then have two equations in two unknowns:

(100000 psi)*(144lb/sqft/psi)-(5000ft*62.4lb/cuft) = 1204 * x + 167 * y
and
13000ft = x + y

I solve for x and y and get:
y (thickness of shale) = 1508 ft
x (thickness of gold) = 11,492 ft

Anything less dense than gold does not have a solution. (And there is nothing on Earth more dense than gold.)

So, to believe that 100,000 psi number, one has to believe that BP drillers are so focused on finding oil that they ignored 11000 ft of strange shiny metal in the mud returns. IMHO, there is something really wrong about this model. Maybe, just maybe, 100000psi is simply wrong.

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WebHubbleTelescope on July 3, 2010 - 1:57pm Permalink | Subthread | Parent | Parent subthread | Comments top

That's a beauty of an analysis. Sticking gold in the equation is genius as it both gives you a solution and points to its preposterousness.

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manofmetal on July 3, 2010 - 2:05pm Permalink | Subthread | Parent | Parent subthread | Comments top

Did you pick up any of your knowledge building a dam on the Arkansas river in the 1970's.

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wrb on July 3, 2010 - 2:11pm Permalink | Subthread | Parent | Parent subthread | Comments top

So the NWO is keeping the gold secret?

Probably plan to flood the market as soon as everyone has converted their savings to gold.

Dastards.

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lotus on July 3, 2010 - 2:13pm Permalink | Subthread | Parent | Parent subthread | Comments top

Dang it, boy! Oh, my poor drowned keyboard.

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sunnnv on July 3, 2010 - 3:02pm Permalink | Subthread | Parent | Parent subthread | Comments top

(And there is nothing on Earth more dense than gold.)

http://en.wikipedia.org/wiki/Density#Densities_of_various_materials

Ummm - what about Platinum, Iridium and Osmium?

One might say "Gold is one of the most dense metals/elements known".

Au 19,250 kg/m^3
Os 22,610 kg/m^3 - 17 % more dense.

Otherwise - a good analogy, thanks for QUANTIFYING things with real numbers.

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motownmutt on July 3, 2010 - 7:39pm Permalink | Subthread | Parent | Parent subthread | Comments top

(And there is nothing on Earth more dense than gold.)

'ceptin': 19.32 g/cc Gold Au 79
19.35 g/cc Tungsten W 74
19.84 g/cc Plutonium Pu 94
20.2 g/cc Neptunium Np 93
21.04 g/cc Rhenium Re 75
21.45 g/cc Platinum Pt 78
22.4 g/cc Iridium Ir 77
22.6 g/cc Osmium Os 76

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manofmetal on July 3, 2010 - 1:37pm Permalink | Subthread | Parent | Parent subthread | Comments top

You are concerned that the Gas pressure in the hole could be up to 100,000 psi. So lets look at the reasonableness of that concern.

Using some simple verifiable facts for a basis of our investigations we can say these things are true and unchangeable:

A cubic foot of water weights 62.4 pounds and has a specific gravity of 1

A cubic foot of limestone has a specific gravity of 2.7 times that of water so it weighs 168.48 pounds.

The well is about 13000 feet below the sea floor that is 5000 feet below the surface or about 18k feet total.

Lets take this step by step:

To estimate total psi of the overburden we can say;

If we stack 5000 cubic feet of water at 62.4 pounds per cubic foot, one on top of the other for 5000 vertical feet we get 312,000 pounds per square foot.
There are 12 inches by 12 inches of area at the bottom of the column so there is 144 sq inches upon which 312,000 pounds rests so we divide and get 2167 psi.

If there is 13,000 feet of limestone that weighs 168.47 pounds per cubic foot and stack that up we get 2,190,240 pounds per sq ft or 15210 pounds per sq inch of overburden.

So we end up with a weight on the formation of 15210 psi and 2167 psi or 17377 psi total weight over the production formation.

So if the weight of the formation is 17K psi and the gas pressure is 11k psi then we are very likely safe assuming that the rock is not holding back gas produced in an area of higher pressure. Logically 17 thousand pounds will hold down 11 thousand pounds.

The rub comes when we look at the totals in a very rough way. There is nearly a pound of pressure per foot if the depth is 18k and the pressure is 17k. Therefore if gas is formed at a depth of 100,000 feet and migrates upward we would be in store for 100ksi pressures that would be held back by a 17k weight. I think we all agree that it is not likely that 17k can hold down 100k of pressure over any geologic time frame, even without the drilling of a well. Therefore any high pressure gas would have leaked out years ago and it is likely that the drill log is right in saying the pressure is in the 11k range. But it is not impossible that gas formed about 20 miles down. And it is possible that it did migrate into the production zone. But it would be a miracle if it stayed there for even a short period of time.

Disclaimer: This is based on very rough numbers and violates rules of thumb that indicate the overburden pressure could be a few hundred pounds less.

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joemichaels on July 3, 2010 - 1:51pm Permalink | Subthread | Parent | Parent subthread | Comments top

Thanks to Manofmetal, Rockman and geek.

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jimvj on July 3, 2010 - 2:27pm Permalink | Subthread | Parent | Parent subthread | Comments top

The above analyses assume that the pressure of the oil in the pocket is entirely due to the weight of the overburden. Is it ever the case that, in addition to overburden, there is pressure due to gas production in the pocket that would pressurize it even more?

The gas production could be due from conversion of liquid oil to gaseous methane, or oxidation to CO2, or even to chemical processes unrelated to the oil.

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ROCKMAN on July 3, 2010 - 3:43pm Permalink | Subthread | Parent | Parent subthread | Comments top

Jim -- That actually is one of the sources of “abnormal” pressure. Normal (or hydrostatic) pressure in the GOM is essentially the pressure from a salt water column at that depth. But “geopressure” develops from of a number of causes. NG generation as one source. Another is actually simpler: is the sediments are compressed during burial and if there are no conduits for the water to be “squeezed” out of the rock the pressure will increase above hydrostatic. This typically occurs when sandstone reservoirs are entirely encased in impermeable shales. That appears to the at least one source of the geopressure in the BP reservoir.

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PaulS on July 3, 2010 - 3:54pm Permalink | Subthread | Parent | Parent subthread | Comments top

There's surely some sort of a limit on how much it can be overpressured beyond what gravity would suggest - after all the shear and tensile strengths of rock are not infinite. So something would fail somehow, and the oil/gas would find its way to the surface...

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MEpatriot on July 3, 2010 - 4:01pm Permalink | Subthread | Parent | Parent subthread | Comments top

How strong is 13,000 vertical feet of rock?

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aflaliz on July 3, 2010 - 5:29pm Permalink | Subthread | Parent | Parent subthread | Comments top

If I understand correctly, the fracture pressure in the Halliburton document's Table 1.11 cited above helps to answer your question. If the pressures are greater than the fracture pressure, the rock fractures and the pressure is released. The estimated fracture pressures are all less than 15000 psi. That is why the 100,000 psi numbers are unbelievable. Those sort of pressures would have fractured the formation.

On a marginally related topic-- mostly out of curiousity -- has anyone run the numbers on how much the pressure should have dropped due to 30+ days of flow? I tried it out, and get a roughly 1000 psi drop, which seems rather high so I might have had an error. I assumed a high permeability-- 1 darcy, a 60 foot reservoir thickness, and 30000 barrels/day outflow.

[Ernest_at_the_Beach]

Let me add this...from the Oil Drum:

Halliburton docs, for reference (see Table 1.11 for pressure stats): http://tinyurl.com/33zsg9f

[Ernest_at_the_Beach]

Update ping.....discussion today at The Oil Drum.

And data from the Halliburton plan for the well.

[Ernest_at_the_Beach]

Link to todays topic from which I excerpted:

BP's Deepwater Oil Spill - Bill Clinton's Views - and Open Thread

Posted by Gail the Actuary on July 3, 2010 - 10:43am

[Ernest_at_the_Beach]

apocalyptic events suggested in the articles at the links below.

Apocalypse in the Gulf: Could a Sinkhole Swallow the Deepwater Horizon Well

http://industry.bnet.com/energy/10005034/apocalypse-in-the-gulf-could-a-...

Gulf Oil Gusher: Methane, Climate & Dead Zones

http://www.huffingtonpost.com/dk-matai/gulf-oil-gusher-methane-c_b_63455...

EPA Says Dispersants OK—But Major Questions Remain

http://ecocentric.blogs.time.com/2010/06/30/epa-says-dispersants-ok%E2%8...

[Sender]

I don't know the technical stuff about calculating the well pressure, but I know that it has to be above the water pressure a mile deep.

I have been wondering, how did the blowout preventer fail? Why is there no way to actuate a manual valve down there by a ROV?

It seems to me that the first requirement for this type of deepwater well would be to have redundant ways to shut it off.

But then, if they could shut it off, it might just blow the valve off the ocean floor and flow anyway.

[Ernest_at_the_Beach]

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[CharlesWayneCT]

It’s funny reading the comments from TOD sometimes. It took a while for example for the commenters to realize that the whole analysis of the weight of the water/rock on the formation was NOT about pressurizing the formation, but was explaining that the formation couldn’t be at a much higher pressure than the weight or else it would fracture the rock and leak out.

You are working to hard in my opinion, but that’s because I’ve pretty much already accepted the 11,000 psi approximation as rational, and don’t feel like I have to keep re-justifying that when people speculated about 100,000psi pressures.

But I guess someone has to do it. I’m more focused on trying to keep people from turning their distrust of Obama into conspiracies about the government trying to hide oil under fresh sand, or the whole “corexit poison rain wipes out america’s breadbasket”.