[dorlomin]

When I first heard about this I had assumed it would be quite old to be so deep underground (10km) But apparently it is "Lower Tertiary trend", this means its younger than 65 million years. How does such young oil get burried underneath so much sediment compaired to the other fields around it?

(Stupid question perhaps but I am curious)

[Auntie_Cipation]

When I first heard about this I had assumed it would be quite old to be so deep underground (10km) But apparently it is "Lower Tertiary trend", this means its younger than 65 million years. How does such young oil get burried underneath so much sediment compaired to the other fields around it?

(Stupid question perhaps but I am curious)

I'd like to know more about this too. I was told, by someone who believes in abiotic oil, that the rock at this depth is "basement rock" -- never been moved or metamorphosed, never been part of the surface.

I looked up abiotic oil in Wikipedia, expecting to find it described as a crackpot fringe theory, but apparently there are more people who believe it than I realized, and more apparent evidence as well.

I don't buy it, but I can not usefully explain why not.

[jeromie]

Add me to that list too. The more interesting aspect to me about this find is the finding of multiple reservoirs so deep. A couple weeks ago, Iran found a lot of oil under existing fields in reservoirs beneath their main pay zone well depth. This find buttresses the finding of Residual Oil Zones beneath the original Pay Zone in US pools where the pool was subjected to regional tilting early in the formation period of the oil pool.

Almost invariably US oil wells never went deeper than just above the oil -water contact line. Long term experiments by a couple of US producers drilled deeper than the oil-water contact line and found the residual oil zone beneath the area where the oil and water are essentially emulsified. These ROZ zones increase the available oil for production. Since, these discoveries are in fields already well advanced in secondary recovery ( water flooding) it will require Enhanced Oil Recovery methods to recover the oil.

My big question is what would the result have been had the primary recovery well depths have been first put down through the Pay Zone to the ROZ?


So we now have oil at very deep levels where the oil supposedly the oil had long ago been converted to gas from the heat.

This Tiber well on land would have been to a depth of 31,000 feet. The usual stuff taught in beginner oil geology is that beyond 7500 feet to 10,000 feet the oil had cooked into gas.

I suspect some new understandings are emerging about oil.

[copious.abundance]

When you read about deepwater finds you kinda sorta need to ignore the water depth. The only thing that really matters is how deep in the *crust* of the earth the oil is.

Let's say you have a land oil reservoir at 15,000 feet. Not hard to believe. Now, put another 15,000 feet of water above it for a total of 30,000 feet. 30,000 feet sounds like it might be too deep for oil without cracking into gas, but it's really only 15,000 feet beneath the surface of the crust of the earth, so it shouldn't be any more hard to believe than a land oil field 15,000 feet deep.

At least that's my understanding.

[copious.abundance]

Here's the actual depth figures:

>>> LINK <<<

-The well, located in Keathley Canyon block 102, 250 miles (400 kilometres) south east of Houston, is in 4,132 feet (1,259 meters) of water.

-The Tiber well was drilled to a total depth of 35,055 feet (10,685 meters) making it one of the deepest wells ever drilled by the oil and gas industry.

So jeromie is right, it *was* below 30,000 feet if drilled on land.

Perhaps the combination of the relatively young age coupled with the deep depth means that it didn't have enough time to crack to gas yet???

Good question, now that I see the #'s.

[jeromie]

The iron clad adage in oil was no oil below 15,000 for years and years. Deffeyes in his book makes a big point about the oil zone being 7500 feet more or less. Well, we have a number of cases now with major oil possibilities well over 20,000 feet deep excluding water depth.

I tried to find out a number of times if this very deep oil had different characteristics than shallower oils and found nothing to indicate a difference that would allow this very deep oil to not cook away from geothermal heat. So far, anyway.

A rather pet interest of mine is the deeper oil of the Appalachin Basin. The wells were shallow and shut in long ago. I have run across oil people commenting that the Appalachin Basin is the least explored basin in North America . These oil pools were barely tapped before losing pressure. Anyway, I wonder if these deep oil pools have qualities similar to Appalachin oils.

Oil orthodoxy seems to be under challenge from a number of key former iron clad rules now violated.

I looked into what BP is doing in both of their deep well blocks in the Gulf and they seem to be opting for Enhanced Oil Recovery from the start. That is very advanced Game Changer CO2 where secondary water flooding is completely omitted . One would think at those depths the associated gas pressure would be awesome.

[Plantagenet]

Marine sedimentation rates are high off active major deltas like the Niger Delta, the Amazon Delta, the Ganges Delta and the Mississippi Delta. As a result you can get relatively "young" sediments buried quite deeply.


Ganges River Delta

[DantesPeak]

I went back and reviewed all the press releases. BP clearly states that this discovery is in terms of barrels of oil equivalent, which includes natural gas. You may remember that Tupi off Brazil is mostly natural gas, and not oil - although the oil they get is expected to be high quality.

No one has made it clear what the ratio of oil to NG is at Tiber.

[dorlomin]

Is it possible that large amounts of sediment have depressed the underlying crust and so the deeper rock is not quite so hot as otherwise?

And as I remember the oil window extends down 6 miles so 10 km would still be in that plausible vicinity. The key is offcourse temperature not depth.

[surfzombo13]

Is it possible that large amounts of sediment have depressed the underlying crust and so the deeper rock is not quite so hot as otherwise?

Could be. The weight of the Greenland ice sheet depresses the center of that landmass.

[SteinarN]

Is it possible that large amounts of sediment have depressed the underlying crust and so the deeper rock is not quite so hot as otherwise?

And as I remember the oil window extends down 6 miles so 10 km would still be in that plausible vicinity. The key is offcourse temperature not depth.

Yes, I read somewhere that the temperature was surpricingly low for it's depth, and that was the reason for oil existing at all at such depths.

Doing a little math, 0.2mm sedimentation each year in 50 million years will yeld a total of 10km of sediments. 0.2 mm/year is not unheard of, especially not to far from a big river delta.

[PrestonSturges]

Large areas of the shallower sediments slide into deeper water. These are big areas, miles across and thousands of feet thick, slipping into deeper water. I ve seen this on maps, and they look like earthquake fault lines..

I think they are generally able to handle this jumbled geology with better seismic mapping techniques, so that it is now worthwhile to do exploratory wells at greater depths. And a lot of these deposits are subsalt (under salt domes), so these trenches were ancient dead seas that collected salt when the Gulf dried up.

Managing output from these fields at depth is complicated because wierd things happen at these depths and pressures, and the geology is complex.

[copious.abundance]

I went back and reviewed all the press releases. BP clearly states that this discovery is in terms of barrels of oil equivalent, which includes natural gas. You may remember that Tupi off Brazil is mostly natural gas, and not oil - although the oil they get is expected to be high quality.

You are wrong. Tupi is mostly oil, not natural gas.

[copious.abundance]

As already explained to Dante last year:

>>> 9 posts down <<<

Oil from the Tupi area is 28-30°API with a gas/oil ratio of about 15-20%

[DantesPeak]

That's old news. Petrobras is finding more gas and less oil than they originally thought.

Basically at the initial Tupi well, they are flaring off most of the gas to get the oil.

Platts Oilgram News

July 9, 2009

Pre-salt Santos well off Brazil seems a bust

Hess also said it will expense the well cost in its second quarter earnings, which to Leite provides further evidence that Guarani is a dry hole. Leite, in a July 8 report, said the well was spudded in March, reached a total depth around 5,404 meters and took 118 days to drill.

Leite said Guarani, drilled on the giant Tupi sub-salt cluster, "reinforces our view that...pre-salt exploration blocks are not 'winning lottery tickets,' as suggested by Petrobras in the early stages of the regulatory discussions on the pre-salt."

The fact that the well was not a discovery also suggests "the larger potential of the pre-salt lies in the northern part of Tupi cluster" rather than the southern section where Guarani was drilled, he said.


Meanwhile, Leite said he believes Seadrill's West Polaris drillship that drilled Guarani will be sublet to Petrobras to explore elsewhere on the Tupi structure.

"Recent news suggests the rig could stay with Petrobras until year-end 2010," he said. "Therefore, we would not expect definitive news on the BM-S-22 before 2011...we see this postponement as a sign of the consortium's lower confidence in the block."

Leite said BM-S-22 was an especially prized block in the Tupi cluster that Petrobras discovered in November 2007 and which quickly became one of the world's most-heralded new oil finds. At the time, the Brazilian company estimated the Tupi structure at recoverable reserves of 5-8 billion barrels of oil equivalent.

But BM-S-22 always carried risks, as Leite outlined in a report last month. Azulao was "somewhat disappointing," he said, despite two oil find notifications sent to ANP in January and February.

And apparently there was "significantly lower" carbon dioxide in Guarani than in the previous successful pre-salt wells, "which would indicate lower oil volumes," said Leite. Also, oil-water contact was evidently found, an undesirable result that "would essentially eliminate the chances of substantially more oil in deeper horizons," he added.

The analyst said he does not question the "huge potential" of the pre-salt play, but rather noting "risks do exist and that expectations on the overall story need to be moderated somewhat."

Credit Suisse had estimated 5 billion boe of resource for BM-S-22 alone, but Leite now says that will need to be "revised downwards significantly, as will (probably) our 36 billion boe estimate for the Tupi cluster as a whole."

http://www.mcgraw-hill.com

[copious.abundance]

Your article says absolutely nothing about the oil-gas ratio of Tupi.

[DantesPeak]

Your article says absolutely nothing about the oil-gas ratio of Tupi.

Funny how you failed to address the issue of BOE gas that is being flared off. So that BOE claimed may be a lot less if they don't plan on selling the gas.

If you have any newer information about how well Tupi is doing, why don't you go ahead and post it.

[copious.abundance]

Your link did not say anything about burning off gas at Tupi. It talked about a disappointing well at Guarani, which is old news by now. Oil exploration involves risks, and this is one of them. Dry holes do happen.

Here is a map of the blocks in the Santos Basin. Tupi is on BM-S-11. Guarani is on BM-S-22, some 75-100 km to the southwest. They are not even the same structure.



Your own article even says:

The fact that the well was not a discovery also suggests "the larger potential of the pre-salt lies in the northern part of Tupi cluster" rather than the southern section where Guarani was drilled, he said.

The northern part of the "Tupi cluster" (which should more accurately be worded "northern part of the Santos Basin") is where Tupi is. Thus, your own article confirms the prospectivity of the Tupi field.

[joewilliams]

The sedimentation rate in GOM is very large as has been pointed out. You can get deep, recent sediments.

The depth (below mudline) to 300 Farenheit is shown in this map:

http://www.searchanddiscovery.net/docum ... ges/08.htm

I'm not sure where tiber is but Keathley canyon is just West of the dark blue stuff. I bet it's in the greenish depth - say 31000 ft BML for 300F

I think the oil window is up to 160C (320 F):
http://www.nuclearhydrocarbons.com/OilWindow.htm

Looks plausible that tiber is oil.

Onshore, sediments are hotter due to contitental crust radioactivity.

[TheDude]

That same map was posted at TOD a few days ago. ROCKMAN elaborated a biton how oil is found at such great depths in this spot:

We all know temp increases with depth. The reason some gradients are so low in the GOM is the rapid deposition in some areas. I don't have numbers at hand but I imagine some older areas in the mid-continet hit temps at less then 10,000' which are much higher then you find at 20,000' in the GOM. There is an area just south of New Orleans which has an unsually thick and young sediment dump. A well 15,000' would have a BH temp as low as one at 9,000' just a 100 miles away.

Here is the S&D paper that graph's from: Geothermal Gradients and Subsurface Temperatures in the Northern Gulf of Mexico, by Joseph Forrest1, Ettore Marcucci and Paul Scott, #30048 (2007). Table 1 shows the range of depths 300F temps are found - the maximum being in Walker Canyon where they've been encountered 56k feet down. Deffeyes no doubt knew about this, for his books he likely left out describing these exceptional situations for the sake of brevity.

Was surprised to find that reservoirs have been found in Pleistocene sediments, too. Doesn't take long for these turbridites to do their thing, apparently. But what triggers the source rock to yield up the hydrocarbons? Faulting? Seems curious that they'd still be active at this late stage.