The life of an oil reservoir
Posted by Heading Out on August 14, 2006 - 11:54pm
Topic: Supply/Production
Tags: depletion, horizontal wells, oil production, water flood [list all tags]
Let me start by assuming that I have a layer of rock that is 300 ft thick, five miles wide and thirty miles long. Let us then assume that this has been folded in the middle, so that it now has trapped oil within all the pores of the rock. And, for the sake of discussion let's assume that it has a porosity of 20%. Now having found this reservoir - which is, let's say some 6,500 ft below the current surface of the ground - back some years ago, the oil moguls of the time decided to drill into it and extract the oil.
Now, this being some time ago, the first thing that our friends did was to drill some oil wells, and this being that long ago they drilled vertical wells one quarter of a mile apart. To make life easier I am now going to consider just a one-quarter-mile section of the reservoir, taken along the length. We assume that the wells are spaced quarter of a mile apart, and that they gave us this one slice. If the slice is 5 miles long, then it has 20 wells set along the section, so that each well will pull the oil out of a box that extends out one eighth of a mile laterally from the well, out toward the next. The total recoverable oil for each well is roughly 10 million barrels, or 30,000 barrels per foot of the oil well in the reservoir.
Showing location of wells quarter-mile apart and in a quarter-mile thick slice along the reservoir. The rock thickness is exaggerated and this is not to scale.
The rate at which the oil flows into the well is related to the difference in pressure between the oil in the rock, and the fluid in the well; the frictional resistance of the rock to the oil flow through it; and the length of the well that is exposed to the rock. Let us assume that the rock resistance remains the same and that production varies directly with changes in the pressure difference and the length of the exposure. And let us start by assuming that the well produces 3,000 barrels of oil a day. (i.e. 10 barrels per foot of well exposed to the rock). Then, in the course of a year the well will produce one million barrels of oil. Connect up the pipes, and away we go.
After five years we notice that the volume coming out of the well is not as much as it used to be, and when we check with the engineer he explains that, as we take the oil out of the ground, so the pressure in the oil reduces, and the flow slows down. Well, bless my bananas, and here we have just promised a new palace to one of the grandkids. So we have a chat with the lads and they tell us of this neat trick they have in Russia. If we pump water into the ground under the oil well, then the water will fill the holes left as the oil leaves, and we can keep the pressure in the oil up, and the oil flow will not drop as fast. So out we go to the site, and we drill secondary wells around the first set that had been put in, and now we pump water back into the ground around the well, and bring the pressure back up to the pressure that we started with. And from then on we are pumping water into the ground as fast, (and soon to tell faster) than we are taking the oil out.
Initial pattern of water flood, adjacent wells flood under the producing central well
Because now there is a little problem that we hadn't thought of when we started this exercise. Over the years we have taken out say 4 million barrels, now as we compress the oil back to the original pressure (we're neglecting the gas issue for now) it will only occupy 60% of the original space, or the top 180 ft of the reservoir. Now at the same pressure we will only get 60% of our original flow, because the length of the well exposed to the rock has been reduced (and flow is related to length and pressure). And this is going to get worse, each year the flow will decline as the length of exposed well in the rock gets smaller.
For example, the next year it will produce at 1,800 bd,(10 barrels/day/ft) but at the end of that year we will have removed (simplifying) 650,000 bd of oil, and so the volume of oil will be reduced by (roughly) 11% of the 6 million barrels we started with, and so the following year the production will come from only 160 ft of the reservoir, and, at the same reservoir pressure, the flow will be reduced because of the shorter exposed length. And the flow will be, accordingly also reduced by 11%, assuming that the overall area remains the same. (Some folks might call this depletion, it is the decline in production with time).
Yikes, and here that palace isn't finished yet. So what can we do. Well it turns out that there is another trick we can pull out of the hat. Apparently some folk in Italy have found a way to turn a drill so that it drills horizontally across the reservoir, rather than vertically down through it. At the same time someone else has come up with this idea, that if you just pump the water in around the edges of the reservoir then it makes a more even lift of the water:oil surface up the well, and there isn't as much chance of water stopping the well from producing while there is still oil available. Bingo, we'll have a couple of those.
We only need two because we can now drill the wells horizontally all the way from the middle to near the edge of the reservoir (one in each direction). So the holes are each two-and-a-quarter miles long and are equal in exposed length to the reservoir of forty of the original wells. Now the length stays the same, but the production drops to 1.5 barrels/ft/day. But, by pumping water into the surrounding wells, we keep the pressure up and hold that production. So now, out of these horizontal wells we get say 18,000 barrels of oil a day. And it keeps pumping. Call the grandkids and have them build an extension on the palace.
Water flood under horizontal wells, in this ideal case the water is fed from the outside of the reservoir and rises as a steady horizontal lift over time - until it reaches the wells.
But wait. When we started doing this, we had taken out of the ground about half of the recoverable oil. We had, in that slice of the reservoir some 200 million barrels of oil. We had produced half of it, and thus had 100 million barrels left. We are now producing it at the rate of 13 million barrels a year (2 wells). But it just keeps pumping, as long as we keep pumping that water in, until . . . . . .the day the water level reaches the horizontal well layer. And we're done, it's all over. Oh, there will be some indications before it happens, water cut will start to rise again, and production drops and this is really an idealized case and production will likely drop before then due to preferential water flow through the ground. But in either case, even if we get all that was there, and we won't, we didn't create any more oil by drilling horizontally, we just got it out faster.
Hmmm! Anyone want to buy a beautiful palace, going cheap, nice view of the Gulf. Peaceful neighbors!
There is one final thought. Our friendly moguls, who gave us that slice, set up the field so that while our slice was producing 60,000 bd, they had another 30 slices, or 7.5 miles of the length of the field also producing, giving them an overall production of 1.8 million barrels a day. After a while they noticed, overall, that the field was dropping in production by 8% a year (they were paying closer attention). To overcome this they just started production in another couple of slices, drilling another 40 wells to make up the drop that year. And so they continue to do this, adding half a mile a year to the length of the reservoir from which they are producing, until, after 45 years, they run out of reservoir to drill in. And in the distance they hear a rather large, rotund lady starting to sing something about "dark, satanic mills".
Now explain to me why Ghawar production is not going to tank if its not already ?
My best guess is that there still able to drill new horizontal wells to offset depletion but it would be nice to just know one fact are the older wells watering out ?
Next can you expand a bit on how the infield drilling offsets depletion how long how much ?
It seems to me that the infield drilling as you get close to depletion results in well that go through there production cycle in a matter of years two to five at most since there basically picking up bypassed oil or oil that would be slow to produce from the current wells because of distance is this true ? So they basically just increase the depletion rate in exchange for keeping production up for say 2-4 years at most. Basically the idea is there extracting out of a much smaller volume then the original field sort of like a mini reservoir a few miles around the well.
Basically the field begins to look like a lot of small fields but pressure mgt is a problem since there all connected.
I'm really really guessing on the production life cycle for infield drilling in depleted reservoirs am I even close ?
What is a normal production profile for infield drilling in old fields.
How many oil fields are now produced with horizontal wells ?
To follow and restate my main question whats the recovery on secondary in field drilling or maintence wells ?
And I have the same questions as the post I'm replying too.
What happens when horizontal wells water out. I've read that if its a multi branch well they will shutoff watered out branches I guess if its not they can put some sort of plug or sleeve in place that covers the offending section but still has a hole in the middle for oil flow.
In general can someone really expand on what happens in older fields using todays recovery methods.
All I know is they drill a lot more wells but it does not stop the decline.
A good remedial instruction on oil field extraction, and all obviously pretty correct.
Of course, the issue still returns to OIP ((Oil In Place) and URR (Ultimate Recoverable Reserves).
It always amuses me to hear people, when the issue of URR is brought up, suddenly often back peddle and say "Well that don't mean anything, what matters is how much can be produced on a daily, weekly, yearly basis, etc.", and then start talking about things like labor shortages, political or war issues, equipment shortages and failures etc.
But if we are discussing geological depletion and using the Hubbert Linearization (HL) none of these "above ground issues" are issues.
The whole idea of HL and geological depletion is based on an very correct count of the starting point. Westexas often makes the argument, the very correct one I think, that at about 50% of Qt, the production will begin to drop, and if you have been using water injection, horizontal drills, and bottle brush along with the 4D finding methods, it may drop quite harshly, since you have been able to evacuate the reservior so efficiently.
Notice, however, the importance of approximate 50% of Qt. To have that number, you must have had a very clear count of what 100% Qt was, or an accurate count of OIP and URR.
This is the problem in fields that have not been third party audited and operated by a firm that has been let us say "restrained" in it's release of information (I may be talking about Aramco, all through it's history, but even more so since 1982.
It goes without saying that the larger the oil fields discussed, the more even a tiny measurement error can mean. A couple of percent difference in URR numbers either way can mean a huge surprise either good or bad, and could move the so called "peak" date by decades. Given that Aramco themselves have estimated their own URR with as much as 100% spread in URR, and outside "guessers" have put the overall OIP and URR both well above and well below Aramco's own top and and bottom estimates,
At some point we are going to have to admit that we have NO IDEA what Saudi OIP and URR ever were, and never did. This is what we should be letting the American people know, and it is equally true of the rest of OPEC and Venesuala and Mexico, among others. It is sheer guesswork.
Westexes makes the case that HL worked on Texas, and worked on the Lower 48. To a lesser extent, it has worked on the part of Alaska we have explored and drilled, and on the North Sea. That is because we started with relatively good information.
There are places where it's anybody's guess: The U.S. Outer Continental Shelf comes to mind, as does most deep ocean prospects. Canada is still guesswork in many places and so is frontier Siberia. These are big areas.
Why would an assumption of the possibility of upside surprise be viable in some of these cases? The major reason is that from 1982 through 1998, oil prices were at historic low prices, inflation adjusted. Oil was flowing cheap and easy from Saudi Arabia, Canterell, the North Sea. Why would oil companies who were busting their butt to return any dividend at all to their own investors and shareholders, spend big money exploring in an environment in which they were having trouble even maintaining their production staff and and infrastructure? Most effort was going to the merger and acquisition efforts just to survive.
Think about that time span again, 1982 through 1998...and with a bit of lag before the money started pouring back in, even a bit longer, you might as well say 20 years.
So we could see some real upside surprises....but the inverse is true too.
I have become more and more convinced that our first and greatest effort MUST be to let the public know that we are running completely blind, and that all possible "case hardening" and contingency planning must be underway. In another string on TOD, there is a story pulled from Energybulletin about the demise of JIT (Just In Time) inventory and planning.
Right now, I cannot imagine anything more dangerous than JIT applied to energy, natural gas and liquid fuel sources. We should be expanding and diversifying our reserve storage, and shifting control outward to small companies, counties, states, maintainence utilities, even hospitals and healthcare agencies. This is the single most valuable thing we can do on a large scale now. Sorry about jumping on the soapbox, but please, think about what I am proposing. It has very little downside and great potential to prevent chaos.
Roger Conner known to you as ThatsItImout
http://resourceinsights.blogspot.com/2006/08/is-just-in-time-nearly-out-of-time_13.html
Oddly, I encountered it (and its info about wheat shortages) about 5 minutes before reading this: http://www.theglobeandmail.com/servlet/story/RTGAM.20060813.wEthanol0813/BNStory/National/home
Strange. I read the Kurt Cobb article referenced in EB and saw nothing about any actual demise in JIT practices. AFAIK, Toyota is still very JIT and trying to get even more of its suppliers to be so. Is there any evidence that JIT is in decline?
What is the 'punishment' for not doing JIT?
- need a warehouse (land and building are taxed)
- taxation on items in inventory
- oppunity cost of using the space for some other purpose (vs the oppertunity cost of not having whatever part)
Without change on taxation, why would anyone move away from JIT?Even discounting ANY taxation inventory has a running cost : the capital used (warehouse+stock proper) x interest rates.
Among the best examples that it is the very logic of markets/efficiency/profits which runs counter the safeguarding of "mission critical" operations.
Some kind of regulation is therefore in order, but that does not mean GOVERNMENTAL regulation.
The only safe regulations would be cultural/societal regulations, but establishing those takes TIME.
Any idea for speeding up such changes?
BTW, I know I am "banned" but to emphasize the sillyness of this you may notice that I was the first to publish the link to Kurt Cobb's article without anybody noticing.
Did I say morons?
(Yeah! I am still awkward, got 42 points)
VS the cost of being without.
Taxation just makes sure you let someone else hold the inventory bag.
The only safe regulations would be cultural/societal regulations, but establishing those takes TIME.
Any idea for speeding up such changes?
Oh, how about a change in the artifical regulation which favors the largest merchants like the tax code?
sillyness of this you may notice that I was the first to publish the link to Kurt Cobb's article without anybody noticing.
You want a medal or just a chest to pin it on?
By this do you mean that the taxation "incentive" results in someone else up the supply chain to bear the cost of inventory so that it makes no difference overall?
This is wrong in all cases, with "taxation incentive" or just the running cost of capital, because :
1) Being subject to the same "incentives" suppliers will have the same policy of reducing inventory.
2) Even is for some reason (dumbness or technical constraints) they do not reduce their inventory they have no reason to INCREASE it.
Therefore the portion of YOUR inventory that you dropped off by JIT is still subtracted from the grand total of all RESERVES along the supply chain.
The "total slack" of the whole chain at the consumer end is decreased.
Yeah! Inventory is doubleplusungood, well known...
http://www.theoildrum.com/story/2006/8/14/9102/35436#11
the link to Is just-in-time nearly out of time? by Kurt Cobb
was posted
At Monday August 14, 2006 at 11:18 AM EST
http://www.theoildrum.com/comments/2006/8/13/232547/321/32#32
was posted with a link to the same material.
So when you said "you may notice that I was the first to publish the link to Kurt Cobb's article " what point were you trying to make?
It's getting tiresome isn't it?
Not only am I a sucker but I am patient.
However, there is more to the point!
If you brought in this topic yourself:
Will the just-in-time religion which swept the world in the 1990s survive such a dynamic?
(so long as the tax code punishes firms for having stock on hand, yes)
It seems this was only to argue against taxation, as you repeated in this thread.
So your biases are beginning to show more clearly.
Am I wrong?
Yes, you are wrong. Feel better now that you have the affermation and attention seeking you want so badly?
So you are DENYING that you are spitting out bullshit in favor of lower corporate taxation and, as a general policy of yours, trying to deviously support the interests of the wealthy and "business as usual" at the expense of survival of mankind and earth current ecology.
Could you back up this gratuitous "affirmation"?
Not only are you a stalker, but you are a poor one. Not actually READING what is posted.
My, my, my.
The tax law exists to benefit large corporations.
Let me repeat that, because you might not understand.
The tax law exists to benefit large corporations.
Large corporations can buy a large number of items and move them through the market chain. If I wish to have built a plastic mold and make lids similar to the tattler lids, I bet I can undercut the $13 per dozen price easy. But, because I do not have a large corporations supply chain, I'm stuck with 4,183,000 lids at the end of the 1st year. As the cost of energy goes up, the remaining lids have FAR more value, not to mention increased demand of home canning lids. Which would be a fine thing (the building is paid for, the storage space is not all that great), but the taxes on inventory kills me over time. And the arms length rules prevent me from dropping the $250k on making the lids, then selling the unsold lids for $10 at the end of the year to myself. Or any of my relatives.
But you go right ahead and think that I'm all about "lower corporate taxation" because that is what gets you to post again and keep your attention seeking behavior engaged. If your attention is hear that means you are not misbehaving in meatspace, and humanity is well served.
Roger, your statement is false. Sorry, but we've got multiple lines of evidence pointing to troubling conclusions including
And there are others I didn't mention. Why do you say we're running blind? HO's story tells us about onshore oil production in older existing fields and mitigating declines there. It's one line of evidence (2nd bullet point above).
For those commenting on JIT etc., there will be an open thread today. I suggest you use it.
-- Dave
I am in a bit of a hurry and have to head out, but just to get you started....I threw together some quick finds....point to be made, we have no idea how much oil and gas is out there....I will talk more on this later....
http://www.msnbc.msn.com/id/5945678/
"A lot depends, of course, on just how much oil remains underground. Many of those who fear a production peak is imminent base their forecast on estimates of what geologists call the "ultimate recoverable resource" of about 2 trillion barrels of oil. But there's disagreement among geologists on that number. A comprehensive study by the U.S. Geological Survey in 2000 estimated that some 3 trillion barrels of oil will ultimately be produced. Adelman argues that the amount of oil left to be produced is "unknowable."
Regardless of how much oil remains in the ground, says Deffeyes, the critical bottleneck is production capacity. "I can't drive into the filling station and say fill her up with reserves."
Deffeyes argues that production capacity has grown more slowly than demand - based on production figures that are a lot more reliable than reserve data.
"Production is a pretty firm number," he said. "Oil gets counted twice: once when it gets produced and once when it goes into the refinery. So we pretty much know how much is produced, and my Thanksgiving Day prediction is entirely based on production."
In case you missed it, peak was in 2000 (at least that's what they said in 1995
http://dieoff.org/page85.htm
http://www.moles.org/ProjectUnderground/motherlode/drilling/frontier.html
The ultimate amount of conventional oil and gas resources left to be discovered in the world is an even more divisive topic. Writing in the March 1998 edition of Scientific American, two oil industry analysts argue that there is only 150 billion barrels of conventional oil left to be discovered. The US Geological Survey estimates that approximately 530 billion barrels more remain to be found.6 Another recent study indicated that the ultimate resources of conventional oil could be two to three times as great "depending on the price consumers can afford to pay."7 Natural gas, all agree, is somewhat, but not drastically, more plentiful.
Roger Conner known to you as ThatsItImout
Of course, we can't afford to pay more in energy terms than it takes to get it out. But don't tell that to an economist.
It just isn't very profitable. Think of energy expensive oil as a sort of natural coal-to-liquids plant. If it's cheaper than making methanol, it works just as well.
Except that it doesn't have great potential. I have documented the fact that the oil industry is not, has not, and never has practiced JIT despite repeated accusations. Even The Oil & Gas Journal issued an apology for having mischaracterized some practices as JIT. If they actually practiced JIT, we would all be better off for the same reasons that Toyota is kicking the snot out of GM and Ford with it: properly understood and applied, it reduces risk, cost, and quality problems simultaneously. It's no accident that Toyota jumped to the fore of the hybrid manufacturers and that they are the creator of JIT.
News of the demise of JIT has been greatly exaggerated. We would all be better off if people learned what JIT is rather than what they think it is. It is not simply cutting storage.
20 ft max each, maybe totalling 300 at times in the old days. Most new fields that I have experience with are 8 ft thick max and down to 3 ft. These are carbonate zones with porosity of closer to 8 percent and they do not produce at all unless drilled horizontally and even then require high pressure sand fracing. Maybe deepwater GOM has thicker zones with greater porosity but I haven't been there in 20 years. Most of those are drilled directional but not horizontal. Most sand reservoirs do not respond as well to horizontal drilling as carbonates. I am not a reservoir engineer however but have more experience on the drilling side of things.
The success of a well depends on "where" you drill in the zone, not just by virtue of drilling horizontally. For instance, if you stay within the upper section of the zone where the hydrocarbons are you may have a producer. Screw up and drill into the lower section where the water is and you have a very expensive water well. The experience in this type of drilling is actually quite limited in the industry. Last time I looked only 8 percent of the total rig count were drilling horizontal wells. It could be up somewhat from that now. Add to that new tricks such as dual laterals and tri laterals where the experience level is even more limited.
There is a change in mindset that a oil company has to go through to have a horizontal drilling program. In the past on vertical wells, all the decisions were made top down from the office. In a horizontal or "geosteered" well, things can change from one minute to the next depending on dip of the formation or perhaps even drilling though a fault. Top down companies pick up off bottom and circulate for hours trying to get someone to make a decision. Consequently they end up spending twice as much money on the well. They blame
"doglegs" for why they give up on horizontals.
As far as horizontals draining the reservoir sooner- perhaps , but my experience is that in the zones we drill it is horizontal or it is nothing. It is not an easy business and there is never a sure thing. Even a potential good well can be screwed up due to human nature.
Good subject for the experts here to shed light on for us?
Most geologists view crude oil, like coal and natural gas, as the product of compression and heating of ancient organic materials over geological time. According to this theory, oil is formed from the preserved remains of prehistoric zooplankton and algae which have been settled to the sea bottom in large quantities under anoxic conditions. (Terrestrial plants tend to form coal, and very few dinosaurs have been converted into oil.) Over geological time this organic matter, mixed with mud, is buried under heavy layers of sediment. The resulting high levels of heat and pressure cause the remains to metamorphose, first into a waxy material known as kerogen which is found in various oil shales around the world, and then with more heat into liquid and gaseous hydrocarbons in a process known as catagenesis. Because most hydrocarbons are lighter than rock or water, these sometimes migrate upward through adjacent rock layers until they become trapped beneath impermeable rocks, within porous rocks called reservoirs. Concentration of hydrocarbons in a trap forms an oil field, from which the liquid can be extracted by drilling and pumping.
Geologists often refer to an "oil window" which is the temperature range that oil forms in--below the minimum temperature oil remains trapped in the form of kerogen, and above the maximum temperature the oil is converted to natural gas through the process of thermal cracking. Though this happens at different depths in different locations around the world, a 'typical' depth for the oil window might be 4-6 km. Note that even if oil is formed at extreme depths, it may be trapped at much shallower depths, even if it is not formed there. (In the case of the Athabasca Oil Sands, it is found right at the surface.) Three conditions must be present for oil reservoirs to form: first, a source rock rich in organic material buried deep enough for subterranean heat to cook it into oil; second, a porous and permeable reservoir rock for it to accumulate in; and last a cap rock (seal) that prevents it from escaping to the surface.
If an oil well were to run dry and be capped, it would be back to original supply rates eventually. There is considerable question about how long this would take. Some formations appear to have a regeneration time of decades. Majority opinion is that oil is being formed at less than 1% of the current consumption rate.
The vast majority of oil that has been produced by the earth has long ago escaped to the surface and been biodegraded by oil-eating bacteria. What oil companies are looking for is the small fraction that has been trapped by this rare combination of circumstances. Oil sands are reservoirs of partially biodegraded oil still in the process of escaping, but contain so much migrating oil that, although most of it has escaped, vast amounts are still present - more than can be found in conventional oil reservoirs. On the other hand, oil shales are source rocks that have never been buried deep enough to convert their trapped kerogen into oil.
The reactions that produce oil and natural gas are often modeled as first order breakdown reactions, where kerogen is broken down to oil and natural gas by a set of parallel reactions, and oil eventually breaks down to natural gas by another set of reactions. The first set was originally patented in 1694 under British Crown Patent No. 330 covering "a way to extract and make great quantityes of pitch, tarr, and oyle out of a sort of stone." The latter set is regularly used in petrochemical plants and oil refineries.
My knowledge of how organic matter gets transformed into oil is admittedly limited. However, from the explanations I have read, I come away with a feeling that the explanations are somewhat vague and incomplete (e.g., 'subterranean heat and pressure break down the organic matter into lighter hydrocarbons').
What I haven't seen a rigorous explanation of is: By why what specific well-defined chemical reactions does this organic matter (proteins, polysaccharides,etc) turn into oil? (When organic matter is subjected to pyrolysis in the lab, the products are very much different from crude oil.)
I am not a beliver in the abiotic theory of oil formation, but I have read a few of the arguments by some of the proponents of abiotic oil, and some very interesting questions are raised.
While I no longer have the specific reference or a link to it, there is a rather lengthy detailed academic paper that asserts, through a statistical thermodynamic analysis, that the subterranean conditions of temperature and pressure do NOT favor the conversion of organic matter into the principal compounds found in petroleum.
I do not know enough about the subject to conclude one way or the other if the author(s) of this paper are correct. So, I wonder if this thermodynamic question has been addressed by any of our petroleum geologists/chemists out there. (?)
There is lots of other evidence for biotic formation, including the presence of other nutrients (nitrogen, phosphorus) in suggestive proportions, the presence of polycyclic aromatics in the oil, etc. Deffeyes' Beyond Oil is good for a discussion of this.
As for abiotic oil proponents, I suggest they go look for it some more. In the end, it doesn't matter how it's formed if you can't find enough of it to pump out.
I did read Deffeyes' Beyond Oil, and, as I recall, the discussion about exactly how oil formed was rather general, though I do remember his mentioning nutrients and various chemical markers indicative of a biological origin. I don't think he actually got into a level of detail where he proposed any specific chemical pathways.
As to the thermodynamic argument, I would partially agree that considerations of reaction kinetics and chemical environment also come into play. However, I think I would be safe to say that the proper thermodynamics are a necessary but not sufficient condition for the formation of petroleum compounds. If the thermodynamics aren't favorable, it's just not going happen regardless if other conditions are favorable.
I think the gist of that thermodynamic paper was that the energy level of the end products (petroleum compounds) is quite a bit higher than the energy level of the starting material (dead organic matter). Usually, when something is thermally broken down, the opposite occurs.
I suppose a rough analogy would be having a chuck of iron oxide (Fe2O3) in an oxidizing environment and expect it to turn into metallic iron at some future point in time. It could sit there for 100 million years, but it just ain't gonna happen.
Now, there are a variety of biological processes that can appear to go against thermodynamics, but they do this merely by importing energy into the system, the overall net effect still being consistent with the thermodynamics. But I haven't heard any explanations that the formation of oil was the result of biological reactions.
Well, I still haven't seen a rigorous, reaction-by-reaction explantion of how you get from dead organic matter to petroleum compounds.
However, I agree that this may be totally academic to the problem of finding oil, but I am curious nonetheless.
Keep in mind that the earth is by no means in a thermodynamic equilibrium, even on a relatively local level. There is molten iron down deep, but oxygen above. Different reactants/products are more mobile, less dense, less miscible than others, so it is different than just putting things in a closed vessel and heating.
Unfortunately, at the moment I cannot point you to the paper which I saw over a year ago. As I recall, it was cited in an article by one of the proponents of abiotic oil. I traced it down and found it to be a very long and detailed discourse on statisitical thermodynamics. As my thermo isn't all that strong, I really didn't follow it all that well. Some of the Russians seem to figure prominently in the abiotic theory.
I will try to dig it up once more, as I am starting to get curious all over again.
I agree that for this to work, there must have been some major natural fractionation of the various organic compounds in the dead organic matter taking place rather than everything 'just going into a big vat and being slowly cooked.'
As I mentioned in my response to Darwinian below, I suspect that there were also some very strong oxidation/reduction reactions taking place.