Joined: Nov 09, 2004 Posts: 9 Location: Taos, New Mexico
Posted: Thu Nov 11, 2004 4:33 pm Post subject: How does what's left determine the extraction rate?
I understand that historically, the point at which half the oil has been removed is the same point at which production starts to decline. But why is this? Why can't production be ramped up after the halfway point, so that production continues to increase for a time, postponing the decline (which, of course, will be steeper when it comes)?
Posted: Thu Nov 11, 2004 4:41 pm Post subject: Re: How does what's left determine the extraction rate?
markcmyers wrote:
Why can't production be ramped up after the halfway point, so that production continues to increase for a time, postponing the decline (which, of course, will be steeper when it comes)?
Well, like you said, that would worsen the steepness of the decline when it happens, but even more importantly, to ramp up production you would use more resources getting at the oil and at some point the amount of resources put into the process would be worth more than the oil you'd be getting in return. Steep steep down from that point.... *thud*
Many factors affect this, but the most important are the extraction rate characteristics of an oil well.
At the beginning of an oil wells life, they are typically under geologic pressure, and flow freely without assistance.
We have discovered that we can insert water (or gas etc) to maintain this positive pressure even after the well no longer "naturally" provides this pumping pressure.
The problem is that either naturally occurring pressure or artificially induced pressure extraction can only go so far. We pressurize the well and it pumps at a given rate... that's it.
If we could find another "giant" field somewhere, we could indeed maintain or increase production. Therein lies the rub. _________________ "When you understand why you dismiss all the other possible gods, you will understand why I dismiss yours." - Stephen F Roberts.
Joined: Nov 09, 2004 Posts: 9 Location: Taos, New Mexico
Posted: Thu Nov 11, 2004 5:14 pm Post subject:
Quote:
...that would worsen the steepness of the decline when it happens
This might be a reason why it's not wise to increase production after peak, but surely wisdom isn't the mechanism that underlies Hubbert's curve.
Quote:
...to ramp up production you would use more resources getting at the oil and at some point the amount of resources put into the process would be worth more than the oil you'd be getting in return...
Yes, there is a point at which net energy is 0, but is this point reached whenever you try to flatten out Hubbert's curve, or would it occur sometime later? Is the point of zero returns the controlling mechanism for the curve? If so, who has demonstrated it?
Is it possible that no one fully understands the mechanism that underlies Hubbert's curve?
Joined: Nov 09, 2004 Posts: 9 Location: Taos, New Mexico
Posted: Thu Nov 11, 2004 5:25 pm Post subject:
Quote:
The problem is that either naturally occurring pressure or artificially induced pressure extraction can only go so far.
I guess my question would be: Is the downside of Hubbert's curve fundamentally a description of declining pressure? Is it just physics, or are there other things at play? Has anyone attempted to prove that the downside of Hubbert's curve can be explained primarily by declining pressure?
The main reason for declining production is the lack of new oil field discoveries.
A given field can produce "X" amount of barrels per day.
Add all the producing fields together... that's the maximum extraction rate. _________________ "When you understand why you dismiss all the other possible gods, you will understand why I dismiss yours." - Stephen F Roberts.
Joined: Nov 09, 2004 Posts: 9 Location: Taos, New Mexico
Posted: Thu Nov 11, 2004 5:49 pm Post subject:
Quote:
The main reason for declining production is the lack of new oil field discoveries.
A given field can produce "X" amount of barrels per day.
Add all the producing fields together... that's the maximum extraction rate.
You seem to be saying that Hubbert's curve tracks the number of producing fields times their various maximum extraction rates. This would entail that all fields produce at maximum capacity all the time, or perhaps close to it. Is this true? If not, then there are additional variables underlying Hubbert's curve.
Joined: Oct 12, 2004 Posts: 1647 Location: Davis, California
Posted: Thu Nov 11, 2004 5:53 pm Post subject:
In most of the conventional oil field wells/fields, initally oil literally flows free from the pressure. The slightest crack will send it gushing up from the ground. However, as oil is withdrawn, the pressure declines. It becomes increasingly more difficult to recover the oil without secondary and tertirary recovery methods. Most methods are there to help bring the pressure back up to pre-peak periods. However, there are some added risks, one not withstanding is that the 3-D topology of the oil well may not be able to sustain the new source of pressure and it will collapse. Since each field is unique, there needs to be fairly tailored methods used, otherwise one risks damaging the field permentantly.
It is analogous to drinking from a slurpee. If one keeps the straw level (like a pump/drill in an oil field), it becomes harder and harder to drink the slurpee. While not completely perfect as an analogy, it can help convey the picture of reduced fluids and pressure as constraints on extraction.
Joined: Nov 09, 2004 Posts: 9 Location: Taos, New Mexico
Posted: Thu Nov 11, 2004 6:00 pm Post subject:
You guys are doing a great job explaining why production inevitably declines
at some point. But nothing you've said is a convincing argument why the decline must follow Hubbert's Curve. Do you see this?
You seem to be saying that Hubbert's curve tracks the number of producing fields times their various maximum extraction rates. This would entail that all fields produce at maximum capacity all the time, or perhaps close to it. Is this true? If not, then there are additional variables underlying Hubbert's curve.
Quote:
Many factors affect this, but the most important are the extraction rate characteristics of an oil well.
Agreed... the cumulative extraction rate for all producing fields = maximum current rate.
Although at current prices, it's hard to imagine any producer holding back. _________________ "When you understand why you dismiss all the other possible gods, you will understand why I dismiss yours." - Stephen F Roberts.
You guys are doing a great job explaining why production inevitably declines
at some point. But nothing you've said is a convincing argument why the decline must follow Hubbert's Curve.
There is no need for decline to follow Hubbert's Curve. Consider, for example, this graph of Russian production:
Joined: Nov 09, 2004 Posts: 9 Location: Taos, New Mexico
Posted: Thu Nov 11, 2004 6:30 pm Post subject:
Quote:
There is no need for decline to follow Hubbert's Curve.
Now we're getting somewhere. If there's no need for decline to follow Hubbert's Curve, then the Curve may not be useful for predicting near-term oil shortages. Is that a reasonable conclusion?
Is it possible that no one fully understands the mechanism that underlies Hubbert's curve?
Yes, that is very possible. This is a very interesting line of inquiry you are pursuing. You'd think that ASPO would have carefully looked into it, but apparently they're too busy carping about the republicans and the dollar.
Now we're getting somewhere. If there's no need for decline to follow Hubbert's Curve, then the Curve may not be useful for predicting near-term oil shortages. Is that a reasonable conclusion?
The predictive power of Hubbert's Curve is a myth. The myth says that Hubbert used some kind of mathematical curve to predict the US48 peak in 1970. In fact, Hubbert never produced any mathematical procedure/formula to justify his prediction. He just eyeballed it, took a guess and happened to be right. He also happened to be wrong about the world peaking in 1995, as Campbell has been wrong 2 or 3 times already.
The problem is that, in order to fit the curve, you must know the total area under the curve (i.e. total production, including the past and future). Unfortunately, nobody knows that number, and there is no scientific way to determine it. So people like Hubbert and Campbell make a guess. That's the bottom line of these predictions. It's like guessing how many beans are in a jar, when the size of the jar is partly hidden by a curtain. It's magic!
Joined: Nov 09, 2004 Posts: 9 Location: Taos, New Mexico
Posted: Thu Nov 11, 2004 8:05 pm Post subject:
Very useful, JohnDenver. Thank you.
I've been studying Peak Oil for only a short time, so I haven't had a chance to check much data. As I understand it, though, the Peak Oil people argue that Hubbert's Curve fits not only the US48, but other producing countries where the supply is in decline. There is, of course, more than a little circularity here, since the Peak Oil people use the model itself to determine how much oil is left.
Clearly, the model is far easier to disprove than prove. As you say, you need to know total reserves in order to prove the model, which is impossible without the model. But to disprove the model, all you need is an uncooperative curve segment, as in your Russian example.
So, JohnDenver, what is it that you do believe about the oil supply?
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