[rockdoc123]

rockdoc, I'm going to ask for a broad generalization, which I'm sure you don't like to do but I'm gonna ask anyway. Is it typical to have different oil bearing zones stacked like this? And are these different zones from different eras of oil formation or different rock types that trapped the same oil?

very typical. Think of the oil and gas source rock as a "kitchen area" where the kerogen is cooked up and the generation of high fluid pressures results in migration away to a source. The migration pathway can be quite complex both along permeable potential reservoirs as well as vertical fractures. As a consequence in many areas oil from one source rock can make its way into a number of horizons of various ages. As an example in the Western Canada Sedimentary basin Devonian source rocks are responsible not just for the accumulations in Devonian reefs (very prolific) but might also be largely responsible for the oil sands deposits. Structural traps which may have high vertical closure have the potential for numerous accumulations. In the Sudan, as an example, Heglig and Unity fields in Southern Sudan have stacked accumulations in numerous sandstones of Early Cretaceous, Late Cretaceous as well as Tertiary age. Another example would be in the Canadian overthrust belt where fields such as Turner Valley that produced from Mississippian carbonates also have production from shallower zones of Jurassic and Cretaceous age. Lots of examples that I can think of. It can be complicated when you have several potential source rocks that are all in the kitchen area which could result in stacked pay coming from different source rocks.
In the case of shale reservoirs there has been no migration, the shale forms both the source, reservoir and seal. But what you can often see is that hydrocarbons have migrated from that source rock to areas nearby. It is possible to have zones of conventional pay immediately above (the example in the Eagle ford), in the middle of (the Middle member in the Bakken) and sometimes well above the shale that acts as self-sourcing. One of the plays quite popular right now in Western Canada is the Devonian Ireton Fm shales. Those shales are a target in of themselves but they are also responsible for large accumulations of hydrocarbons in Devonian reefs and potentially Cretaceous sandstones. Not far above the Ireton is a second unconventional target in the Jurassic Nordegg FM where tight carbonates sit among the very rich Nordegg black shales.
Given that the shales are actually world class source rocks it is inevitable that there will be conventional pools or other unconventional pools associated with them. A similar case in point might be the Austin Chalk which sits above the Eagle ford shales. The Austin chalk is unconventional inasmuch as chalks tend not to flow without fractures being present given they have high porosity (good storage capacity) but extremely low matrix permeability. The Austin Chalk is likely largely sourced from the Eagle ford shales (although there are some other thin shales with the chalk itself).

[C8]

Here is the familiar Growing Gap plot, this one is updated to 2011, I found it at DoTheMath



Here is a logistics curve from the same blog

For global oil resources (all liquids), we have consumed 1.2 trillion barrels so far. The data did not follow a logistic path in its early years, but has done so for the past three decades. If this portion is predictive, it says that our total resource is about 2.4 trillion barrels, putting us half-way along (therefore around the peak of the logistic rate). This by itself is a weak prediction. But the discovery rate we have seen (peaking in the 1960′s) does not lay the groundwork for us to expect a radical departure from the logistic line any time soon.

Ibid

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can anyone explain the second chart (production rate)? Not sure I understand it- thanks

[John_A]

What?

Read the quote from Murphy:

For global oil resources (all liquids), we have consumed 1.2 trillion barrels so far. The data did not follow a logistic path in its early years, but has done so for the past three decades. If this portion is predictive, it says that our total resource is about 2.4 trillion barrels,

Since you didn't read the link, I went and copied a further explanation just for you:

If for each year, we plot the amount of resource produced in that year as a fraction of the total resource extracted to date against the total extracted resource, a logistic function makes a straight, descending line intercepting the horizontal axis at the value of the ultimate resource.

It is not based on ""discovered" reserves" but is a prediction of the ultimate recoverable resource based on past production, it includes past discoveries, past production, current production, future production, reserve growth, new discoveries, new technology and whatever else, that's why its called "total resource".

.

Production graphs, of the type referenced, have nothing to do with estimating anything which isn't producing, let alone hasn't even been found. "Ultimate resource" used by Murphy refers only to currently producing things, so it does NOT include the undiscovered of the USGS, and it may or may not include field growth, and it would only include the few billion barrels produced by the Orinoco, versus the 100's of billions estimated to be there.

To summarize, Murphy can't estimate anything undiscovered with that graph, and if he thinks that only producing resources somehow predict the undiscovered, he would be incorrect. He does not appear to claim that his "total resource" is as big a definition as you then attach to it. Perhaps his "total resource" phrase isn't as inclusive as you state it is?

[Pops]

C8-
"can anyone explain the second chart (production rate)? Not sure I understand it- thanks"

It's math so I can't explain it better than Murphy did.
I know the chart plots each year's production as a percentage of total production up to that time along one axis and total production on the other axis.

Sometimes it can project the ultimate to an amazing degree of accuracy.
He shows several examples at the link of various resources, UK coal for example



Even US oil production:



There are math guys here who can do a better job explaining this, like most things involving numbers it is a mystery to me.

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[Pops]

To summarize, Murphy can't estimate anything undiscovered with that graph, and if he thinks that only producing resources somehow predict the undiscovered, he would be incorrect. He does not appear to claim that his "total resource" is as big a definition as you then attach to it. Perhaps his "total resource" phrase isn't as inclusive as you state it is?

Wait, in your last post you were adding the logistics prediction to the usgs guess to come up with some huge number. But now you say the logistics guess is invalid.

What has changed?

Nothing, except the evidence now doesn't fit you preconception.


At any point more than half way or so along the plot of UK coal production I just posted you could have drawn that same red line and made a pretty good guess at URR without knowing anything except past production.

.

[John_A]

To summarize, Murphy can't estimate anything undiscovered with that graph, and if he thinks that only producing resources somehow predict the undiscovered, he would be incorrect. He does not appear to claim that his "total resource" is as big a definition as you then attach to it. Perhaps his "total resource" phrase isn't as inclusive as you state it is?

Wait, in your last post you were adding the logistics prediction to the usgs guess to come up with some huge number. But now you say the logistics guess is invalid.

The Hubbert linearization is built on production rates, just as the axis show. I believe where I have seen it before, and it has been explained, was at TOD. Wiki seems to cover it as well.


https://en.wikipedia.org/wiki/Hubbert_linearization

"The Hubbert Linearization is a way to plot production data to estimate two important parameters of a Hubbert curve; the logistic growth rate and the quantity of the resource that will be ultimately recovered."

What they mean when they say "resource" is more analogous to reserves, not "resources" in the sense of what the USGS measures, which completely throws out existing production and calls their measure "technically recoverable".

I just found this in cyberspace and figure it is a much better representation of "total resource", which is some number greater than reserves and even reserves plus USGS "technically recoverable".