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Permalink Reply by Two Dogs, Pirate on July 7, 2010 at 8:53

Through millions of years the waters of the Gulf Of Mexico have risen to cover a lot of the mainland bordering the gulf. Some think that this happened 12 or 13 times. As the waters receded entrapments that were formed underwater during high water like shoals and reefs trapped the receding sediments. These sediments created the shale and other formations.

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Permalink Reply by ALongview on July 7, 2010 at 9:04

Thanks for the response twodogs.

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Permalink Reply by Craig Cooper on July 7, 2010 at 9:53

In addition to the things mentioned by Two Dogs, the shoals & reefs can become hydrocarbon reservoirs. They can initially have high porosity & permeability and in certain situations these may be preserved even though the rocks are buried by sediment, mud, etc.

As sea water encroached on the area during the time mentioned in the report, it is believed that there was a topographic feature/hill/mound present (i.e. the Sabine Uplift, Paleozoic strata) which acted as a place for wave action and beach development (focus for shoaling). Farther out from the "shoreline", in the deeper water, reefs grew. Later on, as sediment was dumped into the area from streams & rivers from land to the north, the sea water receded and the shoals & reefs were buried. There are a number of places you can go to see present-day examples of what it may have looked like in the Sabine Uplift area when the shoals and reefs existed: Florida Keys and any one of a number of locations in the Bahamas.

As Two Dogs says, this may have happened a number of times so eventually the area was buried under the ~10,000+ feet of rock we see today.

As for the hydrocarbon type that may be contained in any of the potential reservoirs, it will be a function of the original source sediments/rock, present-day depth (i.e. pressure & temperature) and whether there was an effective path from the source rock to the reservoir; so the answer is a wishy-washy: "it depends" :-)

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Permalink Reply by ALongview on July 7, 2010 at 10:04

Awesome response and a very clear explanation. Just what I needed to understand the processes that took place. Thanks.

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Permalink Reply by Aubrey C. Sanders, Jr. on July 7, 2010 at 11:27

YOU ARE TEACHING THIS COURSE! GOOD WORK!

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Permalink Reply by 4HTSG on July 7, 2010 at 11:31

I have seen Sabine Uplift mentioned many times. Can you give me an idea of where that is? If I remember correctly. someone on another post mentioned that the Uplift was a cut off area for the gas. Any thoughts on that? Thanks.

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Permalink Reply by jffree1 on July 7, 2010 at 11:53

You are thinking of the "Sabine Island", I believe. The play is on the Sabine Uplift.
Here is a description of the Uplift which I copied (without a reference), many moons ago:

Sabine Uplift is a deep-seated subsurface structural feature that lies beneath parts of Louisiana, Arkansas and Texas. Oil and gas production in this region is directly related to this major structural feature. The crest of this subsurface feature lies near the center of Caddo Lake in Caddo Parish, Louisiana.

And this picture shows a rendering of where the Island is supposed to be (brown area at the bottom of the shale):

Sabine Island Map.docx

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Permalink Reply by Marc Stepman on July 7, 2010 at 14:05

Would you mind posting this in a PDF doc?

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Permalink Reply by jffree1 on July 7, 2010 at 15:13

Not at all.

Attachments:

• Sabine Island Map.pdf, 107 KB

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Permalink Reply by Marc Stepman on July 7, 2010 at 14:03

Great reply!!! Load of information. How large was the Sabine Uplift?

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Permalink Reply by jffree1 on July 7, 2010 at 15:31

Marc, that is a question for the experts. What I know on the subject has been gleaned from previous discussions on GHS and from doing a little research. Here is a good article on the region which came out early in 2008.

"Basement Tectonics and Origin of the Sabine Uplift"

Attachments:

• SIPESquarterlyFeb08.pdf, 2.8 MB

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Permalink Reply by Marc Stepman on July 8, 2010 at 3:02

Thanks for the maps and the paper. It does help out. I kinda makes more sense when you have a picture to look at.

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