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47 comments on An oilfield in Arabia

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oilmanbob on August 16, 2006 - 9:58am

Memmel, the horizontal wells make many formations that are "tight" economicially productive as well. The Austin Chalk is a good example of this, or the Barnett-Woodford shale fields. Although fields with good permiability are very possibly depleted faster, in tight formations recovery is increased because the oil can flow in to a well bore quickly enough to be a good investment return, so wells get drilled that would not be drilled by traditional vertical well methods.
The problem is that demand is increasing a hec k of a lot quicker than supply, and these new extraction methods are a lot more expensive on a per barrel basis. I doubt that horizontal drilling can do more than slightly slow the decline rate in production. But, the techniques ought to make a lot of producers rich.

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copelch on August 16, 2006 - 10:55am

Oilmanbob writes:

"I doubt that horizontal drilling can do more than slightly slow the decline rate in production.

Now I'm even more perplexed than before (at least pending HO's upcoming contribution, which I'm looking forward to).

So does horizontal drilling slow down or speed up the depletion rate? It can't to both at once. Or does it all depend on the characteristics of the field in question? Or does HD speed up the depletion rate but at the same time convert a certain percentage of the technically recoverable oil into economically recoverable oil?

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Dave Cohen on August 16, 2006 - 11:56am

Deviated drilling speeds up the extraction rate and thus pushes the envelope on current production at the expense of longet term yields. The depletion rate may be very sharp after the extraction starts declining. In HO's original example, once the water encroachment reaches the drilling contact points, that's pretty much all she wrote.

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frontierenergy on August 17, 2006 - 12:43am

That is absolutely right Dave once the water hits it-its all done. There are essentially two types of horizontal wells-

"Grass Roots" where wells are drilled from the surface and then go horizontal. These are new field development wells where as Oilmanbob noted they wouldnt produce anything otherwise. These are drilled horizontal or they are not drilled at all.

Then there are "re-entry" wells in existing fields where a whipstock is set in an existing vertical well, a window is cut in the casing and a slimhole tool is used to drill out at a very high build rate. These in my experience are only somewhat successful in increasing production and are high risk and expensive. It requires highly skilled people and most hands decline to work these jobs simply because of the stress involved. The better people can pretty much pick and choose where they want to work now anyway.

I can't speak for what is going on in Texas but in my part of the country...the Rockies, re-entry work is very limited. Most of the work going on in the older fields is simply workover. As far as increasing depletion I don't think anyone knows at present on horizontal re-entry on old fields.

Maybe this doesnt clear this up, but to people in my business it is considered apples and oranges between these types of horizontal wells.

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alistairC on August 16, 2006 - 11:57am

You're confusing "decline" and "depletion" I think.

Smart extraction slows the decline in production by accelerating the depletion rate. (I think)

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Dave Cohen on August 16, 2006 - 12:20pm

OK, let's try this again. I said:

Deviated drilling speeds up the extraction rate and thus pushes the envelope on current production at the expense of longet term yields. The depletion rate may be very sharp after the extraction starts declining. In HO's original example, once the water encroachment reaches the drilling contact points, that's pretty much all she wrote.

Decline refers to production drops. Thus the decline rate is the year-on-year percentage drop in a producing field (basin, country).

Depletion refers to the exhaustion over time of URR which is itself some percentage of OOIP.

In my text, the extraction rate is the daily flow (barrels per day) as a percentage of URR.

So, here's what I should have said.

Deviated drilling increases the extraction rate and thus pushes the envelope on current production at the expense of longer term yields. The decline rate may be very sharp once production has peaked after such drilling was inaugurated. In HO's original example, once the water encroachment reaches the drilling contact points, that's pretty much all she wrote.

That's better. Now all our terms are defined and there is even the possibility that we can all understand what we are talking about.

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memmel on August 16, 2006 - 12:29pm

Good post and to agian plaster the same message.

In field drilling esp with advanced recovery maintains production rates but ...

Once the wells start watering out the decline rate increases over time before finally decreasing with production at a low level. The basic cause is once a region waters out it waters out several wells at once the old producers plus the new ones drilled to keep up the production rates then net effect is production rates plumment and your left with stripper wells.

The unknown is what is the general production profile of these new wells how long do they last on average with a high production rate years decades ??? Assuming that the orginal drilling gave decent field coverage. My gut feeling is in field drilling only helps production rates for a few years at most esp with lateral wells since the depletion rate is doubled.

That is my thesis.

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phxbanks on August 16, 2006 - 10:03pm

http://www.foreignpolicy.com/story/cms.php?story_id=3567

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47 comments on An oilfield in Arabia

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