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Permalink Reply by 1kw6x71km1v37 on March 8, 2014 at 10:20

The Austin Chalk in west LA was having a lot of problems with drilling mud clogging the lateral fractures until somebody began "under-balanced drilling" using the formation brine under it's own pressure in place of mud.

Bingo-instant success.

This coincides with the general observation that the Nabors #19 rig working the Masters Creek Field consistently  drilled good wells, while other rigs working the area could not find oil at Wal Mart. And if they did find oil, they couldn't get it out due to downhole issues.

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Permalink Reply by jim weyland on March 8, 2014 at 10:37

cs,

please excuse my ignorance, which concerning matters of drilling and completion, is total.

note: i used to see drilling 'underbalanced' in the offshore daily reports from time to time but never thought to ask why. i think, at least, now, thanks to you, i understand the 'why'; leaving me with the  unanswered 'how'

so, just how do they go about things? i can only assume that they drill with mud until they've finished kicking off and then they let the formation water displace the mud and then drill forward using the surface recovered brine in place of mud.

am i anywhere close? please advise. thanks,

jim

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Permalink Reply by 1kw6x71km1v37 on March 8, 2014 at 16:48

You know, I really can't say just how it worked, whether they used recovered brine or brine as it came out of the fractures into the laterals. But the latter makes more sense, hence the term under-balanced, indicating mud weight/pressure downhole had to be slightly less than pressure in the laterals to keep it all flowing without mud migration into the formation. All I know for sure is that it was critical to keep drilling mud out of the laterals or they would eventually plug up to some degree, and there was no sure nor cheap fix to clean them out and restore flow. I remember some repeated acid treatments on a few wells to keep them going. Some good chalk wells fell off almost to nothing on account of this and the hydrocarbons remain in formation today awaiting the next operator with sufficient cajones to spud anew.

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Permalink Reply by Max on March 9, 2014 at 3:21

“If a company drills a well and it produces 1,000 barrels of oil per day, people will say it’s because it’s good rock.” Gilmer noted. “But that’s not it, it’s something they did.”

Mineral owners have to trust that the companies running the rigs are on top of the game and know all the "tricks" of producing shale formations.  I've always figured that if they're spending millions to drill, they know exactly how to drill the hole and make money come out of it.  Now I wonder how many wells are producing less than what could have been produced.

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Permalink Reply by John Cooper on March 13, 2014 at 2:18

Just to clarify on this article.  The rock has to be 'good' to produce, that is it has to contain hydrocarbons and have properties that allow the completion practices to work.  But that is only half of the equation.  The other half is the drilling and completion practices.  The companies that tend to do the best are the ones that can use a repeatable process, which in turn produce similar results in a given area.  Hope this helps out...

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