Well Casing Details

I have long thought the weakest link in the gas extraction process is the well casing.  Almost all major problems seem to come from gas migration into water aquifers because of bad casings. Fracking has not been a problem and surface spills and accidents can be closely monitored and  quickly remedied.

I would like to know about how wells are cased. I always hear how the wells are triple cased with steel pipe and cement but I think that they actually use a specialized grout. What is the grout recipe? Does it contain hardeners, expansion agents, and/or adhesives to make a better seal? Do they add fibers or other items to resist cracking? Are these additives readily available at the local concrete yard or are they brought in by the operators?

How many yards of grout will a typical wells require? Do they monitor the amount pumped in to ensure a good seal? What happens if they hit a void?

I have heard that they use a laser system to align the steel casing in the center of the borehole to ensure that the grout is the same thickness all the way around the pipe. How does that work?

How are the wells tested when completed? How does the state monitor this? How often are they tested afterwards?  How often are they damaged during maintenance/drilling activities?

I know thats a lot of questions. And I appreciate anyone that helps me understand this process.

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Permalink Reply by George Brown on December 30, 2011 at 7:11am

We're glad to have you back, Homer.

I think the process we use today, as you have described it above, is very safe.  Folks, we are human so we can't make anything we do perfect but we've come a long way baby.  I have 5 abandoned oil wells on my property.  They were drilled in the 1940s. I can't find any trace of four of them but the fifth one is easy to locate.  There is a rusted casing pipe sticking up about two feet from the surface.  It is full of rain water and is rusting away.  I don't know how far down it was drilled, but I'll bet you it goes through the water table and that rusted casing is surely compromised.

I would encourage folks to read the history of oil exploration in what is now Oil Creek State Park in PA. The area today is beautiful but you would never believe it could be if you would read what was done there. Mother nature has an uncanny ability to clean up the messes we make.

2s72s0k9mm8gdPermalink Reply by 2s72s0k9mm8gd on December 30, 2011 at 3:27pm

Have fished in Oil Creek......beautiful place and proof that Man gives himself way too much credit for having a lasting impact on this planet. We are such an arrogant species.

Permalink Reply by Jim Litwinowicz on December 30, 2011 at 3:46pm

It took decades for Oil Creek and other areas to recover. If we do this right, which I am confident we will, the damage will be much less from the start.

Permalink Reply by farmgas on December 30, 2011 at 2:22pm

Nice explanation, Homer....since the horizontal well begins at the kickoff point, is the vertical well drilled deeper to allow for gas in that area to be released and flow up the well?  Otherwise, is the area around the vertical well and for the distance of the curve lost to production?

Permalink Reply by Robert Barr on December 30, 2011 at 7:39am

YES

the drilling practices used in NE Ohio are very similar to what is going to be used. see link below

http://ohiodnr.com/home_page/NewsReleases/tabid/18276/EntryId/326/N...

Permalink Reply by Doug Pierson on December 30, 2011 at 1:42pm

There are a number of videos on utube similar to this one.  7 layers of protection.

http://www.youtube.com/watch?v=AYQcSz27Xp8

Permalink Reply by Jim Litwinowicz on December 30, 2011 at 3:45pm

I'm familiar with the layout of the well and its multiple casings. I know little about the quality control issues.

Normal concrete shrinks as it cures. This would allow gas under pressures of 2000lb/sq in  to travel along the perimeter and contaminate aquifers. Do they use expansive additives to prevent this?

Over time, and as pressures fluctuate, concrete will crack. Do they add fiberglass fibers, steel mesh,  or some other system to reduce cracking and maintain integrity?

How do they keep the steel pipe in the center to ensure a consistent thickness of concrete around the well?

What testing is done during the process and how often is it tested afterwards?

And how many yards/truckloads of cement does each well take on average?

Homer; glad you are back as your expertise is of great value to all of us. And thanks for all you do.

Permalink Reply by Paul Craft on December 30, 2011 at 5:23pm
Research bentonite. It's been used for decades to improve the seal. Centralizers ensure the thickness. We have had hundreds of wells drilled in our township without any problems (knock on wood:-)
Permalink Reply by craig on December 30, 2011 at 5:32pm

Bentonite clay has been used for over one hundred years to make underground structures waterproof, and it works. It comes as a powder and abit of liquid (water) is used to spray it on. When it finally comes into contact with moisture it expands many times the original thickness and forms a perfect seal. That much I know for sure....I live in an underground house we built in 1986.

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