Richard, thanks for the pointers. I can probably include a section about this in the environmental section of my paper, since the cement appears to be the area where most of the failures happen that cause the environmental problems. I wrote a paper that covered the process of fracking and briefly discussed some of the environmental issues. With the help of one of my sociology professors for guidance I intended to write a section on the social issues associated with fracking to add to the paper so I could submit it with my grad school application for sociology. It has been way more complex than I anticipated and at this point I am ready to pull my hair out.
I am thinking about doing some future work on the subject so if I don't cover the cement issue too much here I think it will be something I could definitely use in the future.
Melinda
--- In geology2@yahoogroups.com, Richard Tyndall <richard.tyndall@...> wrote:
>
> Hi Melinda
> If you ever choose to return to the technical side of your project then one area that might prove fruitful in terms of data from a slightly oblique angle would be to look at failure rates in cement jobs. I suspect the data may be difficult to come by from the fracking operations directly but there should be plenty of stats out there which have been collated over the years from conventional drilling operations and as the cementing operations are very similar - if not identical - on both cementing and fracking operations then the data from one, I would contend, would be a good indicator of the likely data from the other. Not perfect science I would agree but it would have a good indicative value and it would then put the onus on the fracking companies to show that your data was wrong.
> Basically as a well is drilled it operates like a reverse telescope. You drill a 36" hole and case it with a 30" conductor. This is then cemented in. Then you drill and 26" hole and run a 20" casing, 17 1/2" hole and 13 3/8" casing, 12 1/4" hole and 9 5/8" casing etc. The actual hole sizes and casing sizes tend to be the same the world over (with some minor variations) and although some hole sections may get missed out in some wells this is a basic pattern that is always followed. The important point is that the casing has to be properly cemented in place. This not only fixes the casing and provides a good string platform for the next hole section but it also seals off the upper portions of the hole. It is this that the fracking companies are relying upon to ensure they are not getting contamination either of drilling/fracking fluids nor of produced gas up into water aquifers.
> And yet cementing is a notoriously difficult and often ineffective operation. Statistically more wells kick during cementing operations than in any other type of drilling operation due to imbalances in the fluids being pumped. At the same time the resulting cement job and seal may not be as good as the operator would like - but it may still be good enough to allow them to complete the well so long as they can persuade the authorities that it is safe. That is no guarantee that a week, a month or a year later that cement job will still be providing an effective seal.
> So looking at stats for cement job failures may well help give some idea of how high the risk of contamination into aquifers is likely to be.
> Richard
>
------------------------------------
Yahoo! Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/geology2/
<*> Your email settings:
Individual Email | Traditional
<*> To change settings online go to:
http://groups.yahoo.com/group/geology2/join
(Yahoo! ID required)
<*> To change settings via email:
geology2-digest@yahoogroups.com
geology2-fullfeatured@yahoogroups.com
<*> To unsubscribe from this group, send an email to:
geology2-unsubscribe@yahoogroups.com
<*> Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/
No comments:
Post a Comment