Wellbore Integrity and Methane A Crisis in the Making

This article was last updated on April 16, 2022

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USA: Free $30 Oye! Times readers Get FREE $30 to spend on Amazon, Walmart…Back in September 2013, I posting this explanation on one of the key potential problems with fracking.  At that time, I did not have access to data regarding the failure of well bores in areas where there has been substantial horizontal drilling and multi-stage fracking on land.  Thanks to researchers at Cornell, we now have some idea about where the potential problems with shale gas may lie.

 
First, let's review.  Here, quoting from my posting in September, is an explanation of how a well is drilled, completed and where the problems with well bore integrity can crop up.
 
When the oil industry drills a borehole to depth, as you can imagine, the sides of the borehole are very unstable and rock continually sloughs into the hole, causing all manner of problems.  To alleviate these problems, a long string of hollow steel production casing of varying diameters is run into the hole to the total depth of the well (or somewhere below or at the depth of the producing formation depending on the type of well).  The diameter of this casing is somewhat smaller than the diameter of the borehole; the space between the walls of the borehole and the outside of the production casing is known as the annulus.   Once the casing is in place, cement is pumped down the casing and flows back up the well between the casing and the sides of the borehole through the annulus.  The cement is allowed to harden and tools are run to ensure that the "cement job" is sound.  The purpose of the cement is three-fold; it holds the casing in place, it prevents the fluids used in the well completion operations from flowing to the surface and it prevents fluids from inside the borehole from flowing into the surrounding formations once the well is completed and on production.  For example, if there is a water-bearing formation above the productive zone, the production casing and cement will seal off that formation, preventing the formation water from flowing into the well bore.
 
Here is a cross sectional diagram comparing a conventional well bore and an unconventional well bore:
 
 
One of the key issues that can cause a completed well bore to fail is related to the cement that is used to fix the production casing in place.  In some cases, the when the cement is pumped down the well bore, it fails to displace the drilling mud in the annulus and in some cases, the cement fails after a period of time.  This failure allows the formation fluids including oil, natural gas or water of varying salinity that are under higher pressure because of the weight of the rock that lies on top of them to flow through the annulus to the surface where the pressure is lower.  It is this problem of well bore integrity that results in contamination of near surface groundwater and the atmosphere.
 
There are two key differences between conventional natural gas production and unconventional or shale gas production:
 
1.) Shale gas wells require much higher volume fracks than conventional gas wells.
 
2.) Shale gas wells require far higher well density than conventional gas wells.
 
These two factors help explain the potential magnitude of the problem with shale gas production.

Let's switch gears for a minute and take a look at a map showing the extent of the Marcellus Shale play both inside and outside of Pennsylvania:
 
Please note the concentration of Marcellus producing wells in the northeast part of Pennsylvania.
 
Here is a more detailed map showing the Marcellus shale producing gas wells (in red) in Pennsylvania, again, noting the concentration of Marcellus producers in the northeast part of Pennsylvania:
 
 
Now that you have all of that background information, let's look at the study by the Cornell-led research team.  The researchers, Anthony Ingraffea, Martin Wells, Renee Santoro and Seth Shonkoff, examined compliance reports