Deep oil and gas formations are under extraordinary pressure from the weight of thousands of feet of rock which can provide a seal. When these layers are pierced by a drill bit, the seal is broken and the pressure released. Water, gas or oil can be forced into the newly opened pathway. That's how an oil well becomes a geyser.
To keep oil, gas and fracking fluids from leaking into aquifers, drilling companies insert as many as three concentric rings of steel pipes inside the well bore and cement is pumped into the gap between the rings of pipe (called the annular space) to ensure a seal.
NOTE: Cement does not contain rocks. If sand is added to cement, the mixture is called mortar. If rocks are also added, the mixture is called concrete.
Except sometimes cementing fails
Cementing is the obvious "weak link,"according to Anthony Corody, a hydrogeologist and consultant to gas companies who has been a defender of fracking. Other scientists emphatically agree.
"That's pretty much the holy grail, good and proper cementing and casing," said Michael Nickolaus, former director of Indiana's Department of Natural Resources, Oil and Gas Division, and special projects director for the Ground Water Protection Council, a group of scientists and state regulators that studies industries' impacts on water. Nickolaus added that if these zones are properly isolated from one another, the issue of groundwater contamination, whether from gas or hydraulic fracturing, goes away.
"If you do a poor job of installing the well casing, you potentially open a pathway for the stuff to flow out," explains ecologist and water resource expert Robert B. Jackson of Duke University's Nicholas School of the Environment. Although many regulations govern well cementing and although industry has strived to improve its practices, the problem may not be fully fixable.
"A significant percentage of cement jobs will fail," Ingraffea says. "It will always be that way. It just goes with the territory." Anthony Ingraffea is an engineering professor at Cornell University and an expert on the controversial technique of fracking .
How cementing fails
The cement is forced down the inside of the casing, around the bottom of the casing, and then up the outside of the casing and into the space. This space is called the annular space.
For the cement job to be good the cement has to "return to the surface." That is, the cement has to be pushed all the way up the annular space so it comes back level to the surface and completely fills the annular space.
Sometimes there can be " void s" (think of caves) in the ground. In that case the cement, instead of filling up the annular space, fills up the void and does not make it to the surface. The annular space is not filled with cement. This is not uncommon a nd it can cause problems to occur .
If the lack of cement is deep enough, water from bad ground water strata can migrate upward into good ground water strata.
If this problem occurs the driller tries pump cement down from the surface through a hose or "tube" into the open annular space. This is called "grouting." Grouting is not as reliable as "circulating" cement down the center of the casing and up the annular space until it returns to the surface.
If the cement is not correctly formulated, or if there is unexpected water pressure from good or bad ground water strata, water can force its way into the cement and "honeycomb" the cement.
This leaves passages for the bad ground water to migrate up to the good groundwater. In addition, it is possible for surface or shallow subsurface pollutants to migrate down into the good groundwater.
After the cement is forced into the annular space, the driller is supposed to wait 8 hours before continuing to drill on down the hole. This is to allow the cement to harden sufficiently to do its job. But it costs the driller money for the drilling rig to sit idle for 8 hours.
In West Virginia, the Surface Owners' Rights Organization regularly gets complaints that drillers do not wait the 8 hours before they start drilling. If the driller does not wait, the new drilling activity can cause cracks and spaces up and down the cementing of the casing.
Also in West Virginia, the driller is supposed to call the state inspector and let them know when the cementing will take place. This is so the inspector can be there to make sure the cement returns to the surface and that the driller waits 8 hours.
But they have 16 inspectors and 45,000 active wells, and in recent years 3000 well work permits a year (though not all permits become drilled wells). That is remarkably like Colorado.
The description above of how cementing can fail is from the West Virginia Surface Owners' Rights Organization website .
In Colorado, do inspectors make sure the cement returns to the surface and that the driller waits 8 hours or do they review cementing logs after the fact?
According to COGCC, there were 17,000 inspections in 2010 by 15 inspectors located throughout Colorado. Most inspections are unannounced.
In June 2011 COGCC responded to a STRONGER (State Review of Oil & Natural Gas Environmental Regulations) questionnaire saying, "Colorado’s casing and cementing regulations provide design standards sufficient for all anticipated well control events, including hydraulic fracturing. COGCC engineers review casing and cement designs during well permitting and cement tickets and cement bond logs prior to approving drilling completion reports. Well construction and integrity are also verified in the field through random field inspections by COGCC field inspectors and engineers during cementing and well stimulation activities."
I n October 2011, STRONGER found in Colorado that in some areas, but apparently not all, conditions of approval on drilling permits require notification to the inspector before the commencement of hydraulic fracturing operations. It is not clear whether and how the inspector is notified of hydraulic fracturing operations on a well that is being recompleted.
STRONGER recommended that COGCC review its notification requirements to ensure they are sufficient to allow for the presence of field staff to monitor hydraulic fracturing operations.
STRONGER also found there is no standard for the maximum depth to which surface casing can be run. Instead, the COGCC staff reviews the proposed surface casing program for each well and determines what is appropriate based on the local geological conditions.
STRONGER recommended the review team recommends that the COGCC review any past instances where problems occurred in the setting or cementing of surface casing in a well to be hydraulically fractured, where casing or cement failures occurred during hydraulic fracturing, and other available relevant information, and consider whether establishing a maximum surface casing depth may be in order to prevent well control or cementing problems that may arise when lost circulation zones or gas-producing formations are penetrated before surface casing is set and cemented.
At West Divide Creek, Colorado, faulty cementing caused fracking chemicals and thermogenic methane to seep into the creek...and it's still seeping.
COGCC staff concluded the West Divide Creek seep was caused by gas migrating up an EnCana gas well borehole that had not been properly cemented. The apparent top of competent cement had fallen to approximately 4050 feet, far below the level required on the permit conditions and far below what was observed at the end of the cementing job. At the time, EnCana engineers interpreted the cement bond log as showing the top of cement at approximately 3500 feet.
On August 16, 2004, following a public hearing, the COGCC commissioners approved an enforcement order ( Order 1V-276 ) and assessed a $371,200 against EnCana. Impact to the surface and ground water by the presence of benzene and methane indicate that Williams Fork Formation gas and benzene are still present in the gas seep area and continue to be a threat to the waters of the state; however, the amount of Williams Fork Formation gas and the associated release of benzene appear to have decreased since April 5, 2004 when EnCana remedially cemented the Schwartz 2-15B Well.
In 2008 there was another seep at West Divide Creek. As of June 21, 2011, monitoring wells show benzene, xylene, biogenic and thermogenic methane, DTW continue to seep into West Divide Creek.
David Neslin, Director, Colorado Oil & Gas Conservation Commission
Submitted May 17, 2011
3. COGCC took enforcement action against Encana relating to its Schwartz 2-15B Well (Enforcement Order 1V-276), after an investigation determined that Encana had performed hydraulic fracturing operations 4 times without notifying COGCC that its cement job had failed (the cement top had fallen), resulting in ground and surface water contamination.
Question. Do you agree that this is a verified case of gas drilling operations causing groundwater contamination?
Answer. The Schwartz 2-15B Well is a verified case of groundwater contamination caused by gas drilling operations, specifically, the failure of a cement job. This episode led the COGCC to impose additional well cementing, testing, and reporting requirements in the vicinity of the Schwartz 2-15B Well. The COGCC also amended Rule 317.o to require all operators in Colorado to run cement bond logs to ensure that proper cement coverage is achieved on all production casing.
Question. Even though the failure of the cement job was the direct cause of the contamination, do you agree that the fact that EnCana performed completion operations that included hydraulic fracturing and flowback water 4 times after the cement top had fallen was a significant contributing factor to the resulting groundwater contamination?
Answer. The COGCC’s investigation determined that the groundwater contamination was not caused by hydraulic fracturing. This determination was based upon the following factors: bradenhead pressures during hydraulic fracturing showed no communication above the top of the cement; normal fracture treatment pressure showed containment of the fracturing fluids within the target zone; no indication of fracturing fluids was detected in the groundwater samples; and the gas seep decreased after remedial cementing of the well, which would not have occurred if hydraulically induced fracturing had caused the seep.
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ana over West Divide Creek Seep 2004
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