By Joyce Hale
The purpose of casing conduits that pass thousands of feet down into the ground is to create a permanently isolated free-flowing path for gas to come to the surface. The casing must be capable of blocking high pressure injections of fracking fluids, being injected into rock formations deep under ground during well construction, and to also restrain returning fluids, along with high pressure gases and naturally occurring toxins. The purpose for multiple walls of casings is to prevent these poisons from contaminating aquifers, which supply drinking water. Aquifers are often drilled through in the downward quest for minerals lying below the water table.
Thousands of years ago naturally occurring seeps of gas in Persia, Greece, and India had temples built over them to provide eternal flames, but it was not until 200 BC, when the Chinese developed the earliest known gas wells, they recognized the energy value of gas and created pipeline delivery systems through bamboo casings. The first gas well in the United States was drilled in Fredonia, N.Y. in 1825, where it successfully provided light for two stores, two shops and a grist mill.
As the need for energy increased, casing technology improved, but the process is still extremely complicated and rife with ways it can go wrong. Gases can escape under a number of conditions from inside the casing as well as in the area between the outer casing and the well bore. While the industry has tried to assure greater safety by building casings with multi-layered concentric pipes, this will never be the answer to stop gas losses at the casing’s outer surface.
Just how do gas well casings fail? Here are some of the ways:
• Tubing leaks — Poor thread connections, corrosion, cracks and ruptures
• Poor drill mud displacement — Failure to clear away drilling waste to allow proper cementing
• Improper cement slurry mixture — Setup and hydration problems; channels in cement that may form allowing gas to vent
• Cement damage after setting — Stress cracks; well bore and seismic activity
While people are most alarmed about fracking, it is important to have as great a concern for casing failures. Incidents occur even in newly constructed wells. Time is not kind to a casing’s viability and deterioration is certain after closure or decades of abandonment. Some claim that in time all casings fail. With as much as 70 percent of toxic fracking fluids left in the ground, and studies showing possibilities of upward fluid migration, little is known about how these deteriorated pathways will eventually contaminate fresh water sources.
Companies should be required to have on-site inspectors during the casing’s cementing operation for assurance that the installation meets the highest standard of protection and follows regulations. Once pollution enters an aquifer, the water can never be cleaned, thus denying all safety for its use and limiting the quantities now available to us.
While earlier societies assigned a spiritual role to the flaming seeps, we have not progressed very far from this type of reverence for gas. Instead, the frenzy for natural gas extraction is being promoted with religious fervor as our salvation. However, neither false gods nor false hopes are the answer for our energy addiction.
From Mud to Cement – Building Gas Wells (Schlumberger – Oilfield Review)
Cracks in the Façade (Environmental Working Group)
Upward Migration of Fluids in the Karoo Basin (Institute for Groundwater Studies – South Africa)