These excerpts are taken from the same, well-written article I referenced in the last two posts. I have broken this article into bite-size pieces for your convenience. Click here to read the entire article.
"While deepwell injection of liquids has occurred safely for over 20 years, there is less experience with injecting gasses like CO2. While most CO2 injections for enhanced oil recovery have occurred safely, problems that have occurred illustrate the unique hazards that utilities and regulators must consider. A few of these potential hazards include the following.
Blowout
Well blowouts occur when gas escapes through old or unknown wells. In January 2001,a natural gas leak from a cracked gas well casing leading to salt caverns and used as a natural gas storage facility resulted in an initial gas explosion below two stores in downtown Hutchinson, KS. The initial gas explosion was followed by an eruption of natural gas and water geysers two miles east of the initial explosion later that day and for several days thereafter. Two people residing in a trailer home were killed as a result of one of the explosions. The gas leak originated from a cracked well casing at a depth close to 600 feet and proceeded to migrate horizontally, traveling along abandoned brine wells and ultimately reaching the surface some distance away from the initial explosion.62
In another case involving CO2, a blowout occurred during drilling at a production well in March 1982 causing the free flow of CO2 at the well head and leakage from ground fractures directly above the site. The high rate of CO2 from the well caused containment not to occur until the following month.63
The report issued a number of recommendations including: determining the potential for CO2 migration along unsealed fault and fracture zones; the potential for magmatic or seismic activity to cause damage to sealing caps resulting in CO2 releases; the potential for wells to transport CO2 to the surface; and implementation of public education and CO2 monitoring programs to minimize impact to human health and the environment from releases.65
The risk of blowout is hard to quantify since there is little information on the number of abandoned wells in the United States. It is difficult to estimate the number of these wells since some do not have observable caps or metal casings that can be detected through sensors. Texas estimates that there are approximately 11,000 orphan abandoned wells that it is gradually closing through a state program.66
Operators of CCS injection wells will have to find, close, and cap abandoned wells within the Area of Review.62
Economic Damage
The saline formations in Texas produce some oil and gas in formations nearby or overlaying the potential injection formations. In addition to well blowout, less apparent seeps from the injection zone into oil and gas producing layers can dilute the value of these deposits and ultimately return the CO2 to the atmosphere.67
Corrosion
As CO2 rises to the top of the injection layer, it may contact closed wells or the cement casings of older wells. If the CO2 reacts with water to form acidic compounds, these acids could start to erode the concrete. As more is eroded, the process accelerates, creating a reinforcing-negative cycle that could allow the CO2 to rise up the abandoned well to drinking water layers. While this problem can be prevented through different well closure approaches, the potential problem will increase the cost of an applicant’s Area of Review study and demonstration.68
This paper does not outline the necessity to deal with other issues such as amending state drinking water laws or amending federal environmental laws such as the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA); Endangered Species Act ESA), Resource Conservation and Recovery Act (RCRA), and CERCLA’s Natural Resource Damage Assessment Act (NRDA). These issues have been addressed by other APPA papers located at www.appanet.org/files/HTM/ccs.html"
