Leaky gas wells are not only a waste of natural resources, but a significant player when it comes to climate change via the release of methane into the atmosphere. Engineers at Penn State University have developed a new type of flexible cement they say can help contain the problem, by being fed into the very fine gaps around deteriorating wells that traditional cements are unable to fill.
While major gas leaks are generally tended to promptly, smaller ones can go unnoticed for some time, even years. With these wells sometimes stretching for miles underground, shifts in temperature and pressure can cause cracks in the cement originally used to secure the pipes and contain the gas, enabling it to filter through into waterways or out into the atmosphere. Repairing the damage can be tricky business.
“In construction, you may just mix cement and pour it, but to seal these wells you are cementing an area that has the thickness of less than a millimeter, or that of a piece of tape,” says Arash Dahi Taleghani, associate professor of petroleum engineering at Penn State. “Being able to better pump cement through these very narrow spaces that methane molecules can escape from is the beauty of this work.”
Taleghani and his colleagues made their new concrete by starting with sheets of graphite that are almost two-dimensional and treating them with chemicals, altering the nanomaterial's surface properties so it is able to dissolve water, rather than repel it. The graphite is then uniformly fed into the cement slurry, where the new properties are key to the strength of the resulting material.
“If we just pour this material in the water and mix it, these small particles have a tendency to stick together and form a conglomerate,” Taleghani says. “If they are not dispersing evenly then the graphite is not as strong inside the cement."
The team carried out experiments using what they call narrow-slow tests to investigate the performance of the new cement, where it was successfully used to seal gaps measuring just 120 microns in thickness. Beyond sealing up damaged gas wells, the team says its new cement could find use in carbon capture applications, too.
“We have invented a very flexible cement that is more resistant to cracking,” says Taleghani. “That’s important because there are millions of orphaned and abandoned wells around the world, and cracks in the casings can allow methane to escape into the environment.”
The research was published in the International Journal of Greenhouse Gas Control.
Source: Penn State University