As Part of my PhD I am investigating how, how fast and how much CO2 may leak from a CO2 reservoir to the surface through faults. Faults are areas within the earth’s crust where layers of rock have been displaced to each other and often form pathways for fluids (water, oil, gas, CO2). I have tried to explain how faults form and their role in my research in this post.
In eastern Arizona, between the towns of St. Johns and Springerville, there is a natural CO2 reservoir in the subsurface. It has been leaking CO2 from the reservoir to the surface in the past – and this leakage is indicated by a certain type of carbonate rock at the surface: Travertine. It forms when CO2 rich fluids reach the surface and can thus be used to track ancient leakage points. This can be easily done by mapping the deposits, something that other geologists had already done for my field area. From the way the deposits are arranged it is (more or less) obvious that faults have played a major role as fluid pathways.
The goal of my fieldwork was to take samples from the known travertine deposits and bring them back to the UK where I will then determine how old they are – by a process called (rock) dating. Once I know how old the different deposits are I might be able to calculate how much CO2 leaked over what period of time. This then might help to assess the risks involved with CO2 storage sites.
I got most of the samples I wanted, to some sites the access was very restricted (“roads” even worse than on the picture below) or they were on private land. Lab work is planned to be finished by the end of the year and to start soonish. I will keep you updated on the progress 🙂
Below are some pictures I took during the fieldwork to give you an idea how the landscape looks like and to prove I actually did some work and not just holidays as some people claim! 😉 (A post with some holiday pictures will come soon as well).