Oil Recovery May Have Triggered Texas Tremors 172
ananyo writes "First came reports of earthquakes caused by hydraulic fracturing and the reinjection of water during oil and gas operations. Now U.S. scientists are reporting tremors may have been caused by the injection of carbon dioxide during oil production. The evidence centers on a sudden burst of seismic activity around an old oil field in the Permian Basin in northwest Texas. From 2006 to 2011, after more than two decades without any earthquakes, seismometers in the region registered 38 tremors, including 18 larger quakes ranging from magnitude 3 to 4.4, scientists report in the Proceedings of the National Academy of Sciences. The tremors began just two years after injections of significant volumes of CO2 began at the site, in an effort to boost oil production. 'Although you can never prove that correlation is equal to causation, certainly the most plausible explanation is that [the tremors] are related to the gas injection,' says Cliff Frohlich, a seismologist at the University of Texas Institute for Geophysics in Austin, who co-authored the study."
Re:But is this....bad? (Score:5, Informative)
...my understanding of fault lines is that there are areas where tectonic plates cross, with one moving over the top of the other, pushing one down and one up. So far so good right?
Half right. Sometimes it cause by plates rubbing against each other but there are other ways to create earthquakes. Since Texas is far away from any fault lines that I know of I don’t think this is the case.
http://en.wikipedia.org/wiki/Intraplate_earthquake [wikipedia.org]
So the model I have understood is, the fault compresses over time as the plates move, and then an earth quake happens when the stress is suddenly released, allowing the plates to slip some amount, relieving the stress and starting the process over again from its new position.
So now if this is an accurate enough description of the process, it seems to me like more frequent, smaller quakes are likely preferable to less frequent larger ones. So could this triggering of earth quakes actually be a....good thing? Is that question even being asked?
It has been asked and the answer is maybe. The energy of small earth quakes is trivial to that of large earthquakes. Small earthquakes might just transmit the stress down the fault line resulting in larger earthquakes later. The current models are not very good and this sort of stuff so no answers yet.
Re:From TFA (Score:4, Informative)
It seems to me that you arent grasping his point, nor are you grasping basic forces.
its not just "hundreds of pounds". its hundred of pounds.....per square inch.
we arent talking about simple hundred of pounds of force.
we're talking about hundred of pounds of pressure per some unit area.
the bigger the area, the greater the net force applied by that pressure.
as the man said, even on a not particularly large rock cavity of say 50x50 feet of bearing area, that mere "hundred" pounds of pressure eqautes to 30E6 pounds of net force being applied to that surface. depending on that rock's configuration, its internal stresses, support from surrounding rock, etc, that force can be redirected and concentrated (stress concentration), such that it leads to failures in the internal structural integrity of said rock or nearby rocks.