We’ve known for 80-100 years that drilling for oil can trigger small tremors. But most oil drilling has been done away from urban areas.

Hot rock may cause tremors, looks like it does in some circumstances. Best we do our first drills/injections in more remote places while we figure out the particulars.

It might well be that we might have to do all our hot rock out in the boonies and port the power to urban areas. Would that be so bad?

As for triggering ‘the big one’, just avoid areas of significant pressure. There’s lots of places where the deep rock formations are present without drilling into the major pressure zones.

[image: DISQUS]

Thanks for your additional input and more detailed, local knowledge of the issue.

”

Those concerns were punctuated in early July when – shortly after AltaRock began its initial drilling –the Geysers area experienced five quakes measuring 3.0 magnitude and above in a matter of only a few weeks.

”

http://lakeconews.com/content/view/10159/764/

Additionally, the tremors at Bern happened when water was introduced into the bore, not during drilling and certainly not when “waste water” was injected, that was not a disposal well, but a hot rocks site.

You’ve mischaracterized the object of what will be done on the project this year — the 24 million gallons of water pumped downhole will only be used to stimulate fracture networks and to test AltaRock’s method for making multiple networks in a single well. Circulating water to generate power–which you appear to think will happen this summer–will actually happen in subsequent years, if at all. Before then, production wells will be drilled into the fracture networks and water circulated between the original well and the new production wells.

This statement is wrong —

“two projects — one in California and one in Oregon — were stopped due to [earthquake concerns] within the past 3 years”

No geothermal projects have ever been stopped in the U.S.because of concerns about earthquakes.

Another wrong statement is to associate earthquakes in the news with fracking. All the “fracking quakes” in the news are associated with the disposal of wastewater from the fracking operations in separate disposal injection wells that have nothing to do with the fracking. To put it another way, hydraulic fracturing for shale gas has never caused earthquakes of concern. Recheck your references on this. This is a problem associated with the companies running the disposal wells, and not with the companies fracking for gas.

That said, yes, hydraulic fracturing for gas (and oil) does fracture rocks — the approach taken is to jack cracks open and keep them open using sand and other propping material. The bigger and wider the cracks, the faster the gas or oil can be drained. Quakes generated here have all been small and not noticeable at the surface.

In hydroshearing, the small fractures that exist in all rocks are eased open and existing natural stresses cause the two sides of a fracture to slip sideways. The fractures are kept open by the natural roughness of the rock faces. Unlike fracking for oil and gas, in geothermal you want the water to go somewhat slowly through the crack network in order to heat it up sufficiently for generating power.

Regarding downhole pressure, in addition to temperature increases, water pressure will increase in the well because of the pressure actively exerted at the wellhead, and also because of the amount of water itself in the well — it increases by about 0.43 psi per foot of water — think of the pressure on your ears at bottom of swimming pool. The target depths in the AltaRock project are between 6,500 and 10,000 feet. You do the math.

I have other issues with this piece, but this is all the time I have.