Date/Time
Date(s) - 11/08/2018
11:30 am - 1:00 pm
Location
Wynkoop Brewery
Categories No Categories
Please Join Us November 8th
at Wynkoop Brewery located at 1634 18th Street in Denver
EVOLUTION OF FAULTING INDUCED BY DEEP FLUID INJECTION, PARADOX BASIN, COLORADO
Roger P Denlinger and Dan R. H. O’Connell
High pressure fluid injection into a nearly horizontal, confined aquifer at 4.3 km to 4.6 km depth induced more than 7000 earthquakes between 1991 and 2012 within once seismically-quiescent Paradox Valley in Colorado. The magnitudes of these induced earthquakes range up to Mw 3.9, and together their hypocenters form vertical, right-lateral strike-slip fault zones. Induced faulting occurs first where these fault zones intersect the aquifer pressurized by the well, then migrates vertically above and below the aquifer. The rakes and strikes of the induced earthquakes are Riedel shear faults that begin at an acute angle to the strike of the fault zone, then evolve into Riedel shear faults nearly aligned with the fault zone as fault slip continues. A fully coupled poroelastic analysis of stress from fluid injection shows that Riedel shears first occur when the effective stresses exceeding Coulomb failure conditions are in the range of 0.35 MPa to 0.4 MPa. The evolution of Riedel shear faults produces an anastomosing fault zone structure that accommodates continued fault slip, reducing resistance to slip as faulting continues.
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