Earthquakes Induced by Hydrocarbon Production: What Texas Can Tell Us About Appalachia Cliff Frohlich Institute for Geophysics University of Texas at Austin

• Sometimes human activityy associated with ppetroleum production causes earthquakes • Earthquakes large enough to cause concern are NOT caused by fracking, but sometimes by the disposal of fluids in injection wells • Why some injection wells cause earthquakes and others do not is still ppoorlyy understood • The vast majority of injection wells don’t cause earthquakes; the vast majority of injection-induced earthquakes are small. But…. a few are not.

• Sometimes human activityy associated with petroleum production (probably) causes earthquakes - Dallas-Fort Dallas Fort Worth TX - Guy AK - Trinidad CO - Youngstown OH - Prague OK - Fashingg TX - Timpson TX

M3.3 M3 3 M4.7 M5.3 M4.0 M5.7 M4.8 M4.8

October 2008 February 2011 August 2011 November b 2011 November 2011 October 2011 May 2012

• Phenomenon widespread geographically, but rare

More than 10 10,000 000 active injection wells in Texas, some i use since in i 1930’s 1930’ Earthquakes are rare, mostly small. If injection was hugely dangerous, we would know…

When Does Fluid Injection Induce Earthquakes? Producingg unconventional gas resources requires…

PROCESS CAUSES EARTHQUAKES Q

never very rarely sometimes • drilling wells XXX • fracking wells XXX • extraction of gas & fluids XXX • injection for fluid disposal XXX

Cliff’s Cliff s Note: Hydrofracturing almost never causes true earthquakes (M>1.5)

When Does Fluid Injection Induce Earthquakes? Producingg unconventional gas resources requires…

PROCESS CAUSES EARTHQUAKES Q

never very rarely sometimes • drilling wells XXX • fracking wells XXX • extraction of gas & fluids XXX XXX • injection for fluid disposal XXX

Cliff’s Cliff s Note: Hydrofracturing almost never causes true earthquakes (M>1.5)

M4.8 earthquake 17 May 2012 Timpson TX Previous P i quakes k nearly unknown in area, and epicenter not close to significant producing fields

Aftershocks occur along linear feature (previously unknown fault?) andd depths d th are 2.525 4.0 km. Within 3 km of seismicity, highvolume injection wells injecting at 1.8 km depth since 2006

Features of the Timpson p earthquakes q • Earthquakes began more than a year after injection commenced • Injection wells relatively high-volume (> 100,000 BWPM) • Earthquakes h k were within i hi 2-3 km k off wells ll • Earthquakes q occurred alongg ppreviouslyy unknown fault • Earthquake depths were at and below depth of injection

NE Texas Survey grey – Barnett B tt Shale Sh l triangles – seismic stations circles: grey – U.S.G.S quakes green – quarry blasts red – new quakes green lines- mapped g pp faults NOTE: Survey identified 8 times as many quakes as reported by USGS All in si six-county co nt area

NE Texas Survey Results • red circles: 2009-2011 earthquakes • yellow squares: injection disposal wells ll with ith maximum i injection i j ti rates t off 150,000 BWPM or greater • white squares and + symbols: lower-volume wells All well well-located located quakes are in 8 clusters within 3.2 km of these high-volume disposal wells. BUT many such wells have no nearby quakes: Johnson vs Parker Counties?

NE Texas Survey • red circles: earthquakes • yellow squares: high-volume high volume wells Quakes are near wells… e g Johnson County e.g., But many wells/counties have no quakes… quakes e.g., Parker County Stephens County Will earthquakes occur near high-volume injection wells elsewhere?

Why quakes induced in some locations and not others?

Regional tectonic stress: • stressmax: vertical NW-SE SE • stressmin i : NW • stressint : NE-SW Favors motion along normal f l aligned faults li d along l direction di i off stressint : NE-SW

Triggered Air hockey table, tilted with air off: friction keeps puck from sliding

Turn on air: friction reduced, puck slides Studies of crustal stress show fault surfaces everywhere t d to tend t be b near failure, f il b butt ffriction i ti prevents t slipping. li i Injected fluids push sides apart, reducing friction, allowing slip

What Can Texas Tell Us About Appalachia? pp • Sometimes human activity associated with petroleum production causes earthquakes

What Can Texas Tell Us About Appalachia? pp • Earthquakes large enough to cause concern are NOT caused by fracking fracking, but by the disposal of fluids in injection wells Producing unconventional gas resources requires…

PROCESS CAUSES EARTHQUAKES

never veryy rarelyy sometimes • drilling wells XXX XXX • fracking wells • extraction of gas & fluids XXX XXX • injection for fluid disposal XXX

What Can Texas Tell Us About Appalachia? • Why some injection wells cause earthquakes and others do not is still poorly understood

What Can Texas Tell Us About Appalachia? • The vast majority of injection wells don’t cause earthquakes; the vast majority of injection-induced earthquakes th k are small. ll But… B t some are not. t

If you are here, you should know about… other “expert” reports on induced earthquake problem. National N ti l Research R h Council C il (2012). (2012) Induced I d d Seismic S i i Potential P i l in i Energy Technologies. Royal Academy of Engineering (2012). Shale Gas Extraction in the UK: A Review of Hydraulic Fracturing. De Pater and Baisch (2011). Geomechanical Study of Bowland Shale Seismicity. Seismicity BC Oil and Gas Commission (2012). Investigation of Observed Seismicity in the Horn River Basin. Ohi D Ohio Dept. t off N Natural t lR Resources (2012) (2012). Preliminary P li i Report R t on the th Northstar 1 Class II Injection Well and the Seismic Events in the Youngstown, Ohio, Area.

The End much of this has been or soon will be published… published NE Texas:

Frohlich et al., Bull. Seismol. Soc. Amer., 2011 Frohlich, Proc. Natl. Acad. Sci, 2012 Justinic et al., Bull. Seismol. Soc. Amer. (in press) S Central Texas: Frohlich & Brunt,, Earth Plan. Sci. Lett.,, 2013 S Texas: Frohlich et al., Bull. Seismol. Soc. Amer., 2012 W Texas: Gan & Frohlich, Proc. Natl. Acad. Sci. (submitted) E Texas: Frohlich et al., al J. J Geophys. Geophys Res. Res (in prep). prep)