posted on Aug, 26 2011 @ 08:38 PM
I hope this is OK. Im a lurker from the Fukushima thread. Since there is interest in o&g ops doing EQ damage, I thought I'd post this. This is bits
and pieces from a report I did two years ago concerning oil and gas operations (O&G ops) and their ability to trigger EQs. I didn't have time to
break it down further.
The o&g boys have known since the early 1900's that drilling caused EQs. We now suspect that there are numerous activities associated with the o&g
biz that can induce EQs or add stress to the lithosphere. All of this information has been presented repeatedly to the MMS, USGS etc and no one seems
Geological Impacts Generated from O&G Operations
Since the 1920’s science and industry have known that oil and gas extraction and fluid injection can cause earthquakes, as these processes change
the pressure within fault lines (Yerkes and Baker 1976). The oil industry has even looked into the threat of liability should an earthquake they start
cause damage (Cypser and Davis 1998).
Hydrocarbon extraction can trigger or induce seismic instabilities at both the local and regional scale. Hydrocarbon extraction causes both a) pore
pressures to decrease, triggering adjustments of the geological structure in response to this depletion and b) crustal readjustments due to the
removal of load from the upper crust, leading to large earthquakes (> M 6) at great distances from the hydrocarbon field.
Fluid injection also induces earth movement. Local hydraulic fracturing due to fluid injection induces seismic-slip on cracks within the injected
reservoir through decreasing the effective stress. (Grasso 1992, Chen and Nur 1992, Segal et al 1994, Segall 1989). However, Sze found a strong
correlation between earthquakes and gas production, but not as much for injection and production, and none for just injection (Sze 2005) suggesting
that extraction was the main driver for earthquake induction in these processes.
Grasso and Sornette reviewed major cases of induced seismicity caused by O&G operations in various parts of the world and found that pore pressure
changes from these operations are sufficient to trigger seismic instabilities in the uppermost crust with magnitude ranging up to 7.0 in otherwise
historically aseismic areas. These observations suggest that a significant fraction of the crust is not far from instability and can thus be made
unstable by minute perturbations (Grasso and Sornette 1998). In areas with known seismic activity and earthquake potential like the SAF and CSZ, this
threat is magnified, and the possibility of inducing even larger earthquakes than M 7.0 must be assumed.
Geologic Dangers From Seismic Exploration
Seismic testing is considered an integral part of O&G exploration. So much so, that the recent government report from the Council on Environmental
Quality, when addressing the use of anthropogenic sound for offshore minerals exploration, stated; "Societal benefits from the full spectrum of
sound-producing activities should be considered along with, and not overshadowed by, any potential negative impacts of those activities" (JCOST
2009). In other words, it doesn't matter how bad the negative impacts might be, they will never be important enough to stop the use of this
exploration tool. The reason for this is simple. Without it, the O&G industry wouldn't be able to locate offshore oil and gas deposits.
The most important thing to understand when considering effects from seismic exploration is knowing that the main tool used is seismic waves. This
needs to be underlined and highlighted with exclamation points. As stated repeatedly above, seismic wave energy has been shown to add stress to fault
zones and trigger other earthquakes, even hundreds of miles away. Yet, for oil and gas exploration, massive continuous bursts of both P and S seismic
wave energy is applied thousands of times to stress zones in a given area. When one considers the fragility of the tectonics in the SAF, MTJ, and CSZ,
this use of low and high frequency sonar in these areas would have to be likened to using a match as a light source to see how much gas is inside a
Longitudinal P-waves generated by earth movement and the sounds we hear are both forms of energy expressed as a compression waveform created by the
vibration of objects, the only difference being the level of magnitude and frequency. P-waves generated in an earthquake are extreme low frequency