Seismic activity directly associated with stimulation operations has been studied extensively. Thousands of fracturing events have been observed using a technique known as microseismic monitoring. As the name implies, the seismic events are expected to be small compared with earthquakes. The monitoring was originally done to make operations more efficient. It is in the interest of the operator to direct the fracturing energy into the oil or gas bearing layer. Properly designed operations achieve this. The monitoring has shown that the vast majority of fracturing operations generate low intensities, well below 1.0 on the Richter scale. A handful of instances of higher levels of seismic activity have been documented (out of hundreds of thousands of wells fractured over the past 50 years). For example, an event of 2.5 was observed in the United Kingdom. Although this has not been fully explained, it is believed to have been associated with a proximal active fault. This appears to be the case for most of the other known instances as well. Virtually all oil and gas operations conduct 3D seismic monitoring prior to planning the wells. Faults can be, and ought to be, identified and avoided.
Posted on: Fri, 19 Sep 2014 19:35:56 +0000
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