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A joint workshop will study evidence for and against injection-induced seismicity – and what can be done to mitigate the problem.
Some things seem to measure higher on the public opinion scale than they do on the Richter scale.
Such is the case with injection-induced seismic events. As a kid growing up near Denver, I constantly felt minor earthquakes associated with the injection of waste from the nearby Rocky Flats nuclear facility. The earthquakes were only one of myriad natural problems associated with this facility. As such, I don’t think they garnered as much attention as the contamination that affected surface water and nearby farmland.
But hydraulic fracturing has earned such an ugly reputation that even a minor earthquake stirs major debate. Recently there have been minor earthquakes – typically measuring less than 3 on the Richter scale – that have fanned the debate on oil and gas activities and have caused concern to local residents.
The industry has not been slow to react. This month the Society of Exploration Geophysicists is teaming with the Society of Petroleum Engineers to host a workshop titled “Injection-Induced Seismicity.” The goal of the two-day workshop is to bring together reservoir engineers, drilling and completion engineers, geologists, geophysicists, geomechanicists, and seismologists to discuss issues associated with injection activities. In addition to hydraulic fracturing, workshop topics will address mining, geothermal extraction, and wastewater disposal. The latter was the topic of a recent study by the University of Texas that concluded that minor earthquakes were more numerous around wastewater injection wells than in other areas.
According to Shawn Maxwell, microseismic technical advisor for Schlumberger and one of the co-chairs of the workshop, attendance was maxed out prior to the middle of August. “That talks to the interest in the topic within the industry,” he said.
He added that plans for the workshop began in 2011, during which time earthquakes in the UK and Ohio provided additional material to discuss. But, he added, this is not a new topic.
Additional sessions will provide an historical overview; examine state-of-the-art monitoring; and discuss the role of geomechanics, particularly what is lacking in predictive geomechanics. The final panel will address what is needed to move forward to reduce the risks and hazards of induced seismicity.
So, given the thousands of wells that are fraced in the US alone every day, why aren’t these seismic events more frequent? Primarily it’s because several elements have to align to cause any sort of subsurface seismicity. “You have to have a fault or a zone of weakness,” said Peter Duncan, founder, president, and CEO of MicroSeismic Inc. and a co-chair of one of the panels at the workshop. “The fault has to be in communication with the fluids that you’re injecting. And the rate of the injection, which is related to the pressure, has to be faster than the rate of leak-off such that you cause pressure to build up.” Additionally, he said, the fault in question needs to be under some sort of stress that is parallel to, not perpendicular or orthogonal to, that fault. “In the circumstance of all of those things, you will induce seismic events.” Maxwell added that monitoring is an area of keen interest, but the workshop also hopes to discuss proactive technologies. “Can you characterize the conditions that result in induced seismicity and predesign the injection to mitigate that?” he asked. “We’re bringing people from geomechanics, academia, national labs, and geological surveys and putting them together with the operations people. That should result in some very informative discussions.”