Despite all recent alarmist headlines, risk of induced seismicity is small, rare and manageable
By Seth Whitehead, EnergyInDepth
Just a day after the United States Geological Survey (USGS) released a report that finds a 50 percent reduction in the number of U.S. citizens who live in areas with the potential for induced seismicity since 2016, a new tool has been introduced that can be used to further reduce the already declining risk.
Stanford University on Thursday unveiled its new Fault Slip Potential software, which it developed to help producers reduce the risk of triggering manmade earthquakes via wastewater injection from oil and gas production.
Available for free download here, the software combines geo-mechanics and pore pressure modeling into an easy-to-use format to assess fault slip potential for saltwater disposal wells.
According to co-developer Mark Zoback, professor of geophysics at Stanford’s School of Earth, Energy & Environmental Sciences, the software is primarily aimed to enable energy companies to conduct seismicity risk assessments and help guide producers and regulators in deciding where to place saltwater wells.
“Our intention is for it to be used as a screening tool in advance (of drilling a wastewater disposal well),” Zoback said during a media call on Thursday. “We can calibrate it to evaluate what’s happened in the past (at current disposal sites), but hope will be use to prevent seismicity.”
Developed along with Stanford graduate student Rall Walsh — who alongside Zoback, has extensively studied induced seismicity in Oklahoma — the software calculates the probability that oil and gas injection activities will trigger fault slippage, illustrated in the following graphic from the supplemental software guide.
Zoback noted during the media call Thursday that ExxonMobil provided technical and operational knowledge and support to Stanford University in developing the software.
This is just the latest example of continued collaboration between regulators, industry and the scientific community to address the issue of induced seismicity.
To be clear, the software does not prevent earthquakes or identify previously unmapped faults. Instead, it helps assess and ultimately reduce risks by determining which faults are likely to be problematic, which Zoback notes if far more important than merely detecting faults,
“Faults are everywhere in the Earth’s crust, so you can’t avoid them,” Zoback said in a press release. “Fortunately, the majority of them are not active and pose no hazard to the public. The trick is to identify which faults are likely to be problematic, and that’s what our tool does.”
The FSP uses three essential pieces of information to determine the likelihood of any given fault slipping: 1.) how much wastewater injection will increase pore pressure at a disposal site, 2.) knowledge of stresses acting on the earth, and 3.) knowledge of pre-existing faults in the area.
The latter information is typically collected by oil and natural gas companies during the exploration process, while the former comes from monitoring earthquakes or wells drilled in the area.
Zoback and Walsh noted that the software has been successfully tested in the field, and that they believe it will become widely used in the near future — particularly with oil and gas activity picking up since the recent market recovery.
“It is timely in the sense that things are picking up again and in the sense that induced seismicity is an agenda item now,” Zoback said. “[E]veryone is well aware of this issue.”
Industry has taken the issue of induced seismicity very seriously, investing over $50 million to reduce earthquake risks since March 2015, amf this software adds to the growing list of technology already used to limit induced seismic risks.
Companies have also helped secure funds for additional seismic monitoring stations and shared proprietary data with scientists and regulators — including information on previously unmapped faults — in efforts to reduce induced seismicity.
Fortunately, these efforts are producing results in the areas of greatest concern. Felt earthquake activity dropped 31 percent in Oklahoma last year and 65 percent in Kansas, while there were no felt earthquakes in North Texas in 2016.
In fact, Oklahoma’s felt earthquakes were down 88 percent during the first two months of this year compared to January and February 2016, and Stanford released a study in December that concluded mitigation measures such as wastewater volume reductions are proving so effective in Oklahoma that the Sooner State state seismic activity could return to background levels in the coming years.
Despite all the recent alarmist headlines, the risk of induced seismicity is small, rare and manageable. And this latest tool from Stanford further illustrates that with increased understanding of induced seismicity, industry can further reduce the risk and even better manage the issue moving forward.