A new tool studying the risk of fault slips
The quiet halls of Stanford University are far removed from the demanding work of an oil or natural gas well, where crews navigate the complex, rugged environment within the earth’s subsurface. Still, researchers in California studying induced seismicity triggered a technological wave now rippling through the oil patch, where operators need real-time answers to reduce the risk of earthquakes thousands of feet underground.
A unique scientific collaboration led by Rall Walsh (a Stanford Ph.D. candidate) and Professor Mark Zoback under the auspices of the Stanford Center for Induced and Triggered Seismicity (SCITS) has resulted in the development of a new software tool for operators and regulators to use in evaluating the risks associated with subsurface waste injection, a process that can potentially cause fault slipping.
This new technology, coupled with ongoing learning from the evolving science and cross-disciplinary technical collaboration, continues to improve the risk management techniques used to prevent induced earthquakes.
The Energy Factor spoke with Dr. Mark Zoback, Professor in Earth Sciences at Stanford, and Darren Pais and Tim Tyrrell, of ExxonMobil and XTO, respectively, about that collaboration.
Why is this tool important and what problem are you trying to solve?
Dr. Mark Zoback: Only a small percentage of faults are active today. The purpose of the technology is to identify those faults that may be reactivated by changing the fluid pressure at depth. This tool allows us to run calculations in a way that incorporates uncertainties in the data to help energy companies assess the probability of seismic activity prior to injection.
Seismic mapping of faults isn’t new, so what is the game changer with this newly developed software?
MZ: The idea of using information about the stresses acting in the earth to identify potentially active faults has been around for a long time. But the data about stress and faults have gotten much better, and that’s allowed us to develop a sophisticated tool that can interpret and incorporate the data while respecting its uncertainties. With this analysis, companies can then make informed decisions about how best to move forward.
Tim Tyrrell: Faults are everywhere in the earth. You can’t avoid them. Most of them are not active and pose no issue. What Stanford has done is create an easy-to-use tool to identify which faults might move with activities associated with oil and natural gas operations. What’s also helpful here is that Stanford has taken a very complicated analysis and made it easier for producers and regulators to use, particularly companies that may not possess the resources to develop their own analytical tools.
What did ExxonMobil bring to the table?
TT: ExxonMobil was able to take what was done in the classroom and bring it to the field. We have the resources to pull people together from many backgrounds – the in-house computer scientists and geological and geophysics experts – that some smaller companies may not have, and then test it in an actual operational situation.
Darren Pais: Not everyone has access to complex and disparate data that have been traditionally used to build such sophisticated models. Processing that data is also challenging mathematically, and can be expensive. What this tool does is allow operators to link data together with simpler models so they can run calculations much more rapidly and study sensitivities.
Can you talk about the process and how you worked with Stanford?
DP: From the outset, this was set up as a strong collaboration. For instance, when we tested the tool, I was the research developer and Tim acted as the business customer, the user out in the field. Tim was willing to test things starting from the earliest prototypes, and point out bugs and issues as the tool was being developed. On the other side, the Stanford team brought its strong technical background. We were lucky to have all these fronts effectively covered on one project.
TT: What I like about all of this is trying to solve complex, technical problems, trying to figure out how to do things faster and safer. We got together with Stanford and our research specialists to ask: What’s going on here? How do I build a tool that someone who’s newer to the field can use?
What about the collaboration with ExxonMobil and the interaction between industry and academia?
MZ: I’m a guy with a foot in the classroom and a foot in the real world, so it was an easy thing for me. But I think ExxonMobil was far ahead in the help they provided in taking the software out of the classroom and into the field. The feedback from them using the software was invaluable and helped us get the tool out for more companies to use.