Antero proactively addresses seismicity issues by carefully evaluating the location of disposal wells prior to use. Antero does not own or operate disposal wells but uses properly permitted and operated third-party Class II UIC wells for wastewater disposal. Third-party disposal wells are vetted in a rigorous selection process before any wells are utilized for wastewater disposal. The process begins with locating existing wells in close proximity to Antero’s areas of operation. Potential disposal wells undergo a desktop audit first by the HSSE department, and a subsequent audit and assessment by the Geology department. A location that exceeds Antero’s risk factors are not authorized for use.
During the Geology department’s investigation, the disposal well proximity to any known mapped faults or seismic events, proximity to other wells, and the targeted injection zone are assessed via United States Geological Survey (USGS) datasets. According to the USGS 2014 Seismic Hazard map, Antero’s operations are located in very low risk areas, meaning low risk of occurrence of the potential for horizontal acceleration. Per the USGS 2018 Short-term Induced Seismicity model, Antero’s area of operations is in the lowest (<1%) chance of potentially minor-damage ground shaking events. Additionally, Antero evaluates company wells within two miles of the third-party disposal well to identify any open zones in common with the disposal well; in case of overlap the company wells are recommended as a candidate for plugging. Additionally, during this assessment and audit process, Antero evaluates the planned injection interval of the third-party disposal well to understand where Antero wells are stratigraphically in relation to nearby wells and actively producing zones. If a location is approved by the Geology department, Antero HSSE department conducts follow-up on site audits of the third-party disposal wells during the on-boarding process. Once the onsite audit is conducted and there are no findings of concern, Antero operations is given the authorization to utilize the third party well for wastewater disposal.
In the Utica play there have been reported instances of induced seismicity likely related to basement faults in connection with hydraulic fracturing and wastewater disposal. The Ohio Department of Natural Resources (ODNR) has their own seismic monitoring array in place across the state. In areas where they have identified the potential for seismic activity, they may request operators to install additional monitoring equipment. As part of this program, there is a set of tiers that determine whether operations can continue, must be modified, or must be halted entirely. Antero has made arrangements with vendors to support this increased monitoring if it is deemed necessary by the ODNR. Monitoring of this nature includes a series of geophones and accelerometers that would be localized around specific completion activity. These sensors gather data constantly and relay it to the vendor to process and manage along with Antero personnel. At this small scale, the resolution of the data is more precise than the statewide array. Although there is no known history of seismic activity across our area of operations in the Marcellus in West Virginia, this monitoring capability is available to us in our operations areas in both West Virginia and Ohio.