Antero undertakes the following practices to prevent impacts to the environment as a result of communication to nearby oil and gas wells.
During the surface hole portion of drilling, Antero employs a variety of measures to comprehensively prevent and reduce impacts to nearby wells and other environmental receptors such as groundwater resources. These measures include the following:
- Use of air instead of drilling mud to remove cuttings from the wellbore. The use of air during the drilling process significantly mitigates the potential impact on other nearby shallow wells and groundwater resources
- Utilization of numerous anti-collision measures to prevent the drilling well from colliding with offset wells
- Deployment of a casing program engineered to prevent the impact to offsetting wells and formations adjacent to our wellbore. Specifically, the surface casing depth and cement program are designed and permitted so that groundwater resources are protected prior to drilling in the hydrocarbon bearing intervals. As part of the final wellbore construction, two subsequent casing strings are run and cemented in place. Depending on the phase of operation being performed, the designed casing and cement program creates up to six barriers between Antero’s drilling/ completion operations and adjacent rock formations and nearby wells. We perform several tests to confirm the integrity of these casing strings prior to their use as a protective barrier. This includes running cement bond logs and pressure testing to maximum anticipated pressures associated with subsequent operations
During the completion phase of operations, potential communication with nearby wellbores is proactively addressed in several ways, including:
- Integrity of the casing tubulars, which provide a physical barrier between high fracture pressures and the shallower completions of nearby vertical wells
- Pressure monitoring and testing, as the integrity of the final casing string and its associated cement sheath is crucial to preventing impacts to nearby wells and environmental receptors. Antero’s final casing string and cement sheath were engineered to withstand the higher pressures associated with fracture stimulations, and were tested using cement bond logging and hydrostatic pressure testing to the highest expected treating pressures. During pumping operations, relevant pressures are monitored by on-site personnel, and in the event of observed anomalies, operations can be ceased in order to significantly reduce the potential to impact nearby wells
- In West Virginia, Antero uses a combination of regulatory agency information, our own data, discussions with offset operators and/or landowners, and physical field surveys to identify active, inactive, orphaned, abandoned, and P&A wells located within 1500 feet of new well locations, from surface through the entire wellbore length. Antero proactively notifies offset well owner/operators with wells within a 1500 foot radius two to three months prior to initiating nearby well completion operations and again one month prior to start of operations, well beyond the 500 foot regulatory requirement. When applicable, Antero also provides a final reminder five days before the start of a nearby well completion operation. If agreed upon between parties, Antero works with offset well operators to review existing well conditions, including confirming its current operating condition and downhole status. Antero alerts regulatory agencies if orphaned wells are discovered. Once offset wells are located and evaluated, Antero develops and implements a well monitoring plan for those identified wells, if applicable. Local geology is also assessed through reviewing historical data, data from previously drilled wells, and seismic survey data. The results of this assessment are used to identify geologic faults and mitigate risks associated with those faults. For both safety and efficiency reasons, Antero relies on technical analysis prior to and during active operations to closely monitor and prevent/mitigate communication between active wells and related potential subsurface issues
- Inspection program of vertical wells assessed as having an elevated risk for being impacted by Antero’s operations. This inspection program promotes the integrity of wellhead and surface equipment at these nearby vertical wells. In some instances, Antero installs pressure-monitoring devices at these wellheads
During the post-completion phase of operations, maintaining well integrity is proactively addressed in several ways, including:
- Ultrasonic testing of pipe thickness at the wellheads and Gas Production Units (GPUs) on high exposure sites
- Use of semi-permanent sand traps (up to six months) to catch produced sand and reduce erosion of equipment
- Remote and local Emergency Shut Downs on the tubing, casing and GPU
- Electronic measurement of pressure on the tubing and casing
- Determination of flow velocities throughout the system to stay below erosional velocity in the tubulars and production equipment
- Annulus pressure monitoring and reporting that meets or exceeds current state requirements
- Supervisory Control and Data Acquisition system for local and remote surveillance of pressures, temperatures, flowrates and hydrocarbon gas detection.
- In addition to 24/7 human monitoring, the system includes automated alarms, reports and notifications
- Pressure testing of tubulars during remedial well servicing operations
- Use of eco-meters (acoustic logs) to read liquid levels and verify tubular integrity
- Use of up-sized wellhead valves and piping to maximize erosional resistance
Of the 416 wells completed since 2017, 0% have experienced subsurface well integrity failures that resulted in a release to the environment. As a result of new downhole completion technology that became available in 2018, Antero began pressure testing all horizontal Marcellus wells to at least 9,500 psi, and all horizontal Utica wells to at least 11,000 psi prior to commencing completion work.
Antero has 1,137 producing horizontal wells, 259 producing vertical wells, and 89 wells which are drilling, completing, or waiting on completion.