Antero prioritizes maintaining environmental conditions, and therefore 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 in lieu of drilling mud to remove cuttings from the wellbore. The use of air during the drilling process significantly mitigates the potential impact to 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 any 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. Several tests are performed to confirm the integrity of these casing strings prior to their use as a protective barrier, including 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 physical barrier between high fracture pressures and the shallower completions of nearby vertical wells and are of paramount importance
- 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.
Antero notifies operators of offsetting vertical wells within 1500’ of Antero’s wellbores, which is 1000’ greater than a new requirement of 500’ recently implemented by WVDEP.
- 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 2-3 months prior to initiating nearby well completion operations and again at 1 month prior to start of operations, well beyond the 500’ regulatory requirement. When applicable, Antero also provides a reminder 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 the well’s current operating condition and downhole status. Antero alerts regulatory agencies if orphaned wells are discovered. Once any 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 any seismic survey data; the results of this assessment are used to identify faults and mitigate any 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, however rare those instances may be.
- Inspection program of vertical wells assessed as having an elevated risk for being impacted by Antero’s operations. One of the latest measures Antero is in the midst of implementing, this inspection program will ensure wellhead and surface equipment at these nearby vertical wells are of adequate integrity. In some instances, Antero will install 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 well heads and Gas Production Units (GPUs) on high exposure sites.
- Use of semi-permanent sand traps (up to 6 months) to catch produced sand and reduce erosion of equipment.
- Remote and local Emergency Shut Downs (ESDs) 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 (SCADA) 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 140 wells completed in 2017, 0% have experienced subsurface well integrity failures that resulted in a release to the environment. Similarly, of the 163 wells completed in 2018, 0% have experienced subsurface well integrity failures that resulted in a release to the environment.
Antero has 1020 producing horizontal wells, 265 producing vertical wells and 113 wells drilling, completing or waiting on completion. Additionally, we have a single well waiting on a sales line, seven horizontal wells have been plugged and abandoned and 14 are under evaluation for further development. We have additionally plugged and abandoned 18 vertical wells over the last 2 years and have agreements in place with the state of WV to plug and abandon 3 vertical wells over the next year. We have 6 additional vertical wells that are inactive. We evaluate our wells for commerciality and pursue timely plugging and abandonment in accordance with regulations of any wells that are no longer commercial.