On November 12th the Alberta Energy Regulator’s (AER) Directive 065: “Resources Applications for Oil and Gas Reservoirs” was updated. The directive defines all key requirements for well applications in Alberta, Canada, including injection/disposal wells. The update has significant new elements for the management of induced seismicity (IS) that apply to both emerging Alberta carbon storage projects as well as other new and legacy injection operations, including wastewater disposal and the nascent geothermal sector. In this article, we discuss some of the key changes.
Introduction of seismogenic well designation
Section 4.1.8.1 introduces a new designation referred to as a “seismogenic well”, which will trigger additional requirements. At its discretion, the AER will assign this designation based on a review of data associated with observed seismic events. While conceptually simple, we expect that in practice this designation will be complicated by two factors:
- Given the sparse nature of the public seismological networks, location accuracy of any perceived induced seismic event is low across large parts of the province. Operators who don’t collect their own monitoring data are exposed to mis-attribution.
- In areas with neighboring disposal wells run by multiple operators it might be difficult to assign causality of any one injection location, in particular where the pressure plumes from those disposal sites interact and create cumulative effects.
If a well is deemed seismogenic by the AER, the operator must submit:
- a seismic risk assessment
- a monitoring, mitigation and response plan (MMR)
- operational data
- seismic monitoring data
- additional data required under the scheme approval
- a traffic light protocol (TLP) for mitigation of future induced events
Legacy projects come into play
The updates will also apply to already existing wells/legacy disposal operations in two situations:
- When the operator applies to amend operating conditions, and
- If an existing disposal well becomes associated with induced seismicity
Hazard assessment required
Applications for all new fluid disposal wells have to include an induced seismicity hazards assessment. At a minimum these assessments need to cover a 10 kilometre radius around disposal wells. As a minimum standard this assessment must use public earthquake catalogues. Optional elements of a hazard analysis in the directive are stress field assessment, mapping of faults and consideration of operational and geological parameters. Probabilistic seismic hazards assessment (PSHA) for induced seismicity is also mentioned as an option. PSHA, a proven practice from engineering seismology, is an excellent approach to yield rigorous, quantitative hazards assessments for locations with good input data coverage. For areas with lesser input data, PSHA can be adapted to deliver thorough and defendable hazards estimates albeit with larger, but quantifiable error bars.
This induced seismicity hazards assessment has to be updated and kept evergreen throughout the life of the project.
MMR plan with TLP thresholds needed
If the hazards assessment shows the area to be “prone to induced seismic events”, a risk assessment together with an MMR plan has to also be included in the application.
If specific infrastructure (essential infrastructure under the defence act) falls within the 10 kilometre radius around the disposal well, infrastructure operators and affected land owners have to be informed as part of the development of the MMR plan. Such engagement might add to the time required to prepare an application.
The MMR plan has to define thresholds for a TLP. TLP threshold magnitude values are not mandated or recommended at this point. However, previous subsurface orders related to induced seismicity suggest that the expectation is between magnitude 1.0 and 2.0 for yellow and between 3.0 and 4.0 for red threshold values. The AER has also published iso-nuisance and iso-damage maps for Alberta (Open File Report 2023-04) that provide excellent guidance for red light thresholds across the province. Whatever the chosen thresholds are, reliable magnitude estimates that are defendable to the AER and the public are of high importance – a key consideration for selecting monitoring instrumentation.
If the lower yellow threshold for TLP is exceeded the operator is mandated to immediately report the event to the Energy and Environmental Emergency’s 24 hour hotline and implement the AER-approved MMR mitigation plan.
If the higher red TLP threshold is exceeded, in addition to fulfilling the yellow requirements, the disposal well has to be returned to a “safe state”. Before returning to regular disposal, a revised MMR plan that mitigates re-occurrence has to be approved by the AER. The process of data analysis, MMR plan revision and AER approval can be expected to take significant time and prolong the disruption of the disposal operation.
Monitoring and mitigation program mandated
Operators are mandated to employ real-time seismic monitoring arrays that are adequate to meet the needs of the approved MMR plan. This means that they must cover the Area of Review (AOR) – 10km circle, or larger if required by AER – with a high enough sensitivity, or magnitude of completeness, that events that would trigger TLP actions are reliably detected. Previous IS experience shows that it is advisable to consider arrays that deliver better magnitudes of completeness than the lowest TLP threshold. This approach provides better delineation and understanding of seismogenic features in the subsurface and in some cases can help predict future event risk and enables proactive management before thresholds are exceeded. Any critical infrastructure within the radius also has to be instrumented with real-time accelerometers to monitor their structural health throughout the lifecycle of the disposal operations.
In summary, the Directive 065 updates significantly strengthen requirements to address induced seismicity risk associated with fluid disposal operations. Additional data, analyses and plans are required for new applications and amendments to legacy injection wells. This includes hazards assessments for all wells and also risk assessments and MMR plans for many operations. Project- or area-specific real-time seismicity and ground motion monitoring throughout the lifetime of the disposal project will be required in many cases. Surface stakeholders will have to be informed when planning the project MMR approach and the collected seismicity data will have to be made available to the public.
With these additions we believe the AER is leading regulators in North America in the responsible management of IS risk and we expect that many other jurisdictions will adopt similar principles as the CCS industry matures.
