Induced seismicity associated with both hydraulic fracturing and saltwater disposal (SWD) activities have been identified in Oklahoma, leading to traffic light regulations based on seismicity magnitudes for deep SWD wells along with hydraulic fracture (HF) stimulations in the Anadarko Basin. Oklahoma regulatory agencies require routine reporting of HF schedules and daily SWD injection data, a critical factor for effective management and identification of causal factors.
Operational protocols have emerged in Oklahoma for safe and compliant operations. These include pre-job hazard assessment and planning, seismic monitoring and reactive mitigation steps if anomalous seismicity occurs. An important first step is detailed subsurface characterization using 3D seismic for input into geomechanical screening to identify structures in orientations susceptible for induced slip. More importantly, integrating historic seismicity is critical to assess expectations for future seismicity. High resolution seismic monitoring during the operation is also essential to continually track potentially seismically active structures and thereby evolve our understanding of seismic hazard, and to track any precursory build up in background seismicity rates. Accurate and sensitive seismic monitoring when integrated with timely operational data helps refine structural mapping, clarify seismic potential and better illuminate causality and enlighten mitigation options. Relatively small operational changes, such as informed changes in well sequencing during zipper operations, made at early phases has been found to help keep seismicity under control and avoid more aggressive changes once anomalous seismicity is occurring. With seismicity impacting various segments of a prudent operating company, early and effective communication across stakeholders is important along with established responsibilities and reaction plans.