Induced seismicity is commonly defined as earthquakes that are caused by a variety of human activities. The U.S. Department of Energy defines it as: “earthquake activity resulting from human activity that causes a rate of energy release, or seismicity, which would be expected beyond the normal level of historical seismic activity.”
Anadarko supports expanding the science, data and knowledge base around induced seismicity and how it may be related to human or industrial activity. We work with federal and state agencies on the development of appropriate regulations and guidance on the management of oil and natural gas operations, including the regulation of processes, materials and water management.
Hydraulic fracturing is an essential process in the modern development of unconventional oil and natural gas reservoirs. Hydraulic fracturing has been around since the 1940s and the associated technology has significantly evolved. The process has become more commonplace as the development of unconventional tight shale oil and natural gas reservoirs gained prominence in the mid-2000s. The hydraulic fracturing process occurs at great depth below the surface (5,000 to 10,000 feet or more) and impacts a relatively small area of rock immediately surrounding the wellbore.
Experts and regulators appear to agree that hydraulic fracturing, or fracking as it is more commonly referred to, is not a significant source of concern for induced seismicity for several reasons including:
- During the hydraulic fracturing process, only a limited volume of water is pumped into the formation for each stage of treatment; and
- Each pumping stage is a one-time event lasting 2-4 hours. The micro-seismic events that are generated from the fracking process are so small that, to be detected, requires sophisticated instruments that either have to be deployed in adjacent wells or on a very tight surface grid around the stimulated well.
Wastewater Injection Wells
Along with the oil and natural gas that are produced, potentially large amounts of natural saline brine water (formation water) may also be produced. This brine water is mainly a remnant of ancient oceans and contains high concentrations of salt and other dissolved minerals, as a result. The brine water must be separated from the oil and natural gas and, in some cases where recycling is not feasible, re-injected back into the Earth through the use of underground injection wells permitted in compliance with federal and state regulations. Such wells are common in oil and natural gas producing areas around the globe.
The relatively recent increase in seismic events in some isolated regions of the United States, including southern Kansas, Oklahoma and northern Texas, have led to numerous studies and increased deployment of seismic monitoring stations across the region. These stations increase data sampling and better enable independent researchers, regulatory bodies and industry partners in their ongoing efforts to study the possible correlation between wastewater disposal and increased seismic activity under unique geological conditions.
Although the seismic activity referenced above is generally occurring in areas where Anadarko has limited or no operations, the company is reviewing the data collected and monitoring the progress of the studies mentioned above, as well as engaging with various independent agencies and other experts to gain better scientific understanding. For instance, Anadarko has joined the Center for Integrated Seismicity Research (CISR) to further improve understanding of the mechanisms that may contribute to induced seismicity.
Furthermore, we use the results and findings of the studies and research in this area to continually improve the procedures and processes we use to assess the potential risk of induced seismicity from wastewater injection operations. Anadarko has adopted a stringent review process that includes evaluating the surrounding area for current and historical seismicity, site geology including mapped faults, well construction data, and other operational parameters.
In addition, Anadarko has implemented comprehensive strategies in our major operations areas, to reduce the need for wastewater injection. These efforts include recycling programs in Colorado, Pennsylvania and Texas.