The Texas Railroad Commission has issued proposed changes to its rules that govern disposal wells.
Fluids that are produced during the drilling, completion and production of oil and gas wells must be disposed of properly, meaning that each well must meet the requirements specified through the TRRC permitting process.
The TRRC has permitted more than 50,000 injection wells in Texas since the 1930s.
Recently, there has been seismic activity near several disposal wells in North Texas. The most recent happened near the town of Azle just north of Fort Worth from November 2013 to January 2014. Some residents in the area have speculated that there is a causation between the disposal wells and the earthquakes.
Even though the tremors have been relatively small (none reaching magnitude 4.0), residents, regulators, and the oil and gas industry are concerned and want to find the reason for the seismic activity and a solution to prevent it in the future.
The TRRC has held meetings on the seismic events, and has hired a seismologist. The Texas Legislature has formed a subcommittee to look into the matter.
The TRRC’s proposed changes to its disposal well rules (Rules 9 and 46) require additional information on its application for a permit such as logs, geologic cross sections and structure maps in an area where conditions exist that may increase the risk of a seismic event. The TRRC said such conditions might include complex geology, proximity of the baserock to the injection interval, transmissive faults or a history of seismic events in the area.
The applicant must report to the TRRC the results of a review of information from the U.S. Geological Survey regarding the locations of any historical seismic events within the estimated radius of the 10-year, five-pounds-per-square-inch pressure front boundary of the proposed disposal well location.
USGS has the ability to detect and locate all seismic events larger than magnitude 2.0 throughout the U.S. It maintains an online database of seismic events in the U.S. from 1973.
A significant problem encountered by the TRRC in writing a regulation for the entire state is that every disposal well is different. Some are commercial disposal wells and designed to take large amounts of fluids at high pressure, while others handle much smaller quantities of fluids and are for private use on the oil lease. Other contributing factors are depth of the well and pressure of the fluids injected into the disposal well.
Even though there are a multitude of factors involved in determining if disposal wells may cause seismic activity, it is certain that everyone involved wants answers as quickly as possible.