Scurry-Fisher County Quakes Lead to Disaster Declaration

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Written by Paul Wiseman for Industrial Info Resources (Sugar Land, Texas)--More than 100 earthquakes have rattled an area around the West Texas town of Snyder, in Scurry County, over the past few days. To date, the highest recorded was a 5.1 quake on Friday, July 26, in nearby Hermleigh. That quake prompted Scurry County Judge Dan Hicks to issue a disaster declaration.

In recent years, the Texas Railroad Commission (RRC) has been monitoring three Permian areas for quakes that likely are caused by produced water injection, but previously this area had not had enough seismic activity to be included. Those areas include: North Culberson-Reeves; Stanton; and Gardendale (Midland-Odessa).

In the areas already under the microscope, SWD activity has been limited over the last three years or so, especially in underground formations where quakes have originated. In most cases, seismic activity has been reduced in those zones since the reductions took effect.

Where Oil and Water Do Mix
Oil wells typically produce much more water than oil. In the Permian, the water-to-oil cut ranges from 4-1 to as high as 10-1 in the Delaware Basin. While a percentage of that water is recycled into hydraulic fracturing, the vast majority is injected underground, in what are known as saltwater disposal wells, or SWDs.

The number of SWD injections in the Permian has increased significantly following the rapid growth of shale/hydraulic fracturing activity since the early 2000s. At the same time, tremors related to the massive levels of injected water have become more of an issue in producing areas, hence the RRC's action.

Responding to the Scurry County quakes, the RRC issued this statement: "The RRC has been investigating the earthquakes that occurred last week in the Camp Springs area along the Fisher/Scurry County line in West Texas. In efforts to reduce seismicity possibly caused by underground injection of produced water, several operators in the area have converted deep saltwater disposal wells to shallow saltwater disposal wells within the last year."

"RRC inspectors have been inspecting saltwater disposal wells within two and a half miles of the cluster of earthquakes, and we will evaluate next steps that can be taken to mitigate earthquakes. We'll continue to take measures necessary to protect the environment and residents in the area."

Earthquake Rocks
Recent quakes are similar to other SWD-caused Permian activity, says Dr. Katie Smye, research associate professor at the University of Texas Bureau of Economic Geology in Austin: "The recent earthquakes occurring on the Scurry-Fisher County line are similar to other clusters of injection-induced earthquakes occurring in the Permian Basin region. Hypocentral depths for these events are currently located at approximately 4 km below the ground surface, and many deep basement-rooted faults in the Permian Basin region extend into the sedimentary layers used for wastewater injection."

She further explained that injection raises the native pore pressure of the formations, which can cause existing faults to slip, adding that this is the case for most induced seismicity in the region.

Surface Damage
In an interview with the Texas Standard, Jay Callaway, emergency management coordinator for the city of Snyder and Scurry County, said: "What we're seeing the most is cracks in the walls and the ceilings. We have had one water line breakage in Snyder from it, happened Monday night [July 22], from the first earthquake." Callaway said utility crews repaired the leak in a timely fashion.

In light of the RRC's quake zone restrictions, some produced water midstream companies have begun pipelining water to the southern Permian Basin, in places like Irion County. So far that has worked, but it begs the question of how long it may be before formations in those regions also pressure up, spreading the earthquake issue.

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