How does wastewater from oil and gas production cause earthquakes?

On the cloudy afternoon of December 15, I was in Houston talking to a colleague on the phone in Midland when a magnitude 3.6 earthquake rocked the oil-rich city. She nearly fell out of her chair, quickly ending the conversation by saying, “I have to watch my kids. It was one of 15,000 earthquakes to hit the West Texas Permian Basin in the past five years.

The Permian Basin has been a prolific economic engine for the state of Texas and is a vital energy resource for the United States. The basin is at the center of America’s shale revolution, employs half of all America’s drilling rigs, produces nearly 5 million barrels of oil a day and has the largest oil shale reserve base on the planet. . Its resources are deep and geographically vast, with one of the thickest hydrocarbon structures in the world extending 300 miles from Big Lake, Texas to Carlsbad, NM.

But the Permian Basin has a problem: a 15 million barrel per day problem. About three barrels of brackish water are produced for every barrel of oil, and that waste water has to go somewhere. Much of this water is discharged into thousands of deep injection wells known as saltwater disposals. Many of these injection wells were drilled on or near old but historically inactive fault lines. Scientists have been warning for years that deep water injection can pressurize these faults and cause earthquakes.

With 5,200 earthquakes in West Texas in 2021, double what was observed in 2020, this is no longer a theoretical discussion. Earthquakes are now affecting cities in West Texas, ranging from Pecos to Big Spring, often weekly. The Texas Railroad Commission, Texas’ primary oil and gas regulator, responded in a pragmatic and data-driven manner by severely limiting sewage discharge in parts of six counties, impacting the daily production of millions of barrels of oil.

The seismic data used by the Railroad Commission is collected by the seismic monitoring program TexNet. In 2015, the Texas Legislature under Governor Greg Abbott passed legislation establishing TexNet to scientifically determine the causes of increased seismic activity through the ongoing collection and analysis of seismic data. The rapid increase in earthquakes in West Texas prompted the Commission to take data-driven regulatory action to mitigate induced seismicity while facilitating the development of the state’s most important energy asset.

Over the past two years, the Board of Railroads has regulated and encouraged the development of multi-customer produced water recycling and storage facilities. These facilities reuse produced water for use in the completion process, reducing reliance on deep well injection into subsurface formations where fault lines exist.

The commission also developed strict commercial recycling permit standards known as Division 6-H11. These rules are critical because they protect West Texas aquifers, waterways and ecosystems from produced water contamination.

Produced water typically contains oil, residual chemicals from the hydraulic fracturing process, and suspended solids, and when improperly stored can create toxic hydrogen sulfide gas. Commercially licensed recycling facilities operating under the new standards are held accountable by strict reporting, bonding, engineering, monitoring and other regulations.

In the final months of 2021, the Board of Railways responded more forcefully with unprecedented seismic response actions that significantly limit the injection of produced water from deep wells in seismically active areas, particularly around population centers of Midland-Odessa. These actions have encouraged the safe recycling of wastewater or, at a minimum, its redirection away from population centers and seismic clusters.

To understand these actions, it is important to understand how operators in the Permian Basin have managed billions of barrels of fresh water and wastewater over the past decade, and how this has evolved.

In the early 2010s, operators were using fresh water from local aquifers to fracture single-well developments. When complete, the sewage by-product was trucked to local disposal wells for injection. At the start of the Shale, there were very few earthquakes, so induced seismicity was naturally not taken into account. In the late 2010s, multi-well development techniques dramatically improved efficiency, but they also increased the demand for fresh water for hydraulic fracturing and deep well injectors for wastewater disposal.

As additional water infrastructure was built to meet growing demands from industry, the water reservoirs supporting the Permian Basin began to signal distress: freshwater aquifers began to decline and rock formations injection began to shake. The Board of Railways took action. Today’s water supply chain relies less on freshwater aquifers and more on the consumption of recycled produced water. Produced water is now transported almost exclusively by pipeline, not by truck, to recycling facilities or discharges farther from population centers or areas of seismic concentration.

Make no mistake about it, deep well saltwater drains are here to stay. With over 2,000 active disposals in Texas, they are an essential tool in the management of produced wastewater. However, with data-driven regulation and thoughtful oversight, the Board of Railroads has encouraged operators to be better stewards of the Permian Basin by recycling produced water where possible or moving it to outflows in outside population centers or seismic clusters when not.

Jason Jennaro is managing director of Breakwater Energy Partners, which has built the largest commercially licensed produced water recycling facilities in Texas. He wrote this column for The Dallas Morning News.

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