New tool predicts earthquakes induced by effects of pumping wastewater from oil and gas operations

New tool predicts earthquakes induced by effects of pumping wastewater from oil and gas operations

A team of geophysicists has developed a new tool by which they can predict earthquakes that take place due to the effects of pumping wastewater from oil and gas operations deep underground. Japanese Advanced Land Observing Satellite (ALOS)’s interferometric synthetic aperture radar (InSAR) is an important addition to predict such human-caused events.

Study’s lead researcher ManoochehrShirzaei, a geophysicist at Arizona State University, said that along with the team they have assessed monthly InSAR data from May 2007 to November 2010. The researchers were able to see the land near Timpson, Texas to be rising three millimeters per year above wastewater wells around two kilometers apart.

The data was entered into their model of pore pressure. Increased pore pressure can result into an earthquake. Shirzaei said that it is the first study that has directly measured the ground uplift from wastewater injection.

“We know that when you inject fluid into the ground it causes surface deformation, but we’d never seen it. For this Timpson study area we got lucky and could see the deformation”, mentioned Shirzaei.

The current research model is dependent on a number of factors, including stiffness of the rocks, wastewater injection depth and volume to calculate the pore pressure in a region. Justin Rubinstein, a geophysicist at the US Geological Survey said that in certain cases, lack of deformation could also signal higher pressures deep underground.

One more thing being revealed by the study was earthquakes are happening after wastewater injection rates are on decline. Shirzaei mentioned that if injections are stopped today then there is a possibility that the earthquake activity will go on for the next decade or so. The researchers are hoping to expand the model to other areas in the central US, where a sharp rise has been seen in earthquakes.

A report published in Scientific American informed, "The study is the first that the authors are aware of to directly measure the ground uplift from wastewater injection. “We know that when you inject fluid into the ground it causes surface deformation, but we’d never seen it,” Shirzaei says. “For this Timpson study area we got lucky and could see the deformation.” Shirzaei hopes the data will allow the team to answer questions like why some injection wells may generate earthquakes and others don’t."

Those two wells injected their wastewater much deeper than the wells situated below the uplift. Many underground features can influence earthquakes. Shirzaei’s model relies on factors such as the stiffness of the rocks, along with wastewater injection depth and volume to calculate the pore pressure in a region. In some places a lack of deformation might even signal higher pressures deep underground, if operators are injecting fluids into less pliable rocks, notes Justin Rubinstein, a geophysicist at the U. S. Geological Survey who also was not involved in this study.

Shirzaei hopes to expand the model to other areas in the central U. S. that have seen a sharp increase in earthquakes and are near oil and gas development, but he is limited by the amount of obtainable data. ALOS is not the only satellite that has InSAR capabilities, and space agencies typically offer the corresponding information for free. If Shirzaei pulled from multiple satellites, the data would be available every few days.

According to a report in Sciencemag by Sid Perkins, "During the past decade or so the oil and gas industry has injected wastewater into deep rocks in eastern Texas, causing Earth’s surface to bulge ever so slightly—and likely triggering a series of tremors there in 2012, a new study suggests. Scientists say the work offers hope that similar analyses of the landscape in other oil- and gas-producing regions could help identify areas at risk of human-caused earthquakes."

According to data provided by the companies that owned the wells, between 2007 and mid-2012 the two injection wells nearest the quakes and another two wells fewer than 10 kilometers away pumped, on average, about 890,000 cubic meters of water into the ground each year. (Or, put another way, that’s about one Olympic swimming pool worth of wastewater pumped underground each day.)

The group’s combination of monitoring uplift of the landscape over time and modeling the effects of wastewater injection on pore pressure “is a powerful approach,” says Shemin Ge, a hydrogeologist at the University of Colorado, Boulder. “It will help advance our understanding of what’s actually going on in rocks near wastewater injection sites.”

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