Nearly 100 small earthquakes that hit northeast Ohio throughout 2011 and into early 2012 were triggered by a now-shuttered wastewater disposal well in Youngstown, according to a Columbia University researcher.

Won-Young Kim, a senior research scientist at Columbia’s Lamont-Doherty Earth Observatory, said 97 small earthquakes, measuring between 0.4 and 1.8 in magnitude, were triggered by injection activity at the Northstar 1 well, a Class II deep injection well owned by Youngstown-based D&L Energy Inc. and operated by Northstar Disposal Services LLC.

In a 13-page report published in the July Issue of “Journal of Geophysical Research: Solid Earth,” Kim said the earthquakes “were induced by the fluid injection at [the] Northstar 1 deep injection well due to increased pore pressure along the pre-existing faults located close to the wellbore in the Precambrian basement.”

Kim said the first detected earthquake, which measured 1.2-magnitude, occurred on Jan. 11, 2011, just 13 days after injection operations began at the well. He said about 700 cubic meters of fluid was injected at that time, at a rate of up to 5 cubic meters per hour and at a surface injection pressure of 13.5 megapascals.

“Total injection volume was a very small quantity when it started to trigger an earthquake, and the injection pressure was relatively low, and hence, there must have been nearly direct fluid conduits to the…trending fault very close to the injection wellbore, and the subsurface condition at the Precambrian basement may have been near critical for the earthquakes to occur,” Kim said.

“The cross correlation between the earthquake series and the injection flow rate series indicates that the peak of seismicity follows the peak pressure with approximately five days lag.”

Kim added that several instances of gaps in surface injection pressure — where there was a sudden drop in injection pressure, followed by prolonged low pressure — took between January 2011 and February 2012, the time period that was studied.

“The drops in injection pressure correspond to two to four days of no pumping at the wellhead, followed by eight to 20 days of gradual increase in injection pressure,” Kim said. “Most of the short and sharp pressure drops correspond to no pump running for a day on national holidays — Memorial Day, [the Fourth of July] and among others. The longer gaps are due to injection tests, on Labor Day, pump maintenance and Thanksgiving holidays, etc.”

The Ohio Department of Natural Resources (ODNR) asked D&L to halt operations at the well at the end of 2011, and it remains offline and depressurized (see Shale Daily, Jan. 5, 2012). An ODNR report found the closest known fault system is the Smith Township Fault, which runs in a northwest-southeast direction in Mahoning County. Maps of the fault indicate that it has had recurrent movement throughout geologic time.

“The earthquakes did not stop immediately after the shutdown of the injection operation at Northstar 1, although the rate and size of earthquakes steadily dropped within a month following shutdown,” Kim said. “Usually, pore pressure buildup from several months of fluid injection would require time to return to the pre-injection level.”

In July, data from the ODNR’s Underground Injection Control (UIC) program showed that injection wells in Ohio handled 14.2 million bbl of wastewater in 2012 (see Shale Daily, July 3). More wastewater came from out-of-state sources (8.2 million bbl, or 57.6% of the annual total) than from operations in Ohio (6.0 million bbl, 42.4%).

But the UIC data also showed that Ohio handled just 3.3 million bbl of wastewater during the first quarter of 2013. That includes 1.8 million bbl (55.4%) of wastewater from out-of-state oil and gas drilling, and 1.5 million bbl (44.6%) from operators in Ohio. It was the smallest amount recorded for out-of-state wastewater since 2Q2011, when Ohio took in 1.6 million bbl.

The U.S. Environmental Protection Agency (EPA) is conducting its own study to determine if there is a correlation between injection wells and earthquakes (see Shale Daily, July 29). Other researchers at the Lamont-Doherty Earth Observatory have recently concluded that earthquakes that occur on the other side of the world could create smaller temblors near wastewater injection sites in the United States (see Shale Daily, July 15).

Scientists have linked a dozen small earthquakes in the Barnett Shale in North Texas to wastewater injection wells that support natural gas drilling (see Shale Daily, Aug. 8, 2012). Arkansas banned disposal wells in a portion of the Fayetteville Shale after quake activity there (see Shale Daily, July 29, 2011; March 4, 2011).