Well Injection, Quakes Linked

Legislative panel told fracking is not big concern

Morgantown Dominion Post
10 October 2012
By David Beard

CHARLESTON — There’s no evidence to date that fracking causes earthquakes — but there is some correspondence between quakes and deep-well injection of wastewater.

Michael Hohn, director of the West Virginia Geological and Economic Survey, based in Morgantown, conveyed this to members of a joint legislative Judiciary subcommittee Tuesday morning.

The U.S. Geological Survey reports: “Earthquakes induced by human activity have been documented in a few locations in the United States, Japan and Canada. The cause was injection of fluids into deep wells for waste disposal and secondary recovery of oil, and the filling of large reservoirs for water supplies. Most of these earthquakes were minor.”

Several injection wells in the Youngstown, Ohio, area were closed this year after a series of 11 quakes — the strongest magnitude 4.0 — in late 2011, according to reports.

Braxton County experienced what Hohn called a “swarm of earthquakes” in 2010 — all of them mild, as high as 3.4, which can rattle dishes.

Hohn pointed out that Braxton has one injection well.

Sen. Clark Barnes, R-Randolph, asked Hohn about the counties immediately northeast — Lewis and Upshur. Hohn said those counties have many more wells, and several months after the Braxton swarm, they experienced two small quakes.

The risk factors for quakes from human activity include proximity to fault lines, how the activity affects the pore pressure of the rock formations where the activity takes place, and the degree the formations are subject to stress and brittleness.

In the case of the West Virginia quakes, no one knew there was a fault line there until the quakes occurred. Now they know one runs southwest to northeast — paralleling the line of the mountains.

Fracking — hydraulic fracturing of the rock formation to allow gas to follow — doesn’t pose much seismic risk, Hohn said. There are 35,000 shale wells and only three instances of seismic activity associated with them — one in England and two in Oklahoma — and the data on one of the Oklahoma quakes are inconclusive.

There are 30,000 injection wells in the nation. An area in central Arkansas experienced about 100 quakes in 2011, before activity at two injection wells was suspended, according to the Center for Earthquake Research and Information. The highest was 4.7, enough to cause some damage.

After the wells were closed, the number and severity of the quakes decreased, leading scientists to believe the quakes were connected to the wells — though not convinced enough to call it proof.

The National Academy of Sciences National Research Council said this in a report this year: “Of all the energy-related injection and extraction activities conducted in the United States, only a very small fraction have induced seismicity at levels noticeable to the public (that is, above magnitude 2.0). ... Hydraulic fracturing to date has been confirmed as the cause for small, felt seismic events at one location in the world. The process of hydraulic fracturing a well as presently implemented for shale gas recovery does not pose a high risk for inducing felt seismic events.”

It continues: “Water injection for disposal has been suspected or determined a likely cause for induced seismicity at approximately 8 sites in the past several decades. However, the long-term effects of increasing the number of waste water disposal wells on the potential for induced seismicity are unknown, and wells used only for waste water disposal usually do not undergo detailed geologic review prior to injection, in contrast to wells for enhanced oil recovery and secondary recovery.”

Hohn said quakes can continue for months or years following injection. It’s hard to evaluate the potential in advance, as there’s no way to locate unmapped faults and measure the stress.

In response to a question from subcommittee co-chairman Delegate Tim Manchin, D-Marion, Hohn said the quakes can become more severe over time. The last Ohio quake was the strongest.

Hohn said that U.S. Geological Survey earthquake expert William Leith told Congress in June there’s still not enough data, but recommended states require seismic monitoring as part of the permitting process.

Hohn told Manchin four monitors ranged as far as a well is deep — about a mile — would cost about $100,000 total.

Manchin asked Hohn if the Braxton quakes have produced evidence of water wells suffering damage or diminished water levels, or of cracked gas well casings. Hohn said he’s had no word on any of that happening.

Hohn said the jury is still out on one potential wave of the future: Carbon capture and sequestration — storing carbon dioxide emissions underground so they don’t produce greenhouse effects.

The National Research Council said this in its report: “Carbon capture and storage differs from other energy technologies because it involves the continuous injection of very large volumes of carbon dioxide under high pressure, and is intended for long term storage with no fluid withdrawal. The large net volumes of carbon dioxide that would help reduce global carbon dioxide emissions to the atmosphere may have potential for inducing larger felt seismic events due to increases in pore pressure over time; potential effects of large-scale carbon capture storage projects require further research.”