BC Hydro responds to concerns about fracking and dam safety by Michael Harris, August 26, 2016, Hydroworld
Recent concerns about fracking near BC Hydro’s hydroelectric power assets have led to a statement from the Canadian utility regarding their safety and stability.
Fracking — a process of subsurface drilling — has been blamed for creating seismically unstable geographical conditions in areas where it is practiced, which could be potentially ruinous to reservoir-retaining infrastructure like dams.
BC Hydro deputy CEO Chris O’Riley said concern around his company’s facilities is minimal, however, given their design and existing agreements with the BC Oil and Gas Commission.
“First, it is important to note that to BC Hydro’s knowledge, there has never been any fracking activity within five kilometers of BC Hydro’s dams,” O’Riley said in a statement. “That said, our dams are built to withstand much larger ground motions associated with higher magnitude events that are much longer in duration than fracking.
“In fact, our dams can withstand events many times larger than those associated with fracking. Fracking by itself cannot generate large magnitude earthquakes.”
Seismicity in the Oil Field by Vitaly V. Adushkin. Vladimir N. Rodionov. Sergey Turuntaev. Institute of Dynamics of Geospheres,. Russian Academy of Sciences, 2000. Much of this article originally appeared in the Schlumberger Russian version of theOilfield Review, Neftegasovoye Obozreniye 5, no.1 (Spring 2000): 4:15. Results in this article were based on data obtained by the local seismic network of Stock Joint Company “Tatneft.” The authors thanks I.A. Iskhakove, head of the TNGF seismic crew and K.M. Mirzoev, chief of the Tatarstan seismic survey, who provided the catalogue of seismice events and the produced and injected fluid volumes data. The support from “Tafneft” and the Russion Foundation for Basic Research (RFBR project #98-05-64547) is gratefully acknowledged.
The gas field was discovered in 1956 and production began in 1962. Over the next 14 years, roughly 600×106 m3 of water, or 106 ton per km2, were injected. …
Beginning in 1976, a series of large earthquakes was recorded. The first significant earthquake occurred on April 8, 1976 at a distance of 20 km [12 miles] from the Gazli gasfield boundary. The earthquake magnitude measured 6.8. Just 39 days later, on May 17, 1976, another severe earthquake occurred 27 km [17 miles] to the west of the first one. The magnitude of the second earthquake was 7.3. Eight years later, on March 20, 1984, a third earthquake occurred 15 km [9miles] to the west of the second earthquake, with a magnitude of 7.2. … Aftershocks occurred in a volume surrounding the three hypocentres. These earthquakes are the strongest of all the known earthquakes in the plain of Central Asia. …
There was no clear relationship between the location of the earthquake hypocenters and any previously known active tectonic structures.
Closer investigation showed that the earthquakes had created new faults.
… In all these cases, the result of human interference was to change the state of stress in the surrounding volume of earth. If the stress change is big enough, it can cause an earthquake, either by fracturing the rock mass—in the case of mining or underground explosions—or by causing rock to slip along existing zones of weakness.
The situation in regions of hydrocarbon recovery is not always well understood: in some places, extraction of fluid induces seismicity; in others, injection induces seismicity.
… Even minor actions can trigger strong seismicity.
… The amassed data indicate that the Gazli earthquakes were triggered by the exploitation of the gas field.
In regions of high tectonic potential energy, hydrocarbon production can cause severe increases in seismic activity and trigger strong earthquakes, as in Gazli, Uzbekistan.
In regions of lower tectonic stress, earthquakes of that magnitude are less likely, but relatively weak earthquakes could occur and damage surface structures.
END REALITY CHECK]
An agreement with the BC Oil and Gas Commission restricts new fracking activity within five kilometers of BC Hydro dams — including the 1.1-GW Site C hydropower plant, while the commission must also notify BC Hydro of any new activities.
“These discussions have been precautionary in nature to ensure appropriate operational and maintenance activities if required in the future,” O’Riley said. “BC Hydro’s dam safety program is fully and independently regulated and the Provincial Comptroller of Water Rights is regularly advised of such discussions, which was done in this case. In 2014, BC Hydro released the results of a world class, six-year seismic study on probabilistic seismic hazards related to our dams, which was communicated extensively to the public.”
The company noted that its earth-fill dams are purposefully designed to have some seepage, and though fracking could increase the amount of flow under and around some infrastructure, the dams’ safety is not an issue.
“Our highest responsibility is public safety,” O’Rley said. “Our dam safety program meets the highest standards including 24/7 instrumentation monitoring, weekly inspections, bi-annual engineering reports and regular reviews of all our dams by international, independent experts. Over the next 10 years, BC Hydro is investing approximately $1.9 billion in dam safety across the province.”
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Luther Residents Rattled After Recent Earthquakes by Grant Hermes, August 17, 2016, News9
LUTHER, Oklahoma – Residents near Luther are recovering after the fourth earthquake in a week rocked homes and neighborhoods Wednesday morning.
According to the News9/Newson6 seismograph, the quake happened around 8:30am. The earthquake was initially recorded as a 4.3 magnitude, but it was later downgraded to a 4.0. The quake was the fourth recorded in the Luther area in a week. A 4.0, 3.2 and 3.5 were all recorded between Aug. 10 and Aug. 17.
“I haven’t felt anything like this one. This one was pretty bad,” Pam Schmidthuber said sitting in the kitchen of her mobile home just east of Luther. She and her husband live roughly a mile from the epicenter of Wednesday morning’s quake
Schmidthuber said she was no stranger to earthquakes, her home has been rocked by them since she moved in a little over a year ago. But normally she said there’s a slight rumble before a quake hits. This one, she said, came without warning.
“I had canning jars falling off my table. I could hear things in the cabinet falling and crashing,” Schmidthuber said. “I looked towards the end of the mobile and we were, it looked like we were on the ocean, it was just waving.”
The force was so strong it nearly knocked her to the floor. When it subsided several minutes later, Schmidthuber said she ran out to her external propane tank to shut off the gas, hoping to avoid disaster.
“I came outside and literally leapt off the porch. It was pretty wet out here this morning. I was barefoot,” She said pointing out a footprint left in the yard.
The earthquake left cracks in the Schmidthuber home. One followed along a seam in the floor where one half of the home now sits lower. It also cracked the drywall joining the main home and an added sunroom. It also knocked loose dirt around the above-ground pool in the back yard.
Matt Skinner, spokesperson for the Oklahoma Corporation Commission, said the Luther area is a “top concern” and that there were still active waste water injection wells in the area although some had been reduced up to 40 percent in recent months.
Schmidthuber said she’s not blaming energy companies or their subsidiaries but is still wondering what it will take to prevent the next quake.
“When you inject where there are fault lines, guess what happens?” she asked. “There’s going to be a reaction for that action.” [Emphasis added]
Oklahoma Corporation Commission Shuts Down Two Wells After This Week’s Earthquakes by Cole Poland, August 19, 2016, News9
OKLAHOMA CITY – The Oklahoma Corporation Commission announced plans to shut down two wastewater wells after this past week’s earthquakes near Luther and Wellston.
The OCC’s Oil and Gas Division’s plan covers wastewater wells that are disposing into the Arbuckle formation.
The two wells to be shut down are within three miles of the latest seismic activity. The shutdown of these wells must be completed by August 25. Additionally, 19 Arbuckle disposal wells within 10 miles [16 kilometres] of the latest seismicity will be further limited in volume.
The area experienced four earthquakes within the last week, the most recent being a 4.0 on Wednesday, August 17. Residents there say they are now dealing with property damage. [Emphasis added]