Hydraulic Fracking Poses Almost No Risk for Causing Earthquakes

The latest word from the NationalResearch Council is hydraulic fracking whether in shale deposits or as a secondary stimulation for a traditional gas or oil well has very low risk for inducing earthquakes that can be felt by people, but underground injection of wastewater produced by hydraulic fracturing and geothermal wells have a somewhat higher risk of causing earthquakes.  Although the vast majority of earthquakes that occur in the world each year have natural causes, earthquakes can be created by mankind.  Induced earthquakes have been documented since at least the 1920s when the first man-made large reservoirs were created behind dams. Other activities that can create (and have created) earthquakes are; controlled explosions used in mining or construction, underground nuclear tests, and energy technologies that involve injection or withdrawal of fluids from the subsurface can also create earthquakes. Man-made earthquakes are caused by changes in pore pressure within the rock due to the impounding of billions of gallons of water or injecting or extracting fluid from a well that may change the stress acting on a nearby fault. This change in stress may result in slip or movement along that fault creating a seismic event.

Historically man-made earthquakes have not been very large nor have they resulted in significant structural damage, but our ability to cause seismic events has increased over time as our technology to drill, pump and explode has advanced. To quantify the hazard and risk from man-made earthquakes requires probability assessments, which may either be statistical (based on data) or analytical (based on scientific and engineering models). Although the general mechanisms that create induced seismic events are well understood, current computer modeling techniques cannot fully address the complexities of natural rock systems in large part because the models generally lack information on local crustal stress, rock properties, fault locations and properties, and the shape and size of the reservoir into which fluids are injected or withdrawn. Geology cannot be simplified or generalized to model earthquake probability which is very specific.

So the National Research Council Board of Life and Earth Studies report titled: Induced Seismicity Potential in Energy Technologies is a data based analysis of earthquakes induced by mankind. This study compiling and analyzing all the data available was requested by the Energy and Natural Resources Committee of the U.S. Senate to assess the potential to cause earthquakes by energy production and related activities after small seismic events reported in Alabama, Arkansas, California, Colorado, Illinois, Louisiana, Mississippi, Nebraska, Nevada, New Mexico, Ohio, Oklahoma and Texas, appeared to be related to hydraulic fracturing, energy development and (true) geothermal energy production. The National Research Council is a nonprofit based in Washington that provides scientific information for government decision-makers under the auspices of the National Academy of Sciences, the National Academy of Engineering and the Institute of Medicine. Its reports are based on data and analysis gathering and scientific analysis of the information gathered.

The report examines the potential for energy technologies -- including shale gas recovery using fracking, carbon capture and storage, geothermal energy production, and conventional oil and gas development -- to cause earthquakes. Hydraulic fracturing, commonly known as fracking, extracts natural gas by injecting huge volume of water mixed with sand, and chemicals in short bursts at very high pressure into deep underground wells. The process cracks the shale rock formation and allows natural gas to escape and flow up the well, along with some wastewater. The wastewater can be discarded in several ways, including injection of the wastewater at a separate disposal well. True geothermal energy harnesses natural heat from within the Earth by capturing steam or hot water from underground. The basic mechanisms that can induce earthquakes from these wells are fluid injection and extraction that are presently well understood. The report examined the data from over 35,000 fractured wells, 108,000 secondary oil and gas recovery wells, 13,000 tertiary oil and gas recovery wells, 6,000 hydrocarbon withdrawal wells, 30,000 waste water disposal wells, 23 liquid dominated geothermal well fields and 1 vapor dominated geothermal field.

Analysis of the data collected at all these sites showed that the net fluid balance (total balance of fluid injected and withdrawn) appears to have the most direct impact on changing pore pressure within the ground. Oil, gas and geothermal wells are typically designed to maintain a balance between the amount of fluid being injected and the amount of fluid being withdrawn to prevent not only earthquakes, but to maximize the well life.  Geothermal wells appeared most likely to induce earthquakes especially the wells in the vapor dominated Geysers site which had 300-400 earthquakes per year (it is in California). In fluid geothermal wells maintaining a constant fluid balance results in a fairly constant reservoir pressure, reducing the number of induced earthquakes significantly. The 23 fluid dominated geothermal well locations experienced 10-40 earthquakes per year.

Only a very small fraction of the hundreds of thousands of oil and gas wells in the United States have induced earthquakes at levels that are noticeable to the public. An increase of  rock pore pressure above ambient levels due to injection of fluids or a decrease in pore pressure below ambient levels due to extraction of oil and gas have the potential to produce earthquakes. However, analysis of the data showed that to create an earthquake, a combination of conditions has to exist simultaneously:

    A. Significant change in net pore pressure in a reservoir,

    B. A pre-existing near-critical state of stress along a fracture or fault, and

    C. Fault rock susceptible to brittle failure.

Oil and gas wells are designed to maintain a balance between the amount of fluid being injected and the amount of fluid being withdrawn to extend the life of the well. This fluid balance helps to maintain fairly constant reservoir pressure and reduces the potential for induced earthquakes. In a conventional oil or gas reservoir the hydrocarbon fluids and associated aqueous fluids in the pore spaces of the rock are usually under significant natural pressure. Fluids in the oil or gas reservoir flow to the surface when penetrated by a well bore aided by pumping once the well is fully developed. The well or wells will produce until reservoirs reach a point when insufficient pressure, even with pumping, exists to allow the wells to continue to produce at commercial volume. To extend the life of a spent well various secondary and tertiary recovery technologies referred to as enhanced oil recovery technologies can be used to extract some of the remaining oil and gas. Secondary recovery and enhanced oil recovery technologies both involve injection of fluids into the subsurface to push more of the trapped hydrocarbons out of the pore spaces in the reservoir and to maintain reservoir pore pressure. Secondary recovery often uses water injection or “water flooding” and tertiary technologies often inject carbon dioxide (CO2). Of the 108,000 oil and gas wells that used water flooding only 18 have had one or more earthquakes. Of the 13,000 CO2 injected sites none have experienced earthquakes.

Shale formations can also contain hydrocarbons either gas or oil or both depending on the formation. The extremely low permeability of these rocks has trapped the hydrocarbons as they developed in the rock and largely prevented them from migrating out of the rock over geologic time. These unconventional gas and oil reservoirs are developed by drilling wells horizontally through the rock and using hydraulic fracturing techniques to create new fractures in the reservoir to allow the hydrocarbons to migrate up the well bore. The water used to fracture the well is quickly released from the reservoir and does not impact the fluid balance. About 35,000 hydraulically fractured shale gas wells exist in the United States; only one instance of an induced earthquake has been identified in which fracking to access the shale gas is suspected, but not confirmed, as the cause.

Overall, hydraulic fracturing or fracking and traditional oil and gas well have a very low risk of creating earthquakes. The waste water disposal wells associated with fracking and secondary well development have been associated with 8 known earthquakes, though there are a total of about 30,000 disposal wells in use, but these earthquakes have captured the headlines and public concern. Wells used only for the purpose of waste water disposal normally do not have a detailed geologic review performed prior to injection and the data are often not available to make a detailed review of these sites possible.  The overall risk turns out to be small, but limited knowledge about the geology prevents modeling. Attempts at modeling of pore pressure, temperature, and rock stress changes induced by injection and extraction to predict producing earthquakes have not been successful except where detailed knowledge of stress changes, pore-pressure changes, and fault characteristics are available for input and that data is almost always not available for disposal wells. The permanent addition of fluid to the subsurface without any fluid removal and the heat gradient associated with geothermal appears to have the most direct impact on changing pore pressure in the subsurface over time and the creation of earthquakes.

Ohio Fracking and Earthquakes

A series of eleven small earthquakes ranging in magnitude from 2.1 and 4.0 have taken place beneath Youngstown Ohio since March 2010. Each earthquake is reported to have had their epicenters near the Ohio Works Drive injection well used by D&L Energy Inc. to dispose of waste water from nearby hydro fracking jobs. D&L began injecting the waste water from the fracking jobs, referred to as brine, into its Ohio Works well in December 2010.

The earthquakes early in the spring led the Ohio Department of Natural Resources, ODNR, to have Columbia University Lamont-Doherty Earth Observatory install seismic monitoring equipment in the area to determine whether there was any relationship between fracking or water disposal activity and the earthquakes. A report is expected in the near future, but after the earthquakes, on December 30th and 31st, use of the disposal well has been halted. ODNR has halted deep well disposal of fracking waste water in the D&L Ohio Works Drive injection well and four other injection wells in the Youngstown area pending analysis of the data collected by the Lamont-Doherty scientists.

In hydraulic fracking on average 2.8 million gallons of chemicals and water is pumped into the shale formation at 9,000 pounds per square inch and literally cracks the shale or breaks open existing cracks and allows the trapped natural gas to flow. While geologists and engineers believe that there is little risk that the fracking “water,” a mix chemicals and water, will somehow infiltrate through the shale and the thousands of feet to reach the groundwater reserves though a fissure created by the fracking, there are other routes of contamination and impact. An now concern is focused in Ohio on the disposal of the flowback water that is not absorbed into the rock formations.

The water that is absorbed into the rock formations may change the formations in ways we do not yet understand, it is the disposal of the flowback that is the focus of this investigation. Though the water in the hydro frack is exempted from the clean water act (by a 2005 act of congress), the flowback which contains “proprietary” chemicals and contaminates from the geological formation is not and must be disposed under state regulations. This is not the first study of earthquakes associated with the disposal of fracking water.

Researchers of the University of Texas at Austin were part of a team of researchers who studied a series of small earthquakes that struck near Dallas, Texas in 2008 and 2009, in an area where natural gas companies had used fracking. The epicenter of the quakes turned out to be about half a mile from a deep injection disposal well under the Dallas-Fort Worth International Airport used to dispose of the fracking fluid. The largest earthquake of the series measured 3.3 on the Richter scale, a very small earthquake. In a study that was published in the Bulletin of the Seismological Society of America, the researchers also reviewed records from US Geological Survey seismic-recording stations in Oklahoma and Dallas. It was concluded by the researchers that the fracking did not cause the earthquakes, but there seemed to be a relationship to the deep well injection of the fracking fluid to the earthquakes.

Columbia's Lamont-Doherty Earth Observatory scientists have the advantage of having placed seismic monitoring equipment in the area before the last few quakes which included the strongest of the series at 4.0 on the Richter scale on New Year’s Eve. The location of the earthquake epicenter is expected to be in the area of the Ohio Works Drive injection well an area of no previous seismic activity. It has been speculated that the earthquakes were triggered by the fluid injected into the well that permeated a previously unknown fault.

Our ability to recover natural gas buried a mile or more beneath the earth has increased. Advances in horizontal drilling which allows a vertically drilled well to turn and run thousands of feet laterally through the earth combined with advances in hydraulic fracking, the pumping of millions of gallons of water and laced with thousands of gallons of chemicals into shale at high pressure have increased our ability to recover natural gas from shale ahead of our knowledge of the consequences of the fracking and disposal of the waste water. Wastewaters from the hydraulic fracturing process must be disposed of safely, and deep injecting wells had been the favored method. There are 177 similar injection wells around the state of Ohio that will remain in use. The Youngstown-area well has been the only site with seismic activity, according to the ODNR. Only five Youngstown area wells have been shut down.

Fracking and Earthquakes

Two weeks ago I happened to talk about the responses of water levels in wells to earthquakes and the limits of our knowledge as to how and why this happens over distances of hundreds even thousands of miles. I questioned what this connection of groundwater to earthquakes might mean for groundwater in areas that are fracked. Fracking or hydraulic fracturing as it is more properly known is the pressurized injection of water with chemical additives into a geologic formation. The pressure used exceeds the rock strength and the fluid cracks open or enlarges fractures in the rocks and shale. As the formation is fractured, a “propping agent,” such as sand or ceramic beads, is pumped into the fractures to keep them from closing when the pumping stops and the pressure is released. Natural gas will flow from the fractures in the rock and shale into the wells increasing the recovery of the methane.

In hydraulic fracking in a shale formation to enhance recovery of natural gas on average 2-3 million gallons of chemicals and water is pumped into the shale formation at 9,000 pounds per square inch and literally cracks the shale or breaks open existing cracks and allows the trapped natural gas to flow. While geologists and engineers believe that there is little risk that the fracking “water,” a mix chemicals and water, will somehow infiltrate groundwater reserves though a fissure created by the fracking there are other routes of contamination and impact. It is believed that the intervening layers of rock would prevent a fissure from extending thousands of feet to the water table; there are other risks in how we build wells and fracture the shale. There have been documented cases of seepage into drinking water wells through improperly sealed or abandoned drilling wells. There are also places where groundwater is only several hundred feet above the gas reserves as they are in Wyoming and groundwater is more easily directly impacted by fracking.

The US Geological Survey has been studying the factors that impact the response of groundwater wells to earthquakes, including the magnitude and depth of the earthquake, distance from the epicenter, and the type of rock that surrounds the groundwater. The depth of the well, whether the aquifer is confined or unconfined, and well construction also influence the degree of water-level fluctuations in wells in response to seismic waves. It has been suggested that some aquifers may even act as resonators, which may amplify the response. The US Geological Survey has been able to add more data points to their information base this past week and someday we may know more about this relationship and groundwater itself, but right now all the US Geological Survey can do is observe and collect data.
http://va.water.usgs.gov/Gw_FS_2008.pdf

Dr. Cliff Frohlich of the University of Texas at Austin was part of a team of researchers who studied a series of small earthquakes that struck near Dallas, Texas in 2008 and 2009, in an area where natural gas companies had used fracking. The epicenter of the quakes turned out to be about half a mile from a deep injection well under the Dallas-Fort Worth International Airport used to dispose of the fracking fluid. The largest earthquake of the series measured 3.3 on the Richter scale, a very small earthquake. In a study that was published in the Bulletin of the Seismological Society of America, the researchers also reviewed records from US Geological Survey seismic-recording stations in Oklahoma and Dallas. It was concluded by the researchers that the fracking did not cause the earthquakes, but there seemed to be a relationship to the deep well injection of the fracking fluid to the earthquakes. The water caused the earthquakes.

This past spring, the Shale Gas Subcommittee of the Secretary of Energy Advisory Board was created to identify the measures that can be taken to reduce the environmental impact and improve the safety of shale gas production utilizing fracking. Dr. Mark Zoback of Stanford University was a member of the committee. He has studied the relationship of earthquakes to fracking and is a strong supporter of replacing coal with natural gas. He feels the risk of earthquake from fracking fluid disposal and all other risks from fracking are manageable. According to Dr. Zoback the risk could be mitigated by treating the water on the surface or shipping the water to a disposal well that isn’t near a fault. He felt the risk could be addressed by oil and gas companies identifying faults near potential well sites, and simply staying away from the faults.
http://www.ouramazingplanet.com/texas-earthquakes-natural-gas-mining-fracking-1152/
http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2011/08/28/BU0L1KS4BU.DTL

Our ability to recover natural gas buried a mile or more beneath the earth has increased. Advances in horizontal drilling which allows a vertically drilled well to turn and run thousands of feet laterally through the earth combined with advances in hydraulic fracking, the pumping of millions of gallons of chemicals and water into shale at high pressure have increased our ability to recover natural gas from shale. Hydraulic fracking is a technology that was unknown 60 years ago. In the past decade the advances in drilling and fracking technology have been adapted to exploit gas in the Barnett shale in the Fort Worth Basin in Texas and applied to a series of major shale gas deposits that could not have been viable without the advances in drilling and fracking. The Fayetteville shale, the Haynesville shale, the Marcellus shale reserves all in the United States and the Horn River shale in Canada are now accessible. At the current rate of natural gas consumption North America is reported to have a 100-year supply of proven, producible reserves and even with expanded use of natural gas, there is more than a generation of currently accessible reserves. This natural gas could profoundly change the future of our nation and would we live in; however we need to be cautious about what other impacts fracking might have especially to hydraulic balance of groundwater.