02. Fracking the Ohio River
Analyzing the Risk of Induced Seismicity
Introduction and Background
This is the second in our series of homeworks focused on evaluating geohazard risks in the vicinity of the Ohio River between Washington Couty, Ohio and Pleasangs Couty West . In this assignment we will appraise whether or not this area shows any potential risk of earthquakes from a plan by the state of West Virginia to sell leases along the Ohio River to produce gas and oil by hydraulic fracturing.
Figure 1. The map above shows the counties where the West Virginia state government has recently voted to lease mineral rights for development of hydrocarbon resources from beneath the Ohio River through hydraulic fracturing methods. Pleasants County is the county of concern for our project.
The state border between Ohio and West Virginia is located along the west bank of the Ohio River – in other words, West Virginia owns most of the river. In December, 2014 the West Virginia state government announced a plan for the state to lease the mineral rights beneath the Ohio River for development of hydrocarbon reserves through hydraulic fracturing operations. These operations can also be expected to yield “flow-back” water – salty brines that can be contaminated with fracking chemicals and/or high levels of natural radioactivity. These fluids must be disposed of safely. Normally that is done by re-injection of the fluids into deep reservoirs at EPA-classified “Type II” deep-injection wells. In this exercise, we will investigate the question of whether or not the injection of these fluids from the fracking operations themselves or from the waste-water disposal injection wells run a risk of triggering unwanted seismicity along the Ohio River.
To evaluate the stability of potential faults in the area, we will turn to the failure criterion for frictional sliding on a pre-existing failure surface, known as “Byerlee’s Law,” as given below:
For n < 200 MPa: s = 0.85n
For n > 200 MPa: s = 50 MPa + 0.6n
In addition, we will need information on the state of stress in the study area. We will use the closest fully determined, high quality stress estimate from the World Stress Map database, as follows:
TABLE 1. Hocking County, Ohio: In situ stress measurement at a depth of 808 m determined using hydraulic fracturing techniques.
azimuth of : |
064° |
Magnitude : |
24 MPa |
plunge of : |
0° |
1/2 ratio: |
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azimuth of : |
064° |
Magnitude of : |
14 MPa |
plunge of : |
90° |
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azimuth of : |
334° |
Magnitude of : |
11.3 MPa |
plunge of : |
0° |
3/2 ratio: |
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While the state of stress given above will vary somewhat from that in the Ohio River region 100 km to the east, the relative stability and uniformity of stress in the stable interior of the eastern U.S. suggests that the above stress state will provide a reasonable first approximation.
Each person in your group should complete the problem set below and turn it in via Isidore. After completing this assignment, compare notes with your teammates and work together to complete the Seismic Risk Analysis section of your site investigation report on Geohazard Risks aong the Ohio River. See Team Writing Assignment 2 for guidelines.
Questions
1. To calculate stresses at various depths below, you will need to calculate the vertical stress at the depth of interest.
a. Assuming the same state of stress as given in Hocking County above, which of the three principle stresses is vertical? What faulting regime would this state of stress correspond to? (normal, reverse, or strike-slip?)
b. In the calculations that follow, you will need the and ratios to calculate the greatest and least horizontal stresses at the depth of interest. Calculate these values and enter them into the highlighted spaces in the Table 1 above.
2. The leading oil and gas “plays” in Ohio are in the Devonian Marcellus shale and the Ordovician Utica/Pt. Pleasant shale formations, respectively. The Ohio Geological Survey has conveniently gathered information relating to oil and gas production from these horizons at
http://geosurvey.ohiodnr.gov/energy-resources/marcellus-utica-shales
In particular, you and your group should review the powerpoint presentation on the Marcellus and Utica plays in Ohio, which is accessible from the above web site or from the link copied below:
http://geosurvey.ohiodnr.gov/portals/geosurvey/energy/Marcellus_Utica_presentation_OOGAL.pdf
For the seismic risk analysis below it is especially important for us to know the depth to these rock layers beneath our region of interest along the Ohio River between Washington County, OH and Pleasants County, WV. We can estimate this information from oil and gas well log data that is publically available through the Ohio Oil and Gas Well Locator (http://oilandgas.ohiodnr.gov/well-information/oil-gas-well-locator). On the following page I copy the Well Summary Cards for the Newell Run Saltwater Injection well, which lies approximately 2.5 km north of the Ohio River. Unfortunately, the Newell Run well does not penetrate all the way to the Utica/Pt. Pleasant Formations. To estimate the depth to this unit, take the depth to the contact between the Clinton and Medina Formations shown on the Newell Run card, and estimate the additional depth to reach the Utica-Pt. Pleasant contact from the Protégé Energy Well. For the Marcellus, take the depth to the base of the formation. Also, convert the depths to meters.
Table 2.
Rock Formation |
Depth (ft) |
Depth (m) |
Marcellus shale: |
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Clinton/Medina Fm: |
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Utica/Pt. Pleasant: |
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3. Now that we understand the general stratigraphic and structural setting of the Marcellus, Clinton/Medina and Utica/Pt. Pleasant formations, we need to understand the basics of hydraulic fracturing (colloquially known as “fracking”), i.e., what kind of fluid pressures are necessary to induce failure.
a. Using the depths given above (converted to meters), calculate v at depth and then use that value to calculate 1 and 3 based on the stress ratios you calculated in question 1 above. Assume that the overburden has an average density of 2400 kg/m3 In addition, calculate the hydrostatic pore fluid pressure (Pf) at depth. Hydrostatic pore fluid pressure assumes that the water in pore spaces forms an interconnected network to the water table, so that pore fluid pressure can be calculated using the formula Pf = wgh (Assume the density of water is w= 1000 kg/m3). The depths (h) you use should be taken from the Table 2 above).
Table 3.
Rock Formation |
Depth (m) |
1 (MPa) |
2 = v (MPa) |
3 (MPa) |
Pf (MPa) |
Pop(MPa) |
Marcellus shale: |
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Clinton/Medina Fm: |
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Utica/Pt. Pleasant: |
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b. Now, use the values for 1 and 3 from Table 3 above to construct Mohr circles on the graph paper at the end of this assignment sheet for the estimated state of stress at the depths of the Marcellus Shale, the Clinton/Medina formations and the Utica/Pt. Pleasant formations. Draw your circles in different colors for each rock type and at each level draw two Mohr circles – one without taking pore fluid pressure into account, and the other adjusted for hydrostatic pore fluid pressures. The effect of pore fluid pressure is to shift the Mohr Circle to the left by the amount of the pore fluid pressure, according to the equation:
n* = n - Pf
where n* is the effective normal stress.
c. Hydraulic fracturing involves increasing pore fluid pressure enough to reduce effective normal stress to the point that the effective normal stress is shifted to the left of the ordinate axis on the Mohr diagram to intersect the tensile failure criterion. This can happen naturally under so-called “over-pressured” conditions, but the hydrocarbon industry has mastered how to do this in a controlled fashion in order to increase permeability and thus production from the ‘fracked’ rocks. In most cases, they are seeking to take advantage of pre-existing fracture systems known as joints. For our purposes, we will estimate the tensile strength of both shale units at T0 = -5 MPa. Draw a red line representing this failure criterion on your diagram, and estimate the pore fluid pressure surcharge over and above the hydrostatic pressure needed in each case to induce hydrofracture (i.e., estimate the over-pressure Pop). Fill that number in the far right column in Table 3 above.
4. Now, to evaluate the risk that hydrofracturie-induced eathquakes, we need to identify potential fault planes in the area. Historical experience suggests that there is relatively low chance that hydrofracturing itself will directly induce felt earthquakes unless one or more of the horizontal bores actually intersect or closely approaches a fault. However, there is increasing evidence that large volume injections of the contaminated, highly saline wastewater produced by fracking into deep disposal wells can produce earthquakes. Your written reports should include a summary of what is known about faults in the vicinity of the Ohio River between Washington and Pleasants Counties. The orientations of the faults are important in evaluating their stability as we will see below, but the vertical and lateral extent of the faults is also important. Simply, put, the larger the fault, the more capable it is of producing a larger earthquake (Fig. 2). Wells and Coppersmith (1994) formulated a scaling relationship between rupture area and magnitude in the form of the equation: M = 0.98 log A + 4.07 (where rupture area A is in km2)
Figure 2. Graphical depiction based on global earthquake catalogs of the logarithmic scaling relationship between rupture area and earthquake magnitude (after Shaw et al., 2009).
a. Commonly, the length of a strike-slip fault rupture is at least three times its depth. So if a given earthquake were to rupture a fault that penetrated the entire sedimentary sequence from Precambrian basement to the surface (~4 km) to the surface, it could well form a rupture >12 km long. Assuming (as is commonly the case) an elliptical rupture area, what would be the area of such a rupture? Applying the equation from Wells and Coppersmith above, what would be the approximate magnitude of such an earthquake? (Show your work).
b. Could a shallow earthquake of that magnitude be of concern if it were to occur directly beneath the Ohio River? What would be the expected intensity of such a quake at its epicenter? How would it compare with the largest and most severe earthquake in Ohio history to date, the 1937 Anna earthquake? (See http://earthquake.usgs.gov/earthquakes/states/events/1937_03_09.php) Another useful comparison would be the 2011 Richmond, Virginia earthquake (see http://earthquake.usgs.gov/earthquakes/eqinthenews/2011/se082311a/#details).
c. A number of resources are useful in building an inventory of known faults in the area. In particular, you should utilize the structure contour maps on basement (Baranoski et al., 2013), on the top of the Trenton limestone (Patchen et al., 2006), and on the top of the Onondaga Limestone (Wickstrom et al., 2006). In particular, take note of the slightly different angle of the Burning Spring Fault as represented on the maps of the Onondaga and Trenton as contrasted with the angle represented in the basement contour map. Presumably the orientation represented in the Onondaga and Trenton is more pertinent here since these are the actual horizons being fracked. Note that I have also provided Baranoski’s structure contour map on Precambrian basement in southeastern Ohio as a scanned overlay in Google Earth format. In the table below, provide a list of the faults in the area with their azimuth’s (angle measured clockwise from North) and, where possible, the length of each fault. For faults over 100 km long, you can simply indicate “>100 km.” Trace each fault using the line tool in Google Earth, and symbolize your faults as heavy red lines. Note that you can save your fault map as an image file from Google Earth using the File Save Image command. Import your map below and use it as a figure in your written paper. Note that some faults are named (e.g., the Rome Trough, the Burning Spring fault, and the Cambridge structural discontinuity). To refer to unnamed faults, assign them letters in your Google Earth map and refer to them by the corresponding letter in the table below:
Fault Name |
Azimuth |
f |
Fault Length |
Rome Trough: |
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Burning Spring: |
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Cambridge Discontinuity |
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Unnamed Fault A |
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Unnamed Fault B |
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d. Once you have the fault azimuths recorded, you can now estimate the angle f that each fault makes relative to the plane of maximum principle stress. Fill in the columns in the table above and mark and label the corresponding point on each of your Mohr Circles at the end of the hand-out. We will again turn to Byerlee’s Law to evaluate the stability or instability of the faults you identified. Plot Byerlee’s Law on your Mohr diagram and use it to evaluate the stability or instability of the faults. In the space below list each fault and identify whether, given our assumptions above, it would be stable, unstable or near-critical (a) under hydrostatic stress conditions, and (b) during fracking.
5. Finally, having conducted the above mechanical analysis, we can also look at whether there is any evidence in the area that past injection activities have triggered induced seismicity. Although there has not yet been widespread fracking activity in Washington County, there are a number of Class II deep injection wells and also some recent small earthquakes in the area. The Google Earth data file I have provided already includes the locations of the two largest of the recent earthquakes in the county. To locate the other epicenters go to the OhioSeis network homepage at: http://geosurvey.ohiodnr.gov/earthquakes-ohioseis/ohioseis-home and open the “Recent Events” list. Scroll down the list looking for events located in Washington County. When you find one, copy the latitude and longitude and paste it into the search window of Google Earth. For example, Lat. 39.4096o North, Long -81.3940o West would be pasted in the form 39.4096, -81.3940 (by convention West longitudes are negative). If you open the Properties for this point and go to the “Style, Color” tab you can choose from a menu of symbols, including an earthquake symbol. You can also copy and paste the description of the earthquake from Ohioseis, and if you wish you may insert a hyperlink that will open the Ohioseis web page in Google Earth. There are also several injection wells in Washington County. The locations of these can be found in the Ohio Oil and Gas well locator web page at: https://gis.ohiodnr.gov/website/dog/oilgasviewer/. The state makes this information open to the public utilizing a leading GIS software package, ARCGIS Online; ARCGIS is the same system taught in UD’s graduate certificate program in Geographic Information Systems. After opening the viewer zoom into Washington County – are you surprised at how many holes have been drilled in this area? I was! Though fracking in the Utica and Marcellus is new, traditional oil production from units such as the Trenton and the Clinton/Medina has a long history in Ohio. Here we are only interested in the injection wells as those are the ones that have occasionally been associated with induced seismicity. Once again, I have already located the first two wells for you. All petroleum-related wells (including Class II injection wells) are assigned unique identifying numbers known as “API numbers” by the American Petroleum Institute. You can locate the wells of interest by using the search tool to locate them using their API numbers, as listed below:
API Number |
Well name |
DTD |
Completion Formation |
Injection Formation |
Injection Pressure |
34167293950000 |
Ohio Oil Gathering Corp. II, SWIW (Salt Water Injection Well) #6 |
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34167295770000 |
Helen F. Hall, SWIW #7 |
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34167296580000 |
Long Run Disposal Well, SWIW #8 |
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34167296850000 |
Newell Run, SWIW #10 (already located on map for you) |
7332 ft 2235 m |
Queenston shale |
Clinton Medina |
1950 psi 13.4 MPa |
34167296180000 |
Greenwood Unit, SWIW #15 |
7451 ft 2271 m |
Queenston shale |
Clinton Medina |
1690 psi 11.7 MPa |
34167297190000 |
Sawmill Run Disposal Well, SWIW #16 |
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As you search for and locate each well above, you can use the “Information” tool to click on the well and open an information pop-up that includes a hyperlink to a Well Summary Report. From the Well Summary Report you can also link to the well card (which generally includes a stratigraphic log) and various other documents relating to the well, typically including the well permit. In the case of an injection well, there should be at least one permit that specifies the maximum allowable surface injection pressure (in psi) that the well is licensed to pump at. In order to consider how this pressure would affect our Mohr circles, convert it to MPa (this is easily done with online conversion utilities). For each well, record the DrilledTotal Depth (DTD), what formation the well was completed in, and what interval the injection is occurring in, and the maximum licensed surface injection pressure in the table above.
Once you have located the wells and the earthquake epicenters study your map to determine whether any of the recent earthquakes occurred in close proximity to an injection well.
a. Considering both the epicentral location and the depth, which earthquake was located closest to an injection well, and how close was it? (Use the measurement tool in Google Earth)
b. Construct a Mohr circle for the depth of the injection well and adjust it for hydrostatic pressure plus the maximum allowed injection pressure for the pertinent well from the table above. In this case we do not know the fault orientation, but does it seem credible that the well could have induced the earthquake?
c. How far is the well in question from the nearest known fault? How far is it from the Willow Island dam site or the McElroy’s Run earthen embankment dam? Could a large earthquake on the fault put the dam at risk/?
d. All things considered, is there einough risk of significant induced seisimicity in the area to merit further investigation of this potential hazard?
References
Baranoski, Mark T., 2013, Structure contour map on the Precambrian unconformity surface in Ohio and related basement features (vers 2.0), Ohio Dept. Natural Resources, Division of the Geological Survey, Map PG-23, Scale 1:500,000, 17 p. text.
Heidbach, O., Tingay, M., Barth, A., Reinecker, J., Kurfeß, D. and Müller, B., The World Stress Map database release 2008 doi:10.1594/GFZ.WSM.Rel2008, 2008.
Ohio Department of Natural Resources, March, 2012, Preliminary Report on Northstar 1 Class II Injection Well and the Seismic Events in the Youngstown Ohio Area.
Patchen, D.G., Hickman, J.B., Harris, D.C., Drahovzal, J.A., Lake, P.D., Smith, L.B., Nyahay, Richard, Schulze, Rose, Riley, R.A., Baranoski, M.T., Wickstrom, L.H., Laughrey, C.D., Kostelnik, Jaime, Harper, J.A., Avary, K.L., Bocan, John, Hohn, M.E., and McDowell, Ronald, 2006, A geologic play book for Trenton-Black River Appalachian Basin exploration: Morgantown, W. Va., U.S. Department of Energy Report, DOE Award Number DE-FC26-03NT41856, 601p., accessible at <http://www.wvgs.wvnet.edu/www/tbr/project_reports.asp>.
Shaw, B. E. (2009). Constant stress drop from small to great earthquakes in magnitude–area scaling, Bull. Seismol. Soc. Am. 99, 871–875, doi: 10.1785/0120080006.
Wells, D. L., and K. J. Coppersmith (1994). New empirical relationships among magnitude, rupture length, rupture width, rupture area and surface displacement, Bull. Seismol. Soc. Am. 84, 974–1002.
Wickstrom, L.H., Perry, C.J., Riley, R.A., and others, 2006, Marcellus & Utica Shale: Geology, History and Oil & Gas Potential in Ohio. Map modified by Powers, D.M. and Martin, D.R.
Figure 3. Map of known bedrock fault systems in Ohio (Ohio Dept. Nat. Res. Div. of Geol. Surv.)
Figure 4. Map of historic earthquake epicenters in Ohio scaled by magnitude.
Figure 5. Locations of deep injection waste disposal wells in Ohio.
GEO301: Structural Geology Name:_____________________________________
MPa
n(MPa)
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MPa
n(MPa)
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Utica/Pt. Pleasants Formations |
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|
MPa
n(MPa)
|
|
|
|
|
|
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|
|
Clinton/Medina Sandstone |
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A nurse on a medical/surgical unit has made the same medication error two days in a row. As the nurse manager, describe how you would decide whether this is a systems problem, or a problem related to the individual nurse. In either case, explain how you (the manager) should correct the problem.
This is shared only with your instructor. Minimum 250 words.
· No title page needed
· One full page typed and double spaced is equivalent to 250 words (your minimum required)
· References and citations should be scholarly, peer-reviewed (no blogs, WIKI, or other school of nursing website) written in Current APA Style
Rubric
Journal Assignment Rubric (1)
Journal Assignment Rubric (1) |
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Criteria |
Ratings |
Pts |
||||
This criterion is linked to a Learning OutcomeCritical Analysis |
|
12 pts |
||||
This criterion is linked to a Learning OutcomeContent |
|
12 pts |
||||
This criterion is linked to a Learning OutcomeMechanics |
|
9 pts |
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This criterion is linked to a Learning OutcomeAPA Format |
|
7 pts |

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