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Publication - Research Publication

Unconventional Oil and Gas: Understanding and Monitoring Induced Seismic Activity

Published: 8 Nov 2016
Part of:
Business, industry and innovation
ISBN:
9781786523952

An independent research project into understanding and monitoring induced seismic activity.

93 page PDF

6.3MB

93 page PDF

6.3MB

Contents
Unconventional Oil and Gas: Understanding and Monitoring Induced Seismic Activity
List of Figures and Tables

93 page PDF

6.3MB

List of Figures and Tables

FIGURES

Figure 2.1: Black circles show the distribution of earthquakes with a magnitude of greater than 5 across Europe. The red line shows the margins of the Eurasian plate. The great majority of earthquake activity is located at the southern margin in Greece and Italy along the collision zone between Africa and Eurasia. The inset shows the distribution of earthquakes in North America. Plate boundary data from Bird (2003). Earthquake Data from the British Geological Survey World Seismicity Database, © NERC 2016

Figure 2.2: Geology of the Midland Valley of Scotland from 1:625 000 scale DigMap BGS©NERC. Potentially prospective units are shown.

Figure 2.3: (b) Extents of potential coal bed methane resource from Jones et al. (2004). (c) Extents of potential shale gas and shale oil resource from Monaghan (2014).

Figure 2.4: Schematic cartoon illustrating relationship between erosion, surface exposure and strata at depth. Cartoon not to scale. The equivalence of the stratigraphic groups shown to component coal and shale-bearing formations is listed in Table 1

Figure 2.5: Faulted limestone pavement, note brittle nature (discrete fault planes )of deformation within the limestone. Lower Limestone Formation, East Ayrshire © BGS, NERC.

Figure 2.6: Interbedded mudstones and ironstones have responded differently to faulting. The mechanically strong ironstone remains relatively undeformed, whereas the mechanically weaker mudstone above has been tightly folded (highlighted by dashed white line). © BGS, NERC.

Figure 2.7: Percentage of described strength from borehole core for six stratigraphic units from engineering geology descriptions in site investigations from the Glasgow area. Image courtesy David Entwisle, BGS.

Figure 2.8: Box and whisker plot of measured uniaxial compressive strength of different lithologies from Carboniferous strata described in engineering geology site investigations from the Glasgow area (note engineering geology classes 1.25-5=weak, 5-12.5=moderately weak, 12.5-50=moderately strong, 50-100 strong, 100-200=very strong). Image courtesy David Entwisle, BGS.

Figure 2.9: Major onshore faults mapped at 1:625 000 scale BGS© NERC DigMap within the Midland Valley of Scotland. Faults are colour coded by orientation.

Figure 2.10: Major onshore faults mapped at 1:250 000 scale BGS© NERC DigMap within the Midland Valley of Scotland. This includes the major faults from the 1:625 000 scale. Note additional complexity and density of faults which is not captured at the 1:625 000 scale.

Figure 2.11: 1:50 000 scale faulting BGS© NERC DigMap . The three dominant trends are still prominent, but the reality of fault spacing and density is better visualised at this scale. Some gaps in the fault dataset reflect the vintage of BGS mapping of the area.

Figure 2.12: Faulted limestone pavement, East Ayrshire. In addition to the faults which displace the limestone, there is a set of orthogonal fractures (with no offset) across the limestone. © BGS, NERC.

Figure 2.13: (a) Historical (yellow circles) and instrumentally recorded (red circles) earthquakes from the BGS catalogue for Scotland. Circles are scaled by magnitude. (b) seismograph stations operated by BGS between 1970 to present. Note that not all station were operational at the same time. (c) Cumulative number of earthquakes as a function of time from 1970 to present. Blue line shows all recorded earthquakes. The red line shows earthquakes with magnitudes of 2.0 ML and above. (d) Annual number of earthquakes from 1970 to present. Earthquake data from the British Geological Survey UK Earthquake Catalogue © NERC 2016.

Figure 2.14: (a) Red circles show instrumentally recorded earthquakes (1970-2015). Symbols are scaled by magnitude. Grey shaded areas show the Mining Reporting Areas (Coal Authority data). Black circles show earthquakes identified as mining-induced during analysis. (b) Cumulative number of earthquakes as a function of time from 1970 to end of 2015. The blue line shows all recorded earthquakes. The red line shows earthquakes removed by the spatial filter and the green line shows the earthquake data after all events in the Mining Reporting Areas have been removed. Earthquake data from the British Geological Survey UK Earthquake Catalogue © NERC 2016.

Figure 2.15: (a) Focal depths as a function of time for earthquakes in the Mining Reporting Areas. (b) magnitudes of mining induced earthquakes as a function of time. The deeper earthquakes may be natural seismicity. Earthquake data from the British Geological Survey UK Earthquake Catalogue © NERC 2016.

Figure 2.16: Schematic showing the number of earthquakes above a given magnitude plotted against magnitude. This shows an exponential distribution leading to the Gutenberg-Richter law. The slope of the lines is the b-value and determines the relative number of earthquakes of different magnitudes. An observed roll-off in the number of earthquakes at low magnitudes shown by the blue crosses is typically seen due to inability of regional seismic networks to detect small earthquakes. Earthquake data from the British Geological Survey UK Earthquake Catalogue © NERC 2016.

Figure 2.17: Magnitude-Frequency distributions for: (a) instrumentally recorded seismicity in Scotland from 1970-2015; (b) instrumentally recorded seismicity in the Midland Valley from 1970 to 2015; (c) historical seismicity in Scotland from 1597 to 1969; and (d) historical and instrumentally recorded seismicity in the British Isles. The blue squares show the observed data. The blue straight lines show the best-fit to the data for a Gutenberg-Richter distribution. The a and b values are given in the top right of each plot. Earthquake data from the British Geological Survey UK Earthquake Catalogue © NERC 2016.

Figure 2.18: (a) Focal mechanisms available for earthquakes in Scotland (Baptie, 2010). The blue and white areas show the compressional and dilatational quadrants and the lines between the quadrants show the strike and dip of the two possible fault planes. The axes of maximum and minimum compression are indicated by the blue and white squares respectively. The blue squares on the map show the location of the earthquakes. (b) a comparison of the stress field with mapped fault orientations. The black lines show the orientation of the maximum horizontal compressive stress, sH, taken from smoothed stress orientations published in the World Stress Map (Heidbach et al., 2010). Green lines show mapped faults. Earthquake data from the British Geological Survey UK Earthquake Catalogue © NERC 2016.

Figure 3.1: Red circles show the seismicity of Texas and South Oklahoma. Circles are scaled by magnitude. Earthquake data from the U.S. Geological Survey ( USGS) ComCat 2. The coloured areas show some of the main shale gas plays from U.S. Geological Survey Digital Data Series 69-Z, Map of assessed shale gas in the United States, 2012.

Figure 3.2: Cumulative number of earthquakes in Texas as a function of time between 1975 and 2015. The red squares show all magnitudes, the blue crosses show events of magnitude 3.0 or above. Earthquake data from the U.S. Geological Survey ( USGS) ComCat

Figure 3.3: Volume of injected fluid (blue line) and earthquakes (red circles, scaled by magnitude) during hydraulic fracturing operations at Preese Hall, Blackpool, between March and June 2011 (after de Pater and Baisch, 2011). There are five distinct hydraulic fracturing stages. Earthquake activity closely correlates with stages 2 and 4. The largest event with 2.3 ML at 02:34 on 1/4/2011 occurred shortly after stage 2. Earthquake data from the British Geological Survey UK Earthquake Catalogue © NERC 2016. Injected fluid volumes provided by Cuadrilla Resources, 2011.

Figure 3.4: Epicentre of Preese Hall earthquakes in April and May 2011 (yellow star), as determined by Eisner et al. (2011). The coloured triangles in (a) show permanent monitoring stations operated by the British Geological Survey at epicentral distances of 75 to 99 km (red), 100 to 149 km (orange) and greater than or equal to 150 km (yellow). The red triangles in (b) show temporary stations deployed after the initial earthquakes on 1 April 2011. The blue triangle shows the location of the Preese Hall well. Topography © Crown Copyright 2016 Ordnance Survey 10037272. Earthquake data from the British Geological Survey UK Earthquake Catalogue © NERC 2016.

Figure 3.5: Location of the Etsho and Tattoo areas in the Horn River Basin (after BC Oil and Gas Commission, 2012). Red circles show the NRCan reported epicentres (scaled by magnitude). Small black dots show well positions. Black squares show wells with the Tattoo and Etsho areas. The black polygons show producing fields. Field and well data obtained from the B.C. Oil and Gas Commission, available at http://data.bcogc.opendata.arcgis.com. Topography data, GTOPO30, US Geological Survey.

Figure 3.6: Coloured circles show earthquakes recorded by Natural Resource Canada between May 2013 and end October 2014. The circles are coloured by date. The yellow stars show the locations of the three largest earthquakes in the sequence, with magnitudes of 4.4, 4.2 and 3.8 Mw. The blue shaded areas show the gas producing areas linked to the seismicity, while the small black dots show well positions. The grey squares show towns. Earthquake data from the National Earthquake DataBase ( NEDB), compiled by Natural Resources Canada. Well data obtained from the Alberta Energy Regulator, available at https://www.aer.ca/data-and-publications.

Figure 3.7: Map showing triggered seismicity west of Fox Creek, Alberta, Canada. The red circles show seismicity recorded by Natural Resources Canada, in the period November 2013 to May 2016. The grey circles show locations calculated for the Crooked Lake sequence between November 2013 and December 2014 by Schultz et al. (2015). Earthquake symbols are scaled by magnitude. Earthquake data from the National Earthquake DataBase ( NEDB), compiled by Natural Resources Canada. Topography data, GTOPO30, US Geological Survey.

Figure 3.8: Circles show earthquake activity in the Raton Basin ( USGS ComCat, 2016). The circles are scaled by magnitude. The two red circles show the magnitude 5 earthquake on 10 August 2005 and the magnitude 5.3 earthquake on 23 August 2011. The grey shaded area shows the extent of the basin (from Coleman and Cahan, 2012).

Figure 3.9: Cumulative number of earthquakes in the Raton Basin with magnitudes greater than 3 as a function of time. Activity increases dramatically shortly after the start of coal-bed methane production (after Rubinstein et al., 2014). Earthquake data from the U.S. Geological Survey ( USGS) ComCat

Figure 3.10: Cumulative count of earthquakes with M ≥ 3 in the central and eastern United States, 1967-2012 (after Ellsworth, 2013). Earthquake data from the U.S. Geological Survey ( USGS) ComCat

Figure 3.11: USGS map displaying 21 areas impacted by induced earthquakes as well as the location of fluid injection wells that have and have not been associated with earthquakes. Credit: U.S. Geological Survey, Open-File Report OFR-2016-1035

Figure 3.12: USGS map displaying the intensity of potential ground shaking with a 1% probability of being exceeded in one year. Both natural and human induced earthquakes are included. Credit: U.S. Geological Survey, U.S.G.S. Open-File Report OFR-2016-1035

Figure 3.13: Earthquakes in the Western Canada Sedimentary basin ( WCSB) with a magnitude of 3.0 or above (after Atkinson et al. (2016). The boxes delineate an area parallel to the foothills of the Rockies where induced seismicity has been observed. Earthquake data from the National Earthquake DataBase ( NEDB), compiled by Natural Resources Canada. Topography data, GTOPO30, US Geological Survey.

Figure 3.14: Cumulative number of earthquakes with a magnitude of 3.0 or above (blue squares) within the parts of the WCSB in the area delineated by the rectangles in Figure 3.13 from 1985 to 2015 (after Atkinson at al, 2016). The blue line shows the increase in number of hydraulically fractured wells. Earthquake data from the National Earthquake DataBase ( NEDB), compiled by Natural Resources Canada. Well data obtained from the Alberta Energy Regulator and the B.C. Oil and Gas Commission, available at https://www.aer.ca/data-and-publications and http://data.bcogc.opendata.arcgis.com.

Figure 4.1: Questions to be addressed to understand and possibly quantify the hazard and risk associated with induced seismicity associated with energy technologies (from "Induced Seismicity Potential in Energy Technologies", National Academy of Sciences, 2012)

Figure 5.1: location calculated using NonLinLoc (Lomax et al., 2009) for the earthquake on 1st April 2011. The location was calculated using 36 phase arrivals from 25 stations. The blue stars show the maximum likelihood location. Red dots show the density-scatter in the location probability distribution function. The Preese Hall site is at (x, y) = (0, 0). Earthquake data from the British Geological Survey UK Earthquake Catalogue © NERC 2016.

Figure 5.2: Location calculated using NonLinLoc (Lomax et al., 2009) for the earthquake on 27 th May 2011. The location was calculated using 18 phase arrivals from 12 stations. The blue star shows the maximum likelihood location. Red dots show the density-scatter in the location probability distribution function. Open triangles show the locations of the two seismometers installed close to the Preese Hall. Earthquake data from the British Geological Survey UK Earthquake Catalogue © NERC 2016.

Figure 5.3: Modelled detection capability for the BGS seismic monitoring network (black triangles) in central Scotland at four points in time: (a) 1970; (b) 1980; (c) 1990; and (d) 2016. The contours show the spatial variation in magnitudes that can be detected. Detection requires a signal in excess of three times the background noise to be recorded at three or more stations. The scoping study area is delineated by the grey shaded area.

Figure 5.4: Modelled peak ground velocity (solid coloured lines) plotted as a function of hyocentral distance .The grey dashed lines show the limits for acceptable vibrations from blasting specified in BS 6472-1 and BS 7385-2. The squares and triangles show observed horizontal and vertical ground motions.

TABLES

Table 2.1: Summary of the Carboniferous stratigraphy of the Midland Valley of Scotland (modified after Browne et al. 1999 and Monaghan 2014; dates from Waters, 2011). The eleven potentially prospective intervals are colour shaded blue for coal-rich interval, green for shale-rich interval and yellow for combined shale- and coal-rich interval. Note that the coal-rich intervals highlighted blue also contain shale but were excluded from the shale resource assessment of Monaghan (2014) due to their current day burial depth largely being < 1 km.

Table 2.2: Summary chart of Midland Valley of Scotland Carboniferous tectonic history (modified from Monaghan, 2014).

Table 2.3: Magnitude of completeness for different periods of time used for Britain by Musson and Sargeant (2008).

Table 4.1: The U.S. Department of Energy Protocol for Addressing Induced Seismicity Associated with Enhanced Geothermal Systems (Steps are listed in the order expected to be followed). Adapted from Majer et al. (2012).

Table 4.2: Seismic response procedure used in Basel, Switzerland (and adapted from the traffic light system proposed by Bommer et al. (2006). The system is based on three independent parameters: (1) public response; (2) local magnitude ( ML); and, peak ground velocity ( PGV))

Table 4.3: Measures for the mitigation of induced seismicity set out in the DECC regulatory roadmap.

Table 4.4: Recommendations Investigation of Observed Seismicity in the Horn River Basin ( BC Oil and Gas Commission, 2012)


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