Data acquisition - Revision history

Klmos: /* Fracture characterization */

2019-07-03T14:58:05Z

‎Fracture characterization

Klmos: /* Pumping tests */

2019-07-03T14:54:26Z

‎Pumping tests

Klmos at 13:06, 24 April 2019

2019-04-24T13:06:47Z

Klmos at 21:39, 5 February 2018

2018-02-05T21:39:57Z

Klmos at 21:37, 5 February 2018

2018-02-05T21:37:31Z

Show changes

Klmos: /* Borehole cores and borehole tests */

2018-01-31T21:15:39Z

‎Borehole cores and borehole tests

Klmos: /* Geology and hydrogeology */

2018-01-31T20:45:39Z

‎Geology and hydrogeology

Klmos: /* Fracture characterization */

2018-01-31T20:35:57Z

‎Fracture characterization

Klmos: /* Aquifer tests */

2018-01-31T20:34:57Z

‎Aquifer tests

Klmos: /* Pumping tests */

2018-01-31T20:07:44Z

‎Pumping tests

@@ Line 121: / Line 121: @@
 == Fracture characterization ==
-[[File:OTVexample.jpg|thumb|600px|Fig. 5: Example of an optical televiewer measurement in Geo18 showing a fracture (dark) at 35.5 m bgs. Courtesy of Geo.]]
+[[File:OTVexample.jpg|thumb|600px|Fig. 5: Example of an optical televiewer measurement in Geo18 showing a fracture (dark) at 35.5 m bgs. This is also reflected on the caliper log (left) and the flow log (right). Courtesy of Geo.]]
 In fractured limestone aquifers, the fractures are the primary travel pathways for substances, and their characterization is important for risk assessment and remedial planning.
 Information about the fracture geometry and location is, however, generally scarce and the determination of appropriate parameters may be challenging.

@@ Line 48: / Line 48: @@
 === Pumping tests ===
 Pumping tests are very useful to characterize the local hydrogeology at a contaminated site.
-Usually, a well is pumped and the drawdown behavior (head changes) in the pumping well and (if available) in neighboring observation wells is measured.
+Usually, a well is pumped and the drawdown behavior (hydraulic head changes) in the pumping well and (if available) in neighboring observation wells are measured.
-This can be done with manual head measurements, if the hydraulic head changes relatively slow.
+This can be done with manual head measurements, if the hydraulic head changes happen relatively slow.
-Fractured aquifers, however, often exhibit a high hydraulic conductivity and the drawdown happens quickly, which makes it hard to manually measure the drawdown caused by the pumping.
+Fractured aquifers, however, often exhibit a high hydraulic conductivity and the drawdown happens quickly, which makes it difficult to manually measure the drawdown caused by the pumping.
 In this case, the head changes can be monitored with programmable pressure transducers (divers), which measure the hydraulic heads at a high measurement frequency.
 Two measurements per seconds or even more are recommended for fracture-flow dominated aquifers or aquifers with a high hydraulic conductivity.
-The drawdown curves have to be interpreted with a suitable tool (e.g. [http://www.aqtesolv.com/ Aqtesolv]), which allows the determination of aquifer parameters like the hydraulic conductivity.
+The drawdown curves can be interpreted with a suitable tool (e.g. [http://www.aqtesolv.com/ Aqtesolv]), which allows the determination of aquifer parameters like the hydraulic conductivity.
-In fractured aquifers, long-term pumping tests with a high pumping rate can potentially give information about the hydraulic conditions in both fractures and matrix.
+In fractured aquifers, long-term pumping tests with a high pumping rate can potentially reveal information about the hydraulic conditions in both fractures and matrix.
 Drawdown curves from long-term pumping tests in fractured limestone aquifers exhibit different stages - first, pumped water is mainly withdrawn from the fractures, followed by a stage with fracture-matrix interflow, and in the last stage, the water is mainly abstracted from the matrix.
 At the Akacievej site, the full drawdown had developed within a time period of about 10 days.
@@ Line 61: / Line 61: @@
 However, it has to be kept in mind that the obtained values only describe the area affected by the pumping test and an extrapolation has to be done with care, especially if the aquifer is very heterogeneous.
-A higher pumping rate can potentially increase the affected area.
+A higher pumping rate can potentially enlarge the affected area.
-Further, in screened wells, the (vertical) location of the screen is important, since water is mainly pumped from the part of the aquifer at the depth of the screen (or in case of an open borehole, of the entire borehole).
+Further, in screened wells, the (vertical) location of the screen is important, since water is mainly pumped from the part of the aquifer at the depth of the screen (or in case of an open borehole, of the open section of the borehole).
-Packers can be installed to separate sections of the aquifer and to determine hydraulic conductivities (transmissivities) for these segments.
+Packers can be installed to separate sections of the aquifer and to determine hydraulic conductivities (or transmissivities) for these sections.
 [[File:PumpTracerTest-images.png|thumb|center|800px| Fig.3: Photos from the pumping test and the tracer tests at Akacievej (spring 2016). From left to right: Pumping well, preparation of tracer injection system, mixing of fluorescein into 1000 L tanks with groundwater, tracer sampling on sampling carousel.]]

@@ Line 4: / Line 4: @@
+|
 * Methods to describe geology and hydrogeology
 * Fracture characterization
 |}
@@ Line 16: / Line 16: @@
 This page gives a description of some useful methods to determine relevant aquifer parameters and to characterize the fracture system.
 Information about the geology and hydrogeology at a site is primarily obtained from locations that provide access to the subsurface, such as outcrops, excavations and boreholes, and from geophysical measurements.
-The national well database ([http://www.geus.dk/UK/data-maps/jupiter/Pages/default.aspx Jupiter]) contains very useful borehole information, such as the location of boreholes, the geology in the boreholes, groundwater analyses, and information about water supply wells.
+The Danish national well database ([http://www.geus.dk/UK/data-maps/jupiter/Pages/default.aspx Jupiter]) contains very useful borehole information, such as the location of boreholes, the geology in the boreholes, groundwater analyses, and information about water supply wells.
-This can be combined with information from geologic maps and interpretations, as, for example, provided by the [http://www.geus.dk/UK/data-maps/Pages/default.aspx Geological Survey of Denmark and Greenland].
+This can be combined with information from geologic maps and interpretations, as, for example, provided by the [http://www.geus.dk Geological Survey of Denmark and Greenland].
 === Borehole cores and borehole tests ===
@@ Line 25: / Line 25: @@
 The information obtained from cores from different boreholes can be spatially interpreted and combined with geologic knowledge from maps to build up a geologic model.
-The collected borehole cores can be analyzed (e.g. determination of porosity, permeability, microfossils) and the depth-discrete stratigraphy at the location of the borehole can be determined.
+Collected borehole cores can be analyzed (e.g. determination of porosity and hydraulic conductivity) and the depth-discrete stratigraphy at the location of the borehole can be determined.
 With a microfossil analysis, the age and the type of limestone can be further characterized.
 However, in limestone geologies with flint layers and a strongly varying hardness with depth, core losses may be significant (Figure 2), and thereby alternative borehole and aquifer tests needed to characterize these areas.
-At the Akacievej site, several cores were taken, and microfossil analyses were conducted to determine the limestone type.
+At the Akacievej site, several borehole cores were extracted, and microfossil analyses were conducted to determine the limestone type.
-The limestone had a strongly varying hardness and losses of especially the crushed material were considerable, despite the use of wireline drilling, which is a good coring method in limestone as the geology is only little disturbed by the drilling.
+The limestone had a strongly varying hardness.
 Especially when drilling through flint inclusions, substantial core losses were observed (Figure 2), because the cooling water flushed out soft material.
 The boreholes, where no cores were extracted, were drilled with different methods: dry drilling (tørboring), symmetrix and DTH drilling.
@@ Line 54: / Line 55: @@
 The drawdown curves have to be interpreted with a suitable tool (e.g. [http://www.aqtesolv.com/ Aqtesolv]), which allows the determination of aquifer parameters like the hydraulic conductivity.
-In fractured aquifers, long-term pumping tests with a high pumping rate can potentially give information about the hydraulic conditions in the fractures and the matrix.
+In fractured aquifers, long-term pumping tests with a high pumping rate can potentially give information about the hydraulic conditions in both fractures and matrix.
-The drawdown curves show different stages - first, pumped water is mainly withdrawn from the fractures, followed by a stage with fracture-matrix interflow, and in the last stage, the water is mainly abstracted from the matrix.
+Drawdown curves from long-term pumping tests in fractured limestone aquifers exhibit different stages - first, pumped water is mainly withdrawn from the fractures, followed by a stage with fracture-matrix interflow, and in the last stage, the water is mainly abstracted from the matrix.
-At the Akacievej site, the full drawdown had developed within a time period of 10 days.
+At the Akacievej site, the full drawdown had developed within a time period of about 10 days.
-For the interpretation of such drawdown curves, specialized dual-continuum solution schemes (e.g. the dual-porosity solution presented in Moench, 1984 <ref>Moench, A.F. (1984), ''Double-porosity models for a fissured groundwater aquifer with fractures skin'', Water resources research, Vol.20, 831-846</ref> or Barker, 1988 <ref>Barker, J.A. (1988), ''A generalized radial flow model for hydraulic tests in fractured rock'', Water resources research, Vol.24, 1796-1804</ref>)  can be employed.
+For the interpretation of such drawdown curves, specialized dual-continuum solution schemes (e.g. the dual-porosity solution presented in Moench, 1984 <ref>Moench, A.F. (1984), ''Double-porosity models for a fissured groundwater aquifer with fractures skin'', Water resources research, Vol.20, 831-846.</ref> or Barker, 1988 <ref>Barker, J.A. (1988), ''A generalized radial flow model for hydraulic tests in fractured rock'', Water resources research, Vol.24, 1796-1804.</ref>) can be employed.
 However, it has to be kept in mind that the obtained values only describe the area affected by the pumping test and an extrapolation has to be done with care, especially if the aquifer is very heterogeneous.
@@ Line 67: / Line 68: @@
 The following report contains a detailed description of a long-term pumping test that was conducted at the Akacievej site in combination with six tracer tests and PCE measurements:
-Mosthaf et al., 2016: Pumping and tracer test in a limestone aquifer and model interpretation <ref>Mosthaf et al. (2016), ''Pumping and tracer test in a limestone aquifer and model interpretation'', DTU Environment</ref>
+* [[:Media:Pumping_and_tracer_test_report.pdf|Pumping and tracer test in a limestone aquifer and model interpretation (PDF)]]
 === Slug tests ===

@@ Line 71: / Line 71: @@
 === Slug tests ===
-[[File:SlugTest.jpg|thumb|Fig.3: Example of a vacuum slug test at the Akacievej site.]]
+[[File:SlugTest.jpg|thumb|Fig. 4: Example of a vacuum slug test at the Akacievej site.]]
 Slug tests are relatively cheap and easy single-borehole aquifer tests, where the water table in a borehole is abruptly changed, for example, by releasing a slug of water into the borehole while monitoring the pressure response, when the water table changes back to its original state again.
 They can be used to obtain approximate values of the hydraulic conductivities at the location of a borehole.
@@ Line 91: / Line 91: @@
 A slug of water can be added into the borehole and the head change monitored.
 For aquifers with a high hydraulic conductivity, a different method is recommended:
-A vacuum is applied on the borehole to pull the water table up at the borehole (Figure 3).
+A vacuum is applied on the borehole to pull the water table up at the borehole (Figure 4).
 The raised water table is then released and the equilibration of the water table measured with pressure transducers with a short measurement interval (several measurements per second).
 This method was particularly useful for slug tests in the highly conductive fractured limestone at the Akacievej site.
-The interpretation of slug tests with standard aquifer test software like Aqtesolv allows for obtaining information about the local hydraulic conductivity.
+The interpretation of slug tests with standard aquifer test software like [http://www.aqtesolv.com/ Aqtesolv] allows for obtaining information about the local hydraulic conductivity.
 For fractured aquifers, a solution scheme that is accounting for the fractures and the dual-porosity aquifers like the Barker-Black (1983) solution can be chosen.
 In very conductive aquifers, an oscillating water table caused by inertia can occur when the slug is released.
@@ Line 121: / Line 121: @@
 == Fracture characterization ==
-[[File:OTVexample.jpg|thumb|600px|Fig.5: Example of an optical televiewer measurement in Geo18 showing a fracture (dark) at 35.5 m bgs. Courtesy of Geo.]]
+[[File:OTVexample.jpg|thumb|600px|Fig. 5: Example of an optical televiewer measurement in Geo18 showing a fracture (dark) at 35.5 m bgs. Courtesy of Geo.]]
 In fractured limestone aquifers, the fractures are the primary travel pathways for substances, and their characterization is important for risk assessment and remedial planning.
 Information about the fracture geometry and location is, however, generally scarce and the determination of appropriate parameters may be challenging.
@@ Line 137: / Line 137: @@
 * open-borehole methods like flexible liners ([http://www.flut.com/ FLUTe]) or televiewers
-[[File:FlowLogs Fractures.png|thumb|500px|Fig.6: Flow logs in boreholes to identify horizontal fractures and high-flow zones. The green lines indicate high-flow zones.]]
+[[File:FlowLogs Fractures.png|thumb|500px|Fig. 6: Flow logs in boreholes to identify horizontal fractures and high-flow zones. The green lines indicate high-flow zones.]]
 Flow logs in boreholes can be very useful to identify highly conductive zones (Figure 6).
 Therefore, a propeller probe is lowered in the borehole and the speed of the propeller rotation is recorded while pumping the borehole.

@@ Line 34: / Line 34: @@
 Other boreholes, where no cores were extracted, were drilled with different methods: dry drilling (tørboring), symmetrix and DTH drilling.
-The following borehole tests were conducted in the boreholes at the Akacievej site:
+The borehole tests at the Akacievej site included:
 * induction probes (electrical conductivity measurement)
 * caliper probes (minimal local borehole diameter)

@@ Line 15: / Line 15: @@
 Knowledge about geology and hydrogeology of a contaminated site is usually limited and not easily obtainable.
 This page gives a description of some useful methods to determine relevant aquifer parameters and to characterize the fracture system.
-Information about the geology and hydrogeology at a site is primarily obtained from locations that provide access to the subsurface, such as outcrops, excavations, and boreholes, and from geophysical measurements.
+Information about the geology and hydrogeology at a site is primarily obtained from locations that provide access to the subsurface, such as outcrops, excavations and boreholes, and from geophysical measurements.
-The national well database ([http://www.geus.dk/UK/data-maps/jupiter/Pages/default.aspx Jupiter]) contains very useful borehole information, like the location of boreholes, the geology in the boreholes, groundwater analyses, information about water supply wells etc.
+The national well database ([http://www.geus.dk/UK/data-maps/jupiter/Pages/default.aspx Jupiter]) contains very useful borehole information, such as the location of boreholes, the geology in the boreholes, groundwater analyses, information about water supply wells etc.
 This can be combined with information from geologic maps and interpretations, as, for example, provided by the [http://www.geus.dk/UK/data-maps/Pages/default.aspx Geological Survey of Denmark and Greenland].
@@ Line 23: / Line 23: @@
 A common method to obtain knowledge about the local geology is to drill boreholes and to take borehole cores.
 Some examples from borehole cores are shown in Figure 1.
-However, in limestone geologies with flint layers and the hardness varying with depth, core losses may be significant.
+However, in limestone geologies with flint layers and a strongly varying hardness with depth, core losses may be significant, as shown in Figure 2.
 The cores can be analyzed and the depth-discrete stratigraphy at the location of the borehole can be determined.
 With a microfossile analysis, the age and the type of limestone can be further characterized.
-However, one has to bear in mind that cores can only represents the geology at the location of the borehole and that the geology can have a strong spatial variability.
+However, one has to bear in mind that cores only represent the geology at the location of the borehole and that the geology can have a strong spatial variability.
-The information obtained from borehole cores can be spatially interpreted and combined with geologic knowledge from maps.
+The information obtained from cores from different boreholes can be spatially interpreted and combined with geologic knowledge from maps to build up a geologic model.
-At the Akacievej site, several cores were taken, and microfossile analyses were conducted.
+At the Akacievej site, several cores were taken, and microfossile analyses were conducted to determine the limestone type.
-The limestone had a strongly varying hardness and losses of crushed material were considerable, despite using wireline drilling, which is an elaborate drilling method for taking cores in limestone, where the geology is only little disturbed by the drilling.
+The limestone had a strongly varying hardness and losses of crushed material were considerable, despite using wireline drilling, which is a good drilling method for taking cores in limestone, where the geology is only little disturbed by the drilling.
-Especially when drilling through flint inclusions, substantial core losses were observed (see for example Fig. 2), because soft material was flushed out by the water required to cool the drill.
+Especially when drilling through flint inclusions, substantial core losses were observed (see for example Fig. 2), because soft material was flushed out by the cooling water for the drill.
 Other boreholes, where no cores were extracted, were drilled with different methods: dry drilling (tørboring), symmetrix and DTH drilling.
-The following borehole tests were usually conducted in the boreholes at the Akacievej site:
+The following borehole tests were conducted in the boreholes at the Akacievej site:
-* electrical conductivity measurements
+* induction probes (electrical conductivity measurement)
-* caliper measurements
+* caliper probes (minimal local borehole diameter)
-* temperature measurements
+* porosity probes (gamma-gamma probes for relative porosity)
-* etc.
+* density probes
 == Aquifer tests ==

@@ Line 67: / Line 67: @@
 At the Akacievej site, the full drawdown had developed within a time period of 10 days.
-[[File:PumpTracerTest-images.png|thumb|center|800px| Fig.1: Photos from the pumping test and the tracer tests at Akacievej (spring 2016).]]
+[[File:PumpTracerTest-images.png|thumb|center|800px| Fig.1: Photos from the pumping test and the tracer tests at Akacievej (spring 2016). From left to right: Pumping well, preparation of tracer injection system, mixing of fluorescein into 1000 L tanks with groundwater, tracer sampling on sampling carousel.]]
 The following report contains a detailed description of a long-term pumping test that was conducted at the Akacievej site in combination with six tracer tests and PCE measurements:
-Mosthaf et al., 2016: Pumping and tracer test in a limestone aquifer and model interpretation <ref>Mosthaf et al. (2016), ''Pumping and tracer test in a limestone aquifer and model interpretation'', Report for Region H</ref>
+Mosthaf et al., 2016: Pumping and tracer test in a limestone aquifer and model interpretation <ref>Mosthaf et al. (2016), ''Pumping and tracer test in a limestone aquifer and model interpretation'', DTU Environment</ref>
 <!-- * [[:Media:Pumping_and_tracer_test_report.pdf|Report about the pumping and tracer test at Akacievej (PDF)]] -->