- Email: [email protected]
Detection of groundwater contamination with hydrocarbons
Russian Geology and Geophysics 49 (2008) 183–186 www.elsevier.com/locate/rgg
Detection of groundwater contamination with hydrocarbons V.M. Fomenko a, *, O.A. Shushakov a, V.S. Kuskovskii b a
b
Institute of Chemical Kinetics and Combustion, Siberian Branch of the RAS, 3 ul. Institutskaya, Novosibirsk, 630090, Russia Institute of Petroleum Geology and Geophysics, Siberian Branch of the RAS, 3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia Received 15 February 2007
Abstract The task was to detect the groundwater contamination with hydrocarbons (gasoline, kerosene, diesel fuel) without drilling special boreholes, by means of NMR geotomography. Near the town of Abakan (Khakasia, RF), experimental measurements were carried out at a gas station where gasoline leakage is possible and the contamination of groundwaters was monitored through observation wells. In the immediate vicinity of the source of pollution, signals with essentially different times of relaxation were rather distinct: Short signals came from hydrogen protons of water, and much longer signals, from hydrogen protons of gasoline. © 2008, IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved. Keywords: NMR geotomography; hydrocarbons; groundwater; contamination; relaxation time
Introduction The method of NMR geotomography is based on the excitation of spin states of hydrogen protons at the resonant frequency in the Earth’s magnetic field and subsequent record of the signal of damped oscillations after the excited pulse is switched off (Fig. 1). At the initial time of measurements, a deflecting radio-frequency pulse is given to the antenna. The current intensity of this radio pulse can range from few to hundreds of amperes. Then this antenna receives an NMR signal from the excited spin states of hydrogen protons. The current intensity of the radio pulse in the antenna controls the depth of sounding. The signal amplitude is proportional to the amount of water; the relaxation-time constant depends on the size of pores in the aquifer and, to some degree, determines this size. A difference between the phase of exciting pulse and the phase of the received NMR signal bears information on electrical conductivity and, hence, on water mineralization. The frequency of magnetic resonance in the Earth’s magnetic field ranges from 1 to 3 kHz depending on the site of measurements. The equipment records only fluids able to move hydrodynamically. The bound, crystallization, or frozen liquids have, as a rule, very short times of spin relaxation and are not recorded.
* Corresponding author.
The equipment for these studies is mounted in a car (or cross-country vehicle and is used for clearing up hydrogeologic and engineering-geologic conditions without drilling, which makes the whole cycle of prospecting works considerably cheaper and less time-consuming. Many years of operation with the NMR geotomograph Hydroscope, developed at the Institute of Chemical Kinetics and Combustion, Novosi-
Fig. 1. Principle of processing of the NMR geotomograph Hydroscope. Current of deflecting pulse (A), signal voltage (nV). E-mail address: [email protected] (V.M.Fomenko) 1068-7971/$ - see front matter D 2008, IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.rgg.2008.02.003
184
V.M. Fomenko et al. / Russian Geology and Geophysics 49 (2008) 183–186
birsk, prove that the method of NMR geotomography can be used to detect groundwater at depths of 150 m and even deeper. With progress in updating the Hydroscope equipment, mathematical programs were developed to calculate the received NMR signals (giving the fluid distribution in depth) as a function of the deflecting radio pulse. The model implies the fluid distribution in horizontal layers at different depths, with different horizontal dimensions much exceeding the antenna sizes. In addition, by measuring the relaxation times, the size distribution of pores can also be estimated. The method and its implications are described in detail elsewhere (Fomenko and Shushakov, 1999; Kuskovskii et al., 2004, 2006; Shushakov et al., 2002). As the operation of the NMR geotomograph is based on the record of signals of free induction of hydrogen protons in the Earth’s magnetic field, theoretically we can record hydrogen present not only in water but also in other compounds with longer relaxation times. Brown (1956) was the first to note this opportunity. Moreover, physical and chemical properties of a substance can be inferred from the relaxation duration. This is true, in particular, for liquid hydrocarbons, e.g., gasoline and kerosene. It is known (Davies et al., 1994; Fordham et al., 1993; Hall et al., 1994) that in the same pores the relaxation times of hydrogen protons were longer for gasoline than for water. The difference is due to different wettability of pore walls with gasoline and water.
Methods and results To confirm in practice that an NMR geotomograph is capable to record the pollution of aquifers by liquid hydrocarbons, we took preliminary measures. First, we updated the instrument, thus allowing it to record NMR signals not only from water but also from liquid hydrocarbons with longer relaxation times. The updated instrument was able to change the duration of exciting pulse and the time of record of nuclear relaxation signals. In the former version the duration of exciting pulse was strictly constant, 40 ms; now we can preset it from few to hundreds of milliseconds. As the time of spin relaxation of hydrogen protons in gasoline is longer than in water; the former time of pulse record, 200 ms, appeared insufficient for recording the signals received from hydrogen protons of gasoline. Therefore, the time of free-induction record was lengthened so that it can be given in the range from 200 to 2000 ms. Second, the study area was chosen near the town of Abakan (Khakasia), and three expeditions were organized to work there. One of the expeditions was international, with participation of the New Mexico Resonance Laboratory (New Mexico, USA). Preliminary results were reported at a symposium (Shushakov et al., 2004). This choice was dictated by the properties of aquifers, which occur in washed pebblestones in the Abakan and Yenisei valleys. The roof of aquifers occurs there at shallow depths of about
5–10 m. Because of leakage of gasoline and other hydrocarbons, local spots of pollution form on the surface of an aquifer. This, in turn, leads to serious problems in water supply. For this reason, the Minusinsk Hydrogeological Party performs monitoring of groundwater pollution with liquid hydrocarbons in and near Abakan. To solve these problems, more than 130 observation boreholes 8–12 m deep were drilled. The layer of gasoline (on the water surface) in these boreholes is often 0.3–0.5 m thick and even layers more than 1 m thick were recorded. The gasoline layer was determined by means of a glass tube with a bottom gate: The tube was plunged into the borehole and then lifted together with a sample to be measured. Water and gasoline occurring in pores of the aquifer wet the pore surface quite differently because of different physical properties. The spin relaxation on the pore surface is more intensive; therefore, the relaxation time of hydrogen protons in water is much shorter than in gasoline, for water wets the pore surface much stronger (Fig. 2). Owing to this difference in properties of water and gasoline, as soon as tens of milliseconds after the beginning of NMR signal record, the level of gasoline signal exceeds the level of water signal, though the initial amplitude of the signal from hydrogen protons of water many times exceeds that of gasoline. Thus, if we expand the signal in a power series of different constants of time relaxation, we will be able to discriminate between water and gasoline signals. Remarkable results were obtained from BH-52 drilled at a gas station near Kalinino Village (Abakan’s suburb). Several days before the measurements, a considerable leakage of A-76 gasoline occurred at this station. Figures 3 and 4 exemplify results of analysis of the gasoline linkage. At the time of
Fig. 2. Relaxation time of hydrogen protons of water is significantly shorter than relaxation time of hydrogen protons of gasoline. 1 — water, 2 — gasoline, 3 — water + gasoline.
V.M. Fomenko et al. / Russian Geology and Geophysics 49 (2008) 183–186
185
Fig. 3. Characteristic curve of the NMR signal amplitude and the time with different pulse magnitude. Abakan, BH-52. Exciting pulse magnitude ranging from 3273 to 5577 A⋅ms, defines the depth of sounding.
Fig. 4. Characteristic curve of the NMR signal amplitude and the time with different pulse magnitude. Abakan, 120 m apart from BH-52.
sampling, the layer of hydrocarbons in BH-52 was 1.15 m, with a depth of drilling of 11 m and a level of hydrocarbon surface in the borehole of 7.8 m. The content of petroleum in the water sample from the borehole was 7.15 mg/dm3, as determined by standard fluorometry. The geological section of the borehole is represented by Quaternary alluvium deposits: 1–4 m — sandy loam, 4–5 m — medium-grained sands, 5–9 m — clay with rubble, 9–11 m — gravel-pebblestone deposits (aquifer). The gasoline and water signals were experimentally identified from measurements at two sites: in the immediate vicinity of the borehole near the source of pollution and far apart (120 m). In the first case, NMR signals with essentially different T∗2 times are highlighted (see Fig. 3). T∗2 is the time of heterogeneous transverse (spin-spin) nuclear relaxation. The plot contains a group of curves with short times of relaxation from hydrogen protons of water and a curve with a much longer time of relaxation from hydrogen protons of gasoline. In the second case, there is only one T∗2 component from hydrogen protons of water (see Fig. 4).
deposits. There, the filtration properties of water-bearing soils are characterized by relatively high parameters (Kf is 50 to 100 m/day). To reveal the potential of this method, the study should be continued in different hydrogeological environments. We believe that this approach is quite promising for without drilling expensive hydrogeological boreholes it allows us not only to locate the groundwater pollution but also to outline haloes of this pollution and keep routine monitoring. We thank V.M. Gruznov and S.V. Morozov for valuable comments on the manuscript.
Conclusions For the first time, a signal from hydrogen protons of pollutant hydrocarbons occurring on the groundwater surface was received in the measurements we made near Abakan by means of NMR geotomography, without drilling boreholes. The experiments were carried out on the terrace of the Yenisei River (the shore of the Krasnoyarsk Water Reservoir) made up of clays, sandy loams, sands, and gravel-pebblestone
References Brown, R.J.S., Fatt, I., 1956. Measurements of fractional wettability of oilfield rocks by the nuclear magnetic resonance method. Trans. Amer. Inst. Miner. Petrol. Eng. 220, 262–264. Davies, S., Hardwick, A., Roberts, D., Spowage, K., Packer, K.J., 1994. Quantification of Oil and Water in Preserved Reservoir Rock by NMR Spectroscopy and Imaging. Mag. Res. Imag. 2 (12), 349–353. Fomenko, V.M., Shushakov, O.A., 1999. Some recent developments in Hydroscope hardware, in: Proceedings of the 1st International Workshop ,,Surface Nuclear Magnetic Resonance (SNMR) —What is possible?", Technical University Berlin, Berlin, pp. 36–41. Fordham, E.J., Hall, L.D., Ramakrishnan, T.S, Sarpe, M.R., Hall, C., 1993. Saturation Gradients in Drainage of Porous Media: NMR Imaging Measurements. AIChE J. 37 (9), 1431–1443. Hall, L.D., Rajanajagam, V., 1987. Thin-Slice, Chemical-Shift Imaging of Oil and Water in Sandstone Rock at 80 MHz. J. Mag. Res. 74, 139–146. Kuskovsky, V.S, Shushakov, O.A., Fomenko, V.M., 2004. The study of groundwater by means of the NMR tomography, in: Proceedings of 6th International Congress “Water: Ecology and Technology of AQUATECH2004”, 1, pp. 184–185. Kuskovsky, V.S, Shushakov, O.A., Fomenko, V.M., 2006. NMR sounding is the new method of hydrogeological exploration, in: Proceedingss of
186
V.M. Fomenko et al. / Russian Geology and Geophysics 49 (2008) 183–186
Annual Session of Research Council of the RAS concerning the problems of geoecology, engineering geology and hydrogeology. GEOS, Moscow, pp. 315–319. Shushakov, O.A., Fomenko, V.M., Kuskovsky, V.S., 2002. Usage of the geophysical NMR tomography for hydrogeological and engineering geological investigations. ENVIROMIS 2002, 1, 15–19.
Shushakov, O.A., Fomenko, V.M., Yashchuk, V.I., Krivosheev, A.S., Fukushima, E., Altobelli, S.A., Kuskovsky, V.S., 2004. Hydrocarbon contamination of aquifers by SNMR detection, in: Benda, G. (Ed.) Proceedings of Waste Management (WM’04) Symposium, Arizona, Tucson. WM4566, pp. 46–49.
Editorial responsibility: G.N. Anoshin 18 July 2007
Detection of groundwater contamination with hydrocarbons V.M. Fomenko a, *, O.A. Shushakov a, V.S. Kuskovskii b a
b
Institute of Chemical Kinetics and Combustion, Siberian Branch of the RAS, 3 ul. Institutskaya, Novosibirsk, 630090, Russia Institute of Petroleum Geology and Geophysics, Siberian Branch of the RAS, 3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia Received 15 February 2007
Abstract The task was to detect the groundwater contamination with hydrocarbons (gasoline, kerosene, diesel fuel) without drilling special boreholes, by means of NMR geotomography. Near the town of Abakan (Khakasia, RF), experimental measurements were carried out at a gas station where gasoline leakage is possible and the contamination of groundwaters was monitored through observation wells. In the immediate vicinity of the source of pollution, signals with essentially different times of relaxation were rather distinct: Short signals came from hydrogen protons of water, and much longer signals, from hydrogen protons of gasoline. © 2008, IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved. Keywords: NMR geotomography; hydrocarbons; groundwater; contamination; relaxation time
Introduction The method of NMR geotomography is based on the excitation of spin states of hydrogen protons at the resonant frequency in the Earth’s magnetic field and subsequent record of the signal of damped oscillations after the excited pulse is switched off (Fig. 1). At the initial time of measurements, a deflecting radio-frequency pulse is given to the antenna. The current intensity of this radio pulse can range from few to hundreds of amperes. Then this antenna receives an NMR signal from the excited spin states of hydrogen protons. The current intensity of the radio pulse in the antenna controls the depth of sounding. The signal amplitude is proportional to the amount of water; the relaxation-time constant depends on the size of pores in the aquifer and, to some degree, determines this size. A difference between the phase of exciting pulse and the phase of the received NMR signal bears information on electrical conductivity and, hence, on water mineralization. The frequency of magnetic resonance in the Earth’s magnetic field ranges from 1 to 3 kHz depending on the site of measurements. The equipment records only fluids able to move hydrodynamically. The bound, crystallization, or frozen liquids have, as a rule, very short times of spin relaxation and are not recorded.
* Corresponding author.
The equipment for these studies is mounted in a car (or cross-country vehicle and is used for clearing up hydrogeologic and engineering-geologic conditions without drilling, which makes the whole cycle of prospecting works considerably cheaper and less time-consuming. Many years of operation with the NMR geotomograph Hydroscope, developed at the Institute of Chemical Kinetics and Combustion, Novosi-
Fig. 1. Principle of processing of the NMR geotomograph Hydroscope. Current of deflecting pulse (A), signal voltage (nV). E-mail address: [email protected] (V.M.Fomenko) 1068-7971/$ - see front matter D 2008, IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.rgg.2008.02.003
184
V.M. Fomenko et al. / Russian Geology and Geophysics 49 (2008) 183–186
birsk, prove that the method of NMR geotomography can be used to detect groundwater at depths of 150 m and even deeper. With progress in updating the Hydroscope equipment, mathematical programs were developed to calculate the received NMR signals (giving the fluid distribution in depth) as a function of the deflecting radio pulse. The model implies the fluid distribution in horizontal layers at different depths, with different horizontal dimensions much exceeding the antenna sizes. In addition, by measuring the relaxation times, the size distribution of pores can also be estimated. The method and its implications are described in detail elsewhere (Fomenko and Shushakov, 1999; Kuskovskii et al., 2004, 2006; Shushakov et al., 2002). As the operation of the NMR geotomograph is based on the record of signals of free induction of hydrogen protons in the Earth’s magnetic field, theoretically we can record hydrogen present not only in water but also in other compounds with longer relaxation times. Brown (1956) was the first to note this opportunity. Moreover, physical and chemical properties of a substance can be inferred from the relaxation duration. This is true, in particular, for liquid hydrocarbons, e.g., gasoline and kerosene. It is known (Davies et al., 1994; Fordham et al., 1993; Hall et al., 1994) that in the same pores the relaxation times of hydrogen protons were longer for gasoline than for water. The difference is due to different wettability of pore walls with gasoline and water.
Methods and results To confirm in practice that an NMR geotomograph is capable to record the pollution of aquifers by liquid hydrocarbons, we took preliminary measures. First, we updated the instrument, thus allowing it to record NMR signals not only from water but also from liquid hydrocarbons with longer relaxation times. The updated instrument was able to change the duration of exciting pulse and the time of record of nuclear relaxation signals. In the former version the duration of exciting pulse was strictly constant, 40 ms; now we can preset it from few to hundreds of milliseconds. As the time of spin relaxation of hydrogen protons in gasoline is longer than in water; the former time of pulse record, 200 ms, appeared insufficient for recording the signals received from hydrogen protons of gasoline. Therefore, the time of free-induction record was lengthened so that it can be given in the range from 200 to 2000 ms. Second, the study area was chosen near the town of Abakan (Khakasia), and three expeditions were organized to work there. One of the expeditions was international, with participation of the New Mexico Resonance Laboratory (New Mexico, USA). Preliminary results were reported at a symposium (Shushakov et al., 2004). This choice was dictated by the properties of aquifers, which occur in washed pebblestones in the Abakan and Yenisei valleys. The roof of aquifers occurs there at shallow depths of about
5–10 m. Because of leakage of gasoline and other hydrocarbons, local spots of pollution form on the surface of an aquifer. This, in turn, leads to serious problems in water supply. For this reason, the Minusinsk Hydrogeological Party performs monitoring of groundwater pollution with liquid hydrocarbons in and near Abakan. To solve these problems, more than 130 observation boreholes 8–12 m deep were drilled. The layer of gasoline (on the water surface) in these boreholes is often 0.3–0.5 m thick and even layers more than 1 m thick were recorded. The gasoline layer was determined by means of a glass tube with a bottom gate: The tube was plunged into the borehole and then lifted together with a sample to be measured. Water and gasoline occurring in pores of the aquifer wet the pore surface quite differently because of different physical properties. The spin relaxation on the pore surface is more intensive; therefore, the relaxation time of hydrogen protons in water is much shorter than in gasoline, for water wets the pore surface much stronger (Fig. 2). Owing to this difference in properties of water and gasoline, as soon as tens of milliseconds after the beginning of NMR signal record, the level of gasoline signal exceeds the level of water signal, though the initial amplitude of the signal from hydrogen protons of water many times exceeds that of gasoline. Thus, if we expand the signal in a power series of different constants of time relaxation, we will be able to discriminate between water and gasoline signals. Remarkable results were obtained from BH-52 drilled at a gas station near Kalinino Village (Abakan’s suburb). Several days before the measurements, a considerable leakage of A-76 gasoline occurred at this station. Figures 3 and 4 exemplify results of analysis of the gasoline linkage. At the time of
Fig. 2. Relaxation time of hydrogen protons of water is significantly shorter than relaxation time of hydrogen protons of gasoline. 1 — water, 2 — gasoline, 3 — water + gasoline.
V.M. Fomenko et al. / Russian Geology and Geophysics 49 (2008) 183–186
185
Fig. 3. Characteristic curve of the NMR signal amplitude and the time with different pulse magnitude. Abakan, BH-52. Exciting pulse magnitude ranging from 3273 to 5577 A⋅ms, defines the depth of sounding.
Fig. 4. Characteristic curve of the NMR signal amplitude and the time with different pulse magnitude. Abakan, 120 m apart from BH-52.
sampling, the layer of hydrocarbons in BH-52 was 1.15 m, with a depth of drilling of 11 m and a level of hydrocarbon surface in the borehole of 7.8 m. The content of petroleum in the water sample from the borehole was 7.15 mg/dm3, as determined by standard fluorometry. The geological section of the borehole is represented by Quaternary alluvium deposits: 1–4 m — sandy loam, 4–5 m — medium-grained sands, 5–9 m — clay with rubble, 9–11 m — gravel-pebblestone deposits (aquifer). The gasoline and water signals were experimentally identified from measurements at two sites: in the immediate vicinity of the borehole near the source of pollution and far apart (120 m). In the first case, NMR signals with essentially different T∗2 times are highlighted (see Fig. 3). T∗2 is the time of heterogeneous transverse (spin-spin) nuclear relaxation. The plot contains a group of curves with short times of relaxation from hydrogen protons of water and a curve with a much longer time of relaxation from hydrogen protons of gasoline. In the second case, there is only one T∗2 component from hydrogen protons of water (see Fig. 4).
deposits. There, the filtration properties of water-bearing soils are characterized by relatively high parameters (Kf is 50 to 100 m/day). To reveal the potential of this method, the study should be continued in different hydrogeological environments. We believe that this approach is quite promising for without drilling expensive hydrogeological boreholes it allows us not only to locate the groundwater pollution but also to outline haloes of this pollution and keep routine monitoring. We thank V.M. Gruznov and S.V. Morozov for valuable comments on the manuscript.
Conclusions For the first time, a signal from hydrogen protons of pollutant hydrocarbons occurring on the groundwater surface was received in the measurements we made near Abakan by means of NMR geotomography, without drilling boreholes. The experiments were carried out on the terrace of the Yenisei River (the shore of the Krasnoyarsk Water Reservoir) made up of clays, sandy loams, sands, and gravel-pebblestone
References Brown, R.J.S., Fatt, I., 1956. Measurements of fractional wettability of oilfield rocks by the nuclear magnetic resonance method. Trans. Amer. Inst. Miner. Petrol. Eng. 220, 262–264. Davies, S., Hardwick, A., Roberts, D., Spowage, K., Packer, K.J., 1994. Quantification of Oil and Water in Preserved Reservoir Rock by NMR Spectroscopy and Imaging. Mag. Res. Imag. 2 (12), 349–353. Fomenko, V.M., Shushakov, O.A., 1999. Some recent developments in Hydroscope hardware, in: Proceedings of the 1st International Workshop ,,Surface Nuclear Magnetic Resonance (SNMR) —What is possible?", Technical University Berlin, Berlin, pp. 36–41. Fordham, E.J., Hall, L.D., Ramakrishnan, T.S, Sarpe, M.R., Hall, C., 1993. Saturation Gradients in Drainage of Porous Media: NMR Imaging Measurements. AIChE J. 37 (9), 1431–1443. Hall, L.D., Rajanajagam, V., 1987. Thin-Slice, Chemical-Shift Imaging of Oil and Water in Sandstone Rock at 80 MHz. J. Mag. Res. 74, 139–146. Kuskovsky, V.S, Shushakov, O.A., Fomenko, V.M., 2004. The study of groundwater by means of the NMR tomography, in: Proceedings of 6th International Congress “Water: Ecology and Technology of AQUATECH2004”, 1, pp. 184–185. Kuskovsky, V.S, Shushakov, O.A., Fomenko, V.M., 2006. NMR sounding is the new method of hydrogeological exploration, in: Proceedingss of
186
V.M. Fomenko et al. / Russian Geology and Geophysics 49 (2008) 183–186
Annual Session of Research Council of the RAS concerning the problems of geoecology, engineering geology and hydrogeology. GEOS, Moscow, pp. 315–319. Shushakov, O.A., Fomenko, V.M., Kuskovsky, V.S., 2002. Usage of the geophysical NMR tomography for hydrogeological and engineering geological investigations. ENVIROMIS 2002, 1, 15–19.
Shushakov, O.A., Fomenko, V.M., Yashchuk, V.I., Krivosheev, A.S., Fukushima, E., Altobelli, S.A., Kuskovsky, V.S., 2004. Hydrocarbon contamination of aquifers by SNMR detection, in: Benda, G. (Ed.) Proceedings of Waste Management (WM’04) Symposium, Arizona, Tucson. WM4566, pp. 46–49.
Editorial responsibility: G.N. Anoshin 18 July 2007