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Interpretation of coal and surrounding strata based on geophysical borehole measurements (In German)
67A
Geophysical techniques
ss224!
852237 Geophysical methods as mapping tools in a strata-bound gold deposit: Huile Mine, South Carolina Slate Belt Wynn, J C; Luce, R W
Geophysics V49, NI, Jan 1984, P37-45
Eeon Geol V79, N2, March-April 1984, P382-388 Very low frequency electromagnetic, magnetic and induced polarisation methods have been used to map gold-bearing metasediments at the Halle gold mine. The very low frequency electromagnetic resistivity data show high resistivity zones that correlate with siliceous units known to host the gold. The magnetic data clearly identify the marie and ultramafic dykes which cut these metasediments and also fill faults that offset them. The induced polarization method allows examination of the mineralized metasediments in two dimensions by giving vertical sections of resistivity and percent frequency effect, parameters which correlate with silica and pyrite content respectively.
852238 Shallow seismic reflections with a propane-oxygen detonator
Singh, S Geoexplora6on V22, N2, April 1984, P89-105 Experimental tests with a propane-oxygen detonator as the seismic source demonstrate the capability of the source to delineate shallow and irregular bedrock between 30-50m. Analysis of initial data indicates that very shallow reflections from reflective interfaces in the antra-alluvial stratigraphy from as shallow a reflector as 5m may also be detected under favourable conditions. It is demonstrated that application of accurate static correlations is critical for shallow and very shallow reflection work. A convenient and accurate method, called the ABO method, for determining thicknesses of the low velocity layer under shotpoint locations is presented.
Cross-hole seismic surveys: applications for studying subsurface fracture systems at a hot dry rock geothermal site Fehler, M; Pearson, C The use ofcrosshole seismic surveys is presented for delineating the location and size of subsurface fracture systems. The radiation pattern for P and S waves emitted by a seismic source in a borehole is derived. An experiment was performed in the crystalline rock of the Hot Dry Rock Geothermal Reservoir, New Mexico, USA. Discrete large-scale fractures were located in the reservoir by sudden change in signal amplitude, wave form or frequency content. A decrease in the average Q due to extensive fracturing was also detected.
852242 Rise times of attenuated seismic pulses detected in both empty and fluid-filled cylindrical boreholes Blair, D P
Geophysics V49, N4, April 1984, P398-410 The Fourier-Bessel theory is used to derive filters representing the influence of both empty and fluid-filled cylindrical boreholes on particle motion induced in rock by a plane P wave incident perpendicular to the borehole axis. Results show that for large wavelengths the effect of the borehole is negligible, though not for small wavelengths, ie ultrasonic frequencies. Both theory and experiment show a similar distortion in the rise time of the pulse travelling past the borehole. The results are relevant to the study of stress wave propagation at ultrasonic frequencies in rock masses to determine rock mass condition.
852243 Case study of stratigraphic interpretation using shear and compressional seismic data McCormack, M D; Dunbar, J A; Sharp, W W
Geophysics V49, NS, May 1984, P509-520 852239 Use of seismic shear waves and compressional waves for lithological problems of shallow sediments Stumpel, H; Kahler, S; Meissner, R; Miikereit, B
Geophys Prospect 1/32, N4, Aug 1984, P662-675 Several specific properties have been derived from in situ shear wave experiments in the shallow sediments of the north German plains. Shear waves differ from compressional waves in that: (1) they are not affected by the degree of water saturation, therefore provide better correlation between velocity and lithology, (2) they generally have lower frequencies, but shorter wavelengths and hence a better resolution of thin layers, and (3) they have lower absorption and hence a better penetration in partially saturated and gas-containing sediments than compressional waves.
852240 Field example of the use of auisotropy parameters derived from resistivity soundings Matias, M J S; Habberjam, G M
Geophys Prospect V32, N4, Aug 1984, P725-739 The use of resistivity methods in situations where the concealed basement rocks are steeply dipping is described. By the example given, it is demonstrated that, over regions of shallow drift, crossed square arrays can provide valuable information in the form of anisotropy parameters. Besides providing orientationally stable resistivity values, estimates can be made of the strike of the basement rocks and a component of their anisotropy.
Surface recorded compressional and horizontal shear wave seismic data were used to detect lateral changes in the physical properties of a elastic unit in the lower Pennsylvanian Morrow formation at the Empire Abu Field, New Mexico, USA. After processing, the shear and compressional interval transit times through this horizon decreased in going from nonproductive to productive thicknesses of sand, resulting in an overall decrease in the ratio of shear to compressionai transit times. The primary mechanism causing change was concluded to be variation in the sand-shale ratio within the Morrow formation
852244 Advances in underground borehole geophysics (In German and English) Dickel, U; Rubel, H J
Giuckauf V119, N22, 24 Nov 1983, P1074-1077 (german). P429-430 (english) Test measurements performed in recent years with British hired equipment proved the potential of underground borehole logging. Borehole measurement made in this way can be reproduced with the aid of a computer in a form to suit any application. Where no core has been recovered in underground boreholes, and for chisel-drilled holes, depth and geological interpretation are now possible.
852245 Interpretation of coal and surrounding strata based on geophysical borehole measurements (In German) Schmitz, D
Gluekauf-forsclumgsh V45, N4, Aug 1984, P181-188 Coal reserves are best proven by boreholes, in addition to core examination, routine measurement of density, sound velocity, resistance and dipmeters, which provide information on the
68A surrounding strata. Determination of coal/rock interfaces on geophysical graphs is possible by an empirical-statistical treatment of logged data. This new method is easily applicable and suitable for computer evaluation. 852246 Suggested methods for surface monitoring of movements across discontinuities Dunnicliff, J (co-ordinator) lnt J Rock Mech Min Sci V21, NS, Oct 1984, P265-276 Four methods are considered as means of monitoring rock movements, to provide an understanding of the behaviour of a rock mass and to assess its stability: Methods are monitoring movement across discontinuities using glass plates; using pins and a tape; using a portable mechanical gauge; and using a remote reading electrical jointmeter. 852247 Location of the Stour buried tunnel-valley using geophysical techniques Barker, R D; Harker, D Q J Engng Geol V17, N2, 1984, P103-115 The Stour Valley between Sturmer and Sudbury is a striking drift-filled channel, termed a 'buried tunnel-valley' after the subglacial mode of its formation. The geophysical surveys conducted in this region have proved to be extremely useful in siting costly abstraction boreholes. A gravity survey proved a fast technique for locating the buried-valley. The resulting Bouguer anomaly map indicates that the density of the boulder clay filling the valley is higher than the underlying chalk. Interpretation of the Bouguer anomaly clearly indicates the subsurface position and calculations of the depth to the base of the valley fill have been attempted. Resistivity sounding surveys confirmed the gravity interpretation and provided more detailed and reliable information on drift lithology and thickness at sites of specific interest for potential abstraction boreholes. 852248 Subsurface geophysical methods used to define geometrical or structural characteristics On French) Price, D G Rev Fr Geotech N23, 1983, P25-29 A general summary of the thirty-four papers presented in session 2 which consider progress in the techniques of using geophysical methods in the assessment of material and mass quality and properties. 852249 Geo-acoustic surveillance of strata conditions and preventive plugging of strata during shaft sinking (In Russian) Tyutyunnik, P M Shakktnoe Stroit N2, Feb 1984, P20-24 Grout curtains were used during the sinking of shafts in complex, fissured, water-hearing ground. A method using low frequency acoustic waves was developed to survey the strata through the grout and to check the plugging of the grouting holes. The method provided a high level of online information on the fissuring present in the strata and on the quality of the grouting.
Presentation and interpretation of data See also: 852082
852250 Computer aided data aquisition and analysis for the consolidation test Cousins, B F Aust Geomech News N7, June 1984, P19-23 852251 In-seam seismic Love wave scattering modeled by the finite element method Asten, M W; Drake, L A; Edwards, S Geophys Prospect V32, N4, Aug 1984, P649-661 The dynamic two-dimensional finite element method allows the computation of reflection, transmission and mode-conversion coefficients of Love-type waves in coal seams. Published field data from two known faults and a dyke are compared with the modelling results, and support the belief that broad-band seam wave data are capable of characterising a seam discontinuity (throw, hade angle, dyke thickness) as well as locating it.
Geophysical techniques
ss224!
852237 Geophysical methods as mapping tools in a strata-bound gold deposit: Huile Mine, South Carolina Slate Belt Wynn, J C; Luce, R W
Geophysics V49, NI, Jan 1984, P37-45
Eeon Geol V79, N2, March-April 1984, P382-388 Very low frequency electromagnetic, magnetic and induced polarisation methods have been used to map gold-bearing metasediments at the Halle gold mine. The very low frequency electromagnetic resistivity data show high resistivity zones that correlate with siliceous units known to host the gold. The magnetic data clearly identify the marie and ultramafic dykes which cut these metasediments and also fill faults that offset them. The induced polarization method allows examination of the mineralized metasediments in two dimensions by giving vertical sections of resistivity and percent frequency effect, parameters which correlate with silica and pyrite content respectively.
852238 Shallow seismic reflections with a propane-oxygen detonator
Singh, S Geoexplora6on V22, N2, April 1984, P89-105 Experimental tests with a propane-oxygen detonator as the seismic source demonstrate the capability of the source to delineate shallow and irregular bedrock between 30-50m. Analysis of initial data indicates that very shallow reflections from reflective interfaces in the antra-alluvial stratigraphy from as shallow a reflector as 5m may also be detected under favourable conditions. It is demonstrated that application of accurate static correlations is critical for shallow and very shallow reflection work. A convenient and accurate method, called the ABO method, for determining thicknesses of the low velocity layer under shotpoint locations is presented.
Cross-hole seismic surveys: applications for studying subsurface fracture systems at a hot dry rock geothermal site Fehler, M; Pearson, C The use ofcrosshole seismic surveys is presented for delineating the location and size of subsurface fracture systems. The radiation pattern for P and S waves emitted by a seismic source in a borehole is derived. An experiment was performed in the crystalline rock of the Hot Dry Rock Geothermal Reservoir, New Mexico, USA. Discrete large-scale fractures were located in the reservoir by sudden change in signal amplitude, wave form or frequency content. A decrease in the average Q due to extensive fracturing was also detected.
852242 Rise times of attenuated seismic pulses detected in both empty and fluid-filled cylindrical boreholes Blair, D P
Geophysics V49, N4, April 1984, P398-410 The Fourier-Bessel theory is used to derive filters representing the influence of both empty and fluid-filled cylindrical boreholes on particle motion induced in rock by a plane P wave incident perpendicular to the borehole axis. Results show that for large wavelengths the effect of the borehole is negligible, though not for small wavelengths, ie ultrasonic frequencies. Both theory and experiment show a similar distortion in the rise time of the pulse travelling past the borehole. The results are relevant to the study of stress wave propagation at ultrasonic frequencies in rock masses to determine rock mass condition.
852243 Case study of stratigraphic interpretation using shear and compressional seismic data McCormack, M D; Dunbar, J A; Sharp, W W
Geophysics V49, NS, May 1984, P509-520 852239 Use of seismic shear waves and compressional waves for lithological problems of shallow sediments Stumpel, H; Kahler, S; Meissner, R; Miikereit, B
Geophys Prospect 1/32, N4, Aug 1984, P662-675 Several specific properties have been derived from in situ shear wave experiments in the shallow sediments of the north German plains. Shear waves differ from compressional waves in that: (1) they are not affected by the degree of water saturation, therefore provide better correlation between velocity and lithology, (2) they generally have lower frequencies, but shorter wavelengths and hence a better resolution of thin layers, and (3) they have lower absorption and hence a better penetration in partially saturated and gas-containing sediments than compressional waves.
852240 Field example of the use of auisotropy parameters derived from resistivity soundings Matias, M J S; Habberjam, G M
Geophys Prospect V32, N4, Aug 1984, P725-739 The use of resistivity methods in situations where the concealed basement rocks are steeply dipping is described. By the example given, it is demonstrated that, over regions of shallow drift, crossed square arrays can provide valuable information in the form of anisotropy parameters. Besides providing orientationally stable resistivity values, estimates can be made of the strike of the basement rocks and a component of their anisotropy.
Surface recorded compressional and horizontal shear wave seismic data were used to detect lateral changes in the physical properties of a elastic unit in the lower Pennsylvanian Morrow formation at the Empire Abu Field, New Mexico, USA. After processing, the shear and compressional interval transit times through this horizon decreased in going from nonproductive to productive thicknesses of sand, resulting in an overall decrease in the ratio of shear to compressionai transit times. The primary mechanism causing change was concluded to be variation in the sand-shale ratio within the Morrow formation
852244 Advances in underground borehole geophysics (In German and English) Dickel, U; Rubel, H J
Giuckauf V119, N22, 24 Nov 1983, P1074-1077 (german). P429-430 (english) Test measurements performed in recent years with British hired equipment proved the potential of underground borehole logging. Borehole measurement made in this way can be reproduced with the aid of a computer in a form to suit any application. Where no core has been recovered in underground boreholes, and for chisel-drilled holes, depth and geological interpretation are now possible.
852245 Interpretation of coal and surrounding strata based on geophysical borehole measurements (In German) Schmitz, D
Gluekauf-forsclumgsh V45, N4, Aug 1984, P181-188 Coal reserves are best proven by boreholes, in addition to core examination, routine measurement of density, sound velocity, resistance and dipmeters, which provide information on the
68A surrounding strata. Determination of coal/rock interfaces on geophysical graphs is possible by an empirical-statistical treatment of logged data. This new method is easily applicable and suitable for computer evaluation. 852246 Suggested methods for surface monitoring of movements across discontinuities Dunnicliff, J (co-ordinator) lnt J Rock Mech Min Sci V21, NS, Oct 1984, P265-276 Four methods are considered as means of monitoring rock movements, to provide an understanding of the behaviour of a rock mass and to assess its stability: Methods are monitoring movement across discontinuities using glass plates; using pins and a tape; using a portable mechanical gauge; and using a remote reading electrical jointmeter. 852247 Location of the Stour buried tunnel-valley using geophysical techniques Barker, R D; Harker, D Q J Engng Geol V17, N2, 1984, P103-115 The Stour Valley between Sturmer and Sudbury is a striking drift-filled channel, termed a 'buried tunnel-valley' after the subglacial mode of its formation. The geophysical surveys conducted in this region have proved to be extremely useful in siting costly abstraction boreholes. A gravity survey proved a fast technique for locating the buried-valley. The resulting Bouguer anomaly map indicates that the density of the boulder clay filling the valley is higher than the underlying chalk. Interpretation of the Bouguer anomaly clearly indicates the subsurface position and calculations of the depth to the base of the valley fill have been attempted. Resistivity sounding surveys confirmed the gravity interpretation and provided more detailed and reliable information on drift lithology and thickness at sites of specific interest for potential abstraction boreholes. 852248 Subsurface geophysical methods used to define geometrical or structural characteristics On French) Price, D G Rev Fr Geotech N23, 1983, P25-29 A general summary of the thirty-four papers presented in session 2 which consider progress in the techniques of using geophysical methods in the assessment of material and mass quality and properties. 852249 Geo-acoustic surveillance of strata conditions and preventive plugging of strata during shaft sinking (In Russian) Tyutyunnik, P M Shakktnoe Stroit N2, Feb 1984, P20-24 Grout curtains were used during the sinking of shafts in complex, fissured, water-hearing ground. A method using low frequency acoustic waves was developed to survey the strata through the grout and to check the plugging of the grouting holes. The method provided a high level of online information on the fissuring present in the strata and on the quality of the grouting.
Presentation and interpretation of data See also: 852082
852250 Computer aided data aquisition and analysis for the consolidation test Cousins, B F Aust Geomech News N7, June 1984, P19-23 852251 In-seam seismic Love wave scattering modeled by the finite element method Asten, M W; Drake, L A; Edwards, S Geophys Prospect V32, N4, Aug 1984, P649-661 The dynamic two-dimensional finite element method allows the computation of reflection, transmission and mode-conversion coefficients of Love-type waves in coal seams. Published field data from two known faults and a dyke are compared with the modelling results, and support the belief that broad-band seam wave data are capable of characterising a seam discontinuity (throw, hade angle, dyke thickness) as well as locating it.