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Borehole transient electromagnetic response of a three-dimensional fracture zone in conductive half-space
189A 894158 Geological mapping and observations in the caverns of La Muela power plant during construction Navalon, N; Gaztanaga. J M; Lopez Marinas, J M Proc Symposium on Rock Mechanics and Power Plants, Madrid, 12-16 September 1988 V1, P217-225. Publ Rotterdam: A A Balkema, 1988
During excavation of the power cavern, detailed geological mapping of the rock mass was carried out. This supplemented information from prior geophysical examination using seismic refraction, microseismic transmission, and up hole tests, for determining rock properties. Underground explosions were used to estimate what effect extending the plant would have on existing structures. The large geotechnical database and results of monitoring wall displacements were used to help design excavation sequence and support.
Geophysical techniques 894159 Integrated seismic refraction surveys for engineering projects Peck, W Aust Geomech News NI6, Dec 1988, P22-24
Seismic refraction data may be misinterpreted if not adequately correlated against reliable subsurface data. The uphole seismic method using a refraction seismographic is described and applied to an open pit mine site investigation. Initial traverse missed the thickest layer of the overburden and the equipment was reset so it recorded second arrivals,detecting the hidden layer. 894160 Application of computer assisted tomography (CAT) to gamma attenuation measurement of soil water content Hainsworth, J M; Aylmore, L A G Aust J Soil Res V26, NI, 1988, PI05-110
The application of CAT to gamma-ray attenuation measurements and the modification of a conventional gamma scanning system to enable changes in the spatial distribution of soil water content to be accurately monitored in soil columns are described. The relatively inexpensive gamma system has similar resolution to X-ray CAT systems. A comparison of the efficiency of several source-detection combinations illustrates their relative advantages and disadvantages. 894161 Electrical response of a leak in a geomembrane liner Parra, J O Geophysics V53, NIl, Nor 1988, P1445-1452
A theoretical analysis of the electrical survey technique to detect a leak in a geomembrane isolating landfill materials is presented. It relies on the insulating properties of the membrane as compared to the fill and subsoil. Mapping of equipotential contours or potential gradients on the surface of the impoundment allows location of leaks. Surveys conducted at a test site show the ability of this technique to determine leakage points. The pole-dipole array is preferred to pole-pole. 894162 Model studies of electrical leak detection surveys in geomembrane-lined impoundments Parra, J O; Owen, T E Geophysics 1/53, Nil, Nor 1988, P1453-1458
Numerical results derived from the analysis of Parra (1988) to detect and locate leaks in geomembranes impounding waste materials are presented. Results are used to aid planning of
electrical surveys and evaluate and interpret measurements. Optimum electrode spacing for detecting single leaks, and techniques to identify a cluster of leaks are examined. Survey speed may be increased if portable leak detection equipment using a vertical dipole is used. 894163 Borehole transient electromagnetic response of a threedimensional fracture zone in conductive half-space West, R C: Ward, S H Geophysics V53, Nil, Not" 1988. P1469-1478
Borehole geophysical methods can be used to detect subsurface fracture zones or mineral deposits which are nearby, but not intersected by the borehole. The surface to borehole transient electromagnetic method (TEM) can be applied to this problem. The method is illustrated with a 3D fracture zone or mineral deposit simulated as a conductive tabular body in a homogeneous half space. The method is promising, but is at present limited by available hardware and modest modelling capabilities. 894164 Time domain electromagnetic soundings for mapping sea-water intrusion in Monterey County, California Mills, T; Hockstra, P; Blohm, M; Evans, L Ground Water V26, N6, Nov-Dec 1988, P711-782
Seawater intrusion into coastal aquifers in the Salinas valley has been recognised since the 1930s. Water quality samples from monitoring wells have been used to quantify intrusion of the "180ft' and '400ft" aquifers. Surface geophysics using TDEM sounding was used to monitor pollution of the surface and '900ft' aquifers. TDEM is well suited for this application as water conductivity increases with level of chloride contamination. 100 soundings were made. Positions of the 500 ppm isochlor from wells and TDEM are in good agreement, with the greater local detail available via the higher TDEM station density. 894165 Characterization of fractured hydrocarbon reservoirs using the EVA (R) acoustic logging tool (In French) Arditty, P C; Mathieu, F; Staron, P Rev Fr Geotech N45, Oct 1988, P21-35
A new method for fractured reservoir characterisation has been developed, based on shear and Stoneley wave attenuation, 2 parameters obtained from processing full waveform acoustic data. Combination of the parameters permits location of individual fractures and fractured zones. The method was successfully tested at an offshore gas field. Full waveform data acquisition and processing with the EVA tool for 3 wells helped to locate fractured zones which yielded satisfactory gas production. 894166 Permeability log with an acoustical method (In French) Morlier, P; Bounoua, N E; Lebreton, F Rev Fr Geotech N45, Oct 1988, P37-50
Wave attenuation and its physical mechanisms in geological media are examined. Attenuation of first arrival P waves as a function of a dimensionless parameter including frequency and permeability is illustrated. A new parameter, Ic, related to log permeability is introduced. Using this, permeability may be inferred from attenuation measurements. The applicability of this acoustic logging is demonstrated by comparing lc logs with flowmeter, resistivity, natural gamma, and SP logs.
C~ 1989 Pergamon Press plc. Reproduction not permitted
During excavation of the power cavern, detailed geological mapping of the rock mass was carried out. This supplemented information from prior geophysical examination using seismic refraction, microseismic transmission, and up hole tests, for determining rock properties. Underground explosions were used to estimate what effect extending the plant would have on existing structures. The large geotechnical database and results of monitoring wall displacements were used to help design excavation sequence and support.
Geophysical techniques 894159 Integrated seismic refraction surveys for engineering projects Peck, W Aust Geomech News NI6, Dec 1988, P22-24
Seismic refraction data may be misinterpreted if not adequately correlated against reliable subsurface data. The uphole seismic method using a refraction seismographic is described and applied to an open pit mine site investigation. Initial traverse missed the thickest layer of the overburden and the equipment was reset so it recorded second arrivals,detecting the hidden layer. 894160 Application of computer assisted tomography (CAT) to gamma attenuation measurement of soil water content Hainsworth, J M; Aylmore, L A G Aust J Soil Res V26, NI, 1988, PI05-110
The application of CAT to gamma-ray attenuation measurements and the modification of a conventional gamma scanning system to enable changes in the spatial distribution of soil water content to be accurately monitored in soil columns are described. The relatively inexpensive gamma system has similar resolution to X-ray CAT systems. A comparison of the efficiency of several source-detection combinations illustrates their relative advantages and disadvantages. 894161 Electrical response of a leak in a geomembrane liner Parra, J O Geophysics V53, NIl, Nor 1988, P1445-1452
A theoretical analysis of the electrical survey technique to detect a leak in a geomembrane isolating landfill materials is presented. It relies on the insulating properties of the membrane as compared to the fill and subsoil. Mapping of equipotential contours or potential gradients on the surface of the impoundment allows location of leaks. Surveys conducted at a test site show the ability of this technique to determine leakage points. The pole-dipole array is preferred to pole-pole. 894162 Model studies of electrical leak detection surveys in geomembrane-lined impoundments Parra, J O; Owen, T E Geophysics 1/53, Nil, Nor 1988, P1453-1458
Numerical results derived from the analysis of Parra (1988) to detect and locate leaks in geomembranes impounding waste materials are presented. Results are used to aid planning of
electrical surveys and evaluate and interpret measurements. Optimum electrode spacing for detecting single leaks, and techniques to identify a cluster of leaks are examined. Survey speed may be increased if portable leak detection equipment using a vertical dipole is used. 894163 Borehole transient electromagnetic response of a threedimensional fracture zone in conductive half-space West, R C: Ward, S H Geophysics V53, Nil, Not" 1988. P1469-1478
Borehole geophysical methods can be used to detect subsurface fracture zones or mineral deposits which are nearby, but not intersected by the borehole. The surface to borehole transient electromagnetic method (TEM) can be applied to this problem. The method is illustrated with a 3D fracture zone or mineral deposit simulated as a conductive tabular body in a homogeneous half space. The method is promising, but is at present limited by available hardware and modest modelling capabilities. 894164 Time domain electromagnetic soundings for mapping sea-water intrusion in Monterey County, California Mills, T; Hockstra, P; Blohm, M; Evans, L Ground Water V26, N6, Nov-Dec 1988, P711-782
Seawater intrusion into coastal aquifers in the Salinas valley has been recognised since the 1930s. Water quality samples from monitoring wells have been used to quantify intrusion of the "180ft' and '400ft" aquifers. Surface geophysics using TDEM sounding was used to monitor pollution of the surface and '900ft' aquifers. TDEM is well suited for this application as water conductivity increases with level of chloride contamination. 100 soundings were made. Positions of the 500 ppm isochlor from wells and TDEM are in good agreement, with the greater local detail available via the higher TDEM station density. 894165 Characterization of fractured hydrocarbon reservoirs using the EVA (R) acoustic logging tool (In French) Arditty, P C; Mathieu, F; Staron, P Rev Fr Geotech N45, Oct 1988, P21-35
A new method for fractured reservoir characterisation has been developed, based on shear and Stoneley wave attenuation, 2 parameters obtained from processing full waveform acoustic data. Combination of the parameters permits location of individual fractures and fractured zones. The method was successfully tested at an offshore gas field. Full waveform data acquisition and processing with the EVA tool for 3 wells helped to locate fractured zones which yielded satisfactory gas production. 894166 Permeability log with an acoustical method (In French) Morlier, P; Bounoua, N E; Lebreton, F Rev Fr Geotech N45, Oct 1988, P37-50
Wave attenuation and its physical mechanisms in geological media are examined. Attenuation of first arrival P waves as a function of a dimensionless parameter including frequency and permeability is illustrated. A new parameter, Ic, related to log permeability is introduced. Using this, permeability may be inferred from attenuation measurements. The applicability of this acoustic logging is demonstrated by comparing lc logs with flowmeter, resistivity, natural gamma, and SP logs.
C~ 1989 Pergamon Press plc. Reproduction not permitted