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Application of multioffset vertical seismic profiling in fracture mapping
155A
Geophysical techniques
and optimum density of measuring network are considered. In addition, problems encountered when applying electrical methods to groundwater pollution caused by immiscible (petroleum) and miscible pollutants are discussed.
See also: 903509 903192 Influence of induced polarization in inductive methods Kaufman, A A, Geoltrain, S; Knoshaug, R N Geoexploration V26, N2. Not" 1989. P75.93
The influence of induced polarisation on frequency and transient responses is examined for three configurations commonly used in electroprospeeting: magnetic field at loop centre, combined loop, and transmitter and receiver as vertical magnetic dipoles. The effects of relatively conductive inhomogeneities, and various methods of separating the inductive effect and induced polarisation are studied. The dipole-dipole array is least sensitive to IP influences. 903193 Application of multioffset vertical seismic profiling in fracture mapping Carswell, A; Moon. W M Geophysics I1"54, N6, June 1989, P737-746
The multioffset VSP method was used to examine fracture zones in a granite batholith in which Atomic Energy of Canada's underground laboratory is sited. Six 2D seismic sections were obtained with shotpoints in a vertical shaft and receivers at the surface. The VSP-CDP transformation which was used to convert the VSP section into conventional type seismic sections tended to stretch shallow reflection events, resulting in reduced resolution. The multioffset VSP configuration was seen to be effective in mapping deep fracture zones. 903194 Porosity identification using amplitude variations with offset: examples from South Sumatra Chacko, S Geophysics 1/54, N8, Aug 1989, P942-951
Batajura formation limestones vary widely from tight platform facies to highly porous reefal facies, making predrill prediction of porosity an important exploration objective. Amplitude-versus-offset seismic modelling was used to distinguish porosities for a proven gas reservoir and a then undrilled reef. Modelling shows porous and tight facies have different reflection coefficient variation patterns with angle of incidence. Modelling predictions and observed data are consistent.
903197 Development of a seafioor geophysical sledge Davis, A M: Bennell, J D; Huws, D G; Thomas, D Marine Geotechnol II8, N2, 1989, P99-109
New techniques for evaluating the sea bed are continually under development. To assist in rapid, inexpensive, and efficient data collection, a seafloor geophysical sledge, which is towed behind a support ship, has been designed. Its instrumentation allows measurement of seismic P and S wave velocity and formation factor. The instrumental layout and sledge design are illustrated, results presented and applications discussed. 903198 Seismic delineation of fissures associated with mining subsidence at Houghton-le-Spring, Co. Durham Goulty, N R; Kragh. J E Q J Engng Geol V22, N3, 1989, P!85-193
Fissures in the Permian Magnesian Limestone overlying the coal measures are of recent origin and clearly associated with mining subsidence. P and S wave seismic refraction profiles have been run across the fissured zone,which is identified by low S wave velocity. The boundary of the zone can be delineated from P wave amplitudes measured at points spanning the zone,using a shot fired in solid ground. The method is suggested for detecting fissures in brittle sedimentary rock over mineworkings. 903199 Discontinuities in a granitic rock mass detected by means of Stoneley waves (In French) Denis, A; Morlier, P; Mctivier, J M Proc International Symposium on Rock at Great Depth, Pau, 28-31 August 1989 VI, P273-281. Publ Rotterdam: A A Balkema, 1989
903195 Pulse shapes from ground penetrating radar. Technical note Reames, F M Geotech Test J VI2, N3, Sept 1989, P244-247
Criteria likely to provide quantitative information on the fracturation of a rock mass through acoustic logging and Stoneley wave examination have been investigated. The granite rock mass for which the data are presented is homogeneous to a depth of 1000m. Fracturation is well known from previous borehole logging. The possibility of using Stoneley wave attenuation to detect and characterise the hydraulic transmissivity of fractures is demonstrated. Further information may be obtained from time and frequency domain analysis of waveforms.
Ground penetrating radar (GPR) techniques have been used to detect delamination or voids between slab and subgrade of highway structures. It is suggested that previous pulse shape computations have not been based on the correct electromagnetic theory, and differences between recorded and predicted pulses are unavoidable. An improved procedure to predict the shape of pulses returning from voids is presented, and new approaches for detection of defects discussed.
903200 Rock mechanical behavior modeling using various downhole measurements Ahmed, U; Crary, S, Markeley, M; Liu, O Proc International Symposium on Rock at Great Depth, Pau, 28-31 August 1989 VI, P329-337. Publ Rotterdam: A A Balkema, 1989
903196 Surface geoelectrics for the study of groundwater pollution survey design Mazac. O: Landa. I: Kelly, W E J Hydrol VIII, NI-4, Not" 1989, PI63-176
Case histories are presented applying the principles set out in earlier work (Mazac et al, 1987). Choice of primary and secondary methods, minimum number of parametric measurements.
Downhole frac tests and tests on cores provide useful information, but not continuous data. Geophysical logging can give continuous readout. Comparisons between log derived properties and results of microfrac and laboratory tests indicate their shortcomings for rocks of certain types and depositional history. An improved method using geophysical log, core and microfrac data to model rock mechanical data is presented. A new multipole acoustic tool for sonic logging in slow rocks is also described.
1990 Pergamon Press plc. Reproduction not permitted
Geophysical techniques
and optimum density of measuring network are considered. In addition, problems encountered when applying electrical methods to groundwater pollution caused by immiscible (petroleum) and miscible pollutants are discussed.
See also: 903509 903192 Influence of induced polarization in inductive methods Kaufman, A A, Geoltrain, S; Knoshaug, R N Geoexploration V26, N2. Not" 1989. P75.93
The influence of induced polarisation on frequency and transient responses is examined for three configurations commonly used in electroprospeeting: magnetic field at loop centre, combined loop, and transmitter and receiver as vertical magnetic dipoles. The effects of relatively conductive inhomogeneities, and various methods of separating the inductive effect and induced polarisation are studied. The dipole-dipole array is least sensitive to IP influences. 903193 Application of multioffset vertical seismic profiling in fracture mapping Carswell, A; Moon. W M Geophysics I1"54, N6, June 1989, P737-746
The multioffset VSP method was used to examine fracture zones in a granite batholith in which Atomic Energy of Canada's underground laboratory is sited. Six 2D seismic sections were obtained with shotpoints in a vertical shaft and receivers at the surface. The VSP-CDP transformation which was used to convert the VSP section into conventional type seismic sections tended to stretch shallow reflection events, resulting in reduced resolution. The multioffset VSP configuration was seen to be effective in mapping deep fracture zones. 903194 Porosity identification using amplitude variations with offset: examples from South Sumatra Chacko, S Geophysics 1/54, N8, Aug 1989, P942-951
Batajura formation limestones vary widely from tight platform facies to highly porous reefal facies, making predrill prediction of porosity an important exploration objective. Amplitude-versus-offset seismic modelling was used to distinguish porosities for a proven gas reservoir and a then undrilled reef. Modelling shows porous and tight facies have different reflection coefficient variation patterns with angle of incidence. Modelling predictions and observed data are consistent.
903197 Development of a seafioor geophysical sledge Davis, A M: Bennell, J D; Huws, D G; Thomas, D Marine Geotechnol II8, N2, 1989, P99-109
New techniques for evaluating the sea bed are continually under development. To assist in rapid, inexpensive, and efficient data collection, a seafloor geophysical sledge, which is towed behind a support ship, has been designed. Its instrumentation allows measurement of seismic P and S wave velocity and formation factor. The instrumental layout and sledge design are illustrated, results presented and applications discussed. 903198 Seismic delineation of fissures associated with mining subsidence at Houghton-le-Spring, Co. Durham Goulty, N R; Kragh. J E Q J Engng Geol V22, N3, 1989, P!85-193
Fissures in the Permian Magnesian Limestone overlying the coal measures are of recent origin and clearly associated with mining subsidence. P and S wave seismic refraction profiles have been run across the fissured zone,which is identified by low S wave velocity. The boundary of the zone can be delineated from P wave amplitudes measured at points spanning the zone,using a shot fired in solid ground. The method is suggested for detecting fissures in brittle sedimentary rock over mineworkings. 903199 Discontinuities in a granitic rock mass detected by means of Stoneley waves (In French) Denis, A; Morlier, P; Mctivier, J M Proc International Symposium on Rock at Great Depth, Pau, 28-31 August 1989 VI, P273-281. Publ Rotterdam: A A Balkema, 1989
903195 Pulse shapes from ground penetrating radar. Technical note Reames, F M Geotech Test J VI2, N3, Sept 1989, P244-247
Criteria likely to provide quantitative information on the fracturation of a rock mass through acoustic logging and Stoneley wave examination have been investigated. The granite rock mass for which the data are presented is homogeneous to a depth of 1000m. Fracturation is well known from previous borehole logging. The possibility of using Stoneley wave attenuation to detect and characterise the hydraulic transmissivity of fractures is demonstrated. Further information may be obtained from time and frequency domain analysis of waveforms.
Ground penetrating radar (GPR) techniques have been used to detect delamination or voids between slab and subgrade of highway structures. It is suggested that previous pulse shape computations have not been based on the correct electromagnetic theory, and differences between recorded and predicted pulses are unavoidable. An improved procedure to predict the shape of pulses returning from voids is presented, and new approaches for detection of defects discussed.
903200 Rock mechanical behavior modeling using various downhole measurements Ahmed, U; Crary, S, Markeley, M; Liu, O Proc International Symposium on Rock at Great Depth, Pau, 28-31 August 1989 VI, P329-337. Publ Rotterdam: A A Balkema, 1989
903196 Surface geoelectrics for the study of groundwater pollution survey design Mazac. O: Landa. I: Kelly, W E J Hydrol VIII, NI-4, Not" 1989, PI63-176
Case histories are presented applying the principles set out in earlier work (Mazac et al, 1987). Choice of primary and secondary methods, minimum number of parametric measurements.
Downhole frac tests and tests on cores provide useful information, but not continuous data. Geophysical logging can give continuous readout. Comparisons between log derived properties and results of microfrac and laboratory tests indicate their shortcomings for rocks of certain types and depositional history. An improved method using geophysical log, core and microfrac data to model rock mechanical data is presented. A new multipole acoustic tool for sonic logging in slow rocks is also described.
1990 Pergamon Press plc. Reproduction not permitted