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Formation pressure prediction with seismic data from the Gulf of Mexico
103A 922238 2D resistivity modeling: an approach to arrays parallel to the strike direction Queralt, P: Pous. J: Mareuello, A
922242 Cress borehole seismic tomography applllcatiom to mineral development Davis, R W; Heinrichs. W E
Geophysics V56, N7, July 1991, P941-950
Min Engng 1/43, Ns, Aug 1991, P1051-1056
An algorithm to obtain the 3-dimensional distribution of potential due to a point source over a 2-dimensional structure is presented. Transformed potential is calculated by finite element analysis. A numerical singularity is found in the case of direction parallel to the strike of the structure, which is resolved by calculating the potential near the singularity and improving the interpolation of the potential. Examples of its use are presented to check the algorithm and to represent common field situations.
The borehole seismic tomography method is described and its theory outlined. Applications to leachate front monitoring during in situ mining and detection of fracture zones and degree of fracturing are briefly examined. Methods of data analysis and resolving power of crosshole seismic tomography are discussed. Expected future applications include foundation investigation, orebody delineation, and rock property mapping.
922239 Seismic sources in open and cased boreholes Winbow, G A
Geophysics 1/56, N7, July 1991, P1040-1050 Linear elastic theory is used to examine the efficiency of downhole seismic sources. Radial sources (airguns, waterguns, implosive sources), which exert a pressure on a section of the borehole wall, and vertically driven sources, clamped to the borehole wail, are examined. Radial sources convert almost all their energy to tube waves which travel along the borehole rather than into the formation. Used near the surface, with change of tube waves to P and S waves radiating into the formation by conversion at the hole bottom or a constriction, they are viable. Vertical sources radiate most of their energy into the formation as P and S waves, but lose efficiency if the case bond slips. 922240 Bedrock topography from magnetic anomalies - an aid to groundwater exploration in hard-rock terrains. Short note Babu, H V R; Rao, N K; Kumar, V V
Geophysics V56, N7, July 1991, P1051-1054 In hard rock terrain, the thickness of the weathered zone over bedrock is an important factor in determining the quantity of groundwater which may be accumulated in the unconfined aquifer over the basement. During weathering, the basement rock loses much of its magnetic properties, and response to magnetic survey is primarily due to the unweathered hard rock. The ground magnetic map can therefore be used to provide an assement of the thickness of the weathered zone, a first order indication of groundwater potential. Application of this method around Hyderabad City, India, is illustrated. 922241 Theoretical evaluation of Modified Wenner Array for shallow resistivity exploration Goyal, V C" Niwas, S; Gupta, P K
Ground Water 1/29, N4, July-Aug 1991, t'582-586 In the Modified Wenner Array the separation of the 2 potential electrodes is gradually varied while that of the 2 current electrodes is constant. The theoretical basis of MWA is critically examined. It is shown that Modified Wenner sounding encompasses Schlumberger, Wenner, and conventional TwoElectrode arrangements. MWA and TEA responses are identical for the range of spacings considered, and their viability as a tool for shallow sounding is identical. Vertical resolution of the MWA in these conditions is superior to that of Wenner or Schlumberger arrays.
922243 Formation pressure prediction with seismic data from the Gulf of Mexico Martinez, R D; King. G A
SPE Form Eval V6, NI, March 1991, P27-32 Formation-pressure logs are derived from seismic data from offshore Louisiana to delineate overpressured zones within a reservoir. Data processing yields seismic velocity and density logs at every seismic trace location. Formation-pressure logs are calculated on the assumption that P wave velocity, mean density, and depth are proportional to formation pressure. The logs are constrained at every depth by estimation of matrix and fluid P wave velocities, derived from porosity and sonic well log data. Results indicate a large region of overpressured shale in the subsurface.
Borehole and core logging See also: 922146, 922156, 922173, 922183, 922383 922244 Use of indicator geostatistics to estimate the probability of encountering abandoned mines in an urban area Ovanic, J; Cawlfield, J D
Bull Assoc Engng Geoi V28, N2, May 1991, P159-169 Areas around Pittsburg are heavily undermined by abandoned workings for which exist few historical data or maps to indicate location or extent. It is thus difficult to predict risk due to subsidence over abandoned workings. The indicator kriging approach is used to analyse the areal distribution of these abandoned coal mines. Borehole information is turned into binary indicator data as a function of borings which hit mine voids. A grid of values representing conditional probability of a location being undermined is developed. 922245 Litholngical interpretation based on monitored drilling performance parameters Pollitt, M D; Peck, J; Scoble, M J
CIM Bull V84, N951, July 1991, P25-29 Four drilling parameters, torque, pulidown pressure, rotary speed, and penetration rate, were measured from an instrumented rotary blasthole drill at Fording River Mine, British Columbia. Gamma, neutron, and core logs were taken from the same and adjacent boreholes. Classical statistical pattern recognition methods are used to attempt to discriminate between rock units. The ability of single or multiple drilling parameters to delineate ground variability in the coal, siltstone, and mudstone strata is examined,
© 1992 Pergamon Press Ltd. Reproduction not permitted
922242 Cress borehole seismic tomography applllcatiom to mineral development Davis, R W; Heinrichs. W E
Geophysics V56, N7, July 1991, P941-950
Min Engng 1/43, Ns, Aug 1991, P1051-1056
An algorithm to obtain the 3-dimensional distribution of potential due to a point source over a 2-dimensional structure is presented. Transformed potential is calculated by finite element analysis. A numerical singularity is found in the case of direction parallel to the strike of the structure, which is resolved by calculating the potential near the singularity and improving the interpolation of the potential. Examples of its use are presented to check the algorithm and to represent common field situations.
The borehole seismic tomography method is described and its theory outlined. Applications to leachate front monitoring during in situ mining and detection of fracture zones and degree of fracturing are briefly examined. Methods of data analysis and resolving power of crosshole seismic tomography are discussed. Expected future applications include foundation investigation, orebody delineation, and rock property mapping.
922239 Seismic sources in open and cased boreholes Winbow, G A
Geophysics 1/56, N7, July 1991, P1040-1050 Linear elastic theory is used to examine the efficiency of downhole seismic sources. Radial sources (airguns, waterguns, implosive sources), which exert a pressure on a section of the borehole wall, and vertically driven sources, clamped to the borehole wail, are examined. Radial sources convert almost all their energy to tube waves which travel along the borehole rather than into the formation. Used near the surface, with change of tube waves to P and S waves radiating into the formation by conversion at the hole bottom or a constriction, they are viable. Vertical sources radiate most of their energy into the formation as P and S waves, but lose efficiency if the case bond slips. 922240 Bedrock topography from magnetic anomalies - an aid to groundwater exploration in hard-rock terrains. Short note Babu, H V R; Rao, N K; Kumar, V V
Geophysics V56, N7, July 1991, P1051-1054 In hard rock terrain, the thickness of the weathered zone over bedrock is an important factor in determining the quantity of groundwater which may be accumulated in the unconfined aquifer over the basement. During weathering, the basement rock loses much of its magnetic properties, and response to magnetic survey is primarily due to the unweathered hard rock. The ground magnetic map can therefore be used to provide an assement of the thickness of the weathered zone, a first order indication of groundwater potential. Application of this method around Hyderabad City, India, is illustrated. 922241 Theoretical evaluation of Modified Wenner Array for shallow resistivity exploration Goyal, V C" Niwas, S; Gupta, P K
Ground Water 1/29, N4, July-Aug 1991, t'582-586 In the Modified Wenner Array the separation of the 2 potential electrodes is gradually varied while that of the 2 current electrodes is constant. The theoretical basis of MWA is critically examined. It is shown that Modified Wenner sounding encompasses Schlumberger, Wenner, and conventional TwoElectrode arrangements. MWA and TEA responses are identical for the range of spacings considered, and their viability as a tool for shallow sounding is identical. Vertical resolution of the MWA in these conditions is superior to that of Wenner or Schlumberger arrays.
922243 Formation pressure prediction with seismic data from the Gulf of Mexico Martinez, R D; King. G A
SPE Form Eval V6, NI, March 1991, P27-32 Formation-pressure logs are derived from seismic data from offshore Louisiana to delineate overpressured zones within a reservoir. Data processing yields seismic velocity and density logs at every seismic trace location. Formation-pressure logs are calculated on the assumption that P wave velocity, mean density, and depth are proportional to formation pressure. The logs are constrained at every depth by estimation of matrix and fluid P wave velocities, derived from porosity and sonic well log data. Results indicate a large region of overpressured shale in the subsurface.
Borehole and core logging See also: 922146, 922156, 922173, 922183, 922383 922244 Use of indicator geostatistics to estimate the probability of encountering abandoned mines in an urban area Ovanic, J; Cawlfield, J D
Bull Assoc Engng Geoi V28, N2, May 1991, P159-169 Areas around Pittsburg are heavily undermined by abandoned workings for which exist few historical data or maps to indicate location or extent. It is thus difficult to predict risk due to subsidence over abandoned workings. The indicator kriging approach is used to analyse the areal distribution of these abandoned coal mines. Borehole information is turned into binary indicator data as a function of borings which hit mine voids. A grid of values representing conditional probability of a location being undermined is developed. 922245 Litholngical interpretation based on monitored drilling performance parameters Pollitt, M D; Peck, J; Scoble, M J
CIM Bull V84, N951, July 1991, P25-29 Four drilling parameters, torque, pulidown pressure, rotary speed, and penetration rate, were measured from an instrumented rotary blasthole drill at Fording River Mine, British Columbia. Gamma, neutron, and core logs were taken from the same and adjacent boreholes. Classical statistical pattern recognition methods are used to attempt to discriminate between rock units. The ability of single or multiple drilling parameters to delineate ground variability in the coal, siltstone, and mudstone strata is examined,
© 1992 Pergamon Press Ltd. Reproduction not permitted