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Improved Fourier terrain correction, Part I
SITE INVESTIGATIONS:DATA
965209 Numerically simulated direct shear testing of in sit,. joint roughness profiles B. B. Thapa, T. C. Ke, R. E. Goodman, C. Tanimoto & K.
217A
processing systems. Systems also need to be customised to enable geologists, geophysicists, business analysts and surveyors to use the system effectively at their desktops. (Author)
Kishida, International Journal of Rock Mechanics & Mining Sciences, 33(1), 1996, pp 75-82.
965210 Estimates of formation sound speed from ultrasonic
965214 Theoretical and numerical issues in the determination of reflector depths in seismic reflection tomography K. P. Bube, R. T. Langan & J. R. Resnick, Journal of Geophysical Research, 100(B7), 1995, pp 12,449-12,458. Some theoretical results for the undiseretized problem regarding the possible ambiguity between slowness and depth are presented. These results indicate that the depths of the reflectors are determined in theory except for edge effects, but a sufficiently large aperture at the reflector is necessary to resolve this ambiguity in practice. The slowness field, however, does have some undetermined features. (from Authors)
reflections J. A. Davidson, S. L. Morriss & A. L. Podio, SPE Formation Evaluation, 10(2), 1995, pp 72-78. Presents preliminary results from experimental research concerning the ultrasonic refiectivity of rock samples. The goal is to determine whether meaningful petrophysical properties can be obtained through the analysis of reflected acoustic signals of the type produced with the new generation of ultrasonic borehole televiewers. Sound speed estimates in reasonable agreement with those determined by use of standard experimental techniques have been obtained for a variety of sandstone samples. Signal-processing techniques for the analysis of waveforms recorded in an attenuating mud-filled borehole have been developed and tested in the laboratory. (from Authors)
965215 3-D seismic tracking with probabilistic data association C. A. Woodham, W. A. Sandham & T. S. Durrani, Geophysics, 60(4), 1995, pp 1088-1094. The method under consideration was originally developed for tracking targets in a cluttered environment and uses Probabilistic Data Association to assess the probability of each return being the correct return. This theory has been modified for use in seismic event tracking. The tracker successfully picks out the chosen horizon in both synthetic and real 3-D data sets. The accuracy of the 3-D tracker may be improved by tracking through the data set in two perpendicular directions and correlating the results. (from Authors)
The availability of the Borehole Scanner System (BSS), which provides a high resolution digital image of the unrolled borehole wall, has made it possible to measure in situ joint roughness profiles intersecting a borehole. This paper describes the simulated direct shear test performed on the in situ roughness profiles obtained using the BSS and how the results compared to laboratory direct shear test results and the results of a kinematic simulation of the shearing process. (Authors)
965211 Use of neural network methods to predict porosity and permeability of a petroleum reservoir P. M. Wong, I. J. Taggart & T. D. Gedeon, AI Applications, 9(2), 1995, pp 27-37. The genetic approach was used in predicting porosity and permeability values from wireline logs and lithofacies information in reservoirs, using a back-propagation neural network method. For the data considered, the fine-scale simulation approach combined with the use of neural networks provides realistic and accurate porosity-permeability predictions when compared to the core data. (from Authors) 965212 Two EXCEL macros for tracing deviated bureholes using cubic splines and calculation of formation depth and thickness S. I. Ozkaya, Computers & Geosciences, 21(7), 1995, pp 851858. Two short EXCEL function macros are presented for calculation of borehole deviation, true vertical thickness, and true stratigraphic thickness. The function macros can be used as regular EXCEL functions. The calling formula, arguments, and their type are described and application is demonstrated on an example data set. The borehole bearing and drift between any two observation points are estimated by fitting a cubic spline curve to three adjacent observation points at a time. (from Author)
Processing and interpretation of data 965213 GIS in hydrocarbon exploration and production J. Tarleton, Geomaties Info Magazine, 9(11), 1995, pp 33-38. A GIS is an ideal access tool to spatial-related data for retrieval, query and presentation of information. However, systems need to be able to access corporate databases and integrate results from seismic reservoir modelling and image-
965216 Use of traveltime skips in refraction analysis to delineate velocity inversion H. C. Tewari, M. M. Dixit & P. R. K. Murty, Geophysical Prospecting, 43(6), 1995, pp 793-804. Under certain favourable circumstances, when a low-velocity layer (LVL) is considerably thicker than an overlying highervelocity layer (HVL), the velocity inversion can be seen in the form of a traveitime skip. Model studies show that in such cases the length of the HVL traveltime branch can be used to determine the thickness of the HVL and the magnitude of the traveltime skip in order to determine the thickness of the LVL. (from Authors) 965217 Improved Fourier terrain correction, Part I R. L. Parker, Geophysics, 60(4), 1995, pp 1007-1017. A description of a new Fourier technique is given for calculating the gravitational attraction of a layer with an irregular top surface for application in the terrain correction of marine gravity surveys in shallow water. The new approach divides the attraction into two parts: a local contribution from the material within a cylinder around each observation point and the attraction from the matter outside the cylinder. Two examples, one artificial and the other based on a survey around Guadalupe Island, illustrate the application of the new technique. (from Author)
965218 Generalized gravity gradient analysis for 2-D inversion D. K. Buffer, Geophysics, 60(4), 1995, pp 1018-1028. A generalized approach to structural interpretation from gravity data consists of: 1) determining vertical and horizontal gradient profiles perpendicular to the strike of a 2-D gravity anomaly, 2) determining the structural geometry from the gradient space plot, and 3) locating profile positions of structural corners from the vertical gradient profile. (from Author)
965209 Numerically simulated direct shear testing of in sit,. joint roughness profiles B. B. Thapa, T. C. Ke, R. E. Goodman, C. Tanimoto & K.
217A
processing systems. Systems also need to be customised to enable geologists, geophysicists, business analysts and surveyors to use the system effectively at their desktops. (Author)
Kishida, International Journal of Rock Mechanics & Mining Sciences, 33(1), 1996, pp 75-82.
965210 Estimates of formation sound speed from ultrasonic
965214 Theoretical and numerical issues in the determination of reflector depths in seismic reflection tomography K. P. Bube, R. T. Langan & J. R. Resnick, Journal of Geophysical Research, 100(B7), 1995, pp 12,449-12,458. Some theoretical results for the undiseretized problem regarding the possible ambiguity between slowness and depth are presented. These results indicate that the depths of the reflectors are determined in theory except for edge effects, but a sufficiently large aperture at the reflector is necessary to resolve this ambiguity in practice. The slowness field, however, does have some undetermined features. (from Authors)
reflections J. A. Davidson, S. L. Morriss & A. L. Podio, SPE Formation Evaluation, 10(2), 1995, pp 72-78. Presents preliminary results from experimental research concerning the ultrasonic refiectivity of rock samples. The goal is to determine whether meaningful petrophysical properties can be obtained through the analysis of reflected acoustic signals of the type produced with the new generation of ultrasonic borehole televiewers. Sound speed estimates in reasonable agreement with those determined by use of standard experimental techniques have been obtained for a variety of sandstone samples. Signal-processing techniques for the analysis of waveforms recorded in an attenuating mud-filled borehole have been developed and tested in the laboratory. (from Authors)
965215 3-D seismic tracking with probabilistic data association C. A. Woodham, W. A. Sandham & T. S. Durrani, Geophysics, 60(4), 1995, pp 1088-1094. The method under consideration was originally developed for tracking targets in a cluttered environment and uses Probabilistic Data Association to assess the probability of each return being the correct return. This theory has been modified for use in seismic event tracking. The tracker successfully picks out the chosen horizon in both synthetic and real 3-D data sets. The accuracy of the 3-D tracker may be improved by tracking through the data set in two perpendicular directions and correlating the results. (from Authors)
The availability of the Borehole Scanner System (BSS), which provides a high resolution digital image of the unrolled borehole wall, has made it possible to measure in situ joint roughness profiles intersecting a borehole. This paper describes the simulated direct shear test performed on the in situ roughness profiles obtained using the BSS and how the results compared to laboratory direct shear test results and the results of a kinematic simulation of the shearing process. (Authors)
965211 Use of neural network methods to predict porosity and permeability of a petroleum reservoir P. M. Wong, I. J. Taggart & T. D. Gedeon, AI Applications, 9(2), 1995, pp 27-37. The genetic approach was used in predicting porosity and permeability values from wireline logs and lithofacies information in reservoirs, using a back-propagation neural network method. For the data considered, the fine-scale simulation approach combined with the use of neural networks provides realistic and accurate porosity-permeability predictions when compared to the core data. (from Authors) 965212 Two EXCEL macros for tracing deviated bureholes using cubic splines and calculation of formation depth and thickness S. I. Ozkaya, Computers & Geosciences, 21(7), 1995, pp 851858. Two short EXCEL function macros are presented for calculation of borehole deviation, true vertical thickness, and true stratigraphic thickness. The function macros can be used as regular EXCEL functions. The calling formula, arguments, and their type are described and application is demonstrated on an example data set. The borehole bearing and drift between any two observation points are estimated by fitting a cubic spline curve to three adjacent observation points at a time. (from Author)
Processing and interpretation of data 965213 GIS in hydrocarbon exploration and production J. Tarleton, Geomaties Info Magazine, 9(11), 1995, pp 33-38. A GIS is an ideal access tool to spatial-related data for retrieval, query and presentation of information. However, systems need to be able to access corporate databases and integrate results from seismic reservoir modelling and image-
965216 Use of traveltime skips in refraction analysis to delineate velocity inversion H. C. Tewari, M. M. Dixit & P. R. K. Murty, Geophysical Prospecting, 43(6), 1995, pp 793-804. Under certain favourable circumstances, when a low-velocity layer (LVL) is considerably thicker than an overlying highervelocity layer (HVL), the velocity inversion can be seen in the form of a traveitime skip. Model studies show that in such cases the length of the HVL traveltime branch can be used to determine the thickness of the HVL and the magnitude of the traveltime skip in order to determine the thickness of the LVL. (from Authors) 965217 Improved Fourier terrain correction, Part I R. L. Parker, Geophysics, 60(4), 1995, pp 1007-1017. A description of a new Fourier technique is given for calculating the gravitational attraction of a layer with an irregular top surface for application in the terrain correction of marine gravity surveys in shallow water. The new approach divides the attraction into two parts: a local contribution from the material within a cylinder around each observation point and the attraction from the matter outside the cylinder. Two examples, one artificial and the other based on a survey around Guadalupe Island, illustrate the application of the new technique. (from Author)
965218 Generalized gravity gradient analysis for 2-D inversion D. K. Buffer, Geophysics, 60(4), 1995, pp 1018-1028. A generalized approach to structural interpretation from gravity data consists of: 1) determining vertical and horizontal gradient profiles perpendicular to the strike of a 2-D gravity anomaly, 2) determining the structural geometry from the gradient space plot, and 3) locating profile positions of structural corners from the vertical gradient profile. (from Author)