SITE INVESTIGATIONS:BOREHOLES Verifying drillholes have mostly confirmed the good correlation between geophysical interpretation and drilling results. -from English summary
197A
analysis of ground water and computer studies. -from Author
Borehole and core logging 944198 G r o u n d - p e n e t r a t i n g r a d a r simulation in engineering a n d archaeology D. Goodman, Geophysics, 59(2), 1994, pp 224-232. Forward modeling of ground penetration radar is developed using exact ray-tracing techniques. Structural boundaries for a ground model are incorporated via a discrete grid with interfaces described by splines, polynomials, and in the case of special structures such as circular objects, the boundaries are given in terms of their functional formula. In the synthetic radargram method, the waveform contributions of many different wave types are computed. Using a finely digitized antenna directional response function, the radar cross-section of buried targets a n d t h e effective area of the receiving antenna can be statistically modeled. Attenuation along the raypaths is also monitored. -Author
944199 Synthetic seismograms for a long s p r e a d of seismometer stations J . H . Rnsenbanm, Geophysics, 59(3), 1994, pp 450-463. The assumption that the earth is made up of plane-parallel, homogeneous, elastic layers, which can exhibit transverse isotzopy and moderate constant-Q attenuation, leads to an effective method of modeling the response from a point source into a long spread of seismometer stations. The structure and symmetry properties of the propagator matrices describing the response are the same for isotropic and transversely isotroplc layers. Synthetic seismic panels for a regional model of a west Texas well site exhibit strong, shot-generated surface waves. A very simple model, based on a south Texas well site, shows the effects of transverse isotropy and the rcverberatory nature of converted signals generated by a surface P-wave. -Author
944200 The use of cross well seismology to c h a r a c t e r ize a n d monitor a s t r e a m e d oil reservoir B. N. P. Paulsson, M. E. Smith, K. E. Tucker & J. W. Fairbom, in: Comprehensive rock engineering. Vol. 3, ed J.A. Hudson, (Pergamon), 1993, pp 651-669. Cross well seismic tomo~raphy is developing into an important tool for reservotr management and within the last few years there have been some notable advances in our understanding of its imaging capability. This paper discusses the results of the time-lapsed cross well tomography surveys at Midway-Sunset. The first cross well survey, onducted in July of 1989, prior to foam injection, was one to provide a first mapping of the steam chest. Steam injection into the pattern had started in 1982, and a considerable steam chest had developed. The second survey was conducted in August, 1990, 14 months after foam injection commenced, and after significant changes were seen in the observation and producing wells. -from Authors
944201 Geophysics in town planning - a case study B. Lal, Journal - Geological Society of lndia, 43(1), 1994, pp 67-73. Geophysical surveys as aid to urban evaluation in the Vidyadhar Nag .at area adjacent to Jaipur city, Rajasthan, nave oeen conctucted. DC resistivity surveys over area covered by sand and dunes indicated the presence of a moderately thick surface layer underlain b y a potable aquifer zone. The results of the magnetic survey show normal structural behaviour. Subsequently, Jaipur Development Authority has undertaken construction of urban complex with a high rise structure in the area. The pa~per presents the geophysical results along with chermcal
944202 Using borehole images for target-zone evaluation in horizontal wells N. F. Hurley, D. R. Thorn, J. L. Carlson & S. L. W. Eiehelberger, American Association of Petroleum Geologists Bulletin, 78(2), 1994, pp 238-246. Horizontal wells are rarely horizontal. Instead, operators commonly try to drill such wells into particular rock layers, or target zones, which may or may not be truly horizontal. Target-zone evaluation concerns whether a horizontal well was successfully located and drilled in a given rock layer. Borehole-imaging logs provide a powerful tool for stratigraphic interpretation and target-zone evaluation in the Austin Chalk, Niobrara Formatton, San Andros Formation, and other units. This study uses borehule images generated by Schlumberger's Formation MicroScanner (FMS), a microconductivity logging device. STRATLOG software has been used to display borehole profiles by combining FMS data on fracture intensities and bedding-plane intersections with gamma-ray logs, mud logs, and boreholedeviation surveys. To aid in planning future wells, multiple penetrations of the same horizon can be detected and used to calculate highly accurate bedding-plane dips. -from Authors 944203 Subsurface fracture spacing: comparison of inferences from slant/horizontal a n d vertical cores J. C. Lorenz & R. E. Hill, SPE Formation Evaluation, 9(1), 1994, pp 66-72. Comparison of cores from a slant/horizontal and three vertical wells at the same site shows that fracture spacing is irregular, significantly less than bed thickness, and cannot be derived from vemcal-well data. Fracture spacing measurements must be filtered properly to be useful in reservoir models. -Authors 944204 Static delays in acoustic logging J . P . Leveilie & R. B. Neff Jr, Geophysics, 59(3), 1994, pp 362-370. Borehole-consistent analysis of compressional wave arrivals in full-waveform acoustic logs reveal arrival-time anomalies of tens of microseconds. These anomalies are correlated with llthology and are similar for logging sondes of different geometries. A possible explanation is given in terms of the Fourier phase spectrum of the first compressional arrivals. The theoretical delays depend on the formation elastic parameters, the borehole geometry and the properties of the borehnle fuid. -from Authors 944205 Wavelet t r a n s f o r m : application to acoustic logging N. Thizion, J. Mars, P. Volant & J. L. Marl, Revue Instirut Francais du Petrole, 49(2), 1994, pp 149-163. The wavelet transform can be used to develop the process which allows group and p h a s e velocity measurement of dispersive waves. The method has been applied to acoustic data to measure formation velocities. The behavior and the accuracy of the method have been checked on synthetic full waveform acoustic data. The method was applied to dispersive waves of the Stoneley type and to flexural modes whose low frequency components are propagated at the formation shear velocity. A raw measurement of the phase velocity of a flexural mode gives an estimate of the shear velocity with an error of about 5%. The use of a wavelet transform yields an accurate study of dispersion and gives a shear velocity measurement with an error of less than 1%. However, all the examples presented are based on the use of synthetic data, which are not corrupted by noise and were obtained with a numerical model. -from Authors 944206 Contribution of the 3-D visualization of acoustic borehole signals (full waveforms) to a quick formation evaluation A. Rousseau & D. Jeantet, Journal of Applied Geophysics, 31(1-4), 1994, pp 213-260.