Radiation from seismic sources in cased and cemented boreholes

SITE INVESTIGATIONS:BOREHOLES 945119 A new geophysical method to measure soil profiles for dynamic analysis of soil embankments P. Michaels, in: Hydrogeology, waste disposal, science

and politics. Proc. 30th symposium on engineering geology and geotechnical engineering, Idaho, 1994, ed P.K. Link, (Idaho State University), 1994, pp 331-343. The method is to acquire shear-wave borehole data following blow count measurements. Measurements of the shear wave amplitudes and velocity dispersion are jointly inverted to produce a soil profile of the elastic and inelastic properties needed for dynamic analysis by computer programs such as SHAKE or DESRA-2. Since the measured profiles correspond exactly to the parameters needed by the computer programs, improved dynamic evaluations can be made without employing conversion charts or empirical formulae. The resulting profiles will be valid over a broad range of frequencies, since the correct differential equation is used in place of simpler constant Q models. -from Authors

945120 Test observation of crustal strains by two extensometers with super-invar rods of different coefficients of expansion (in Japanese) T. Furuzawa, F. Ohya, M. Teraishi & Y. Sonoda, Journal - Geodetic Society of Japan, 39(4), 1993, pp 363-376. Test observations of crustal strain were carried out by two extensometers on common bases in an observation vault of Takajo observatory in Southwest Kyushu, Japan. These extensometers are composed of two different type invar rods, one of which is conventional super-invar (S-I) and the other is new super-invar whose coefficient of expansion is much lower than that of the conventional one. The new S-I extensometer is less influenced by temperature changes in the vault. The coefficient of linear expansion of both materials were numerically estimated from the observation data in the period of initial drift and from the heating experiments data. The coefficient of expansion of the conventional S-I is about 1 × 10-6/'C and that of the new S-I is less than 1 × 107/'C. -from English summary

945121 Electromagnetic ray-trace tomography A.G. Nekut, Geophysics, 59(3), 1994, pp 371-377. Electromagnetic (EM) tomography can be used to estimate the distribution of electrical rock properties between boreholes. For typical oil field well spacings and reservoir electrical characteristics, crossweU EM measurements are sensitive primarily to the electrical conductivity, not the permittivity. Ray-tracing methods normally associated with undamped propagating waves can also be applied to the rapidly attenuated, diffusive EM waves encountered in the petroleum reservoir environment. Thermal noise considerations place an upper limit of approximately 20 skin depths on the separation between wells. -from Author

945122 More reliable shear-wave data from VSPs using the CIPHER technique T. Gut, W. Sollner, E. Luschen & H. A. K. Edelmann, First Break, 12(3), 1994, pp 123-129. The observation of seismic shear waves, recorded with three-component multilevel .geophones in boreholes, provides information on seismic anisotropy, which may be caused primarily by preferred orientations of microeracks. However, as a complementary tool to standard P-wave vertical seismic profiles (VSPs), shearwave VSPs with horizontal vibrators require additional survey time and processing costs. Enhancement of quality and reduction of costs were reasons for the implementation of a new seismic source radiating circularly polarized shear waves for applications in VSPs. The CIPHER technique (Circularly Polarized Horizontal Excursion Radiation) generates all horizontal stress orientations at the same time. It consists of a combination of two linear horizontal vibrators in orthogo-

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nal orientations generating sweep signals differing in phase by 90". -from Authors

Borehole and core logging 945123 The identification of basalt flow features from borehole television logs W. Bennecke, in: Hydrogeology, waste disposal, science

and politics. Proc. 30th symposium on engineering geology and geotechnical engineering, Idaho, 1994, ed P.K. Link, (Idaho State University), 1994, pp 371-383. Basalt flows can be divided into four zones: an up[~er vesicular zone; a columnar zone; a central zone; anu a lower vesicular zone. The upper vesicular zone can be further subdivided into four subzones: an upper vesicular subzone; a transitional subzone; a lower vesicular subzone; and a bubble train subzone. Some specific features found in the borehole TV logs were: bubble-trains, vesicle plumes, borehole extensions, and pipe vesicles. The overall distinctions for the zones were based on their vesicularity. An overall pattern of vesicles was found to be a progression of small numerous vesicles at the top of a flow which increase in size, but decrease in number, towards the center of the flow. The opposite is true starting at the bottom of the basalt flow where small vesicles are numerous, but increase in size while decreasing in number towards the center part of the flow. -from Author 945124 Results of a downhole formation microscanner study in a Jura-Triassic-aged sedimentary deposit (Passaic Formation) J. A. Fischer, J. J. Fischer & R. J. Bullwinkel, in:

Hydrogeology, waste disposal, science and politics. Proc. 30th symposium on engineering geology and geotechnical engineering, Idaho, 1994, ed P.K. Link, (Idaho State University), 1994, pp 359-370. Studies to determine the structural and geohydrologieal properties of the Passaic Formation were performed at two sites. Both sites are located in north-eastern New Jersey, within the Jura-Triassic-aged Newark Basin. The Formation MieroScanner tool was used in four wells drilled for these projects (two at each site). In addition to this microresistivity tool, a suite of other oil field geophysical tools (Gamma, Induction, Dipmeter, Temperature, and Neutron probes) were also utilized. The data collected with the Formation MicroScanner were correlated with detailed logs and the continuous core retrieved from three of the wells. Pump test data was also obtained at both sites. The geophysical data obtained at both sites allowed the direct identification of fractures and their orientation in relation to bedding. Fracture and bedding apperture size and orientation were measured. The results, as presented in this paper, show a high degree of inhomogencity at both sites rather than the conventional layer cake model. -from Authors 945125 A comparative study of gamma-ray bore hole logging and radiometric core assay data: a case study from Dudra area, Singhbhum district, Bihar, India G. Mandal, Journal of Atomic Mineral Science, 1, 1993, pp 119-124. A comparative study has been carried out on percentage eU30 s values obtained from radiometric assay of boreholc cores and gamma-ray logging of boreholes in Dudra area. An attempt has been made to statistically evaluate the data obtained from these two methods. The data taken for the study consist of the product of the average grade and the thickness of the intercepted uraniferous zones in eleven borcholes which satisfy the minimum mining width criteria. Correlation coefficient of 0.989 points to a very good correlatability between the values obtained by the above two methods indicating that core assay can be used to check the gamma ray log data in such zones. -Author 945126 Radiation from seismic sources in cased and cemented boreholes R.L. Gibson Jr, Geophysics, 59(4), 1994, pp 518-533. Computation of the radiation patterns for cased and uncased boreholes in various formations shows that the amplitude reduction, because of the introduction of casing,

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SITE INVESTIGATIONS:TESTING

is a function of both source type and of formation velocities. Axial stress sources are less affected by the casing than either radial stress or volume-injection sources, and as formation velocity decreases, the effect of the casing becomes more significant. The new generalized stationaryphase solution also shows that as frequency approaches 1000 Hz, the results obtained by low-frequency approximations for stress sources can be inaccurate and that the energy radiated from the source becomes more highly directed in the horizontal directions. -from Author 945127 Hydrological aspects of geophysical borehole measurements in crystalline rocks of the Black Forest H. Wilhelm, W. Rabbel, E. Luschen, Y.-D. Li & M. Bried, Journal of Hydrology, 157(1-4), 1994, pp 325-347. One of six wells drilled into the crystalline rock of the Black Forest basement during the German Continental Deep Drilling Project (KTB) site survey has been used to detect hydraulically active fractures and to identify their character. Various logging methods were applied successfully to discriminate between fractures andbreakouts and to identify open and closed fractures and water-consuming or water-expelling fractures. -from Authors 945128 Accuracy in borehole temperature measurements V.V. Gordienko, V. A. Badanov, O. V. Veselov, O. V. Zavgorodnyaya & Yu. G. Shvartsman, Geophysical Journal, 12(3), 1994, pp 331-339. An analysis is presented of 250 temperature measurements on 90 boreholes in various parts of the CIS. It is found that it is possible to determine temperatures accurately (with an error of a few hundredths of a degree). However, in many cases the error is 0.5-1.0"C (sometimes more). Primarily, this is due to not completely correct thermometer calibration. It is concluded that there is a need for periodic checking by all organizations concerned with geothermal studies. -Journal summary 945129 Novel procedures accurately measure drilling mud dynamic filtration M. E. Chenevert, S. A1-Abri & Liang Jin, Oil & Gas Journal, 92(17), 1994, lap 62-66. New equipment and test procedures can determine dynamic mud cake properties such as equilibrium cake thickness, porosity, permeability, compressibility, and erosion resistance. The following were developed to study dynamic filtration: a dynamic filtration cell; a recommended filtration medium; a mudcake thickness device; mudcake porosity determination method; calculation methods for shear rate determination beneath a rotating cone; determination of equilibrium cake thickness, erosion resistance, and compressibility; and preferred filtration display techniclues. Each development is discussed in detail, and typical filtration results are presented from a test study. -from Authors 945130 Effect of temperature and pore size on the hydraulic properties and flow of a hydrocarbon oil in the subsurface E. L. Davis, Journal of Contaminant Hydrology, 16(1), 1994, pp 55-86. Theory predicts that for a given ~aorous medium, the effect of different fluid properties or Changes in temperature on capillary pressure are due to changes in interracial tension and contact angle of the system. The capillary pressuresaturation curves measured here for hydrocarbon oil-water do not have a constant capillary pressure ratio with saturation when compared to the water-air system, and changes in ratio were found when comparing the water-air curves measured at different temperatures. Also, the curves show the residual wetting and nonwetting phase saturations are greatly affected by temperature and sometimes by the fluid pair. -from Author 945131 The rock-mechanical aspects of drilling a North Sea horizontal well S.-W. Wong, C. A. M. Veeken & C. J. Kenter, SPE Drilling & Completion, 9(1), 1994, lap 47-52. In view of the high cost of extended reach horizontal drilling, a borehole stability study was conducted to determine

the range of mud weights suitable for drilling the first horizontal well in a North Sea oil field. The stability of the borehole was assessed using three methods that differ in complexity, cost, and conservatism. The study shows that drilling the horizontal section is feasible from a rockmechanical viewpoint if a mud weight slightly above the pore pressure is used. -Authors 945132 Horizontal aquifer movement in a TheisThiem confined system D . C . Helm, Water Resources Research, 30(4), 1994, pp 953-964. The skeletal matrix of an aquifer is known to move laterally toward a discharging well. The mechanisms by which it moves relative to the welt have been only partially studied in the past. Examining the relation of drawdown to volume strain for an assumed poroelastic solid has been a common approach. By way o f contrast, the present study examines the relation of the velocity of solids (aquifer matrix) to their hydraulic driving forces. A new formulation of the Darcy-Gersevanov law of water ttowing relative to moving solids is applied to a Theis-Thiem confined aquifer. The aquifer is found to start with a maximum velocity when the pump is turned on and then to decelerate as time progresses. Dimensionless type curves of horizontal movement of the skeletal matrix are calculated. -from Author 945133 Liquid influx to a borehole in an elastoplastic stratum T. N. Krechetova & L. M. Marmorshtein, Geophysical Journal, 12(5), 1994, pp 681-686. A general method is considered for evaluating the effects of rock strain on infiltration characteristics for elastoplastic deformation. A method has been implemented for the liquid inflow to a borehole in the elastoplastic stratum. Numerical results are given for hypothettcal strata with various forms of plasticity. -Journal summary

Suggested testing methods and standards 945134 Variacoes de volume em solo colapsivel medi. das atraves de ensaios de laboratorio e campo (Volume change measurements in collapsible soil by laboratory and field tests) S.R. De Melo Ferreira & W. Alvarenga Lacerda, Solos e Rochas, 16(4), 1993, pp 245-253. Collapse characteristics of a quartz sand from the city of Petrolandia are determined by laboratory and field tests on undisturbed material. This pal~.r presents the development and construction of new eqmpment, the expanso--eolapsometer, which p.ermits the field measurement of volume change of the soil at different depths under a variable vertical stress and controlled rate ofinnundation. The volume change measured in situ is about 11% less than the minimum values measured at the laboratory. The collapsibility under geostatic stress increases up to a depth of 1,25m, and decreases for increasing depth. -from English summary 945135 Laboratory and field determinations of smallstrain shear modulus for a structured Champlain clay G. Lefebvre, D. Leboeuf, M. E. Rahhal, A. Lacroix, J. Warde & K. H. Stokoe I'I, Canadian Geotechnical Journal, 31(1), 1994, pp 61-70. Values of small-strain shear modulus G , , . , for a Champlain Sea clay deposit were obtained T3oth under an embankment built I8 years ago, and outside of the area influenced by this embankment. In addition to verifying the two methods, comparison of in situ and laboratory values allowed evaluation of the influence of the sampling and the need to correct the laboratory values to account for the age of the deposit. The test program also made it possible to verify the influence of the deposit's consolidation and the