bluuebunny/crossref_metadata_2025_split huggingface dataset:
SELECTION OF SEISMIC PICKING BASED UPON THE DIP, MOVE‐OUT AND AMPLITUDE OF EACH EVENT*
Authors: GAROTTA ROBERT 
Published: April 2006

AbstractThe general use of continuous CDP seismic lines means that the neighbourhood of each depth point can be considered according to two sets of co‐ordinates:— the co‐ordinates of the abscissa on the seismic lines and the reflection time, which allow investigation of the local dip of coherent events;— the co‐ordinates of the reflection time and the move out, which allow investigations of the average velocity for these same events.The combination of both investigations for each coherent event is a very convenient operation for the seismologist, and can provide some useful interpretation aids such as velocity profiles, or information on the interval velocities.The principles which we use consist in the examination of a large range of possibilities, of which only the most coherent are chosen.Some examples are shown.
RECENT DEVELOPMENTS IN WELL VELOCITY SURVEYS AND THE USE OF CALIBRATED ACOUSTIC LOGS*
Authors: KENNETT P. , IRESON R. L. 
Published: April 2006

AbstractIn recent times, velocity surveys at marine well locations have been performed using non‐explosive energy sources such as air‐guns and gas guns. In addition, surveys in land wells have been successfully carried out using a modified version of the air‐gun. This paper illustrates some of the characteristics of these devices and compares the data obtained from typical surveys with conventional dynamite surveys.Since data obtained from well velocity surveys using non‐explosive sources are now commonly recorded on tape, they lend themself to further digital processing and interpretation techniques that were not previously so conveniently available. Some examples of these processes, e.g. the examination of attenuation, frequency and energy content of the recorded well geophone signals, are given in the paper. Examples of some other digital processes, using calibrated Acoustic logs, whether recorded digitally in the field or subsequently converted from analogue recordings, are also given in the paper. These include the construction of an Acoustic log in the vertical axis from logs obtained in deviated wells.
ONDE AMORTIE DE TYPE RAYLEIGH À L'INTERFACE DE DEUX MILIEUX SOLIDES À FORT CONTRAST DE DENSITÉS ET DE VITESSES*
Authors: GUPTA S. K. , MARTEL L. 
Published: April 2006

RésuméL'onde amortie de type Rayleigh à l'interface de deux milieux solides à fort contraste de densités et de vitesses est étudiée théoriquement et expérimentalement sur un modèle à deux dimensions plexiglas‐laiton.
MODÈLES ANALOGIQUES ÉLECTRONIQUES DU PROCESSUS D'EXPLOSION DANS LES ROCHES*
Authors: ENESCU D. , CÎNDEA I. 
Published: April 2006

AbstractThe first part of the contribution deals with the generalization of the solution given by Sharpe and states the elements of the mathematical model of the explosion generating longitudinal waves. The generalization of Sharpe's solution consists in finding out the response of the medium to a pressure p(t) applied at the source, for any value of the ratio K=Vp/Vs covering the range √2 ÷∞.The second part contains the results of the calculation and design of three electronic analog models of the explosion process in rocks. The first is represented by electrical circuits separated by emitter follower circuits. The scheme of the second model has electrical circuits and elements of operational calculus (integrator, summation instrument). The electrical circuits are represented by the two filters simulating the selective effect of the explosion in rocks. The third model is a logical programming scheme of the problem on an analog computer.For the calculus of the electrical parameters of the three schemes we have taken into account scaling of the physical and geometrical parameters of the medium and of the explosion which should ensure the simulation of the explosion process in rocks of all kinds of importance in seismic prospecting.
CORRELATION A DISTANCE*
Authors: BOIS P. 
Published: April 2006

AbstractThe automatic picking of seismic sections becomes delicate with the presence of blind zones breaking up the continuity of horizons. This makes it difficult to establish correlations between reflections coming from above and below these blind zones.With the help of a certain number of characteristic parameters, a computer capable of storing a great quantity of data makes it possible to identify the horizons bounding a blind zone. Once this investigation has been made, the coherence between these horizons still has to be measured by making a factorial analysis of these different parameters. The statistical decision functions involved in this analysis are well adapted to computer logic. They enable the probability to be given with which the horizons located above and below blind zones correspond.A program has been worked out to provide the degree of coherence between such horizons.
RESISTIVITY ANALYSIS FOR PLANE‐LAYER HALF‐SPACE MODELS WITH BURIED CURRENT SOURCES*
Authors: MERKEL R. H. 
Published: April 2006

AbstractBoundary‐value problems in steady‐state current flow were solved numerically for one and two layers over a half‐space. Solutions were obtained for layers of various resistivities where one of the current sources was placed below the surface and the second kept at some finite distance from the drill hole. When a fixed surface dipole receiving pair was used, it was found that as the buried source approached a conductive region, quite good determinations of the depth to the conductor could be made, hence reducing the possibility of extended drilling in “dry” holes resulting from poor surface data and/or interpretation. Numerous models were generated to find the optimum positioning of the two current electrodes for different field situations of this type. It was also found that by placing a current source in the conductive region, better resolution of the lateral extent of a possible ore zone could be obtained, due both to the more rapid convergence of the apparent resistivity to the resistivity of the conductor, and the fact that a smaller separation in the receiving dipole could be used. Numerous analog models were constructed to verify the digital results. Surface and down‐hole resistivity field data are compared to show the strength of this technique in delineating structure.
SISMIQUE MINIERE A HAUTE FREQUENCE*
Authors: CODET P. , DAMOTTE B. , ERB E. , LAVERGNE M. , LAYOTTE P. C. 
Published: April 2006

ResumeLa sismique réflexion a été mise en œuvre dans des galeries de mines avec un appareillage nouveau: dispositifs appropriés, géophones spéciaux, chaîne d'enregistrement haute fréquence (30–2000 hertz).Des réflexions à des fréquences de l'ordre de 600 à 1200 hertz ont été obtenues dans les cas favorables sur des couches de charbon de l'ordre du mètre situées jusqu'à une soixantaine de mètres sous la galerie.Une bonne compacité des terrains situés autour de la galerie est une condition nécessaire à l'obtention de réflexions. Les accidents affectant les couches peuvent alors être visibles.
THREE‐DIMENSIONAL OPTIMUM MULTICHANNEL VELOCITY FILTERS*
Authors: HUBRAL PETER 
Published: April 2006

AbstractDesign procedures and characteristics of three stacking filters are discussed which may find application in various three‐dimensional velocity filtering problems. These filters are derived in the time‐domain as optimum multichannel Wiener filters. Random stationary functions are assumed as stochastic models for the seismic traces. All power and crosspower spectra which are the basic elements of the multichannel normal equations are statistically averaged according to specific three‐dimensional considerations. Various properties of the input traces may be incorporated in the design of the optimum filters. With fairly general assumptions about the input these filters are deterministic in the sense that they are applicable to a broad class of input traces with similar statistics in amplitudes and arrival times of signals.
A FOURIER METHOD FOR THE REGIONAL‐RESIDUAL PROBLEM OF POTENTIAL FIELDS*
Authors: SYBERG F. J. R. 
Published: April 2006

AbstractAn equivalent stratum model is used to provide an explanation for the power spectrum characteristics of potential fields.The power spectrum of observed magnetic fields is found to consist of effects due to sources which can be represented by apparent monopoles and dipoles. Similarly, the power spectrum of observed gravity fields is found to consist of two groups of effects. A matched filter is proposed whereby the effects due to the two components in the potential field can be separated. As a consequence of the established theoretical expressions a scheme is suggested whereby the aliasing power of sampled data can be estimated. Also, the concepts of downward continuation, reduction to the pole, and reduction to pseudo‐gravity of magnetic fields are re‐examined in light of the theoretical expressions due to the equivalent stratum model.
INVESTIGATION OF SOME NON‐LINEAR PHENOMENA OF INDUCED POLARIZATION USING A PHYSICAL‐AND‐MATHEMATICAL MODEL*
Authors: FINZI‐CONTINI G. , BENVENUTI G. 
Published: April 2006

AbstractThe electrical behaviour of a polarizable sample formerly studied (Time‐Domain) through both the classical and the condenser methods is simulated using the theoretical responses given by a three dimensional physical‐and‐mathematical model, which has been proposed in a previous paper by one of us on the basis of certain hypotheses.The apparent capacitance responses of the sample are qualitatively simulated in order to tackle the problem under this point of view; moreover, an attempt to obtain a quantitative simulation of experimental data within the limits of the present reliability of the model, using theoretically obtained Model Master Curves characterized by dimensionless parameters, is done.This research is carried out in the frame of a broader study referring to a possible scheme of simulation of the so‐called induced ionic polarization, concerning a number of idealized pseudo‐reversible, potentially irreversible, non‐linear phenomena.
INTERPRETATION OF THE GRAVITY ANOMALY OVER A CAUSATIVE BODY WITH CIRCULAR SYMMETRY*
Authors: PAUL M. K. 
Published: April 2006

AbstractThe interpretation of the gravity anomaly on a horizontal plane over a causative body having circular symmetry about a vertical axis is considered from a rather unconventional approach. As the analytical expression for the gravity effect of a circular body assumes a closed form only on the axis of symmetry, the interpretation in this approach is carried out with the anomaly profile along the axis—which leads to simpler and faster computation.A numerical method is developed for computation of the anomaly profile along the vertical axis from the horizontal radial profile of the symmetric anomaly by upward continuation. Provision is also made for an end correction when the radial profile has only a limited extension.Some simple geometrical shapes are assumed for the causative body. Its parameters are then determined from least squares fitting of its gravity effects to the observed (upward continued) vertical profile (i) by the steepest descent method and (ii) by the Newton‐Raphson method.Some applications of these methods are demonstrated.
AN ITERATIVE METHOD FOR THE SOLUTION OF ANON‐LINEAR INVERSE PROBLEM IN MAGNETIC INTERPRETATION*
Authors: KUNARATNAM K. 
Published: April 2006

AbstractA method is presented for determining the lower surface of a two‐dimensional body producing a magnetic anomaly when its upper surface and the intensity of magnetization are given. The magnetization vector is assumed to lie along a specified direction but the sense of magnetization may be different in different vertical sections of the body and may be regarded as unknown. The method is illustrated using the computed anomalies of some theoretical models.
COMPUTER CALCULATION OF RESISTIVITY PSEUDOSECTIONS OF A BURIED SPHERICAL CONDUCTOR BODY*
Authors: SCURTU E. F. 
Published: April 2006

AbstractThe use of the electrical image method in calculating the potential of a source in the presence of a buried conductive sphere proves to be difficult because of the great number of terms making up the potential formula. The disadvantages contained by this method are avoided here by resorting to the theory of graphs. In view of this aim the “propagation” of the electrical images due to the sphere has been represented by an infinite graph to which an infinite matrix has been attached.Taking this as a basis several FORTRAN IV programs for the computation of resistivity pseudo‐sections for various electrode configurations have been coded, and a great deal of such pseudo‐sections have already been calculated with an IBM‐360 computer. Using these results, recommendations regarding both the methodology of the geoelectrical prospecting of spherical shaped conductors and the most suitable way of building resistivity pseudo‐sections are developed.
ECHO‐LOG — EIN GEOPHYSIKALISCHES MEßVERFAHREN ZUR BESTIMMUNG VON FORM VON AUSSOLUNGSHOHLRÄUMEN IM SALZGEBIRGE*
Authors: WIERCZEYKO E. 
Published: April 2006

AbstractMit der vorliegenden Arbeit wird das Echo‐Log als ein geophysikalisches Meßverfahren zur Bestimmung von Form und Volumensverteilung von Aussolungshohlräumen im Salzgebirge vorgestellt. Hierzu werden neue terminologische Begriffe wie Echo, Echostrahl, Echostrahler, Echozeit, Echogramm usw. erläutert. Weiter wird über die Meßausrüstung, Durchführung der Vermessung sowie die Ergebnisdarstellung berichtet.In einem letzten Abschnitt wird zwischen Echos, die auf einem direkten Weg von der Hohlraumfläche zurückgeworfen werden und anderen bei der Registrierung erfaßten Empfangssignalen unterschieden.In this paper the Echo‐Log is presented as geophysical measuring method for determining form and volume spread of leached cavities in salt formations. Therefore, new terminological definitions like Echo, Echo Beam, Echo Transducer, Echo Time, Echogram etc. will be explained. Furthermore, also the measuring equipment, execution of a survey and the presentation of the results will be described.In the last paragraph the difference between Echo directly reflected from cavity walls and other in the cavities registered signals will be discussed.
TRANSIENT ELECTROMAGNETIC RESPONSE OF A CONDUCTING SPHERE EXCITED BY DIFFERENT TYPES OF INPUT PULSES*
Authors: VERMA S. K. 
Published: April 2006

AbstractA technique utilizing the convolution theorem is developed to obtain the time‐domain electromagnetic response for a number of input pulses from the given step‐function response. For illustration an idealized model of a homogeneously conducting non‐permeable sphere placed in a uniform field is considered. The nature of the responses due to different types of pulses and their usefulness in estimating the constitution parameter of the sphere are discussed. To show the applicability of the suggested technique to generalized systems, calculations for a conducting permeable sphere are presented in the appendix.
A NOVEL HIGH‐SPEED ALGORITHM FOR SUMMATIONAL TYPE SEISMIC VELOCITY ANALYSES*
Authors: ROBINSON J. C. , ALDRICH C. A. 
Published: April 2006

AbstractVelocity analysis of reflection seismic data has increased in popularity with petroleum exploration personnel to such an extent that it now constitutes a significant tool in the routine digital processing program. One drawback to such an analysis is its computational cost, resulting from the numerous mathematical calculations required by a digital computer to extract comprehensive velocity information.The subject algorithm affords a computational cost saving of approximately one order of magnitude over a straightforward summational type velocity analysis with little sacrifice in accuracy. The utility of the algorithm is demonstrated on some Offshore Louisiana seismic data and a comparison of the results reveals that they are almost identical with a conventional velocity analysis.The algorithm is based on the concept that a normal‐moveout pattern of time shifts may be accurately applied over a considerable span of zero‐offset times to a CDP trace gather, rather than only at a single zero‐offset time. With each application however, the rms‐velocity associated with the moveout pattern is different. A specific relationship which associates an rms‐velocity with a zero‐offset time for the same moveout time delay pattern is approximated by numerical simulation studies on a digital computer.
A GENERAL TECHNIQUE FOR THE DIRECT INTERPRETATION OF RESISTIVITY DATA OVER TWO‐DIMENSIONAL STRUCTURES*
Authors: LEE T. 
Published: April 2006

AbstractThe indirect method of interpreting resistivity data is capable only of limited success because of the difficulty of calculating type curves for complex structures. Consequently a need arises for a direct method of interpretation for complex generalized structures.Such a technique for the direct interpretation of apparent resistivity data, obtained by electrical soundings carried out over two‐dimensional structures, has been developed from an examination of the Hankel transform of such data. The method is based on the observation that the asymptotic expansion of the Hankel transform is critically dependent upon the minimum distance between the measuring device and the surface of discontinuity in resistivity.The variation in the across strike direction may be mapped by a sequence of depth soundings made parallel to each other and separated in the across strike direction.
SYSTEM APPROACH TO AIR‐GUN ARRAY DESIGN *
Authors: GILES B. F. , JOHNSTON R. C. 
Published: April 2006

AbstractTo specify intelligently a nondynamite source in a marine seismic data‐collection system, it is important to use all known parameters of the system—source, receiver, and recording‐system characteristics. A technique has been developed to design the far‐field pressure pulse of an air‐gun array by taking these parameters into account.Important source variables to consider are interaction among guns in the array and the depth of the array. Near‐field pressure signatures of individual guns, which are relatively unaffected by boundaries, have been used to‘construct’the far‐field pressure pulse of the array by considering these variables. Comparison between constructed pulses and measured far‐field pulses shows substantial agreement.Streamer depth and recording‐system bandpass should also be considered when designing an air‐gun array. Comparison of far‐field pressure pulses for several bandpasses clearly shows the importance of considering this variable; e.g., the initial pulse is severely attenuated when a high‐cut filter is used. Likewise, an additional filtering effect due to the streamer's proximity to the surface should be taken into account.Design of an air‐gun array using the principles just outlined are illustrated by an example.
ACOUSTIC WAVES ALONG OILFILLED STREAMER CABLES *
Authors: WEICHART H. F. 
Published: April 2006

AbstractThere are different types of acoustic noise induced in streamer cables. One type consists of pulsed waves preferentially generated by vertical motions of the towing ship or of the tail buoy. The pulsed waves travel along the streamer with low attenuation and a velocity about 15% less than the velocity of water. Frequencies observed lie between 5 and 15 Hz.These pulsed waves are well known and for the last few years acoustic isolator sections have been used to reduce their generation. But under bad weather conditions and especially in cold water these waves become stronger. Recent investigations demonstrated that the pulsed waves are able to produce a high noise level even in new streamers with acceleration cancelling hydrophones. We point out that the material of the hoses has a dominant effect on the amplitude picked up by the hydrophones.Acoustic theory is applied to understand the phenomenon of these waves.
A NEW PARAMETER FOR THE INTERPRETATION OF INDUCED POLARIZATION FIELD PROSPECTING (time‐domain) *
Authors: PATELLA D. 
Published: April 2006

AbstractIn a previous paper it has been shown that we can relate the transient IP electric field Ep, existing in a rock after a step wave of polarizing current, with the steady‐state current density Jss during the current step wave as follows: Ep=ρ'Jss.This relation may be interpreted as a generalized Ohm's law, valid in linear cases, in which ρ’(fictitious resistivity) is defined as the product of the true resistivity ρ with the chargeability m.Supposing Ep=—grad Up and applying the divergence condition div Jss= o, one can, for a layered earth, obtain a general expression for the depolarization potential Up as a solution of Laplace's equation ∇2Up= o.Since the mathematical procedure for the solution of this last equation is identical to that used in resistivity problems, we propose now the introduction of an apparent fictitious resistivity ρ'a (defined as the product of the apparent resistivity ρa with the apparent chargeability ma) as a new parameter for the interpretations of IP soundings carried out over layered structures with a common electrode array.The most general expression of ρ'a as a function of the electrode distance turns out to be mathematically identical to the general expression of ρ'a. Therefore it is possible to interpret a ρ'a field curve using the same standard graphs for resistivity prospecting with the usual method of complete curve matching.In this manner a great deal of work is saved since there is no need to construct proper ma graphs for the interpretation of IP soundings, as it has been done up to now.Finally some field examples are reported.
INDUCTIVE SOUNDING OF A STRATIFIED EARTH WITH TRANSITION LAYER RESTING ON DIPPING ANISOTROPIC BEDS *
Authors: NEGI J. G. , SARAF P. D. 
Published: April 2006

AbstractThe generalised three layer boundary value problem with a transition layer sand‐witched between an isotropic overburden and dipping anisotropic substratum is discussed assuming that plane electro‐magnetic waves are incident normally over the air‐earth inter‐face. The tangential electric (Ey) and magnetic (Hx) fields and the expression for surface‐impedance (Ey/Hx) have been evaluated at the earth's surface. Through numerical analysis it is shown that changes in the values of the parameters m (coefficient of anisotropy), h (thickness of the transition layer), α (angle of inclination of the dipping beds), and b (conductivity ratio between substratum and upper layer) modify the amplitude and phase‐variation curves (with skindepth) significantly.
MAGNÉTOMÈTRE DIFFÉRENTIEL À HAUTE SENSIBILITÉ*
Authors: COLLIN C. R. , SALVI A. , LEMERCIER D. , LEMERCIER P. , ROBACH F. 
Published: April 2006

AbstractThe aim of this article is to describe the double resonance magnetometer system designed and built by the Division de Magnétométrie of the C.E.N. Grenoble, and used by the Département des Recherches Minières du CE.A.For the measurement of magnetic anomalies of geological origin it is necessary to make differential measurements between a mobile instrument which scans the region of interest and a fixed compensatory instrument.The apparatus described here features the following main characteristics:— it gives a direct numerical measurement of the differential magnetic field between the two instruments with an accuracy of 0.01 gamma (10‐7 Oe).— it is designed to be easily operated in geological field work (light weight, low power, possibility to make continuous measurements along a given profile, the measuring signals being radio‐linked there are no wires connecting the instruments).Firstly we describe the components of the magnetometer itself namely: double resonance magnetometer heads and differential numerical magnetometer. Secondly we describe the measuring technique.