bluuebunny/crossref_metadata_2025 huggingface dataset:
AUTOMATED STATIC CORRECTIONS*
Authors: HILEMAN J. A. , EMBREE P. , PFLUEGER J. C.
Published: April 2006

The widespread use of common depth point techniques has emphasized the need for accurate static corrections. Manual interpretation methods can give excellent results, but a computer technique is desirable because of the great volumn of data recorded in common depth point shooting. The redundancy inherent in common depth point data may be used to compute a statistical estimate of the static corrections. The corrections are assumed to be time‐invarient, surface‐consistent, and independent of frequency. Surface consistency implies that all traces from a particular shot will receive the same shot static correction and all traces from a particular receiver position will receive the same receiver correction.

Time shifts are computed for all input traces using crosscorrelation functions between common depth point traces. The time shift for each trace is composed of a shot static, a receiver static, residual normal moveout if present, and noise. Estimates of the shot and receiver static corrections are obtained by averaging different sets of the measured time shifts. Time shifts which are greatly in error are detected and removed from the computations.

The method is useful for data which has a moderate to good signal to noise ratio. Residual normal moveout should be corrected before estimating the statics. The program estimates the statics for correctly stacking common depth point traces but it is not sensitive to constant or very slowly changing static errors.
PROTEE A SELF‐ADAPTING DECONVOLUTION AND DERINGING PROGRAM*
Authors: D'HOERAENE J. , WLODARCZAK R.
Published: April 2006

Deconvolution and deringing are well known subjects and it is not necessary to state again their objectives nor the basical methods used to reach them. Let us just remember that, generally, among many others, the two following assumptions are made for simplification purposes:

—for deconvolution, it is assumed that the recorded seismic signal is constant, meaning that its shape is the same all along the time interval during which the trace is to be deconvolved;

—for de‐ringing, it is assumed that the ringing period is constant and that the intensity of the ringing phenomenon is independant of the time.

With these two assumptions, a single constant operator can be applied for deconvolving, deringing or both. In most cases, the time variations of the signal or of the ringing are small enough and the error resulting of the application of a constant operator is acceptable. It results into a slight increase of the noise level or into a small residual ringing in the processed trace.

When this noise or the residual ringing are too important, the assumption of a constant signal and ringing period must be rejected. This is the case that is examined here according to the following steps:

—short definition of the problem;

—fast evaluation of some possible solutions;

—the selected solution: resulting approximations and how to obviate them, computing method and a remark about the operators;

—theoretical example: the efficiency of the process used is evaluated on data in which the results aimed at are known; the influence of the selection of numerical values to be assigned to the parameters is examined;

—real cases: comparison of results obtained with the Protee process and with more conventional processes assuming a time invariance or including a weighted composition of several conventional processes each with a different operator.
INTERPRETATION OF REFRACTED‐DIFFRACTED WAVES DUE TO DYKES*
Authors: FACSINAY LÁSZLÓ , SÁGHY GYÖRGY
Published: April 2006

This paper gives an interpretation of a specific type of refracted‐diffracted waves. The solution is supported by the good accord of data in seismic and magnetic interpretation. Beyond solving the problem of the phenomenon, the interpretation of such events shows that in the exploration of dykes and intruded formations the refracted‐diffracted waves can—under favourable conditions—also render some useful information.
SEISMIC REFRACTION MEASUREMENTS IN THE BALTIC SEA*
Authors: BUNCE ELIZABETH T.
Published: April 2006

Abstract

Seismic refraction measurements were made in two areas of the Baltic Sea in June 1967. The refraction data were obtained in the course of the transmission measurements program of Operation MILOC BALTIC 67.

Three profile pairs were obtained, two in the area south of Öland Island, Sweden, the third to the east, north of the peninsula of Hel, Poland. The water depths vary from 60 to 90 meters between the areas.

The receiving positions for the two profiles south of Oland Island are only 46 km apart but the structures differ markedly. The northern section, only 500 m thick, shows a rather thin sedimentary cover above 350 m of 3.7 km/sec material that in turn overlies 5.6 ‐ 5.9 km/sec velocity material. The southern section, almost 2 km thick, has an equivalent amount of low velocity material, and a layer about 1 km thick having velocity 4.8 km/sec that overlies 6.0 km/sec velocity material. The eastern profile shows high velocity material, 5.6 km/sec, at 2.5 km depth.

Correlation of the layers determined by seismic refraction with nearby geology suggests that the structural change south of Öland Island may represent the boundary of the Sarmatian Shield in this region.
THEORETICAL RESISTIVITY ANOMALIES ACROSS A SINGLE VERTICAL DISCONTINUITY
Authors: AL‐CHALABI MAHBOUB
Published: April 2006

Abstract

Electrical resistivity anomalies of a symmetrical four‐electrode co‐linear system across a single vertical discontinuity are treated in relation to: a) the ratio of potential electrode separation to the current electrode separation that are employed in the system and b) the angle which the electrode alignment makes with the discontinuity. Several conclusions are extracted from this treatment and methods for obtaining an optimum sensitivity of the system, with respect to these parameters, are shown. Disadvantages of special arrangements, such as the Wenner configuration, are indicated. Methods are outlined to utilise variations in the apparent resistivity plot for determining the angle between the electrode alignment and the discontinuity, quantitatively or qualitatively. These variations include certain deviations from the standard curves obtained in longitudinal traverses made at right angles to the discontinuity. Also, a comparison is made between longitudinal and cross traverses, in relation to the discontinuity.
CONTRIBUTION DU TRAITEMENT NUMERIQUE A L'ANALYSE ET A INTERPRETATION DES ENREGISTREMENTS REFRACTION*
Authors: PERALDI R.
Published: April 2006

Abstract

The tools used in digital processsing have received little application, to date, to refraction seismic.

It seems however that some problems encountered in the analysis of refraction records could be solved through techniques which are of common use in processing of reflection seismic data (correlation, stacking, f and k filtering).

The experiments made with some of these techniques revealed the possibility of a more complete refraction record analysis, allowing the study of later arrivals.

The interpretation of these records could also, to a fairly large extent, be automated by means of digital processing.

While recording, some care ought to be taken to allow identification and interpretation by digital processing of as many events as possible. However, the results shown here have been obtained from fairly old analog records, for which no particular care had been taken, which makes it possible to complete and revise the interpretation of previous studies using the same processing techniques.

Long line refraction shooting is justified for marine surveys in some areas, particularly where reflection is disturbed by singing; improvements in analysis and interpretation would therefore prove very useful for a faster and more thorough interpretation.
IDENTIFICATION OF SEA‐FLOOR SEDIMENTS USING UNDERWAY ACOUSTICS*
Authors: LI W. N. , SMITH D. TAYLOR
Published: April 2006

Abstract

Laboratory measurements, and a few in situ observations, show that saturated marine sediments have interdependent mechanical and acoustical properties, Acoustically, of particular importance are the acoustic impedance, velocity of sound and the sound attenuation coefficient of the sediment. The first two properties can be measured relatively easily from a surface ship; the measurement of attenuation however, is more problematical. It is suggested that this can be achieved by a quantitative treatment of the acoustic data collected during routine sub‐bottom profiling over a variable thickness of superficial sediments. In the assessment of four different sediment locations in the Irish Sea it was found that quantitative treatment of the acoustic signals yielded both a value of the attenuation coefficient as well as a measure of the frequency dependence of the attenuation. In addition a statistical analysis of the signal intensities seems to provide an indication of the relative roughness of the bottom and sub‐bottom interfaces. From the wide range of information provided the mechanical properties of the sea‐floor sediment may be estimated.
AERIAL RADIOMETRY OF EL ALAMEIN OILFIELD, EGYPT, U.A.R.*
Authors: EL SHAZLY E. M. , MESHREF W. M. , FOUAD K. M. , AMMAR A. A. , MELEIK M. L.
Published: April 2006

Abstract

Total gamma airborne radiometric survey of El Alamein area in the Western Desert has been carried out by the Atomic Energy Establishment. The flight lines are directed north‐south with 500 m spacing, while the ground clearance is about 50 m. Superimposition of the radioactivity profiles over El Alamein Oilfield shows a general decrease of gamma radiation in the central part of the structure framed by zones of relatively higher values. The aerial radioactivity of El Alamein Oilfield is described and it is correlated with some reported radiometric characteristics of other oil bearing structures. The distribution of aeroradiometric measurements over El Alamein Oilfield and its environment has been found to be lognormal.
INTERPRÉTATION DIRECTE DES COURBES DE SONDAGE ÉLECTRIQUE ET LE PROBLÈME DE DIFFÉRENTS DISPOSITIFS DE MESURE *
Authors: SZARANIEC EDWARD
Published: April 2006

Direct interpretation methods of resistivity curves are discussed, which use the kernel function of the apparent resistivity. This function results from the consideration of the problem of diverse electrodes configurations.

Several expressions for the determination of the kernel function of the potential from the kernel function of the apparent resistivity are given.
FIXED SOURCE SYSTEM IN A CONDUCTIVE ENVIRONMENT *
Authors: BEZVODA VÁCLAV
Published: April 2006

Measuring systems with a fixed source fed with alternating current at sound frequency are used almost exclusively at the present time for a quick search for conductive zones in an environment with a high specific electrical resistivity. Owing to this fact it is useful to measure in a gradient configuration, i.e. to compare the quantities of the corresponding parameters of the field in two relatively close points oriented in the direction of the assumed change of the field. In this way we can obtain a suppression of the impact of the wider environment, since, in principle, we record the first derivative, i.e. the amount of the change only.

The present article points out some possibilities of the application of the system with a fixed source in non‐magnetic environment with arbitrary resistivity.
SIGNAL ET BRUIT EN MAGNETOTELLURIQUE *
Authors: CHAIZE L. , LAVERGNE M.
Published: April 2006

Les precédés classiques permettant de reconnaître le signal magnétotellurique à travers les bruits sont rappelé: en particulier les bruits ? enregistrement, ou ayant leur origine au voisinage immédiat des déecteurs, sont éiminés par les procédés classiques ? autoet intercorrélation. Ľ identification des bruits cohérents est beaucoup plus délicate: par exemple les pulsations provenant de sources de champs dont ľ uniformitéň atteint pas au moins une centaine de kilomètres en prospection pétrolière, un millier de kilomètres en physique du globe.

Un grand nombre ? enregistrements des 5 composantes, Hx, Hy, Hz, Ex, Ey, du champ magnétotellurique ont été effectués en France à différentes périodes de ľ année, (a) dans des champs de source non uniformes au voisinage de lignes de traction électrifiées et de lignes de transport ?énergie, et (b) dans des zones à forte variation latérale de résistivité sur les flancs de grosses structures et au bord de la mer.

Les moyens pour repérer la non‐uniformité sont étudiés. La mesure de la composante verticale des pulsations magnétiques est un bon procédé pour estimer ľ uniformité du champ. Si H vertical/H horizontal est inférieur à 10%, on peut pratiquement supppser ľ uniformité et appliquer les formules classiques de restitution des résistivités vraies. Si H vertical/H horizontal est supérieur à 10% il n'y a pas uniformité et il est difficile de savoir si la non‐uniformité est due à un champ de source non uniforme ou à des hétérogénéités ou anisotropies autour du point de mesure. Différents procédés permettant de lever cette indétermination sont donnés.

La précision de la restitution des profondeurs en fonction de la précision des mesures des résistivités apparentes est étudée.
AN ELEGANT, UNIVERSAL NOMENCLATURE FOR ELECTROMAGNETIC MOVING SOURCE‐RECEIVER DIPOLE CONFIGURATIONS *
Authors: PARASNIS D. S.
Published: April 2006

The transmitter and receiver coils and the line joining them in an electromagnetic moving source‐receiver system can, in principle, have an infinity of mutual orientations. Let the direction of a survey line (traverse direction) be x and let the vertical plane through it be the x‐z plane and let the z‐axis be a line in this plane perpendicular to the z‐axis, then the y‐axis of an orthogonal coordinate system is automatically determined. A definite coordinate system, dependent on the mutual coil orientation alone, and independent of the spatial direction of the survey line or alterations in it, is thus associated with each point. The geometry of a moving source‐receiver configuration is uniquely defined by specifying (i) the direction cosines a, b, c of the transmitter coil axis T, (2) the direction cosines d, e, f of the line L joining the transmitter and the receiver coils and (3) the direction cosines g, h, i of the receiver coil axis R. Hence a set of indices conveniently written as T a, b, c L d, e, f R g, h, i describes the geometry and also enables “reconstruction” of the system uniquely and without the risk of confusion inherent in such incomplete descriptions as “vertical coil system”, “horizontal coil system” etc. Degeneracy arises if the traverse direction is vertical. How this is overcome is described in the paper. To the above indices may be appended the indices T, the distance between T and R and v, the frequency.

For example, the most common “horizontal coplanar coil system” has the indices T 001 L 100 R 001. An airborne wing‐tip system with coil axes in the flight direction is specified by T 100 L 010 R 100. Other examples are given in the paper. Maps and data sheets of moving source‐receiver systems should be marked with the appropriate set of indices.
PROSPECTING BY THE GEOTHERMIG METHOD*
Authors: KRČMÁŘ B. , MAŠÍN J.
Published: April 2006

Abstract

A high sensitivity thermometer using a thermistor sensing element was designed for practical measurements in the field.

The most suitable procedures for the elimination of diurnal and seasonal variation of temperature, the influence of vegetation cover and of other effects were investigated.

Positive results of geothermic measurements have been acquired on sulfide deposits. By far the most important results of geothermic measurements have been obtained in hydrogeological problems, e.g. the investigation of circulation of underground water. In the case of prospection for cold mineral waters the combination of geothermic measurements with gasometric analyses is very useful. As the classical domain for geothermic investigation, prospection for hot water is to be mentioned.
DIAGRAMS FOR THE EVALUATION OF PROTON MAGNETOMETER READINGS*
Authors: ZAGORAC ŽELJKO
Published: April 2006

Abstract

Two alternative types of diagrams are shown which allow the direct conversion of readings taken by certain types of proton magnetometers into magnetic field strength. The accuracy of these diagrams is discussed and found to satisfy the requirements.
EARTH CRUST INVESTIGATION USING CONVERTED WAVES*
Authors: DRAGAŠEVIĆ T.
Published: April 2006

Abstract

The conditions for creating and recording converted waves in the area of the Panonien basin are considered. Comparison between the characteristics of converted waves recorded in the field and characteristics of converted waves calculated for the model which approximately corresponds to lithophysical conditions of the area is made.

The comparative interpretation of the crustal structure along the profile, using different types of waves, is given.
ON THE ELECTRICAL BEHAVIOUR OF A POLARIZABLE SAMPLE STUDIED BY THE NORMALIZED TIME‐INTEGRAL AND BALLISTIC METHODS*
Authors: FINZI‐CONTINI GIOVANNI
Published: April 2006

Abstract

In this paper the experimental data obtained studying the decay of a sample of pisolitic bauxite both by a ballistic method and the normalized time‐integral procedure are compared.

This comparison allowed me to note two peculiarities. First, the apparent capacitance of the sample, as well as its normalized time‐integral, seems to show a characteristic behaviour within the same interval of the charging time. Secondly, while the apparent capacitance plotted versus time (measured from the energization interruption instant) appears to assume values which seem to tend towards asymptotic value of the apparent capacitance, it is to be noted instead that in these circumstances the relative normalized time integral shows no tendency to reach any limiting value.
ETINCELEURS MULTIELECTRODES A HAUTE RESOLUTION*
Authors: CASSAND J. , LAVERGNE M.
Published: April 2006

Resume

Les étinceleurs àélectrodes multiples, permettent ?améliorer considérablement la finesse de la sismique à haute resolution.

Un pouvoir séparateur de ľordre de 2 mètres peut être obtenu jusqu'à une profondeur de l'ordre de 150 mètres avec des étinceleurs à 1000 joules, comportant quelques centaines ?électrodes. Plusieurs enregistrements sont présentéd.
SISMIQUE REFLEXION EN EAU PROFONDE*
Authors: CASSAND J. , FAIL J. P. , MONTADERT L.
Published: April 2006

Résumé

On présente des profils de sismique réflexion obtenus dans la partie Sud‐Est du Golfe de Gascogne en eau profonde avec raccordement au plateau continental.

La technique employée était celle du Flexotir à un ou deux canons en couverture triple. La charge totale par tir était égale à 50 ou 100 grammes suivant les cas. La vitesse du navire était ?environ 6,5 nœuds, ce qui a permis de couvrir 1000 kilomètres de profil en 9 jours de travail. La distance entre traces sur les coupes est de 60 mètres, ce qui per‐met une étude assez détaillée.

De bons résultats ont été obtenus par des fonds allant jusqu à 4000 mètres. La pénétration sous le fond atteint souvent 5 secondes (temps double).

Le Flexotir constitue une méthode de prospection sismique bien adaptèe àľocéano‐graphie de grande reconnaissance.
DIRECT LOCATION OF OIL AND GAS BY THE SEISMIC REFLECTION METHOD*
Authors: PAN POH‐HSI , DE BREMAECKER J. CL.
Published: April 2006

Abstract

The seismic velocity of sedimentary rocks is determined by the porosity, the velocity in the matrix and that in the fluid. The last two are known experimentally. The velocity can be measured from the surface. By applying the time average equation we can find the porosity. If the only difference at two points is the nature of the fluid in one layer, the ratio of the reflectivities of the layer at these points determines the nature of the fluid; this ratio is equal to the ratio of the amplitudes at these points. The size of the reservoir can then be found.

The method can be applied to both oil exploration and production. It is more accurate in the latter case because more information is available than in the former case. The method is also more effective in developing discovered fields than the conventional method of relying only on the geological structural configurations.
AN ELECTRICAL RESISTIVITY PROFILE IN HAWAII WITH NOVEL ELEVATION CORRECTION*
Authors: ADAMS Wm. MANSFIELD
Published: April 2006

Abstract

In order to locate relatively optimum sites for drilling exploratory holes for fresh water, an electrical resistivity survey was conducted along the new Mahukona‐Kawaihae Road on the west flank of the Kohala Mountain. Two resistivity soundings made at the same stations, using the Schlumberger electrode configuration, determined an a spacing of 275 feet for horizontal profiling with the Wenner array.

The correlation coefficient of the elevation to profile data was 0.41. A procedure for removing elevation effect from observed apparent resistivity was developed. Based on the reduced resistivity profile, four relatively optimum sites for additional exploration, such as by drilling, are specified. There is no specific interpretation of the data that can definitely indicate the occurrence of large underground reservoirs of fresh water anywhere along the profile. This is because the interpretation of horizontal profiling data is essentially relative and not absolute.
LA RESISTIVITE APPARENTE COMME TRANSFORMATION LINEAIRE DU POTENTIEL ET LA TRANSFORMATION INVERSE*
Authors: SZARANIEC EDWARD
Published: April 2006

Abstract

The apparent resistivity is considered as a linear transformation of the potential by an operator in the form of an infinite matrix A. The inverse transformation expresses the potential as a function of the apparent resistivity or of the difference of potentials. It is found by calculation of the inverse matrix‐1A. The relation between apparent resistivities for different arrays is expressed as a product of transformations.
CORRELATION OPTIQUE EN LUMIERE COHERENTE*
Authors: FONTANEL A. , GRAU G.
Published: April 2006

Abstract

Fontanel, A., G. Grau, 1971, Corrélation optique en lumière cohérente, Geophysical Prospecting 19, 98–117.

This paper describes a general bidimensional two‐step method of correlation (or convolution) making use of the theory of holography.

In the first step the light diffracted by one of the two plane transparent objects to be correlated interferes with the light diffracted by the other one. The hologram thus generated is photographed in the focal image plane of a convergent lens. Owing to the quadratic detection property of the photographic emulsion, the square of the modulus of the product of the spectra of the two objects considered is recorded on the photographic plate.

In the second step the convolution product of the two objects appears when the hologram is illuminated with a beam of coherent light.

In its geophysical application this optical method of convolution makes it easy for us to obtain the autocorrelogram of a seismic cross‐section. This method also makes it possible to correlate each of the seismic traces by special precalculated optically‐recorded filters.
THE INFLUENCE OF INDUSTRIAL STRAY CURRENTS ON THE MEASUREMENT OF EARTH POTENTIALS AND THEIR ELIMINATION*
Authors: FRÖHLICH R. K.
Published: April 2006

Abstract

Simultaneous observations of electrical earth‐potentials along parallel measuring lines offer a simple but useful method to study telluric and stray‐current potentials. Different correlation‐factors between the records of both observation points can help to separate telluric from industrial stray‐current potentials. A method is suggested to eliminate disturbing impulses of stray currents from continuous telluric current recordings as those made at observatories.

The influence of stray currents can also be eliminated from potential readings of an artificial current as applied in geoelectric measurements with the four‐point‐method. The elimination is possible by a simultaneous observation of the stray‐current potentials on an equipotential line of the artificially generated field. The recording examples show an appreciable improvement of the signal‐noise ratio without increase in the current. The method is useful for geoelectrical prospecting in areas which are contaminated by industrial noise.
A CONTROL OF TWO‐DIMENSIONAL MAGNETIC INTERPRETATION BY THREE‐DIMENSIONAL MODEL BODY ANOMALIES*
Authors: LEHMANN HANS‐JÜRGEN
Published: April 2006

Abstract

In magnetic routine interpretation the comparison of two‐dimensional model curves with measured magnetic anomalies is widely used for an approximate evaluation of the position and depth of magnetic models.

Before starting an interpretation of a survey by means of two‐dimensional models, it is very useful to have an idea of the shape of anomalies caused by extended but finite bodies, taking into account various strike directions: Three sets of anomalies of thin plates (horizontal length 19, downward length 9, width 1) dipping 30°, 60°, and 90° resp. for various strike directions and an inclination of 20° were computed. Some of these anomalies, e.g. those with nearly N‐S strike direction look rather complicated, and at the first glance one would not expect that they are caused by such simple bodies.

Several profiles crossing the computed anomalies perpendicularly were interpreted two‐dimensionally. For less extended anomalies the depths determined for the top of the plates are 10‐20% too small, the magnetization amounts to 50–75 % of the value of the finite bodies. The interpretation of the profiles covering more extended anomalies gave very accurately the same values for the position, depth and magnetization for the two‐dimensional body as for the original three‐dimensional model.

Anomalies of vertical prisms with varying extensions in the y‐direction were computed. Their differences in amplitude and in the distance maximum‐minimum show that interpretation of short anomalies by two‐dimensional methods yields depth errors of up to 20 percent.

To see the possibilities of the separation of superimposed anomalies dike anomalies were added to the anomaly of a broad body in great depth and several attempts were made to interpret parts of the composite anomalies. The interpreted bodies lie too deep. In complicated cases the depth values can have large errors, but experienced interpreters should be able to keep the errors in the range of one third of the depth values.
CONTRIBUTION TO SIGNAL BY ELEMENTS OF THIN VERTICAL CONDUCTING VEIN IN DIPOLAR EM SYSTEMS*
Authors: ROY A. , JAIN SHEEL C.
Published: April 2006

As an extension of the eddy current pattern computed by Koefoed and Kegge (1968) for a thin vertical infinitely‐conducting half‐plate in presence of oscillating magnetic dipoles, this paper computes the contribution to the (electro‐) magnetic anomaly at the receiver by each element of the vein separately. Twelve contour diagrams for such elemental contributions are presented as samples. Two points of general interest stand out: (1) The contributions from different portions of the vein are not all of one sign; the contribution from one part may cancel that from another; and (2) The portion of the vein nearest to the transmitter‐receiver system does not necessarily make the largest contribution to the total measured signal.
PREDICTION ERROR FILTERS, WHITE NOISE AND ORTHOGONAL COORDINATES*
Authors: DOUZE E. J.
Published: April 2006

Abstract

Optimum filters can be computed using orthogonal coordinates obtained from the eigenvalues and eigenvectors of the autocorrelation matrix. The method is used to obtain unit distance prediction error filters. The output of a unit distance prediction error filter when applied to the input wavelet is an impulse at zero time. The effect on the output of added white noise is easily obtained using the approach through the orthogonal coordinates. The added white noise results in output wavelets which are no longer impulses at zero time. The decrease in time resolution gives a filter that does not increase undesirable high frequency noise as much as filters computed without white noise.

Orthogonal coordinates with little signal energy can be omitted from the filter computation resulting in output wavelets resembling those computed using added white noise.
RAPID NUMERICAL EVALUATION OF TWO‐DIMENSIONAL GRAVITY PROFILES*
Authors: LONGMAN M. J. , LEAMAN D. E.
Published: April 2006

A precise method of gravity interpretation is described which uses tables for the attraction of rectangular prisms in all positions relative to a given point. Hence the attraction of any body or combination of bodies may be assessed without complicated mathematical procedures.
REVIEW ON THE BASIC THEORETICAL ASSUMPTIONS IN SEISMIC DIGITAL FILTERING*
Authors: FINETTI I. , NICOLICH R. , SANCIN S.
Published: April 2006

Abstract

A review of the most significant mathematical properties of digital operators and an introduction to their important applications to seismic digital filtering is given.

Basic definitions in the time‐series field and the principles of digital filtering are introduced starting from the Z‐transform domain.

Predictive decomposition for stationary stochastic processes and inverse operators are also discussed.

Applications of digital filtering to seismic signal concern the predictive deconvolution, characteristics of dispersive and recursive operators, matched filters, and multichannel operators.

A brief discussion on frequency, wave number, and velocity filtering phylosophy is given at the end of the paper.
SELECTION OF SEISMIC PICKING BASED UPON THE DIP, MOVE‐OUT AND AMPLITUDE OF EACH EVENT*
Authors: GAROTTA ROBERT
Published: April 2006

Abstract

The 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

Abstract

In 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

Résumé

L'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

Abstract

The 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

Abstract

The 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

Abstract

Boundary‐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

Resume

La 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

Abstract

Design 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

Abstract

An 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

Abstract

The 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.
TWO‐DIMENSIONAL MASS DISTRIBUTIONS FROM GRAVITY ANOMALIES*
Authors: QURESHI I. R. , IDRIES F. M.
Published: April 2006

Abstract

The oscillatory character of the solution obtained by Qureshi and Mula's method for the direct determination of two‐dimensional mass distributions from gravity anomalies is examined.
INTERPRETATION OF THE GRAVITY ANOMALY OVER A CAUSATIVE BODY WITH CIRCULAR SYMMETRY*
Authors: PAUL M. K.
Published: April 2006

Abstract

The 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

Abstract

A 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

Abstract

The 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

Abstract

Mit 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

Abstract

A 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

Abstract

Velocity 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

Abstract

The 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.