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- Volume 7, Issue 1, 1959
Geophysical Prospecting - Volume 7, Issue 1, 1959
Volume 7, Issue 1, 1959
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AMMONIUM NITRATE: ECONOMY BLASTING AGENT FOR OIL EXPLORATION*
Authors T. O. HALL and J. MARTINAbstractMajor savings for operators of seismic parties have been achieved by the use of prilled ammonium nitrate as a substitute for gelatin dynamite in areas where shot holes are dry. Pound for pound, the prills appear to have the same energy yield as 60% gelatin dynamite, and some improvement of records has been noted where prills are used. Safety problems are less with ammonium nitrate than with dynamite, and the development of efficient field handling techniques prevents the loss of production.
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ASPECTS THÉORIQUESIET PRATIQUES DE LA DÉTERMINATION DES VITESSES D'INTERVALLE EN SISMIQUE RÉFLEXION*
Authors J. Y. CHEREAU and Y. LEDOUXAbstractConventional or continuous velocity logging generally fail to solve the problem of velocities in the whole area of a seismic survey. Surface measurements often bring a large amount of additional information: effect of shallow layers, change of facies, correlations. The authors present a theoretical view on the physical meaning of interval velocities. After a short synthesis of the diverse formulae formerly proposed (Faust, West), the practical manner of using these formulae and the accurate interpretation obtained with the help of geological and geophysical data are shown. Several characteristical examples are finally explained and commented on.
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LABORATORY DETERMINATIONS OF ELASTIC PROPERTIES OF SOME LIMESTONES
Authors J. KUIPER, W. M. L. VAN RYEN and O. KOEFOEDAbstractUsing a resonance method, determinations have been made of the longitudinal bar velocity and of Poisson's ratio of thirteen different chemically pure limestones. The relation between the velocity and the density showed far less scatter than in the determinations previously published; this is primarily attributed to the high purity of the specimens used. The measurements further showed a tendency of the values of Poisson's ratio to increase with increasing density.
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THE USE OF ELECTRONIC DIGITAL COMPUTORS FOR THE EVALUATION OF GRAVIMETRIC TERRAIN CORRECTIONS*
More LessAbstractA method is described in which the major part of gravimetric terrain corrections may be estimated by digital computing methods.
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SOME DEPTH FORMULAE FOR LOCAL MAGNETIC AND GRAVITY ANOMALIES
By R. A. SMITHAbstractSome mathematical inequalities are proved and their relevance to the interpretation of local magnetic and gravity anomalies is discussed. They can be applied to the readings of either a vertical magnetometer or a total field magnetometer or a gravimeter and yield a maximum possible value for the depth below the earth's surface of the top surface of the body producing the anomaly.
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THE FIELD OF A D. C. ELEMENT, APPLIED TO GONDUCTIVELY ENERGIZED PENCILFORMED ORE BODIES
More LessAbstractThe electric and magnetic field of a direct‐current element, embedded in a space consisting of two halfspaces differing in conductivity and permeability, is given in a form suitable for integration along a cable. From these formulae is obtained the field when one end of a D.C. cable is grounded in a highly conducting, pencilformed ore body, considered as a line electrode with uniform current leakage. Numerical examples are given for a horizontal line electrode. The formulae should be useful as a first approximation to the A.C. case. The validity of this is shortly discussed.
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IMPÉDANCES ET MATRICES CARACTÉRISTIQUES EN PROSPECTION ÉLECTROMAGNÉTIQUE*
By J. LOEBAbstractAn analogy is established between the propagation of an electromagnetic field in a horizontally stratified conductive medium and that of currents in a linear electric network. This analogy will allow us to know in which case measurements executed at the surface of the ground can provide information about the properties of deeper layers. The situation is the same as when one tries, by means of impedance measurements at the input terminals, to know the properties of electric lines or lumped networks.
A symmetrical linear network establishes between:
Voltages V1 and V2 (respectively at input and output terminals)
Currents I1 and I2 (respectively at input and output terminals), the relationship
is called the “phase constant” and Z the characteristic impedance The table
is called “characteristic matrix”
If one then takes the horizontal components of an electromagnetic field, one can compare the voltage V with the horizontal electric field E (in volts m‐1) and the current I with the horizontal magnetic field H (in Amp m−1)
For plane waves in vacuum, one gets (Schelkunoff)
Z=C (velocity of light)
A layer whose thickness is D has a phase constant
⌈= 2 πD/λ (λ= wavelength)
For plane waves in a conductive, non magnetic medium whose conductivity is δ, one gets
For the system of waves created by a point‐source one expresses the solution, since it is classical, as a sum or integral of different modes. For each of these modes, one can still write a bilinear relationship similar to (1), and calculate Z and ⌈.
A generalization of this result is given.
Boundary conditions that exist at the surfaces of separation are met by writing the continuity of E and H. This condition exactly corresponds to the fact that there one V and one I at the junctions of various sections of lines, or networks.
The characteristic matrix of a cascade of networks‐or here that of a horizontally stratified ground– is the product of the matrixes of each network. If, in addition, one knows the end impedance–here the conductivity λn of the last layer, supposed to be infinite–one can compute the input impedance Re of the whole system. In electromagnetic prospecting, it is Re that conditions the observable field.
Inversely, if measurements were infinitely accurate, the. knowledge of the surface field would give all the thicknesses D and conductivities δ of intermediate layers, in the same way that impedance measurements at the input terminals of a cable would allow to locate any failure. The imperfection of measurements causes the elements located too far away (from the point of view of wave attenuation) to escape detection.
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DIFFERENTIAL ELECTRIC LOG*
Authors U. COLOMBO, G. SALIMBENI, G. SIRONI and I. VENEZIANIABSTRACTA new logging method, which makes use of specific chemical reactions to locate petroleum or other minerals has been developed. The method has been named “Differential Electric Log” (CED).
In this paper the application to the CED method of redox (reduction/oxidation) reactions is discussed. A series of organic oxidants was found, capable of undergoing reaction with crude oil, sulphur, mineral sulphides, lignite. A small amount of an oxidant of this type is added to the drilling fluid and pumped into the borehole where reaction takes place in correspondence with layers containing oxidizable minerals. Two SP logs, recorded before and after the oxidation, are compared and the presence of such minerals is thus detected.
A theoretical hypothesis explaining the mechanism of the potential change due to the chemical reaction is proposed both in the case of electronically conducting and non conducting minerals. The influence of redox potential on SP is discussed.
The results of laboratory experiments on several different oxidizable ores and those of field tests performed on pyrite, lignite, and oil wells are reported on and discussed on the basis of the theoretical hypothesis proposed.
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ON THE DETECTION OF A SPRING OF MINERAL WATER AT BAD PETERSTAL, SCHWARZWALD, AS A RESULT OF PREVIOUS CO2– MEASUREMENTS IN THE GROUND AIR
By E. BUDDEAbstractIn nine small areas in the Black Forest measurements were made of the CO2 content of ground air, using a method which is based on the difference in heat conductivity between CO2 on one side and N2 and O2 on the other. Measurements during four days yielded four strong CO2 anomalies. At one of these a well was sunk, which gave a considerable discharge of mineral water.
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Volumes & issues
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Volume 72 (2023 - 2024)
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Volume 71 (2022 - 2023)
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Volume 70 (2021 - 2022)
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Volume 69 (2021)
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Volume 68 (2020)
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Volume 67 (2019)
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Volume 66 (2018)
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Volume 65 (2017)
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Volume 64 (2015 - 2016)
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Volume 63 (2015)
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Volume 62 (2014)
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Volume 61 (2013)
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Volume 60 (2012)
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Volume 59 (2011)
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Volume 58 (2010)
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Volume 57 (2009)
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Volume 56 (2008)
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Volume 55 (2007)
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Volume 54 (2006)
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Volume 53 (2005)
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Volume 52 (2004)
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Volume 51 (2003)
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Volume 50 (2002)
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Volume 49 (2001)
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Volume 48 (2000)
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Volume 47 (1999)
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Volume 46 (1998)
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Volume 45 (1997)
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Volume 44 (1996)
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Volume 43 (1995)
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Volume 42 (1994)
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Volume 41 (1993)
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Volume 40 (1992)
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Volume 39 (1991)
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Volume 38 (1990)
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Volume 37 (1989)
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Volume 36 (1988)
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Volume 35 (1987)
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Volume 34 (1986)
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Volume 33 (1985)
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Volume 32 (1984)
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Volume 31 (1983)
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Volume 30 (1982)
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Volume 29 (1981)
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Volume 28 (1980)
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Volume 27 (1979)
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Volume 26 (1978)
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Volume 25 (1977)
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Volume 24 (1976)
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Volume 23 (1975)
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Volume 22 (1974)
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Volume 21 (1973)
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Volume 20 (1972)
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Volume 19 (1971)
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Volume 18 (1970)
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Volume 17 (1969)
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Volume 16 (1968)
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Volume 15 (1967)
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Volume 14 (1966)
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Volume 13 (1965)
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Volume 12 (1964)
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Volume 11 (1963)
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Volume 10 (1962)
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Volume 9 (1961)
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Volume 8 (1960)
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Volume 7 (1959)
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Volume 6 (1958)
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Volume 5 (1957)
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Volume 4 (1956)
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Volume 3 (1955)
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Volume 2 (1954)
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Volume 1 (1953)