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  • Society of Exploration Geophysicists  (8)
  • Physics  (8)
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  • Society of Exploration Geophysicists  (8)
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  • Physics  (8)
RVK
  • 1
    Online Resource
    Online Resource
    Society of Exploration Geophysicists ; 2003
    In:  GEOPHYSICS Vol. 68, No. 5 ( 2003-09), p. 1510-1518
    In: GEOPHYSICS, Society of Exploration Geophysicists, Vol. 68, No. 5 ( 2003-09), p. 1510-1518
    Abstract: Field and numerically simulated data show that coplanar induction measurements (σ xx and σ yy ) are affected by both conductive and resistive muds. The effect is, for a resistivity contrast of 10 or less between the formation and mud, approximately proportional to the resistivity contrast. The borehole effect is generally stronger for a decentralized tool. In the perpendicular eccentricity mode, the eccentricity effect on σ xx or σ yy can be greater than 100% of the true formation responses. We demonstrate that dual‐frequency processing can reduce the eccentricity effect by an order of magnitude. We investigate the effect of invasion for both circular and elliptic invasions. For circular invasion, the effect on σ xx , σ yy , or the coaxial measurement (σ zz ) is characterized by a critical invasion thickness. For invasion thinner than the critical thickness, the effect is minimal. The effect increases rapidly as invasion thickness increases beyond the critical thickness. For elliptic invasion, both the σ xx and σ zz responses are similar to those of the corresponding inner circular invasion. Beyond a long‐to‐short‐axis ratio of three, an elliptic invasion behaves like a long, thin fracture.
    Type of Medium: Online Resource
    ISSN: 0016-8033 , 1942-2156
    RVK:
    Language: English
    Publisher: Society of Exploration Geophysicists
    Publication Date: 2003
    detail.hit.zdb_id: 2033021-2
    detail.hit.zdb_id: 2184-2
    SSG: 16,13
    Library Location Call Number Volume/Issue/Year Availability
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  • 2
    Online Resource
    Online Resource
    Society of Exploration Geophysicists ; 1968
    In:  GEOPHYSICS Vol. 33, No. 3 ( 1968-06), p. 481-488
    In: GEOPHYSICS, Society of Exploration Geophysicists, Vol. 33, No. 3 ( 1968-06), p. 481-488
    Abstract: During an investigation of alluvium using a shallow refraction seismograph, time‐distance curves obtained indicated two refraction interfaces. The shallower of the interfaces is the ground‐water table, whose depth was obtained with an accuracy of ±10 percent. The deeper interface is either the surface of the bedrock or the base of the weathered zone on the bedrock. If this lower interface is the surface of the bedrock, the velocity of seismic waves in the weathered material will be considerably lower than if the interface is the base of the weathered zone. Using this criteria makes it possible to determine whether the seismic wave is refracted from the surface of the bedrock or the base of the weathered zone.
    Type of Medium: Online Resource
    ISSN: 0016-8033 , 1942-2156
    RVK:
    Language: English
    Publisher: Society of Exploration Geophysicists
    Publication Date: 1968
    detail.hit.zdb_id: 2033021-2
    detail.hit.zdb_id: 2184-2
    SSG: 16,13
    Library Location Call Number Volume/Issue/Year Availability
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  • 3
    Online Resource
    Online Resource
    Society of Exploration Geophysicists ; 1975
    In:  GEOPHYSICS Vol. 40, No. 3 ( 1975-06), p. 527-529
    In: GEOPHYSICS, Society of Exploration Geophysicists, Vol. 40, No. 3 ( 1975-06), p. 527-529
    Abstract: Comparison between measurements on spheres and cylinders shows that a short cylinder with axial ratio (length/diameter) ≃0.9 and susceptibility ≃0.8 (cgs) has an effective demagnetizing factor N ≃ 3.7 both in the axial and radial directions. Hence, for a short cylinder with high susceptibility, the sum of the effective demagnetizing factors in three mutually perpendicular directions is less than 4π. This is important to know e.g., when determining the magnetic properties of highly magnetic magnetite ore samples.
    Type of Medium: Online Resource
    ISSN: 0016-8033 , 1942-2156
    RVK:
    Language: English
    Publisher: Society of Exploration Geophysicists
    Publication Date: 1975
    detail.hit.zdb_id: 2033021-2
    detail.hit.zdb_id: 2184-2
    SSG: 16,13
    Library Location Call Number Volume/Issue/Year Availability
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  • 4
    Online Resource
    Online Resource
    Society of Exploration Geophysicists ; 1953
    In:  GEOPHYSICS Vol. 18, No. 4 ( 1953-10), p. 894-907
    In: GEOPHYSICS, Society of Exploration Geophysicists, Vol. 18, No. 4 ( 1953-10), p. 894-907
    Abstract: The theory and practical application of the second derivative method of gravity interpretation have been discussed by Elkins (1951) in a very interesting paper based partly on an earlier paper by Peters (1949). In this paper, Elkins shows how the second derivative may be computed at the center of a series of concentric circles using the arithmetic means of the gravity values, assumed to be continuous, around each circle. A method is here proposed which does not use a continuum of gravity values but instead requires only a series development. The approximation formulas needed for the routine calculations can be derived by a method different from that of Elkins and the least squares adjustments he used can be dispensed with. Two hypothetical examples using the formulas derived by the series method are given and the results are compared with those computed by Elkins’ formula.
    Type of Medium: Online Resource
    ISSN: 0016-8033 , 1942-2156
    RVK:
    Language: English
    Publisher: Society of Exploration Geophysicists
    Publication Date: 1953
    detail.hit.zdb_id: 2033021-2
    detail.hit.zdb_id: 2184-2
    SSG: 16,13
    Library Location Call Number Volume/Issue/Year Availability
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  • 5
    Online Resource
    Online Resource
    Society of Exploration Geophysicists ; 1968
    In:  GEOPHYSICS Vol. 33, No. 6 ( 1968-12), p. 1020-1021
    In: GEOPHYSICS, Society of Exploration Geophysicists, Vol. 33, No. 6 ( 1968-12), p. 1020-1021
    Abstract: Mr. Sendlein’s discussion suggests two errors in the author’s paper. These were errors in the plotting of the data and not in the data itself. In reply to Mr. Sendlein, the following three items will be discussed: 1. The method of determination of velocities from the time distance curve; 2. Reliability of velocities determined; and 3. The interpretation of the time‐distance curve for station 87+00.
    Type of Medium: Online Resource
    ISSN: 0016-8033 , 1942-2156
    RVK:
    Language: English
    Publisher: Society of Exploration Geophysicists
    Publication Date: 1968
    detail.hit.zdb_id: 2033021-2
    detail.hit.zdb_id: 2184-2
    SSG: 16,13
    Library Location Call Number Volume/Issue/Year Availability
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  • 6
    Online Resource
    Online Resource
    Society of Exploration Geophysicists ; 1953
    In:  GEOPHYSICS Vol. 18, No. 4 ( 1953-10), p. 909-912
    In: GEOPHYSICS, Society of Exploration Geophysicists, Vol. 18, No. 4 ( 1953-10), p. 909-912
    Abstract: The errors involved in the second derivative coefficient sets of Elkins and myself are not as divergent as one would expect from the respective standard deviation figures, [Formula: see text] and [Formula: see text] , given by the authors of the discussion.
    Type of Medium: Online Resource
    ISSN: 0016-8033 , 1942-2156
    RVK:
    Language: English
    Publisher: Society of Exploration Geophysicists
    Publication Date: 1953
    detail.hit.zdb_id: 2033021-2
    detail.hit.zdb_id: 2184-2
    SSG: 16,13
    Library Location Call Number Volume/Issue/Year Availability
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  • 7
    Online Resource
    Online Resource
    Society of Exploration Geophysicists ; 1966
    In:  GEOPHYSICS Vol. 31, No. 3 ( 1966-06), p. 630-637
    In: GEOPHYSICS, Society of Exploration Geophysicists, Vol. 31, No. 3 ( 1966-06), p. 630-637
    Abstract: Six American geophysicists spent three weeks in the U.S.S.R. during the early fall of 1965 as members of an exchange delegation in petroleum geophysics set up under the terms of a treaty on technical exchanges between the U. S. and the U.S.S.R. The group visited eleven different activities located in four cities, Moscow, Oktyabr’skiy, Krasnodar, and Leningrad. These activities included a number of geophysical and geological research institutes, the Moscow State University, and the Gubkin Institute. The principal difference between exploration geophysics in the U.S.S.R. and in the Western countries is the great emphasis in Soviet oil exploration on regional studies as a preliminary to the more direct search for petroleum deposits. As a result of such emphasis, their exploration program involves much greater use than ours of long refraction lines, electrical prospecting, and aeromagnetic surveys with close line spacing. Reflection work follows conventional lines without such recent refinements as common depth point shooting, impact sources, or vibrators. A possible reason these newer field techniques are not used is that no processing equipment appears to be generally available for compositing signals from more than one tape on to a single channel. Seismic shear waves generated at the surface have given reflections from depths as great as 5,000 ft but they have thus far been used only on an experimental basis. A technique of recording “exchange” (PS) waves from earthquakes has been employed for mapping basement depths in regional investigations.
    Type of Medium: Online Resource
    ISSN: 0016-8033 , 1942-2156
    RVK:
    Language: English
    Publisher: Society of Exploration Geophysicists
    Publication Date: 1966
    detail.hit.zdb_id: 2033021-2
    detail.hit.zdb_id: 2184-2
    SSG: 16,13
    Library Location Call Number Volume/Issue/Year Availability
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  • 8
    Online Resource
    Online Resource
    Society of Exploration Geophysicists ; 1967
    In:  GEOPHYSICS Vol. 32, No. 2 ( 1967-04), p. 302-310
    In: GEOPHYSICS, Society of Exploration Geophysicists, Vol. 32, No. 2 ( 1967-04), p. 302-310
    Abstract: Gish‐Rooney type electrical resistivity equipment was employed to map the location and structural attitude of gilsonite veins in the Uinta Basin, southeast of Vernal, Utah. Horizontal profiles at right angles to the strike of the dike‐like gilsonite veins were made using the Wenner electrode configuration. Very sharp anomalies with a peak apparent resistivity value of the order of 20,000–25,000 ohm‐cm were observed. The peak values were measured over the center of the vein, but smaller auxiliary highs were also observed, symmetrically spaced on each side of the vein. The position of the auxiliary high varied as a function of the electrode spacing and was found to occur when the current stake was located in the gilsonite. The observed field profiles were compared with various theoretical profiles computed from theoretical apparent resistivity expressions derived through the use of images. The best correlation was obtained when the theoretical model was assumed to have an infinite resistivity relative to that of the surrounding material. This correlation supports the conclusion that the gilsonite veins, because of their extremely large resistivity and their vertical attitude, act as a vertical insulating sheet to the flow of electrical current in the ground.
    Type of Medium: Online Resource
    ISSN: 0016-8033 , 1942-2156
    RVK:
    Language: English
    Publisher: Society of Exploration Geophysicists
    Publication Date: 1967
    detail.hit.zdb_id: 2033021-2
    detail.hit.zdb_id: 2184-2
    SSG: 16,13
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
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