The immediate urge for gravity meter surveys in boreholes is the desire to improve the gravity method itself but there are other potential uses for data so obtained. Borehole gravity surveys, through the influence of density, would be related to numerous important rock properties such as the velocity of seismic waves, the coefficient of reflection, the electrical resistivity, lithology, porosity, and the kinds and states of fluids in the rock. Therefore, in addition to improvement in gravity prospecting, the data would bear upon seismic techniques and, depending on accuracy and detail, upon the interpretation of lithologic and electric logs. The more obvious of the possible uses are indicated and some of the problems and inherent limitations holding up development are discussed.
Certain qualifications of this report should be mentioned. In most parts of the text and tables crew‐months for quite different kinds of crews are added as though they were equivalent, i.e., conventional shooting is lumped with horizontal stacking, with nonexplosive sources, etc., digital recording is not distinguished from analog, marine crews are not separated from land crews, Sparker, Gas Gun, and explosive marine are not distinguished. No distinction is made between crews working a normal month and those, like bush and some marine, that may work a 30‐day month. A similar situation exists in the case of gravity. All this is somewhat like adding apples and oranges.
Petroleum geophysical exploration in the Free World, consisting of seismic, gravity, ground magnetic, and other nonairborne geophysical methods, rose 1.6 percent in 1963 over 1962. This is in contrast to the 10 percent drop between 1961 and 1962. It is the first upswing since 1956 and, however modest, is welcome. It is 30 percent down from the 1956 level. Airborne magnetometer activity rose nominally from 433,473 line‐miles in 1962 to 434,943 in 1963.
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