Project Mohole-Phase II, Stage 'A' Report, Magnetic Susceptibility and Magnetic Intensity Logging Tool

摘要

Tentative criteria were established for the magnetic susceptibility instrument and the magnetometer. Preliminary investigation of the applicable measurement techniques indicated that: (1) The flux-gate principle should be the technique used in the development program for the magentometer; (2) a multicoil magnetic susceptibility system should be developed for measuring rock susceptibility in the bore-hole; (3) the major problem in the development of both instruments would be the required operation of these instruments in the hostile Mohole environment. The more pertinent conditions imposed under which the instruments must operate were: within a 7 1/2-inch diameter bore-hole 35,000 feet deep, immersed in a highly conductive fluid, in ambient pressures up to 25,000 psi, in ambient temperatures up to 200C, and over a 42,000-foot 7-conductor logging cable. A development program for these instruments was initiated. The results of this development program were that: (1) A magnetometer could be built having the required accuracy and resolution while operating in the environment imposed by Mohole conditions; (2) a magnetic susceptibility instrument appears feasible, but additional work must be performed in determining the most optimum coil system. (Author)