Spontaneous potential log apparatus with randomly occurring noise

Abstract

In the disclosed and illustrated embodiment, an improved method and apparatus for obtaining an improved spontaneous potential log is set forth. On a single sonde, multiple spontaneous potential electrodes, aligned vertically along the length of the sonde at spaced location, are positioned to transverse a well bore as the sonde is pulled from the well to obtain a measure of spontaneous potential from each electrode. The apparatus and method further discloses means multiplexing the signals from the several spontaneous potential electrodes whereupon the signals are converted by an analog to digital converter into digital words. By synchronizing with the multiplexing, a digital word is obtained for each electrode at a time such that such electrode is read at a common elevation. The several digital words are then input to delay lines, there being one delay line for each electrode, wherein the delay occurs in multiples of T where T equals the time delay between electrodes. The data is thus time shifted (equal to well depth shifting) so that the spontaneous potential measured at a particular elevation for each electrode is synchronized to thereby permit addition of all the data. Randomly occurring noise is reduced in magnitude. Signals of interest are enhanced compared to the noise.