Patent GB-1305351-A (GB)
IPC: G01V1/44
Filed: 1971-04-19
Abstract: 1305351 Borehole well logging INSTITUT FRANCAIS DU PETROLE DES CARBURANTS ET LUBRIFIANTS 19 April 1971 [31 March 1970] 25413/71 Heading G1A [Also in Division H4] Characteristics of geological formations traversed by a borehole are determined by:- (1) producing a number of quantities indicative of natural γ radiation from the formations in the same number of energy ranges (2) alternately transmitting acoustic waves having longitudinal and transverse propagation (3) measuring the travel times between a pair of receivers in contact with the formations, of each of the sound waves (4) measuring the attenuation of each of the sound waves during its transmission between the two receivers. The information produced as electrical signals may be recorded, and the recording may be elaborated to indicate at least one characteristic, or the signals may be applied to a computer for automatic elaboration. The characteristics investigated may be clay content, content of carbonates, quartz content, cationic exchange capacity, porosity, or mobility. Articulated pad 8, Fig.2, carrying transverse acoustic transmitter 19, vertically spaced acoustic receivers 17, 18 and the y ray detector is pressed into contact with the formations by a pad 9 under the control of hydraulic devices 11a, 11b. The longitudinal acoustic transmitter 20 is mounted in the main sonde body in the same diametral plane as transmitter 19 together with a power supply panel 21, electronic assemblies 22a, 22b, for the processing of detector and receiver outputs for transmission to the surface, and a device 11 connected to the hydraulic devices and producing a signal indicative of the borehole diameter. The γ detector includes a sodium iodide crystal scintillator encased in a low absorption material such as aluminium, and a reference source 15 is included together with a second scintillator 14 coupled to a second photo-multiplier, layers 13b and 16 blocking # rays from the first photomultiplier and γ rays from passing into the formation from the reference source. The # ray detector enables identification of y rays from the reference source in the first photo-multiplier output by their time coincidence. The information is amplitude modulated on pulses of constant duration for transmission to the surface. Acoustic transmitters 19 and 20 are Piezo-electric and magnetostrictive respectively and frequencies 80-250 KHz and 20-80 KHz are exemplified. Apparatus for processing the first half cycles of received acoustic waves for indicating attenuation wherein the pulses are first lengthened and gated to produce pulses of the same duration, one pulse is inverted, and the ratio of their logarithms is determined, is described with reference to Figs.4 and 5 (not shown), and the circuitry producing transmission time signals from the first half cycles of received acoustic waves in which the time interval of reception affects amplitude modulation of a pulse to be sent to the surface is described with reference to Figs.6 and 7 (not shown). A mathematical analysis is included and the determinations of constants  by measurement on core samples is suggested. The y ray measurements are stored digitally and the read out is synchronized with the acoustic measurement transmission. Suitable computers are described with reference to Figs. 10 and 11 (not shown).