GB1221471A - Transducer rotating mechanism for borehole logging tools - Google Patents

Abstract

1,221,471. Well-logging; ultrasonic couplings. MOBIL OIL CORP. 1 March, 1968, No. 10111/68. Headings H4D and H4J. [Also in Division G1] A mechanism which permits a 360 degree rotation of the radiant energy transducer assembly of a borehole logging tool without significant attenuation of the energy by the tool comprises a rigid member connected between upper and lower parts of the tool, the transducer assembly being mounted for rotation about the member. The radiant energy may be nuclear, acoustic or light. In the Fig. 2 acoustic embodiment directional lead zirconate titanate transmitting transducers 34, 71 and receiving transducers 36, 72 are glued to flat faces on generally cylindrical members 62, 68 which are linked by rods 64, 65 and rotatable as an assembly about a mandrel 24 joining a nose portion 30 of the logging tool to an upper portion 23. A sleeve 32a (either a hard, acoustically opaque material with an acoustically transparent circumferential port, or made of flexible neoprene) provides an acoustic " window " and also retains oil used as a couplant. The transducer assembly is rotated by a motor either via gears 112, 106, 102, 100 (both the motor and the transducer assembly being subjected to ambient borehole hydrostatic pressure) or via a synchro transmitter/receiver combination (the motor and synchro transmitter being at atmospheric pressure, the synchro receiver and transducer assembly being at borehole pressure, and the pressure differential being absorbed by a bulkhead). Electrical connection to the transducers is made via feed-through insulators 95 and slipring assembly 80, 82, 83. Borehole logging.-For providing a C-scan cathode ray tube (CRT) display of aromatics in the borehole wall, echoes of ultrasonic pulses transmitted by transducer 34 or 71 and received by the same transducer or tranducer 36 or 72 are fed uphole to intensity-modulate the CRT beam. Depth signals produced by a measuring sheave on which the logging tool support cable runs control the vertical sweep of the CRT beam; signals fed uphole and indicating the angular position of the transducer assembly control the horizontal sweep of the CRT. The range at which the transducer transmission and reception beams intresect (i.e. are focused) is predetermined by selection of the transducers (which are angled differently on members 62, 68) and by adjustment of the spacing of members 62, 68 along rods 64, 65.