Acoustic well logging device for detecting shear and compressional waves
AssigneeMobil Oil Corporation
InventorRichard L. Caldwell
Life of this patent
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Abstract
Novel acoustic logging tools are disclosed for logging unconsolidated formations. These tools include point force shear wave, and multidirectional compressional wave transmitters. A plurality of receivers with sensitivities matched to these transmitter types are provided for selectively gathering P wave and S wave information. The transmitters and receivers are located, sequenced and gated to ensure that high quality wave data is rapidly and reliably collected.
Claims18
A well logging device for continuously logging the shear and compressional wave transmission characteristics of materials located adjacent to a borehole;
- comprising:
- (a) a plurality of selectively activatable transmitters, said transmitters comprising at least a first multidirectional acoustic transmitter and a second point source acoustic transmitter;
- (b) a plurality of receivers, at least one for each transducer, mounted on said device in spaced relation from said transmitters, said receivers comprising at least a first compressional wave receiver exhibiting a relatively greater sensitivity to acoustic waves produced by said first transmitter, and at least a second shear wave receiver exhibiting relatively greater sensitivity to acoustic waves produced by said second transmitter;
- and,
- (c) sequencing means for selectively energizing each of said transmitters in response to the detection of at least one wave by at least one of said receivers;
A method for acoustically logging an open borehole disposed through poorly consolidated materials such as unconsolidated sands or coal overburdens, comprising the steps of:
- (a) providing a logging device having a plurality of transmitters thereon, said transmitters comprising at least one point source type transmitter and at least one multidirectional compression wave type transmitter, said logging device further comprising a plurality of receivers disposed in spaced apart relation to said transmitters, said receivers comprising at least one shear wave type receiver showing increased sensitivity to waves produced in a borehole by said point source type transmitter, and a compressional wave type receiver showing relatively greater sensitivity to compressional waves produced by said compressional wave type transmitter;
- (b) placing said logging device within said borehole to be logged;
- (c) sequentially and periodically activating said transmitters to produce periodic shear and compressional waves within materials adjacent to said boreholes;
- (d) sequentially permitting selected ones of said receivers to transmit information for collection to cause said shear wave receiver to receive and transmit information relating to said shear waves produced by said shear wave transmitter, and to cause said compressional wave receiver to receive and transmit information relating to said compressional waves produced by said compressional wave transmitter;
- (e) recording said shear wave and compressional wave information transmitted from said receivers;
- (f) moving said device through said borehole while periodically repeating steps a-e.
Dependencies are inferred from the claim text.