Reference signal encoding for seismic while drilling measurement

Details Reference signal encoding for seismic while drilling measurement Reference signal encoding for seismic while drilling measurement

1999-01-21

2000-06-20

Oda, Christine K.

Data processing: measuring, calibrating, or testing

Measurement system in a specific environment

Earth science

702 14, G01V 140

Patent

active

060788682

ABSTRACT:
A method for making seismic while drilling (SWD) measurements by determining and analyzing the reference signal downhole near the drill bit and sending a limited quantity of information to the surface by measurement-while-drilling (MWD) telemetry. In one embodiment, a library of anticipated drill bit wavelets is stored in memory downhole and in memory at the surface. The best matching wavelet is identified by the processor downhole and then a code identifying the wavelet and a scaling factor is sent to the surface. At the surface, the best matching wavelet is retrieved based on the code received and then a reconstructed signal is created using the retrieved wavelet and the scaling factor. In another embodiment, key characteristics of the signal such as central frequency, frequency band, etc., are calculated downhole and transmitted to the surface. These key characteristics are then used to reconstruct the reference signal which is then used for correlation of surface detected signals.

REFERENCES:
patent: 4926393 (1990-05-01), McClellan et al.
patent: 5792072 (1998-08-01), Keefe
patent: 5868201 (1999-02-01), Bussear et al.
patent: 5899958 (1999-05-01), Dowell et al.
patent: 5924499 (1999-06-01), Birchak et al.

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