E - Fixed Constructions – 21 – B
Patent
E - Fixed Constructions
21
B
349/4
E21B 21/08 (2006.01) E21B 47/18 (2006.01) G08C 23/00 (2006.01)
Patent
CA 1213666
Abstract of the Disclosure Data signals indicative of subsurface well physical measurements and t or geophysical measurements are transmitted through the drilling mud by pressure pulsations originating at a downhole apparatus. Two closely spaced pressure sensors measure mud pressure pulsations in a mud line at a surface location. Both of the measured pressure pulsation signals are time shifted an amount equal to the travel time of the upwardly and downwardly propagation acoustic velocity in the mud between the two pressure sensors by separate time delay circuits. Summing circuits separately combine the original and delayed signals to cancel the respective upwardly and downwardly propagating energy from the two pressure data signals. An estimator circuit and a deconvolution circuit process the composite signals to derive an estimated primary signal representing upward traveling energy. The resulting pressure data signal is then processed by each of n matched filters to determine the presence or absence of one of n symbols in the residual data signal. Each output of the filtered data signals is then input to a "Largest of" Bayesian detector to identify either the presence of a symbol or absence of the data signal. A method is provided for recovery of data in a well logging while drilling system wherein a data signal originating from a downhole apparatus is transmitted to the earth's surface through drilling mud. In the method, pressure wave energy in a mud flow line at the earth's surface is measured in two spatially separated locations; then at least one two-dimensional velocity selective filter which in the preferred embodiment is a velocity selective filter such as a velocity notch filter two intermediate signals representing the upward and the down- ward traveling composite pressure signals.
455552
Dresser Industries Inc.
Macrae & Co.
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