ACOUSTIC LOGGING METHOD Russian patent published in 1994 - IPC

FIELD: geophysical testing of wells. SUBSTANCE: probing acoustic pulses are modulated by pseudorandom periodical sequence. In this case at least one period of pseudorandom periodic sequence is radiated. This period consists of single acoustic pulses which have initial phases of 0 and K=(q⁽²ⁿ⁺¹⁾-1)/(q-1),, as well as misses of radiation. Number of single acoustic pulses and radiation misses in the sequence period are set to be equal to K₊=(q²ⁿ+qⁿ)/2,, K_-=(q²ⁿ-qⁿ)/2, π, where K is general number of single acoustic pulses with initial phases 0 and p and misses of radiation in sequence period; K is number of single acoustic pulses with initial phase to be equal to 0; K is the number of single acoustic pulses with initial phase q=p^m, p is a prime number, m and n are natural numbers. Durations of radiation misses and time intervals, at which acoustic pulses have to be radiated, are equal. Law of single acoustic pulses and radiation misses sequence in the period of the sequence are set in such a manner, that periodic autocorrelation function of modulating sequence could not have non-zero lobes during the whole period. Correlation of the signals being received are performed with the same period of modulating sequence, moreover, signals are selected in M+2 time intervals, where M is number of periods in sequence radiated. Duration of any time interval is equal to period of the sequence. Selected signals are synchronously stored during the time interval being equal to the duration of medium response under testing. EFFECT: improved precision of testing. 2 cl, 2 dwg, 2 tbl