METHOD OF ACOUSTIC LOGGING Russian patent published in 1994 - IPC

FIELD: geophysics, measurement technology. SUBSTANCE: in this method recurrent pseudorandom sequences are generated being cyclically shifted by more than the width of a medium response. The sequences each have at least one period and consists of unit acoustic pulses in initial phases O and π and radiation blanks. The number of unit acoustic pulses and radiation blanks is set equal to K=(q⁽²ⁿ⁺¹⁾-1)/(q-1), K₊=(q²ⁿ+qⁿ)/2, K=(q²ⁿ-qⁿ)/2, where K is the total number of unit acoustic pulses in initial phases O and π and radiation blanks; K₊ is the number of unit acoustic pulses in initial phase O; K_- is the number of unit acoustic pulses in initial phase π; q = p^m; p is a prime number; n and m are natural numbers. The widths of a radiation blank and a unit acoustic pulse are equal. The law of alternation of unit acoustic pulses and radiation blanks in any sequence period is specified so that a periodic autocorrelation function is ideal; the time of the period of a sequence radiated is set no less than the total duration of medium responses to be investigated, which are caused by the action of each of radiators. The pulse sequences each of which is formed for just one of radiators are transmitted into medium by all radiators at the same time. The signals received are correlated with one period of the modulating sequence used by each of the radiators. The signals produced by generation of an individual sequence by each of the radiators are detected during (M+2) time intervals (M is the number of sequence periods), each of which is equal to the sequence period time. The signals detected are accumulated synchronously. EFFECT: more reliable logging results. 2 cl, 2 dwg