SU693318A1 - Nuclear magnetic logging device - Google Patents

Description

(54) yCtPOftCTBO FOR SCHBRNO-MAGNETIC TAGING

The invention relates to methods of well logging, and specifically to the technique of nuclear magnetic logging. Nuclear magnetising logging devices are known that calculate the initial amplitude UQ of the free nuclear procession signals from two values of the signal envelope measured at different times l. The closest technical solution is a device for calculating the initial amplitude of the signals of the dermal magnetic logging, containing a series-connected AC amplifier and an envelope detector, two integrators, a multiplier link, one input of which is connected to the output of the first integrator, and the second - to the output of the functional converter and a control unit that synchronizes the operation of integrators 2. The first integrator integrates the signal over a long period of time. and the second for a short period; ka overlapping with the first. In addition, the known device contains a dividing scheme that determines the ratio of the values of the signals integrated at two different time intervals, and the functional converter generates, by the value of the ratio of the measured values, the correction factor, which in order to obtain the UQ value is multiplied by a signal from the integrator with a short interval integration time. A disadvantage of this device is a functional relationship, from which the correction factor is calculated and which must be corrected when the integration time settings of any of the integrators change. This moment does not allow for the operational reorganization of the parameters of the integration schemes in the logging process, and therefore, does not allow for the analysis of signals in a fairly wide circle, in the range of values of the consistent decay time. The device is intended only for calculating the initial amplitudes of the signals and does not allow the determination of the values of the constant attenuation times of the signals, which is required in a number of cases. The method of calculating the initial amplitude UQ from the results of two measurements does not allow obtaining high accuracy of the results, since one of the measurements was obtained by integrating the signal over a short period of time, at which the effect of averaging interference is insignificant. The purpose of the invention is to simplify the device and expand its functionality by enabling the calculation of both the initial amplitude of the signals and the constant decay time, as well as the possibility of calculating the specified parameters over the entire range of values of the constant decay time of the signals. The goal is achieved by the fact that the detector output is connected to the input of a logarithmic function converter, the output of the multiplying link is connected to the input of the second integrator, and the input of the first integrator is connected to a constant reference voltage source. The block diagram of the device shown in the drawing. The device comprises an AC amplifier 1, an envelope detector 2, a functional converter 3, a multiplier link 4, integrators 5 and 6, a control unit 7. The output of the integrator 6 is the output of the device. The operation of the device is dried as follows. A voltage is applied to one Input of the multiplying link 4, which corresponds to the signal voltage envelope. The logarithm operation is performed with the functional converter 3. The second input of the multiplying link is connected to the output of the integrator 5, which performs the function of the sawtooth voltage generator, for which the reference voltage UQ is applied to the input of the integrating link and the control input angle is applied connected to the output of the control unit 7. The integrator 6 performs the integration of the resulting voltage generated by a multiple link. 8.4 It is known that the expression for the envelope of the free procession of the nucleus is AJUdbu e, where Ifg is the initial amplitude of the signal, (is the characteristic of the signal attenuation rate., Voltage U, (i) at the output of the function converter changes according to the law U, (t ) n Jo-dt. At the second input of the multiplying link 4 from the output of the integrator 5, a falling saw voltage is applied, varying according to the law, TJ2 (t) for time values t satisfying the condition Ч 4 t Uo (tb O at RT, where Uu. is the initial voltage of the falling saw, UQI, is the reference voltage, t is the constant time 5, dT is the integration interval of si1. Thus, at the end of the dt integration interval, the voltage U (t) at the output of the integrator 6 is determined by the following ratio Ujft) to J (enUo-8-t) (u, -UQn where K - the transfer coefficient of the integrator 6. It is obvious that in order for the device to calculate the logarithm of the initial amplitude of the free procession, it is necessary and sufficient to implement the following relations Tl. DT (АТ - (- 1,5tH) К-441 ± 1 & At the same time, the output voltage of the integrator 6 will be Cr, 1Go. Similarly, to calculate the characteristic of the decay rate, it is necessary and sufficient that tr: zT (t At the same time, the output voltage The device will be equal to the value in, 5G. Thus, the restructuring of the device from the mode of calculating the initial amplitude of the signal pa, the mode of calculating the decay characteristic, and setting the integration scheme to the optimal interval DT, corresponding to a certain range of values fi, causes two simple operations: change of the reference voltage Chop applied to the integrator 5, and the transfer coefficient K of the integrator 6. This allows you to quickly make the necessary adjustment in the logging process and expands the functionality of the device.

Pho. the invention

A device for magnetic magnetic logging, containing in series an AC amplifier and

. Sources of information taken into account during expert evaluation

1, Lime universities. Oil and Gas, 1974, MJ 4, p. 68-70.

2. US patent number 3479579,.

CL, 324-05, published. 1966 (prototyp), ie, envelope doctor, two integrator, multiplier link, one KOTOfioro input: WNI11nn with the output of the first integrator, and the second with the output of the function converter and a control unit that synchronizes the work of the integrators, o By the fact that, in order to consolidate the device, expansion of its functionality, the output of the doctorator is connected to the input of the functional I1 converter, the output of the coupling link is connected to the input of the second integrator, and the input of the first integrator is connected to the constant support source go voltage