SU1562878A1 - Apparatus for limiting increments in meter of arrival time of acoustic signal - Google Patents

Abstract

The invention relates to the field of well logging using an acoustic method. The purpose of the invention is to increase the measurement noise immunity. The essence of the invention is that in one cycle the output parameter of the meter is allowed to change by an amount not exceeding the confidence value, which during logging changes depending on the lithology. For this, a block of analysis of signs, a block of analysis of amplitudes of time increments and a block of analysis of the ratio of increments with a confidence interval are entered into the device. According to their commands, in the block of formation of the confidence interval, its increase or decrease for each clock cycle by a certain amount occurs. The increase begins if, in several neighboring premises, the signs of the time increments on the first and second probe are the same, and their absolute values are not only greater than the confidence interval, but also have an increasing character. A decrease occurs either when the increments below both the confidence interval are established on both probes, or under the condition that their signs in two adjacent measurement cycles on the near and on the far probes are opposite. 8 il.

Description

The invention relates to the field of well logging using an acoustic method.

The purpose of the invention is to increase the noise immunity of measurements.

FIG. 1 shows a block diagram of the device; in fig. 2 is a block diagram of the measurement break; in fig. 3 is a block diagram of the formation of a confidence interval; FIG. 4 is a diagram of a symbol analysis block; Fig. 5 is a diagram of a ratio analysis block with a confidence interval; in fig. 6 is a block diagram of the amplitude analysis block; in fig. 7 - experimentally removed dependences of the probability of a false decision to increase the confidence interval; in fig. 8 shows the experimentally obtained dependences of the average absolute error of measuring the interval time.

FIG. 1-6 denote the module transmission circuit 1, the measurement interruption block 2, the principal formation unit 3

interval, the character analysis unit 4, the amplitude analysis unit 5, the ratio analysis unit 6 with the confidence interval, the matching circuit 7 and 8, the OR circuit 9, the matching circuit 10, the counter 11, the comparison circuit 12, the reversing counter 13, the shaper 14 reduction steps , minimum indicator 15, adder 16, increment code generator 17, RS-flip-flop 18, Shift register 19, comparison circuits 20 and 21, matching circuits 22 and 23, OR-NOT 24 circuit, OR circuit 25, shift register 26, circuit OR-NOT 27, coincidence circuit 28, counter 29, comparison circuit 30, memory circuit 31; shift register 32 and coincidence circuit 33.

The device is designed to work with two-probe acoustic equipment with alternate transmission of information, where the algorithm of the meter consists of the fact that in each step, i.e. the signal is emitted into the rock, the difference between the previous and the new time of the signal is calculated (increment D-), and then the value of its output parameter is changed by this value (taking into account the sign). In this case, each measurement cycle consists of 2 cycles: in the first, the determination of the time of arrival of the signal at the near, and in the second, at the far probes.

The description of the proposed device is made for the case when the information processing in the signal of the time of arrival of the signal is performed in digital form.

The device works as follows.

At the input of the device (Fig. 1), positive increments are received from one time meter to one input, and negative increments to the other. They represent a burst of pulses, the number of which corresponds to the absolute value of the increment. In the transmission circuit 1 of the module, they are combined on one bus and are then fed to the input of the measurement break unit 2. Here, the increment module (/ L, /) is compared with the maximum value (D06), at which in this step it is allowed to change the output parameter of the time ticker. The value of this increment comes from block 3 of the formation of the confidence interval. Once

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the condition / D; / hells is fulfilled from the output of block 2 to the meter a command is issued that prohibits further testing of the difference between the new and the old value of the signal arrival time.

The change in the value of the confidence interval is made on the basis of an analysis of the increments in several measurement cycles. In this case, two. For this purpose, the block 4 of the analysis of signs, the block 5 of the amplitude analysis and the block 6 of the ratio analysis with the confidence interval are entered into the device. The command to increase D comes in the presence of signals at the outputs of all these blocks.

The signal at the first output of the 4th character analysis unit appears if the increment signs on both the first and second probes are the same in two adjacent measurement cycles (i.e., 4 cycles more time) .- This command is sent to the first input of the coincidence circuit 7, to the other two inputs of which signals from blocks 5 and 6 arrive.

At the output of block 5, a signal occurs if the condition / A is fulfilled in 3 cycles of the cycle; / / L;, /, i.e. they are progressively changing.

At the output of block 6, a signal appears if, in 3 cycles, the increment is greater than the C / L confidence interval; ).

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Thus, if in 3 consecutive clock cycles the conditions / D D;, / and / L j / D sections are fulfilled, and at the very beginning of the fourth, i.e. at the moment of occurrence of the first pulse + D; or -D; all of them will have the same sign, the coincidence circuit 7 will work and issue a command to increase the confidence interval by a certain amount. As a result, in the same 4th cycle, unit 2 will allow the output parameter of the meter to be changed to a greater value than before. The increment value by which this increase in the meter actually occurred is from the measurement breakage unit 2 supplied to unit 3 and stored there. It will now be the new confidence interval.

The new D qoe value is memorized only when a special signal is received at the second input of block 3, coming from the output of block 8, a coincidence pulse is sent to one input, which synchronizes the operation of all device blocks, the other command to increase D ov and the third - signal from the second output of block 5, denoting that the increment in this cycle is greater than the previous one

C / A; s A; - (/).

Thus, memorizing a new

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happens if in 4 cycles

The increment signs of increment are the same, and their amplitudes are more trustworthy and have an increasing character of change. This process of buildup will occur as long as all these conditions are met .. Only / L; 6. The hells, the signals at the output of the measurement break unit 2, and consequently, the block 6, will stop, the coincidence circuit will close and the buildup will stop.

The reduction of the confidence interval begins when one of the following two conditions is fulfilled. The first of these is if the signs of training in two adjacent measurement cycles and on the first and second probes are different. Signals indicating the fulfillment of this condition appear on the second output of the 4th character analysis block. It uses the scheme OR 9 to arrive at the 3rd input of block 3 of the shaper of the confidence interval, where during each clock it causes a decrease in A dow by a certain amount. The decrease in the confidence interval also occurs when a command arrives at the second input of the OR circuit from the second output of block 6. It occurs if the absolute value of the increment on both channels is less than the confidence interval, i.e. if / A; / L Aob and / A;., /.

The measurement break unit (Lig. 2) works as follows.

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A burst of pulses, characterizing the increment module, is fed through a coincidence circuit 10 to the counting input of counter 11. The current increment value code from its output is fed to the comparison circuit 12, to the second input of which the confidence interval code arrives. As soon as the current increment value becomes greater than La0 &, the comparison circuit 12 issues a command to the time meter to stop its processing. At the same time, coincidence circuit 30 is closed. In this case, the counter 11 contains the recorded value of the spent meter

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increments, the code of which is fed to the block 3 of the formation of U st.

The unit of formation of the confidence interval (Fig. 3) operates as follows.

The code of the increment processed in the time meter goes to the information buses of the reversible counter 13, which, when commanded by the synchronous input, transfers it to the output. The reduction command is given to the shaper 14 steps

a decrease, where a burst of pulses is formed, the number of which corresponds to the value by which the confidence interval should decrease in one stroke. These pulses are fed to the subtractive input of the reversing counter 0 13 and reduce its content. If at the same time the number recorded in it becomes less than a certain value, the minimum indicator 15 will work and prohibit the operation of the downformer 14 of the decrease step, thus excluding the reduction of U below the permissible level. The number recorded in the counter 13 is fed to the input of the adder 16, the second input of which receives a signal from the shaper 17 of the increment code. In the normal state, its output is a number equal to zero, so the output of the adder 16 is the value recorded in the counter 3. When a command is received to increase A dow, the code of the number 17 appears at the output of U d by one tact.

Block analysis of signs works as follows (Fig. 4).

Packs of pulses that characterize the magnitude of positive or negative increments are sent to the RS-trig-, ger 18. Therefore, depending on the sign of the increment in a given tact, it occupies a strictly defined position. With the arrival of the clock pulse C0, the shift register 19 at the beginning of the next clock will record this state in the first cell. The previous information is shifted. As a result, in the shift register 19, the recorded information about the increment signs appears in the last 4 bars. Comparison circuits 20 and 21 analyze the signs on each probe in adjacent cycles. If the signals at the inputs of such a scheme are different, the unit at its output is one, if the same} is zero. With two units at the input of the scheme. 22 matches at its output, there appears a command to decrease D

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If the signs are the same in the 3 previous and in the new Takt, then either the coincidence circuit 23 or the OR-NOT 24 circuit will work. The output signal of the OR circuit 25 is a resolution to increase AcjQB.

The unit for analyzing the relationship with the confidence interval (Fig. 5) operates as follows.

The information input of the shift register 26 receives a signal from the output of measurement breakdown unit 2. If the increment is less than Ldoe, the unit comes, if the Boltz is a logical zero ,. At the end of each clock cycle, these signals are recorded in the shift register 26. If

in 3 ticks of the order, the increase of the increment over D a0b would work, the OR-NOT 27 scheme would work, thereby giving permission for its increase. If in 2 cycles pod d / D; DoD, the coincidence circuit 28 is triggered, thereby giving the command to decrease the confidence interval.

The amplitude analysis unit (Fig. 6) works as follows.

Increment module / D; I, in the form of a number of pulses, goes to the counting input of the counter 29, and from its output already the code of this increment goes to the input of the comparison circuit 30. The second input of circuit 30 receives the increment value that existed in the previous cycle, recorded in memory circuit 31. At D; at the output of the comparison circuit - a logical one, and for b., Ј - D zero. This information at the end of each clock cycle is entered into the shift register 32. If it turns out that in 3 clock cycles a new increment value is greater than the previous one, the coincidence circuit 33 is triggered, giving permission to increase D, 06. At the end of each cycle, an entry is made in the circuit 31 for storing the new increment value, and then resetting the counter 29.

Thus, additional information is used in the device to decide to increase the confidence interval. To obtain it, an analysis of the dynamics of change in the absolute values obtained by the measured value of the increments is carried out. FIG. 7 shows the experimentally derived probability dependences.

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of making a false decision about increasing the confidence interval by the symbol analysis unit (curve 32), the ratio analysis unit with the confidence interval (curve 34) and the amplitude analysis unit (curve 33) depending on the signal-to-noise ratio at the input of the correlation meter of the arrival time Signal analysis of information in 4 cycles). By signal is meant the actual value of the voltage of the first two periods of the received acoustic signal. It can be seen from the graph that at high levels of interference, the probability of generating a false command to increase the confidence value in the analysis block with the confidence interval (curve 34) is very large. Therefore, in these conditions, noise immunity in a known device is determined mainly only by analyzing the increment signs (curve 32). The use of more information in the proposed device and on the dynamics of change of the increment, as is evident from the course of curve 33, dramatically reduces the probability of a false increase in the confidence interval, thereby increasing the noise immunity of measurements

FIG. 8 shows the experimentally obtained dependences of the average absolute error of measurement of the interval time (D) (referred to the signal period tc) on the signal-to-noise ratio 36 at the input of the correlation meter of the signal arrival time 35, in which the proposed device was embedded (analysis of increments in 4 neighboring cycles 36).

The use of the device makes it possible to reduce the absolute measurement error of the interval time, which is the main parameter in acoustic logging, by approximately four times.

Claims (1)

Invention Formula A device for limiting increments in an acoustic signal arrival time meter containing two coincidence circuits, an OR circuit and a measurement interruption unit, the first output of which is the output of the device as a whole, characterized in that, in order to increase the noise immunity of the measurements, the module is introduced into the device , a confidence interval formation unit, a symbol analysis unit, an amplitude analysis unit, a ratio analysis unit with a confidence interval, wherein, in the transmission circuit of the module, both inputs are connected It is connected with both information inputs of the character analysis block and are the inputs of the device as a whole, and its output is connected to the information inputs of the measurement breakdown block and amplitude analysis block. In the first coincidence circuit, the first, second and third inputs are connected respectively to the first outputs of the character analysis block, the amplitude analysis unit and the ratio analysis unit with a confidence interval, and the output is associated with the first inputs of the second coincidence circuit and the confidence interval formation unit, in the second coincidence circuit the second input d connected to the second output of the amplitude analysis unit, the third input is connected to the clock, the device input as a whole, and the output is connected to the second input of the confidence interval formation unit; for the OR circuit, the first and second inputs are connected respectively to the second outputs of the character analysis unit and the analysis unit corresponding to the confidence interval, and the output - with the third input of the confidence interval formation unit; for the measurement breakdown unit, the first output is connected to the information input c, a ratio analysis block with a confidence interval; a second output connected to a fourth input of a confidence interval formation unit; and a second information input connected 0 with the output of the confidence interval formation block, while the clock inputs of all the blocks are connected to the clock input of the device as a whole. Cn LogoutAyumandanauor / 8 will measure. - 1 eleven R CQ 4 v 4w No. 2 at. i § § j x u I one and Nomandana Aub / B Meas. 0 tfej increase dg0g 0,1 0.20,30,1 Q5 0,6 0,70,8 Q9 1,0 Another Fig.1Asig FIG. five zapamina. Allowed on. (j8elu.chie ldov shit 0.1 0.2 0.3 0, b 0.5 0.6 0.1 0.8 0.9 1.0 & a Acus Fig.c 35