SU1723546A1 - System for determining absorption of elastic waves - Google Patents

Abstract

The invention relates to seismic exploration and seismology and can be used in studying the structure of the geological environment, the physicomechanical properties of rocks, in delineating hydrocarbon deposits, as well as in direct searches for oil and gas deposits. The aim of the invention is to increase the reliability of determining the absorption of elastic waves. The purpose of the invention is achieved by introducing a dispersion determination unit, a control unit, a storage device, as well as an absorption coefficient determination unit implementing the following algorithm: an 1 / 2rlnEk / En + H / r.1 / 2AHInEki / Ek2-, where, an is absorption; g is the distance from the ground drill to the bottom of the well; Ek, En - parameters of wave processes; H - bottom depth; Ek, EH, Ek2 are the current values of the parameters for different depths of drilling. 2 Il. SO with

Description

The invention relates to the field of seismic exploration and seismology and can be used in studying the structure of the geological environment, the physicomechanical properties of rocks, in the delineation of hydrocarbon deposits, as well as in direct searches for oil and gas fields.

The known method for determining the absorption of longitudinal and transverse zoln on the basis of borehole acoustic measurements 1. The absorption coefficients of elastic waves are determined by a known method by the amplitude change on the basis of measurements equal to the distance between the source and receiver of ultrasonic vibrations placed in a special probe. cable.

A disadvantage of the known method is the complexity and high cost of its technical implementation, requiring the use of expensive depth equipment, as well as low data reliability, since measurements are made on small bases, which causes a shallow depth of wave penetration into the rock, resulting in characterize the rocks only in the modified zaglinizirovan.toy when VJ

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the barrel area. In addition, measurements are made at ultrasonic frequencies that do not correspond to the frequencies of mass seismic surveys, and the data obtained can be used in ground-based work only very approximately due to the frequency-dependent nature of the absorption.

There is also known a method for determining the seismic wave absorption, based on ground-based measurements of the energy characteristics (dispersion) of extended sections of seismograms obtained by explosive or shock excitation of an elastic field 2. The absorption coefficient is determined by the ratio of the dispersion of two sections of seismic recording .

The disadvantage of this method is low reliability due to the lack of accurate reference to the depths of certain rocks and low detail of studies associated with the averaging of characteristics over a long record, covering large depth intervals with the inclusion of horizons with different physicomechanical properties. .

The closest to the claimed technical solution is a method for determining the attenuation coefficient, based on joint processing of the wave field recorded by the elastic sensor at the bottom of the well and the wave field recorded on the surface near the wellhead 3. At the same time, the attenuation coefficient is calculated on digital computers by dividing the spectra of signals on the bottom and on the surface.

The disadvantage of this method is the low accuracy of determining the attenuation coefficient, since The method does not take into account and does not exclude the influence of the rejection factors. The attenuation coefficient depends not only on the bottomhole distance — the ground sensor and the properties of the rocks through which the bottom signal and surface propagate, but also on the characteristics of the bottomhole signal spectrum.

The signal spectrum at the bottom is determined by the dynamic characteristics of the bit operation, which depend, in turn, on the drilling mode (bit rotation frequency, axial load), the drill string layout, and the physical and mechanical properties of the rocks on the bottom face. In general, these properties of a bottomhole source can be defined in a generalized form as a function of the source of excitation (or in a narrower sense, as the transfer characteristic of the bottomhole – bit system).

During the drilling process, this function changes due to the change of rocks, varying modes, changes in the hydraulic program, etc. Therefore, the spectrum of the signal on the surface will characterize not only the change in the properties of rocks in the path of elastic waves between the face and the surface, but also the change in the mining and technological conditions of drilling.

As a result, the attenuation coefficient, determined in the known method as a result of dividing the spectra of the downhole and ground signals, has unsystematic distortions due to the difference in the source functions at different depths (inconsistency of the excitation conditions). In addition, in a known method, the requirements for the drilling conditions at which measurements are made are not formulated.

The disadvantage of this method is the complexity of its technical implementation. The registration of the wave field in the downhole zone of wells requires the use of special sensors and the organization of linkages with the face. Measurements made using telemetry systems in conditions of great depths, intense vibrations, high pressures and temperatures are unreliable, complex and expensive operation. In addition, the use of sensors with different characteristics for measurements on the bottom and on the surface introduces additional distortion and reduces the reliability of the results.

The aim of the invention is to increase the reliability and determination of the absorption coefficient and simplify the technical implementation.

The positive effect created by this technical solution is to provide a significant increase in the informativity of seismic prospecting, to increase the reliability of forecasting the geological section, detailing and decontamination of deposits and mineral deposits. An increase in the detail of studying the physicomechanical properties of the section is also provided, which determines its place in the complex of methods for direct exploration of oil and gas fields.

The goal is achieved by adding a sinking sensor to the system for determining the absorption of elastic waves, as well as sequentially interconnected and with an amplifier unit, a process dispersion calculating unit, an absorption coefficient calculating unit, a plotter, and a control unit and a memory device. . The proposed system, when determining the absorption coefficient, avoids the use of expensive and complex measuring devices, and also eliminates the need to use special communication lines with the bottom for transmitting the downhole signal, since measurements are made on the surface of the earth.

Figure 1 shows the functional block diagram of the implementation of the proposed system.

Fig. 2 shows the detailing of the absorption coefficient calculating unit 11 (detailing the scheme for determining the absorption of longitudinal waves, i.e. the first subunit, is given. The scheme for determining the absorption of the transverse waves in the second subblock is similar and is not shown in FIG.).

Fig. 1 shows a functional block diagram of the proposed system, which includes a sensor 1 for longitudinal oscillations of a drill string, a sensor 2 for transverse oscillations of a drill string, a sensor 3 penetrations, a sensor 4 for longitudinal vibrations and a sensor 5 for transverse vibrations propagating in rocks, a block 6 of filters , block 7 of amplifiers, block 8 of calculating the dispersion of processes, control block 9, storage device 10, block 11 of calculating the absorption coefficient, plotter 12.

Fig. 2 shows the detail of the block 11 for calculating the absorption coefficient of longitudinal waves, i.e. the first subblock, including the first divider 13, the first block of logarithm 14, the differential circuit 15, the second divider 16, the multiplier 17, the third divider 18, the second block of logarithm 19, the first adder 20, quadr 21, the second adder 22, the power block 23, the fourth divider 24, the third log block 25.

The system is implemented as follows.

Elastic waves, excited by bottomhole bits, are sensed by transducer 1.2 longitudinal and transverse waves, respectively, mounted in the upper part of the drill string and transducers 4.5 of the same type, mounted on the surface of the earth. The depth of the bottom is recorded by the penetration sensor 3, issuing from its counter the depth values (penetrations) (for example, through a binary search) in block 9 (performed on two comparators and two electronic keys, for example, on triggers) and on the selsyn of block 12.

Before starting, in the first comparator of the control unit 9 dial the code of the initial Depth H (for example 1000 m), and in the second comparator the code of another fixed depth In (for example 1100 m), which are necessary for calculating the "n absorption in the drill string". When another fixed depth is reached, the code of the current depth of the transmitter 3, which is applied to the first input of the comparator, coincides with the code of the depth H, at the second input of the first comparator. At the same time, a control signal is generated at the output of the comparator, from which the electronic key (trigger) is triggered and resolution is given (closes the circuit) to pass the signal from sensors 1.2 on the drill string (swivel) through blocks 6.7 and block 8 for calculating the dispersion and further in the storage device (memory) 10, because the inputs of block 11 are pre-locked at one of the states of the input trigger of this block. At the same time, the depth input Hi is supplied to the third input of memory 10 through the first output of the CU 9. The first comparator is turned off and the signal from sensor 3 begins to flow to the second comparator. Thus, in the memory unit 10, the value of the dispersion of the drillstring crk, and the depth value Hi are supplied. With

reaching another fixed depth H2, the code of the current depth from sensor 3 coincides with the depth code Hi in the second comparator BU 9, as a result of which the second electronic key BU 9 opens the third and

the fourth (inputs) triggers of the dispersion calculating unit 8, the memory 10 is disconnected from the unit 8 via the first output of the CU 9 (with a trigger triggered by the depth signal H). The same signal opens according to

reset of input 1.2 of block 8 (input triggers),

as well as outputs 1,2,3 block 10, due to

which signals from memory 10 are called in block 11

calculation of the absorption coefficient.

After performing these procedures, the signal from sensors 1,2,4,5 begin to flow continuously into blocks 6, 7, 8, 11 with output to block 12. The signal from penetration sensor 3 goes to plotter 12 and via control unit 9 to block 11.

Electrical signals from sensors 1,2,4,5 are filtered in filter unit 6 and amplified in amplifier unit 7. Next, the signals arrive at block 8 for determining the dispersion of wave processes.

From block 8 (outputs 1, 2, 3, 4), the current values of the dispersion come to block 11 (to inputs 1, 2, 3, 4) for determining the absorption coefficient, where synchronously to the eighth input from the third output of the CU 9 are inputted from

sensor 3 also includes the values of the current drilling depth H needed to calculate the absorption coefficients. The fifth input of the block 11 from the first output of the charger 10 also causes the values of the dispersion during drilling

depths Hi. The first comparator BU 9 is blocked. The signal corresponds to the situation, the depth Ns is the second electronic key of the second comparator of the CU; the prelocked inputs 1.2 of the block 11 are locked, the circuits between the blocks 7 and 8 are closed for passing signals from ground sensors 4,5 (lines 3,4) and the output 3 of the CMS 9 To pass the signal, the current depth H is in block 11, the outputs 1,2,3 of memory 10 are opened to transfer signals from the memory 10 to block 11, and Hi and the inputs 1,2 in memory 10 are locked. The H22 signal of the second output of the CU 9 is fed to the input 7 block 11.

Thus, the signal depth H211 goes to block 11 from block 8: dispersion value (V2 for H2 depth, current dispersion values of O2kp, O2ks, crnpi crns, and in block 11, the dispersion values for HI depth are also recalled from block 10: o2kp ,, and the value of H1, and from the CU 9, the signals H2 and H come into the block 11. These values provide absorption in the column Ok. In combination with the dispersion values in the frnp rocks, s and in the OKOS column, these information signals are entered into the corresponding the functional elements of block 11, together with the constant I2, are pre-VV -degenerate in block 11, the absorption coefficients provide a longitudinal and transverse waves ap and as. After passing the signal on the depth of the second comparator 9 is blocked BU and BU from 9 to unit 11 postupayut.tolko current depth value N.

Claims (1)

The invention includes a system for determining the absorption of elastic waves, comprising sensors for longitudinal and transverse vibrations of a drill string, sensors for longitudinal and transverse vibrations of a rock, and a filter unit and an amplifier unit, successively connected to each other with sensors, characterized in that , a penetration sensor is additionally introduced into it, as well as a unit for calculating the dispersion of processes, and a unit for calculating the coefficient nta absorption, plotter, as well as a control unit and a memory device, with the penetration sensor connected to the input of the control unit and the first input of the plotter, the control unit, the dispersion determining unit of the first and second outputs are connected to the communication line between the amplifier unit and the process dispersion calculation unit connected respectively to the first and second inputs of the memory devices, the first and second outputs of the storage device are connected respectively to the fifth and sixth inputs, the absorption coefficient determination unit, and the third output of the storage device connected to the ninth input of the absorption coefficient determination unit, the first output of the control unit is connected to the third memory input, the second and third outputs of the control unit are connected respectively to the seventh and eighth inputs of the absorption coefficient determination unit, the control unit and the absorption coefficient determination unit are also connected between a reset line, when This block for determining the absorption coefficient includes four dividers, three logarithms, a difference block, a multiplier, two adders, a quad, a power block, and the first block output determining the dispersion is connected to the second input of the first divider and in parallel with the first input of the third divider, the third output of the dispersion determining unit is connected to the second input of the third divider, the output of which is serially connected to the input of the second logarithm unit and the second input of the first adder, the first output of the memory device is connected to the first the input of the first divider, the output of which is connected in series with the input of the first logarithmic unit, and the multiplier; the second output of the memory device The second output of the control unit is connected to the second input of the differential unit, the output of which is connected to the first input of the second divider, the third output of the control unit is connected to the second input of the second divider, and is connected in series with the quad, second adder and power block. , the output of the second divider is connected to the second input of the multiplier, the output of which is connected to the first input of the first adder, output the power block is connected to the second input of the fourth divider and to the input of the third logarithm block, the output of which is connected to the third input of the first adder, the output of which is sequentially connected to the first input of the fourth divider and plotter.