RU2322579C1 - Acoustic system for productive well zone treatment - Google Patents

Abstract

FIELD: oil and gas industry, particularly to stimulate oil and gas production along with increased hydrocarbon product recoverability.

SUBSTANCE: acoustic system comprises master oscillator and serially connected pulse-phase converter, switching power amplifier, linkage and logging cable. Device also has acoustic radiator and power supply device with input linked to power mains bus and output connected to power supply bus of switching power amplifier. Device additionally includes parametric feedback circuit, support voltage driver circuit and compensation unit linked between logging cable outlet and acoustic radiator leads. Parametric feedback circuit input is connected with power supply device output, input thereof is linked to input of support voltage driver circuit input. The second support voltage driver circuit input and output are connected between master oscillator output and pulse-phase converter input. To increase acoustic treatment efficiency three-conductor cable is used. Two conductors of the cable are connected in parallel at input and output of logging cable to increase driving power of downhole acoustic radiator.

EFFECT: increased efficiency of acoustic productive well zone treatment due to increased energy efficiency within extended acoustic oscillation range with power supply from industrial power mains.

2 cl, 2 dwg

Description

The invention relates to the oil and gas industries and can be used to intensify gas and oil production while increasing the recoverability of hydrocarbons.

The use of acoustic treatment technology for the productive zone of wells is one of the most effective and environmentally friendly methods of restoring and improving the filtration properties of the reservoir [1-5], used to increase the production rate of unproductive wells and for rehabilitation of wells considered unpromising.

Known technological acoustic systems (TAS) [3], using ground-based generator devices and downhole acoustic emitters connected by a downhole power cable. The advantage of a TAS with a power borehole cable is the possibility of using a high-voltage (up to 1-3 kV) and high-current (up to 20-50 A) transmission lines for the excitation signal of a borehole acoustic emitter, which ensures the required power of acoustic vibrations affecting the production zone of the wells. The disadvantages of such systems include the significant complexity and limited scope associated with the possibility of tripping operations only on an open wellbore on a string of tubing.

Technological acoustic systems are known [2, 4], which use a geophysical cable mounted on a typical geophysical elevator to transmit an electrical signal for exciting a borehole acoustic emitter (AI). This type of TAS provides wide technological possibilities for applying the acoustic treatment technology for the productive zone of wells as part of the geophysical support of well repair operations. It does not require special use of the tubing string to deliver AI to the productive zone. The composition of the known TAS, as a rule, includes small-sized borehole AI with a diameter of up to 40-45 mm, providing delivery through the tubing string of diameters of 2.5 ″ - 3.0 ″, which allows acoustic processing of existing gas, gas lift and fountain producing wells without stopping work.

Small-sized borehole AIs as part of well-known TAS using a geophysical cable have a limited acoustic power of not more than P _a = 400-800 W and a reduced coefficient of electro-acoustic conversion η _a ≤ (0.3-0.5). The nominal excitation power of such borehole AIs is P _n = 1000-2000 VA and can be provided through the cable KG-3 along the core-to-core line with a cable length L = 2.0-3.0 km. In most cases, with deeper wells for L = 4.0-5.0 km, the electric power P _{n is} limited by the cable parameters.

The power of acoustic vibrations in the well-known TACs, on the one hand, is limited by the use of low-efficiency AI of low energy intensity, and on the other hand, by the limited capabilities of the transmission line of the electrical excitation signal through a geophysical cable. The consequence of the limited acoustic power is the low efficiency of the use of known TAS for the intensification of gas and oil production.

Closest to the proposed one is the TAS described in the patent [5], which uses a highly efficient borehole AI made on the basis of piezoelectric materials [6, 7], with a maximum acoustic power of up to 5 kW with an electro-acoustic conversion efficiency of η _a = 0.7 -0.8, which distinguishes the prototype device from known devices.

An additional advantage of the prototype device is the expanded frequency range of the excitation of acoustic vibrations for the implementation of the parametric radiation mode, which is characterized by the greatest efficiency of impact on the reservoir. Signal generation in the relative range of ± 20% of the center frequency f _o provides the possibility of processing the productive zone of the well by oscillations of the combination frequencies corresponding to the resonant frequencies of the multiphase structure of the collector.

The TAC prototype contains a serially connected master oscillator, a phase-pulse converter (FIP), a generator device made on a multi-channel key power amplifier (KUM), a matching device, a geophysical cable and emitter, and also a power supply device made on a power rectifier connected between the bus power supply networks and KUM power supply bus. The industrial network 3F, 50 Hz, 380 V is used as the power supply network.

Compared with well-known TASs using a geophysical cable connecting a ground-based generating device and a borehole acoustic emitter, the prototype device provides greater acoustic vibration power due to the increased electroacoustic conversion efficiency of a highly efficient borehole AI. However, the acoustic power in the prototype device is limited by the ability to transmit energy of the electrical excitation signal through a geophysical cable.

For a power transmission line through a geophysical cable, two conditions should be distinguished that determine the excitation power of a borehole AI.

Firstly, the maximum input power P _{in is} limited by the maximum allowable voltage of the cable U _additional input resistance of the cable Z _I :

Secondly, the net electric power P _R at the cable output does not exceed the value

where K _P is the transmission coefficient of power through the cable;

φ _n - phase shift between current and load voltage.

For a KG-3 geophysical cable with linear core resistance R _w = 20-24 Ohm / km with a cable length of 2-3 km and a coordinated load resistance Z _n = 50-80 Ohm in the technological range of operating frequencies 10-30 kHz for a typical transmission line "vein-vein" provides the transmission coefficient for power K _p = 0.3-0.4. In this case, the resistance at the input of the cable is Z _in = 110-140 Ohms.

The permissible effective voltage of the geophysical cable between the conductors of the transmission line is U _add = 700 V. As a result, the maximum power at the input of the cable (1) reaches P _inmax = 3-4.5 kVA. Moreover, even in the case of an active coordinated load (cosφ _n = 1), the total electric power (2) at the cable output does not exceed P _R = 1-1.7 kW. The assessment shows that in the prototype device, in the best case, the acoustic power is:

Accordingly, in the well-known TAS [5] for a typical well depth, the existing energy potential of an acoustic emitter is not realized.

The highlighted disadvantage of the prototype device is compounded in the sub-band of the operating frequencies of the combined oscillations in the conditions of power supply from an unstabilized industrial network.

The first factor is associated with the pronounced reactive nature of the load when generating broadband signals.

For AI from piezoelectric materials in the subrange of operating frequencies f = f _o (1 ± 0.2) for the resonant frequency f _{o, the} reactive component of the impedance is comparable with the active component, which corresponds to cosφ _n = 0.7. At the edges of the range, the value of cosφ _n decreases to 0.3-0.2. As a result, according to (2), the active component of the AI excitation power decreases, and the maximum acoustic power (3) does not exceed 0.5-1 kW, and drops to 0.2-0.4 kW at the edges of the operating frequency range. The reduced energy efficiency in the extended frequency band in the prototype device prevents the generation of high-band wide-band acoustic vibrations, which leads to a decrease in the productivity of processing the well productive zone.

The second factor is due to a decrease in the nominal power under conditions of an unstabilized supply voltage while limiting the maximum output voltage to the maximum permissible value for the geophysical cable. A possible increase in the voltage of the power supply network from the nominal value is influenced by a decrease in energy efficiency and, as a consequence, the effectiveness of acoustic processing of the well productive zone in the prototype device. For an industrial power supply network 3F, 380 V, 50 Hz, short-term changes reach up to + 20% -25%, which corresponds to an increase in voltage K _u = 1.2.

With direct power supply to key power amplifiers from the rectified mains voltage, the maximum output voltage generated at the output of the matching device is

where U _n - rated voltage at the input of the cable.

From the condition of reliable operation, the maximum voltage value should not exceed the maximum permissible values specified by the cable parameters U _max ≤U _add. Accordingly, in the prototype device, the nominal output voltage does not exceed the value

Therefore, the rated power at the cable input for a given input impedance Z _in = 110-140 Ohm transmission line through a geophysical cable is

Thus, the nominal excitation power of the AI, respectively, the nominal acoustic power P _{a of} vibrations acting on the productive zone, decreases by 1.4 times and does not exceed 0.3-0.7 kW

The analysis of the principle of operation of the prototype device shows that the nominal acoustic power R _a.n from the conditions for ensuring reliable operation and a significant reactive nature of the load is significantly less than the maximum possible value for a given transmission line through a geophysical cable:

where cosφ _n = 0.3-0.7;

K _u ≈ 1.2;

P _a.n ≈P _a.mach · (0.2 ... 0.5).

A typical core-to-core transmission line of the KG-3 geophysical cable provides an input impedance of at least Z _in = 110-140 Ohms with a power transmission coefficient of not more than K _p = 0.3-0.4 with a cable length of λ = 2-3 km and less K _p <= 0.2, λ = 4-5 km. As a result, the maximum acoustic power in the prototype device does not exceed

The disadvantages of the prototype device include the low efficiency of acoustic processing of the productive zone of oil and gas wells, due to reduced energy efficiency in the extended operating frequency range when powered by an unstabilized voltage of an industrial network under conditions of limiting the allowable voltage and input power for the core-to-core transmission line of the KG geophysical cable -3.

The objective of the present invention is to increase the effectiveness of acoustic processing of the productive zone of the well by increasing energy efficiency in an extended frequency range of acoustic vibrations when powered by voltage from an intentional network.

To solve the problem in a well-known technological acoustic system for processing a productive zone of a well, which contains a master oscillator and a phase-pulse converter in series, a key power amplifier, a matching device, a geophysical cable, as well as an acoustic emitter and a power supply device, the input of which is connected to the power network bus , and the output is to the power bus of the key power amplifier, an additional parametric feedback circuit is introduced, formed the voltage reference and a compensation device connected between the output of the geophysical cable and the terminals of the acoustic emitter, while the input of the parametric feedback circuit is connected to the output of the power supply device, and the output is connected to the control input of the voltage generator, connected by another input and output between the output of the master oscillator and phase-in converter input.

In addition, an increase in the effectiveness of acoustic processing of a well’s productive zone can be achieved by using a three-core cable by connecting two cores in parallel at the input and output of a geophysical cable, thereby increasing the excitation power of the borehole acoustic emitter.

The technical result from the use of the present invention is to ensure stabilization of the nominal voltage at the input of the geophysical cable at the maximum acceptable level provided that the supply voltage changes, or rather compensation of the reactive component of the acoustic emitter impedance in an extended operating frequency range, which ensures an increase in the nominal acoustic power of vibrations affecting the productive the area of wells and, as a result, increase the effectiveness of acoustic th processing gazoneftedobychi to intensify and increase the recoverability of hydrocarbons.

An additional technical result is provided by increasing the transmission coefficient for the power of the excitation signal, downhole acoustic emitter through a three-core geophysical cable.

The structure of the claimed device is illustrated in figure 1, the timing diagrams of the signals explaining its operation are shown in figure 2.

The proposed device (Fig. 1) contains a power supply device 1, a key power amplifier 2, a phase-pulse converter 3, a driver 4, a matching device 5, a geophysical cable 6, an acoustic emitter 7, and a newly introduced parametric feedback circuit 8, a shaper 9 voltage reference and compensation device 1. An additional feature of the implementation of the proposed device is the parallel connection of two cores of a three-core geophysical cable 6.

Introduction to the composition of the known device of new blocks and connections made it possible in the proposed device (Fig. 1) to increase the excitation power and thereby increase the efficiency of processing the productive zone of the well.

Shaper 9 of the reference voltage provides the formation of a sawtooth signal U _p quasi-sinusoidal with an amplitude proportional to the voltage supplied to the input of the shaper 9 with a current frequency specified by pulses U _t supplied to the other input of the shaper 9 (figure 2).

In the simplest case, the shaper 9 can be performed on the RC circuit, providing an exponential increase in the reference voltage, and a key element, providing a sharp decline to zero of the reference voltage during a short clock pulse.

The parametric feedback circuit 9 is intended for transmitting to the control input of the driver 9 a control voltage proportional to the voltage of the power supply KUM 2. Chain 9 may contain a resistive divider and a galvanic isolation link.

The compensation device 10 is designed to compensate for the capacitive component of the AI load and is performed on an inductive element connected in parallel or in series with the conclusions of the acoustic emitter 7.

The work of the proposed TAS is as follows. The voltage of the industrial power supply network is rectified and filtered in the power supply device 1, at the output of which a constant unstabilized voltage is formed E. The nominal and maximum value of which is E _n = 520 V and E _max = 630 V, voltage E is supplied to the KUM2 power bus, to the inputs control which receives pulsed signals from the outputs of the phase-inverter 3.

The formation of pulse signals V _1FIM , V _{2FIM is} carried out by a phase-pulse converter 3 with an operating frequency f, and the time shift is determined by the width of the pulse-width modulated pulses V _PWM (Fig. 2).

The operating frequency f is set by clock pulses U _{T of} double frequency 2f from the master oscillator 4. The pulse signals V _1FIM , V _{2FIM are} amplified by the power of the signals of the key amplifier 2, made, for example, according to a bridge circuit. As a result, the output AFB formed multi-polarity pulse voltage with a pulse V _AFB amplitude equal to the supply voltage E and pulse duration t _and given signal V _PWM pulses.

The matching device provides suppression of the high-frequency components of the pulse voltage V _KUM and selects the first harmonic, the amplitude of which is determined by the expression

where T = 1 / f is the period of the operating frequency;

K _su - transfer coefficient matching device.

The electrical signal from the output of the matching device 5 through the geophysical cable 6 and the compensation device 10 is supplied to the inputs of the acoustic emitter 7.

An acoustic emitter made of piezoactive materials in the form of coaxially arranged cylindrical transducers [7] converts the energy of an electrical signal into the energy of electrical vibrations. The directivity pattern (DD) of acoustic vibrations in the axial plane of the AI is 5-15 degrees, which ensures the processing of the productive zone of the well of a cylindrical acoustic wave, coaxial to the active part of the emitter.

The acoustic effect on the near production zone ensures the cleaning of perforations and the restoration of the filtration properties of the pore collector signals, which is achieved by improving the flow of oil and gas from the reservoir into the production zone. The effectiveness of acoustic intensification of gas and oil production depends mainly on the power of acoustic vibrations and on the frequency band of acoustic exposure.

In the proposed TAS, the maximum permissible level of acoustic power is achieved, limited by the transmission line of the electric signal with an extended range of operating oscillation frequencies, thereby increasing the efficiency of acoustic processing of the well's productive zone.

Firstly, in the claimed technical solution, stabilization of the nominal voltage U _n at the input of the cable is provided at the maximum permissible level U _add , which ensures reliable signal transmission through the geophysical cable, which, under conditions of power supply from an industrial power supply network, increases the rated power to the maximum value:

As a result, in comparison with the prototype device, an increase in acoustic power by K _u ² ≈ 1.4 is provided.

This effect is achieved by providing in the proposed device a parametric dependence of the pulse duration t _{and the} signal V _PWM on the voltage of the rectified power supply network E. The voltage E from the output of the power supply device 1 through the parametric feedback circuit 8 is supplied to the input of the reference voltage shaper 8, where a piecewise quasi-sinusoidal voltage

when t∈ [t _to ; t _to + T / 2] for U _p (t),

where K _p - transfer coefficient of the target in parametric feedback.

The clock moments t _k U _n voltage decreases to zero and then carried recycled for generating a reference voltage.

The pulse voltage of the signal V _PWM is formed as a result of comparing the voltage U _p with a given level of control voltage:

To ensure a nominal operating mode in the range of variation of the supply voltage E _min ≤E≤E _max level U ₀ set equal

As a result, from the condition of equality U ₀ = U _{p the} pulse duration t _{and the} signal V _PWM is determined from the expression

For the above dependence of t _and (E) from (15), stabilization of the amplitude of the output voltage of the operating frequency (10) is achieved at the output of the matching device 5 when the supply voltage changes:

Thus, in the proposed device, the implementation of the maximum input power mode at the input of the cable (11) is achieved under conditions of power supply from an industrial power supply network.

The task of achieving maximum active power at the cable outlet in the proposed device is provided by the introduction of the compensation device 10. The impedance of the acoustic emitter 7, made on piezoactive materials, has a pronounced capacitive character at cosφ _n = 0.3-0.7. In this case, the compensation of the reactive component of the load is effectively ensured by the use of an inductive compensation element L _k connected in series or parallel to the cable output. The value of the inductance L _k is selected from the condition of ensuring full compensation of the reactive component at the center frequency f _{p of the} operating range cosφ _n (f _p ) = 1. Moreover, in the frequency range 0.7f _p <f <1.3f _p , the value cosφ _n (f _p ) ≥0.7 is achieved.

As a result of the introduction of the compensation device 10, the active power at the cable output entering the load increases 1.4 times at the center frequency of the operating range and more than 2 times at the boundary frequencies of the broadband signal:

where φ _k is the phase shift between current and voltage at the input of the compensation device 10;

cosφ _k = 0.7-1.0 for 0.7f _p <f <1.3f _p ,

k _p - power transmission coefficient through the cable.

When fulfilling the conditions for stabilizing the voltage at the cable input at the maximum acceptable level and compensating the reactive component of the load impedance, the proposed device proposes to use the transmission signal of the borehole emitter 7 through a three-wire cable along the "2zh-1zh" line (two wires-one core). In this case, an increase in the power transfer coefficient k _p by 20-25% is achieved, as well as a decrease in the input cable resistance to

Z _{BX 2zh-1zh} = 70-80 Ohm.

The result is an increase in power at the cable output at a given maximum allowable voltage U _add = 700 kW to

Accordingly, the value of the active power at the cable output increases.

For a typical cable length of 2-3 km, k _{p (2zh-1zh)} = 0.4-0.5, the value of P _R reaches P _R = 2-3 kW, which ensures an increase in the acoustic radiation power to 1.5-2 kW .

Thus, in the claimed TAC, the combination of introduced blocks and connections provides an increase in the acoustic power of processing the productive zone of the well by more than two times in comparison with the known devices with a geophysical cable with an expanded range of operating frequencies, which achieves a significant increase in the effectiveness of acoustic processing technology. So when using well-known TASs, the application efficiency does not exceed 60-70% in the case of a special selection of productive formations for permeability and porosity. The application of the proposed TAS ensures a processing efficiency of at least 80%, including when using processing technology for productive formations with reduced permeability and porosity. The implementation of the proposed TAS allows to ensure an increase in well production by more than 40% and to restore low-yield wells.

Information sources

1. Kuznetsov O.L., Efimov S.A. The use of ultrasound in the oil industry. M .: Nedra, 1980, 190 p.

2. Pechkov A.A., Shubin A.V. The result of work to increase well productivity by acoustic exposure. Geoinformatics, 1998, No. 3, 16-23.

3. Bogolyubov B.N. and others. Intensification of oil production by low-frequency acoustic exposure // Development and operation of oil fields. No. 9, 2000, pp. 80-85.

4. Patent of Russia No. 2026969. The method of acoustic impact on the bottom-hole zone of the reservoir.

5. Patent of Russia No. 2162519. The method of acoustic processing of the productive zone of the well and a device for its implementation. Etc. 04.24.1999.

6. Patent of Russia No. 2047280. Acoustic emitter. Published in BI No. 30 dated 10.27.95.

7. Certificate for utility model No. 762. Acoustic cylindrical emitter. Registered January 27, 1996.

Claims (2)

1. An acoustic system for processing a productive zone of a well, comprising a master oscillator and a phase-phase converter, a key power amplifier, a matching device, a geophysical cable, and an acoustic emitter and a power supply device, the input of which is connected to the power bus, and the output to the power supply bus of the key power amplifier, characterized in that it includes an additional parametric feedback circuit, a voltage reference driver, and a compensation device connected between the cable output and the terminals of the acoustic emitter, while the input of the parametric feedback circuit is connected to the output of the power supply device, and the output is connected to the control input of the driver of the reference voltage, connected by another input and output between the output of the master oscillator and the input of the phase-pulse converter. 2. The acoustic system according to claim 1, characterized in that the geophysical cable contains three conductors, two of which are connected in parallel at the input and output of the geophysical cable.

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