Sound wave receiving device and method with tunable sensitivity

Abstract

The invention discloses a sensitivity-tunable sound wave receiving device and a sensitivity-tunable sound wave receiving method. The sensitivity-tunable sound wave receiving device comprises a supporting hollow circular tube, the outer side of the hollow circular tube is sleeved with a sensitization sheet; the sensitization sheets are a pair of pi-radian sheets, and the pi-radian sheets are symmetrically arranged on the two sides of the hollow circular tube; a plurality of through holes are symmetrically and uniformly distributed in the outer sides of the hollow circular tube and the sensitization sheet; bolts penetrate through the through holes and are connected with nuts to fix the hollow round pipe and the sensitization sheets. The spring is sleeved on the nut at the middle position of the hollow circular tube and the sensibilization sheet; a weak grating fiber is wound on the outer side of the sensitization sheet, and the spring bears compression force generated when the weak grating fiber is wound on the sensitization sheet. Backward Rayleigh scattering is enhanced through the weak grating, and the signal-to-noise ratio of the receiver is improved; the adjusting bolt can realize adjustment of the compression amount of the spring, thereby realizing continuous adjustment of the tension of the optical fiber, and realizing continuous tuning of the sensitivity of the sound wave receiver. The weak grating can improve the multiplexing capability of the receiver, and meets the long-distance array receiving requirement of the detection of the sound wave receiver.

Description

Technical Field

[0001] The invention belongs to the field of geophysical well logging, and in particular to a sensitivity-tunable acoustic wave receiving device and method. Background Art

[0002] Acoustic logging is one of the important logging methods for geophysical logging. It is a physical logging method that receives acoustic wave signals propagating in the formation, analyzes the speed, amplitude and waveform of the acoustic wave, and then analyzes the formation information. At present, acoustic logging mainly includes two categories: traditional electrical acoustic wave transducers and optical fiber acoustic wave receivers. Fiber optic detection has the characteristics of high sensitivity, anti-electromagnetic interference, integrated sensing, passive design, simple structure, high reliability, and easy miniaturization. It supports multiple deployment methods such as point-type, quasi-distributed and distributed, and can meet the requirements of long-term continuous monitoring. It has become a hot spot in acoustic logging research.

[0003] There are three main types of fiber optic acoustic logging: point-based, quasi-distributed, and distributed, which have been used for seismic exploration. It mainly includes logging construction and data processing and interpretation. Limited by the sensitivity of instruments and equipment, strict research is required for data processing and interpretation. Detailed data processing is required to obtain refined interpretation models and evaluation results. However, fiber optic acoustic logging currently has the problems of long interpretation cycle and multiple solutions. It is difficult to quickly improve the data interpretation and evaluation level by improving the algorithm, which restricts the rapid development of fiber optic acoustic logging.

[0004] Since the formation information is relatively complex, there are both fracturing and inter-well seismic acoustic signals with strong vibration signals, as well as weaker acoustic signals such as injection and production profiles and leakage. It is difficult for the same fiber optic acoustic receiver to be compatible with receiving both strong and weak acoustic signals. The equipment has a high sensitivity and can capture weaker downhole acoustic signals, but the stronger acoustic signals may exceed the detection threshold; the signal is low in sensitivity and can capture stronger downhole acoustic signals, but it is difficult to extract weaker acoustic signals. It is difficult for one device to be compatible with multiple downhole acoustic signal sources.

[0005] As oil and gas resources move towards deeper formations and complex oil and gas reservoirs, the requirements for increasing oil and gas reserves and production have become clearer. The potential of old oil and gas fields and the exploration and development of new oil and gas fields have put forward higher requirements for fiber optic acoustic logging in multiple scenarios such as injection and output profiles, wellbore integrity, fracturing monitoring, CCUS, etc., and there is an urgent need for an acoustic receiver that can adapt to multiple operating scenarios and is compatible with different strong and weak signals, in order to obtain a refined oil and gas reservoir distribution model and oil and gas movement law in the well. Therefore, it is very important to develop an acoustic receiver with tunable sensitivity to meet a variety of operating environments with different acoustic sensitivities. Summary of the invention

[0006] In order to solve the problems existing in the prior art, the present invention provides a sensitivity-tunable acoustic wave receiving device and method, which are used to solve the problems in the background technology. The present invention enhances backward Rayleigh scattering through a weak grating to improve the signal-to-noise ratio of the receiver; the adjusting bolt can adjust the spring compression amount, thereby realizing continuous adjustment of the optical fiber tension and continuous tuning of the acoustic wave receiver sensitivity; the weak grating can improve the multiplexing capability of the receiver and meet the long-distance array reception requirements of the acoustic wave receiver detection; the cylindrical design can realize the detection requirements of various wellbore environments; the anti-bending optical fiber can meet the needs of smaller-sized receivers, improve the miniaturization level of the acoustic wave receiver, and meet the acoustic wave detection requirements of small wellbores and ultra-small wellbores.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A sensitivity-tunable sound wave receiving device comprises a supporting hollow circular tube, a sensitivity-enhancing sheet, a weak grating optical fiber, a spring, a bolt and a nut;

[0009] The outer side of the hollow circular tube is provided with a sensitivity enhancement sheet; the sensitivity enhancement sheet is a pair of π radian sheets, and the π radian sheets are symmetrically arranged on both sides of the hollow circular tube;

[0010] The outer sides of the hollow circular tube and the sensitization sheet are symmetrically and evenly distributed with a plurality of through holes;

[0011] The bolt passes through the through hole to connect the nut to fix the hollow circular tube and the sensitivity enhancement sheet; the spring sleeve is arranged on the nut in the middle position of the hollow circular tube and the sensitivity enhancement sheet;

[0012] A weak grating optical fiber is wound around the outside of the sensitivity enhancement sheet, and the spring bears the compression force generated by the weak grating optical fiber being wound around the sensitivity enhancement sheet.

[0013] Preferably, the weak grating optical fiber is a bend-resistant Bragg grating optical fiber, and the outer surface of the weak grating optical fiber is coated with a high-temperature resistant coating.

[0014] Preferably, the hollow circular tube, sensitizing sheet, spring, bolt and nut are all made of high temperature resistant materials.

[0015] Preferably, the height of the hollow circular tube is not less than the height of the outer sensitizing sheet.

[0016] Preferably, the bolt diameter is smaller than the inner diameter of the hollow circular tube and the circular through hole on the sensitizing sheet.

[0017] Preferably, the inner diameter of the spring is larger than the outer diameter of the bolt.

[0018] Preferably, a gap is set between two π radians sensitizing sheets.

[0019] Preferably, the weak grating optical fiber is evenly wound on the outside of two π radian sensitivity enhancement sheets to form an independent sensing receiving section, and the receiving section contains at least two weak gratings.

[0020] Preferably, the weak grating optical fiber is wound on the outside of two π radian sensitivity enhancement sheets with a constant tension, and the constant tension range is 0.1-0.5N.

[0021] A method for receiving sound waves with tunable sensitivity comprises the following steps:

[0022] Step 1, pass the screw rods of the bolts through the circular through holes from the inner side of the hollow circular tube, and put the nuts on the screw rods extending from the outer side of the hollow circular tube and tighten them;

[0023] Step 2, respectively put the nuts on the screws extending from the outside of the hollow tube, close to the nuts in step 1;

[0024] Step 3, put the springs on the screws outside the nuts respectively;

[0025] Step 4, symmetrically pass the circular through holes on the two π-radian sensitivity enhancement sheets through the outer screws of the spring in step 3;

[0026] Step 5, nuts are installed on the screws extending out of the sensitization sheet in sequence and tightened;

[0027] Step 6: Tighten the outermost nut to reduce the gap between the two sensitive sheets by compressing the spring, but without contacting them.

[0028] Step 7, using a winding machine to evenly wind the weak grating optical fiber around the circumference of the sensitivity enhancement sheet with a certain tension, and fixing both ends of the optical fiber with high temperature glue;

[0029] Step 8, remove the four nuts on the outside of the sensitizing sheet, so that the weak grating optical fiber can withstand the pressure transmitted by the spring through the two π radian sensitizing sheets.

[0030] Compared with the prior art, the present invention has the following beneficial technical effects:

[0031] The present invention provides a sensitivity-tunable acoustic wave receiving device, which adjusts the pre-tension of the optical fiber by tuning the tension of the sensitizing spring, thereby adjusting the responsiveness of the sensitizing sheet to the acoustic wave, and further adjusting the length change of the optical fiber induced by the acoustic wave, thereby realizing the sensitivity tuning of the acoustic wave receiver to the acoustic wave detection. By optimizing the design of the sensitizing structure of the optical fiber acoustic wave receiver, the sensitivity of the received acoustic wave signal is improved by using four springs to symmetrically and evenly increase the sensitivity; the compression of the spring is adjusted by the bolt feed amount, thereby adjusting the circumference of the circular contour formed by the sensitizing sheet, changing the elongation of the optical fiber on its surface, and realizing the continuous tunability of the acoustic wave sensitivity; all components are made of high-temperature resistant materials, thereby further improving the heat and pressure resistance of the receiver; the anti-bending grating optical fiber can further improve the miniaturization level of the receiver; the cylindrical sensitizing sheet design improves the compatibility of the receiver in different well conditions. The present invention provides a sensitivity-tunable acoustic wave receiver with the characteristics of tunable sensitivity, few components, simple structure, reliable packaging, and resistance to high temperature and high pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a three-dimensional diagram of a sensitivity-tunable acoustic wave receiver structure of the present invention.

[0033] Figure 2 The figure is a top view of a sound wave receiver structure with tunable sensitivity according to the present invention.

[0034] Figure 3 This is the acoustic wave spectrum received by Example 1.

[0035] In the attached drawings: hollow circular tube 1, sensitizing sheet 2, weak grating optical fiber 3, spring 4, bolt 5, nut 6, through hole 7. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

[0037] like Figure 1 and Figure 2 As shown, a sensitivity-tunable sound wave receiving device of the present invention comprises a supporting hollow circular tube 1, a sensitivity-enhancing sheet 2, a weak grating optical fiber 3, a spring 4, a bolt 5 and a nut 6.

[0038] The hollow circular tube 1 is a hollow thin-walled cylindrical structure, with two groups of circular through holes symmetrically and evenly distributed on the outside, and each group of two upper and lower through holes 7 for radially fixing four bolts 5 on the outside of the hollow circular tube 7.

[0039] The bolts 5 are four high temperature resistant bolts, which are evenly placed at four symmetrical through holes 7 on the outside of the hollow circular tube 7 and fixed by nuts 6 .

[0040] The sensitivity enhancement sheet is a pair of π radian sheets 2, which together form an ideal hollow circular through hole corresponding one-to-one to the circular through hole on the outside of the hollow circular tube, and are used to fix two groups of bolts 5.

[0041] The weak grating optical fiber 3 is a bend-resistant Bragg grating optical fiber, and a high-temperature resistant coating is coated on the outer surface.

[0042] The nut 6 is a high temperature resistant nut, which is matched with the high temperature resistant bolt 5 .

[0043] The materials of the hollow circular tube 1, the sensitizing sheet 2, the spring 4, the bolt 5 and the nut 6 are high temperature resistant materials.

[0044] Two groups of circular through holes 7 are evenly distributed on the outer side of the hollow circular tube 1, and have the same positions and sizes as the two groups of circular through holes on the π-radian sensitivity enhancement sheet.

[0045] The height of the hollow circular tube 1 is not less than the height of the outer sensitizing sheet 2 .

[0046] The diameter of the bolt 5 is slightly smaller than the inner diameter of the circular through hole on the hollow circular tube 1 and the sensitizing sheet 3 .

[0047] The inner diameter of the spring 4 is larger than the outer diameter of the bolt 5 .

[0048] Bolts 5 fix the hollow circular tube 1 and the sensitizing sheet 2.

[0049] A spring 5 is sleeved on the fixing bolt 5 between the outer side of the hollow circular tube 1 and the sensitivity enhancement sheet 2 .

[0050] The weak grating optical fiber 3 is evenly wound on the outside of two π radian sensitivity enhancement sheets 2 to form an independent sensing receiving section, and the receiving section contains at least two weak gratings.

[0051] The sensitizing sheet 2 is a large-diameter hollow cylinder evenly split into two pieces, forming two sheets of equal area with π radians.

[0052] The weak grating optical fiber 3 is wound on the outside of two π radian sensitivity enhancement sheets 2 with a constant tension, and the constant tension is 0.1-0.5N.

[0053] Before the weak grating optical fiber 3 is wound around the outside of the π radian sensitivity enhancement sheet 2, the nut 6 is tightened to fasten the sensitivity enhancement sheet into an approximate cylinder, so that the spring 4 sleeved on the bolt 5 is subjected to compression force.

[0054] When the π radian sensitivity enhancement sheet 2 is fastened into an approximate cylinder, a certain gap is ensured between the two sheets.

[0055] After the weak grating optical fiber 3 is wound around the outside of the π radian sensitivity enhancement sheet 2, the outer fastening nut 7 must be removed to ensure that the optical fiber can withstand the pressure transmitted by the spring 4 on the bolt through the sensitivity enhancement sheet 2.

[0056] A method for manufacturing an acoustic wave receiver with tunable sensitivity comprises the following steps:

[0057] S1: Pass the screw rods of the four bolts through the four circular through holes 7 from the inner side of the hollow circular tube 1 respectively, and put the nuts 6 on the screw rods extending out of the hollow circular tube 1 and tighten them.

[0058] S2: Four nuts 6 are respectively put on the screw rods extending from the outer side 1 of the hollow circular tube, close to the nuts 6 in S1.

[0059] S3: Put four springs 4 onto the screw rods outside the two nuts 6 respectively.

[0060] S4: The circular through holes 7 on the two π-radian sensitivity enhancement sheets 2 are symmetrically passed through the outer screws of the spring 4 in S3.

[0061] S5: nuts 6 are installed on the screw rods extending outwardly from the outer sides of the sensitizing sheets 2 in sequence and tightened, so that the two π-radian sensitizing sheets 2 form an approximate circle.

[0062] S6: Further tighten the outermost nut 6 to reduce the gap between the two sensitizing sheets 2 by compressing the spring 4, but without contacting them.

[0063] S7: Use a winding machine to evenly wind the weak grating optical fiber 3 around the sensitizing sheet 2 with a certain tension, and fix the two ends of the optical fiber with high-temperature glue.

[0064] S8: Remove the four nuts on the outside of the sensitivity enhancement sheet 2, so that the optical fiber can withstand the pressure transmitted by the spring 4 through the two π-radian sensitivity enhancement sheets 2.

[0065] Example 1

[0066] A hollow tube with an outer diameter of 30 mm is used as a supporting hollow circular tube, four highly sensitive springs are used as sensitivity-enhancing springs, a hollow circular tube with an outer diameter of 50 mm is evenly split into two equal-area π radian sensitivity-enhancing sheets, and the supporting hollow circular tube, the spring, and the sensitivity-enhancing sheets are assembled into a highly sensitive downhole optical fiber acoustic wave receiver matrix using bolts and nuts. The weak grating optical fiber is wound around the outside of the circumferential sensitivity-enhancing sheet with an outer diameter of 50 mm with a constant tension and is closely wound for 45 turns to ensure that the middle sections of the two weak grating optical fibers separated by 5000 mm all fall on the closely wound area on the outer surfaces of the two π radian sensitivity-enhancing sheets, thus forming a complete highly sensitive downhole optical fiber acoustic wave receiver.

[0067] A signal generator is used to connect an acoustic wave transducer through a power amplifier as a transmitting sound source system, one end of a weak grating optical fiber is connected to a demodulation system as a sound wave receiving demodulation system, and the transmitting sound source system and the sound wave receiving demodulation system are placed in a water pool at the same time.

[0068] like Figure 3As shown, the signal generator controls the sound source to emit a 9 kHz, 500 ms interval sinusoidal pulse sound wave signal. The sound wave signal causes the change in the length of the optical fiber outside the sensitization sheet, modulating the back Rayleigh scattered light signal. The demodulation system obtains the sound wave signal of the weak grating in the optical fiber by demodulating the phase information of the back Rayleigh scattered light, and then associates the position information to detect the sound wave signal. By adjusting the feed amount of the nut close to the spring to 1mm, 2mm, 3mm, and adjusting the compression amount of the spring, the tension of the optical fiber can be adjusted to obtain sound wave signals of different sensitivities. The received sound wave signal is shown in FIG. Figure 3 shown.

[0069] The above is only a detailed description of the specific implementation of the present invention, rather than a limitation of the present invention. Various substitutions, modifications and improvements made by relevant technical personnel without departing from the principle and scope of the present invention are included in the protection scope of the present invention.

Claims

1. A sound wave receiving device with tunable sensitivity, It is characterized in that It comprises a supporting hollow circular tube (1), a sensitivity enhancement sheet (2), a weak grating optical fiber (3), a spring (4), a bolt (5) and a nut (6); The outer side of the hollow circular tube (1) is provided with a sensitivity enhancement sheet (2); the sensitivity enhancement sheet (2) is a pair of π radian sheets, and the π radian sheets are symmetrically arranged on both sides of the hollow circular tube (1); The outer sides of the hollow circular tube (1) and the sensitizing sheet (2) are both symmetrically and evenly distributed with a plurality of through holes (7); The bolt (5) passes through the through hole (7) and is connected to the nut (6) to fix the hollow circular tube (1) and the sensitivity enhancement sheet (2); the spring (4) is sleeved on the nut (6) at the middle position between the hollow circular tube (1) and the sensitivity enhancement sheet (2); A weak grating optical fiber (3) is wound around the outer side of the sensitivity enhancement sheet (2), and the spring (4) bears the compression force generated by the weak grating optical fiber (3) being wound around the sensitivity enhancement sheet (2).

2. A sound wave receiving device with tunable sensitivity according to claim 1, It is characterized in that The weak grating optical fiber (3) is a bend-resistant Bragg grating optical fiber, and the outer surface of the weak grating optical fiber (3) is coated with a high-temperature resistant coating.

3. The acoustic wave receiving device with tunable sensitivity according to claim 1, It is characterized in that The hollow circular tube (1), the sensitivity-enhancing sheet (2), the spring (3), the bolt (5) and the nut (6) are all made of high-temperature resistant materials.

4. The acoustic wave receiving device with tunable sensitivity according to claim 1, It is characterized in that The height of the hollow circular tube (1) is not less than the height of the outer sensitizing sheet (2).

5. The acoustic wave receiving device with tunable sensitivity according to claim 1, It is characterized in that The diameter of the bolt (5) is smaller than the inner diameter of the circular through hole on the hollow circular tube (1) and the sensitizing sheet (3).

6. The acoustic wave receiving device with tunable sensitivity according to claim 1, It is characterized in that The inner diameter of the spring (4) is greater than the outer diameter of the bolt (5).

7. The acoustic wave receiving device with tunable sensitivity according to claim 1, It is characterized in that A gap is set between the two π radian sensitivity enhancement sheets (2).

8. The acoustic wave receiving device with tunable sensitivity according to claim 1, It is characterized in that The weak grating optical fiber (3) is evenly wound on the outside of two π radian sensitivity enhancement sheets (2) to form an independent sensing receiving section, and the receiving section contains at least two weak gratings.

9. The acoustic wave receiving device with tunable sensitivity according to claim 1, It is characterized in that The weak grating optical fiber (3) is wound on the outside of two π radian sensitivity enhancement sheets (2) with a constant tension, and the constant tension range is 0.1-0.5N.

10. A method for receiving sound waves with tunable sensitivity, It is characterized in that The following steps are involved: Step 1, pass the screw rods of the bolts (5) through the circular through holes (7) from the inside of the hollow circular tube (1), and put the nuts (6) on the screw rods extending from the outside of the hollow circular tube (1) and tighten them; Step 2, respectively sleeve the nuts (6) onto the screws extending from the outside of the hollow circular tube (1), close to the nuts (6) in step 1; Step 3, respectively put the springs (4) on the screws outside the nuts (6); Step 4, symmetrically pass the circular through holes (7) on the two π-radian sensitivity enhancement sheets (2) through the outer screws of the spring (4) in step 3; Step 5, nuts (6) are sequentially installed on the screws extending from the outside of the sensitizing sheet (2) and tightened; Step 6, tighten the outermost nut (6) to reduce the gap between the two sensitivity enhancement sheets (2) by compressing the spring (4), but without contacting them; Step 7, using a winding machine to evenly wind the weak grating optical fiber (3) around the sensitizing sheet (2) at a certain tension, and fixing both ends of the optical fiber with high temperature glue; Step 8, remove the four nuts on the outside of the sensitivity enhancement sheet (2), so that the weak grating optical fiber (3) can withstand the pressure transmitted by the spring (4) through the two π radian sensitivity enhancement sheets (2).

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