Downhole orientation identification sensor based on fiber grating three-component detector and manufacturing method thereof

Abstract

A kind of borehole orientation identification sensor based on fiber grating three-component detector and manufacture, the sensor is composed of cylindrical metal shell and sensing part, there are threaded holes on the upper and lower cylindrical bottom surface of cylindrical metal shell, sensing part is connected with metal shell by clamp;Sensing part is composed of anisotropic cylinder and fiber grating, wherein anisotropic cylinder couples the strain of outside to fiber grating, and the twist angle of three-component detector and the stretch length of optical cable are inverted by monitoring the change of center wavelength of fiber grating in real time.The present application uses fiber grating and anisotropic cylinder combination as sensing main body, during the process of three-component detector downhole, the twist angle and stretch length of three-component detector can be inverted, the error of inverted twist angle and stretch length is small, and the present application has the characteristics of low cost, simple manufacture, anti-electromagnetic interference and the like.

Description

Technical Field

[0001] This invention belongs to the field of fiber optic sensing technology, specifically relating to a well location identification sensor based on a fiber optic grating three-component detector. Background Technology

[0002] Three-component vertical seismic profiles (VSPs) can receive various types of waves, providing rich seismic wave information for subsequent processing and interpretation. However, three-component acquisition receives vector wave fields, and the polarity and amplitude of the seismic response recorded by the X and Y horizontal components vary with the source-receiver azimuth. Therefore, the actual placement orientation of the three-component geophone is extremely important for multi-component data processing. During the installation process, rotation of the three-component geophone is unavoidable. Due to uncertainties in the installation conditions and the fact that the geophone reaches its designated position, we cannot determine whether the Z component of the three-component geophone is vertical or whether the X component is parallel to the survey line. In this situation, different types of seismic waves in the acquired seismic data have energy projections on each component—that is, shear wave energy on the Z component and P-wave energy on the horizontal components—severely affecting subsequent wavefield separation, imaging, and inversion. Therefore, it is essential to invert the rotation angle of the three-component geophone, which is crucial for three-component seismic data processing.

[0003] Traditional methods use the energy approximation method to calculate the rotation angle of the detector, which involves a large amount of data calculation and is highly complex. This method is particularly limited in the current application of large-scale three-component exploration. Therefore, it is necessary to study a well-drilled location identification sensor based on a fiber optic grating three-component detector to determine the rotation angle of the detector. Summary of the Invention

[0004] In order to overcome the problems in the existing technology where the three-component geophone rotates randomly during the well running process, which seriously affects the subsequent wave field separation, imaging and inversion, the purpose of this invention is to provide a well location identification sensor based on a fiber optic grating three-component geophone, which has the characteristics of simple structure and accurate measurement.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A well location identification sensor based on a fiber optic grating three-component detector includes a semi-cylindrical metal shell (1), characterized in that the semi-cylindrical metal shell (1) has four M2 threaded holes A (2), B (3), C (4) and D (5); a semi-arc clamp A (6) has two M2 holes A (7) and B (8), and a semi-arc clamp B (9) has two M2 holes C (10). Hole D(11); Threaded hole A(2) and hole A(7) coincide, threaded hole B(3) and hole B(8) coincide, threaded hole C(4) and hole C(10) coincide, threaded hole D(5) and hole D(11) coincide; semi-circular clamp A(6) and semi-circular clamp B(9) clamp the compliant column and fix it inside the semi-cylindrical metal shell (1) through holes A(7), holes B(8), holes C(10) and holes D(11).

[0007] Furthermore, the semi-cylindrical metal shell (1) is made of elastic alloy 3J22.

[0008] Furthermore, a method for fabricating a well-drilled location identification sensor based on a fiber optic grating three-component detector is characterized by comprising the following steps:

[0009] Step a: Prepare a cis-cylinder with oppositely spiraling grooves:

[0010] Step a1: Make two semi-cylindrical molds using 3D printing. The molds have spiral protrusions with opposite directions of rotation inside.

[0011] Step a2: Pour the condensation-type silicon disulfide liquid rubber and the curing agent into a beaker at a ratio of 100:2 and mix them evenly.

[0012] Step a3: Slowly pour the mixed silicone into the mold until it is full, and cover the two sides of the semi-cylindrical mold with transparent plastic sheets;

[0013] Step a4: Let the mold stand for 12 hours until the silicone has cured and solidified. Then, remove the cis-converting column from the mold to successfully produce a cis-converting column with a spiral groove on the outside.

[0014] Step a5: Place the two cured semi-cylindrical cis-cylindrical cylinders back into the mold and pour a small amount of proportionally mixed silicone onto the surface of the semi-cylindrical cis-cylindrical cylinders. Then merge the mold into a cylinder and enclose it with two 3D printed rings.

[0015] Step a6: After the mold described in step a5 has been left to stand for 12 hours, take out the complete cylindrical cis-converted cylinder. The cis-converted cylinder has two spiral grooves with opposite directions of rotation.

[0016] Step b: Fiber gratings are laid on the surface of the compliant cylinder obtained in step a6.

[0017] Step b1: Arrange fiber gratings in the spiral grooves of the compliant column obtained in step a6.

[0018] Step b2: Place the optical fiber coated with polyimide into the spiral groove of the compliant column mentioned above.

[0019] Step b3: Fiber optics with gratings are laid in the recessed groove of the above-mentioned compliant column.

[0020] Step b4: Apply 770-6 treatment agent to the surface of the optical fiber to form a thin film. Use 998-3T silicone to attach the optical fiber with the film at one end to the cis-conversion column and let it stand for 12 hours to complete the bonding.

[0021] Step b5: Twist the compliant column obtained in step b4 360° in the opposite direction of the spiral groove, then put the fiber grating in and stick it with 998-3T silicone. After standing for 12 hours, the fiber is stuck on the compliant column and the fiber also retains a certain amount of prestress.

[0022] Step b6: Repeat the above steps to apply prestress to the other optical fiber with a grating.

[0023] Step c: Fix the compliant cylinder obtained in step b6 onto the rotary displacement stage, control the torsion angle of the rotary displacement stage and stretch the compliant cylinder, record the center wavelength value of the fiber grating sensor, plot the relationship curve between the center wavelength and the stretching amount and torsion angle, and respectively deduce the stretching length and torsion angle.

[0024] Furthermore, the curing agent is organotin.

[0025] Furthermore, the semi-cylindrical metal shell (1) has a diameter of 60 mm and a length of 160 mm; the compliant column has a diameter of 17 mm and a length of 160 mm.

[0026] Furthermore, within the range of 0-10mm in stretching amount and within the range of 180° clockwise rotation, the rotation angle of the compliant column is linearly related to the center wavelength of the fiber optic grating sensor.

[0027] Furthermore, the relationship between the center wavelength offset of the fiber optic grating sensor and the strain at the measuring point caused by the deformation of the soft manipulator can be expressed as: Δλ B =λ B ·(1-p ε )·ε; where Δλ B It is the shift of the center wavelength, p ε It is the optical constant of the optical fiber.

[0028] Furthermore, the semi-cylindrical mold is semi-enclosed.

[0029] Furthermore, the coating layer of the optical fiber is polyimide.

[0030] Furthermore, the fiber grating etched on the optical fiber has a length of 3 mm.

[0031] The beneficial effects of this invention are as follows:

[0032] This invention relates to wellbore location identification research based on a fiber optic grating three-component geophone. By spirally winding two optical fibers around a conformal column, the torsional angle and tensile length of the conformal column can be simultaneously determined. This invention has a simple structure and low manufacturing cost. It lays the foundation for real-time monitoring of the angle rotated by the three-component geophone during the wellbore process.

[0033] It should be understood that the foregoing general description and the subsequent detailed description are illustrative and explanatory, and should not be used as limitations on the content claimed in this invention. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure of the present invention.

[0035] Figure 2 This is a schematic diagram showing how the center wavelength of grating 1 changes with the torsion angle when stretched to lengths of 2mm and 4mm respectively.

[0036] Figure 3 This is a schematic diagram showing how the center wavelength of grating 2 changes with the torsion angle when stretched to lengths of 2mm and 4mm respectively.

[0037] Figure 4 This is a schematic diagram showing the inversion of the torsion angle when stretched to lengths of 2mm and 4mm respectively.

[0038] Figure 5 This is a schematic diagram showing the inverted stretching lengths when stretched to 2mm and 4mm respectively.

[0039] Figure 6 A schematic diagram of a semi-cylindrical mold for making a compliant cylinder. Detailed Implementation

[0040] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the present invention is not limited to the following embodiments.

[0041] like Figure 1 As shown, the well location identification sensor based on a fiber optic grating three-component detector includes two optical fibers coated with polyimide, each fiber optic grating etched on it, and a conformal column made of silicone. The two fiber optic gratings are encapsulated within the silicone body to form the conformal column. The conformal column is then fixed inside a metal casing.

[0042] The working principle of this embodiment is as follows: During the downhole process, the three-component geophone rotates randomly, thereby causing the metal shell of the compliant cylinder to rotate. The three-component geophone has a certain weight, which stretches the metal shell of the compliant cylinder, causing torsional and tensile stresses on the metal shell. The metal shell transmits torsional and tensile strains to the compliant cylinder, which in turn transmits the strain to the fiber grating. The center wavelength of the fiber grating drifts. Based on the center wavelength drifts of the two fiber gratings, the torsional angle and tensile length of the compliant cylinder can be simultaneously calculated. Therefore, the torsional angle of the three-component geophone can be calculated simultaneously.

[0043] The formulas for retrieving the tensile length and torsional angle of a compliant cylinder are as follows:

[0044]

[0045]

[0046] φ is the torsion angle, Δb is the stretching amount, a is the helical rise angle of the fiber wound with the compliant cylinder, v1 is the Poisson's ratio of the compliant cylinder material, and V2 is the Poisson's ratio of the fiber.

[0047] Example

[0048] The fiber is coated with polyimide, the fiber grating is 3mm long, and a fiber grating is engraved on each fiber. The fiber is placed in a spiral groove and a certain prestress is applied. It is then glued with 998-3T silicone to complete the fabrication of the compliant column with embedded fiber.

[0049] To verify the beneficial effects of the present invention, the inventors conducted the following experiments using examples:

[0050] Fix the upper end of the compliant cylinder and the lower end to the rotary displacement stage. Connect the optical fiber to the SM130 demodulator from Micro-Optics Technology Co., Ltd. The rotary displacement stage has a step size of 15°. First, stretch the compliant cylinder by 2mm, then twist it clockwise from 0° to 180° in 15° intervals. Next, stretch the compliant cylinder by 4mm and twist it clockwise from 0° to 180° in 15° intervals. Figure 2 When the stretching length remains constant at 2 mm, the wavelength of FBG1 increases linearly with the increase of the torsion angle. After stretching the compliant cylinder to 4 mm, the relationship line between the wavelength of FBG1 and the torsion angle also shifts upwards in parallel. Figure 3 When the stretching length is kept constant at 2 mm, the wavelength of FBG2 decreases linearly with the increase of the torsion angle. After stretching the compliant cylinder to 4 mm, the relationship line between the wavelength of FBG2 and the torsion angle also shifts upward in parallel.

[0051] exist Figure 4In theory, the inverted torsion angle increases with increasing torsion angle. When stretching a compliant cylinder by 2mm, the inverted torsion angle also increases linearly with increasing torsion angle, with very little error compared to the theoretically inverted torsion angle. When stretching a compliant cylinder by 4mm, the inverted torsion angle also increases linearly with increasing torsion angle, with very little error compared to the theoretically inverted torsion angle. Figure 5 In the experiment, when the stretching length is 2 mm, as the torsion angle increases, the inverted stretching length approximates a straight line, with very little error compared to the theoretical stretching length of 2 mm. Similarly, when the stretching length is 4 mm, as the torsion angle increases, the inverted stretching length also approximates a straight line, with very little error compared to the theoretical stretching length of 4 mm. The resulting error may be due to the hysteresis of the compliant column or the nonlinearity of the silicone material.

[0052] Experimental results show that when fiber optic grating sensors are spirally arranged in a compliant cylinder, they can simultaneously reproduce the torsional angle and tensile length of the compliant cylinder.

[0053] Therefore, this invention can simultaneously invert the torsional angle and extension length of a compliant cylinder, with small errors in the inverted torsional angle and extension length. Furthermore, the torsional angle of the three-component detector can be calculated. This invention has a simple structure and is easy to manufacture. It lays the foundation for real-time monitoring of the torsional angle of the three-component detector in compliant cylinders.

Claims

1. A method for fabricating a well location identification sensor based on a fiber optic grating three-component detector, characterized in that, Includes the following steps: Step a: Prepare a cis-cylinder with oppositely spiraling grooves; Step b: Fiber Bragg gratings are laid on the surface of the compliant column obtained in step a: the coating of the optical fiber is polyimide, the length of the fiber Bragg grating is 3mm, one fiber Bragg grating is engraved on each optical fiber, the optical fiber is placed in the spiral groove and a certain prestress is applied, and it is glued with 998-3T silicone to complete the fabrication of the compliant column with embedded optical fiber. Step c: Fix the compliant cylinder obtained in step b on the rotary displacement stage, control the torsion angle of the rotary displacement stage and stretch the compliant cylinder, record the center wavelength value of the fiber grating sensor, plot the relationship curve between the center wavelength and the stretching amount and the torsion angle, and respectively deduce the stretching length and the torsion angle. The formulas for retrieving the tensile length and torsional angle of a compliant cylinder are as follows: （1） （2） For the twist angle, This is the amount of stretching. The spiral ascent angle of the fiber-optic acclimatized cylinder. For compliant columns, the material Poisson's ratio is... Poisson's ratio for optical fiber; The well location identification sensor based on a fiber optic grating three-component detector includes a semi-cylindrical metal shell (1), which has four M2 threaded holes A (2), B (3), C (4) and D (5); a semi-arc clamp A (6) has two M2 holes A (7) and B (8), and a semi-arc clamp B (9) has two M2 holes C (10) and D (11); threaded holes A (2) and A (7) coincide, threaded holes B (3) and B (8) coincide, threaded holes C (4) and C (10) coincide, and threaded holes D (5) and D (11) coincide; the semi-arc clamp A (6) and the semi-arc clamp B (9) clamp the compliant cylinder and fix it inside the semi-cylindrical metal shell (1) through holes A (7), B (8), C (10) and D (11); During the process of lowering the three-component geophone into the well, it rotates randomly, thereby causing the metal shell of the compliant cylinder to rotate. The three-component geophone has a certain weight, which stretches the metal shell of the compliant cylinder, causing the metal shell to generate torsion and tension. The metal shell transfers the torsional strain and tensile strain to the compliant cylinder, which in turn transfers the strain to the fiber grating. The center wavelength of the fiber grating drifts. Based on the center wavelength drift of the two fiber gratings, the torsional angle and tensile length of the compliant cylinder are simultaneously inferred, thereby calculating the torsional angle of the three-component geophone.

2. The method for fabricating a well location identification sensor based on a fiber optic grating three-component detector according to claim 1, characterized in that, The semi-cylindrical metal shell (1) has a diameter of 60 mm and a length of 160 mm; the compliant column has a diameter of 17 mm and a length of 160 mm.

3. The method for fabricating a well location identification sensor based on a fiber optic grating three-component detector according to claim 1, characterized in that, Within the range of 0-10mm in stretching amount and within the range of 180° clockwise rotation, the rotation angle of the compliant column is linearly related to the center wavelength of the fiber optic grating sensor.

4. The method for fabricating a well location identification sensor based on a fiber optic grating three-component detector according to claim 1, characterized in that, The semi-cylindrical metal shell (1) is made of elastic alloy 3J22.

Images