Method for determining perforation damping spring parameters based on pressure wave spectrum analysis

Abstract

The invention discloses a method for determining perforation damping spring parameters based on pressure wave spectrum analysis. The method comprises the following steps: 1) acquiring pressure wave data during perforation of different reference oil and gas wells; 2) establishing a pressure wave database under different well condition parameters; 3) selecting pressure wave data corresponding to the reference well under approximately same well conditions; 4) obtaining a time-domain pressure curve according to the pressure wave data, and obtaining a frequency-domain pressure curve through spectral analysis; 5) processing the frequency domain pressure curve to obtain a key frequency; 6) determining the design reference frequency of the perforation damping spring according to the key frequency; (7) determining the inherent frequency of the perforation damping spring according to the optimal shock insulation frequency ratio; (8) according to the inherent frequency of the perforation damping spring, the function relation of the spring wire diameter, the spring intermediate diameter and the number of effective turns is obtained; and 9) determining the numerical values of the spring wire diameter, the spring pitch diameter and the number of effective turns according to the structural constraint. The method belongs to the technical field of oil-gas well oil pipe transmission perforation, parameters are reasonably determined, and the application effect is good.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oil tubing transmission perforation of oil and gas wells, and relates to a method for determining parameters of perforation shock-absorbing springs based on pressure wave spectrum analysis. BACKGROUND

[0002] In the operation of perforation testing combination, a perforator generates strong low-frequency impact pressure waves when perforating, which are propagated around the explosion point through the pipe string connection link, well medium and casing wall. Therefore, a shock-absorbing tool needs to be installed in the perforation pipe string to absorb the pressure waves so as to avoid damage or fracture of the pipe string and testing tool caused by low-frequency impact. A Chinese document (DOI: CNKI: SUN: JXGU.0.2015-02-113) provides a design theory of longitudinal shock absorber. The document makes in-depth analysis on the selection of spring material and section, and adopts a rectangular section spring with greater stiffness coefficient to absorb more vibration capacity. The stiffness of the rectangular section spring with the same section area is greater than that of the circular section spring, but the increase of the stiffness will increase the natural frequency, and the increase of the natural frequency will increase the probability of resonance of the spring under the action of perforation explosion wave, which may cause damage to the perforation pipe string. A Chinese patent (publication number: CN107100598B, publication date: 2018.06.29) provides a perforation shock absorber device. The invention uses two different springs to absorb the vibration energy of the pipe string when perforating. A Chinese patent (publication number: CN205477558U, publication date: 2016.08.17) provides a perforation shock absorber for cable transmission. The perforation shock absorber described in the utility model has a spring built-in, and a wire passing structure is arranged in the inner diameter, which meets the requirements of cable transmission perforation. The above-mentioned documents and patents mainly describe the main mechanical structure of the shock absorber, and do not involve the parameter design of the spring.

[0003] The perforation shock-absorbing spring, which is the core shock-absorbing element of the shock-absorbing tool, mainly uses the experience method or the structure constraint of the shock-absorbing tool to determine the related parameters of the perforation shock-absorbing spring in the prior art, which leads to poor matching of the natural frequency of the prepared perforation shock-absorbing spring and the frequency of the pressure wave, poor actual shock-absorbing effect of the shock-absorbing tool, and even resonance, which causes damage to the pipe string or the packer. Therefore, it is urgent to develop a new method for determining the parameters of the perforation shock-absorbing spring to better serve the perforation combination process technology. SUMMARY

[0004] The application aims to provide a method for determining the parameters of the perforation shock-absorbing spring based on pressure wave spectrum analysis, which solves the problem of poor matching of the natural frequency of the perforation shock-absorbing spring and the frequency of the impact pressure wave generated when perforating in the prior art.

[0005] The technical scheme adopted by the present application is a method for determining the parameters of a perforation shock absorption spring based on pressure wave spectrum analysis, which is implemented according to the following steps:

[0006] Step 1: Collect a large amount of pressure wave data of perforation in different reference oil and gas wells by using a downhole pressure gauge;

[0007] Step 2: Establish a pressure wave database under different well condition parameters, specifically involving the parameters of well depth, technology, temperature, pressure and shot thickness;

[0008] Step 3: According to the well condition of the target application well, select the pressure wave data corresponding to the reference well under approximately the same well condition from the pressure wave database;

[0009] Step 4: Obtain the time domain pressure curve according to the pressure wave data selected in step 3, and obtain the frequency domain pressure curve through spectrum analysis;

[0010] Step 5: Process the frequency domain pressure curve to obtain the key frequency;

[0011] Step 6: Determine the design reference frequency f o of the perforation shock absorption spring according to the key frequency;

[0012] Step 7: Determine the natural frequency f s of the perforation shock absorption spring according to the best shock isolation frequency ratio;

[0013] Step 8: Obtain the functional relationship of the spring wire diameter d, the spring middle diameter D and the effective number of turns n according to the natural frequency f s of the perforation shock absorption spring;

[0014] Step 9: Finally determine the numerical values of the spring wire diameter d, the spring middle diameter D and the effective number of turns n according to the structural constraints of the shock absorption tool.

[0015] The present application has the beneficial effect that the perforation shock absorption spring parameters determined by the method have a best shock isolation frequency ratio of the natural frequency to the perforation pressure wave frequency, and when applied in the preparation of a perforation shock absorption tool, the best shock absorption effect can be achieved in actual perforation, and the problem of poor matching caused by resonance of the perforation string due to impact pressure waves is effectively avoided. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a flowchart of the method of the present application;

[0017] Figure 2 is a time domain pressure curve diagram obtained in example 1 of the method of the present application;

[0018] Figure 3 is a frequency domain pressure curve diagram obtained in example 1 of the method of the present application;

[0019] Figure 4Time domain pressure curve chart obtained in the method embodiment 2 of the present application;

[0020] Figure 5 Frequency domain pressure curve chart obtained in the method embodiment 2 of the present application;

[0021] Figure 6 Time domain pressure curve chart obtained in the method embodiment 3 of the present application;

[0022] Figure 7 Frequency domain pressure curve chart obtained in the method embodiment 3 of the present application. DETAILED DESCRIPTION

[0023] The present application will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] Reference Figure 1 The method for determining the parameters of the perforation shock-absorbing spring based on the pressure wave spectrum analysis, according to the following steps:

[0025] Step 1: A large number of pressure wave data of perforation in different reference oil and gas wells are collected by using downhole pressure gauges.

[0026] A large number of collection refers to a plurality of reference oil and gas wells, and each reference oil and gas well is collected only once.

[0027] Step 2: A pressure wave database under different well condition parameters is established, which specifically involves parameters such as well depth, process, temperature, pressure, and perforation thickness.

[0028] The parameters of the process refer to drill pipe transmission, perforation testing combined operation, segmentation, and detonation mode.

[0029] Step 3: According to the well condition of the target application well, the pressure wave data corresponding to the reference well under the approximately same well condition is selected from the pressure wave database.

[0030] Step 4: The time domain pressure curve is obtained according to the pressure wave data selected in step 3, and the frequency domain pressure curve is obtained through spectrum analysis;

[0031] The time domain pressure curve is extracted from the pressure wave data, and this process is a mature existing technology.

[0032] The frequency domain pressure curve is generated by using the spectrum analysis method, and the existing technologies include but are not limited to signal processing methods such as Fourier transform, wavelet transform, and Hilbert transform.

[0033] Step 5: The key frequency is obtained by processing the frequency domain pressure curve,

[0034] Specifically, the maximum pressure value P of the pressure wave is extracted max to 50% P maxThe frequency data between the two frequencies is taken as the key frequency. This key frequency is the data of an interval, which is determined according to the actually measured pressure value, and is not data defined in advance, so there is no allowed range.

[0035] Step 6: Determine the perforation shock-absorbing spring design reference frequency f o according to the key frequency

[0036] Specifically, the lowest frequency f min in the key frequency is determined as the perforation shock-absorbing spring design reference frequency f o .

[0037] Step 7: Determine the perforation shock-absorbing spring natural frequency f s according to the optimal shock isolation frequency ratio

[0038] Specifically, the shock isolation frequency ratio f s is the perforation shock-absorbing spring natural frequency, λ < 1, f o (f min ) is less than f s , the perforation shock-absorbing spring does not absorb the pressure wave energy of the frequency f o , and does not have a shock-absorbing effect; λ = 1, f o (f min ) is equal to f s , the perforation shock-absorbing spring resonates and intensifies the damage to the perforation string; λ > 1, f o (f min ) is greater than f s , f s enters the shock isolation zone; by determining the optimal shock isolation ratio λ, f s can be determined

[0039] According to the prior art knowledge, the ratio λ of the external excitation frequency f o to the spring natural frequency f s is greater than the system enters the vibration isolation zone, the greater the shock isolation frequency ratio λ, the better the spring vibration isolation effect, and in engineering, the shock isolation frequency ratio λ is generally taken in the range of 2.5-5.0.

[0040] Step 8: According to the perforation shock-absorbing spring natural frequency f s , the function relationship of the spring wire diameter d, the spring diameter D, and the effective number of turns n is obtained

[0041] Specifically, by the spring wire diameter d, the spring diameter D, and the effective number of turns n can be determined

[0042]

[0043] Wherein, G is spring shear modulus, d is spring wire diameter, D is spring diameter, n is spring effective number of turns, p is spring material density, P is spring stiffness, and m is spring mass.

[0044] Step 9: according to the constraint of the shock-absorbing tool structure, the values of the spring wire diameter d, the spring diameter D and the effective number of turns n are finally determined.

[0045] Specifically, the constraint condition is D i -d>D>D o +d. i D is the constraint value of the large diameter of the perforation shock-absorbing spring in the shock-absorbing tool, and D o is the constraint value of the small diameter of the perforation shock-absorbing spring in the shock-absorbing tool. The specific values of D, d and n are finally obtained from D = mu d, mu [5, 8].

[0046] The constraint condition is determined by the mechanical structure of the shock-absorbing tool. The spring is installed in the shock-absorbing tool, and the spring is located between the shell of the shock-absorbing tool and the central rod of the shock-absorbing tool. Therefore, the large diameter D+d of the spring is smaller than the inner diameter D i of the shell of the shock-absorbing tool, and the small diameter D-d of the spring is larger than the outer diameter D o of the central rod of the shock-absorbing tool. Therefore, D+d < D i and D-d > D o are combined together, that is, D i -d > D > D o +d.

[0047] The working principle of the application is that a large amount of pressure wave data during perforation of different reference oil and gas wells is collected by using a downhole pressure gauge, and a pressure wave database under different well conditions is established, which specifically relates to well depth, technology, temperature, pressure, shot thickness and the like. When designing the shock absorber spring, the pressure wave data under approximately the same well condition is selected from the pressure wave database according to the well condition of the application well; the time domain pressure curve is obtained by extracting the data, and the frequency domain pressure curve is generated by spectrum analysis on the time domain pressure curve; the frequency data between the maximum pressure value and 50% of the maximum pressure value of the pressure wave is extracted, and the lowest frequency therein is determined as the design reference frequency of the perforation shock-absorbing spring; according to the shock-absorbing principle, a suitable shock isolation ratio is designed to determine the natural frequency of the perforation shock-absorbing spring; finally, the parameter values of the spring wire diameter, the spring diameter and the effective number of turns of the spring are determined in combination with the constraint of the shock-absorbing tool structure.

[0048] Embodiment 1

[0049] As shown in the following steps, the method for determining the parameters of the perforation shock-absorbing spring based on the spectrum analysis of the pressure wave is implemented according to the following steps: Figure 1

[0050] Step 1: a large amount of pressure wave data during perforation of different reference oil and gas wells is collected by using a downhole pressure gauge. ​

[0051] Step 2: Establish a pressure wave database under different well condition parameters, including well depth, process, temperature, pressure, and shot thickness.

[0052] This data is too much, involving a large amount of database data, which is not listed here.

[0053] Step 3: According to the well condition of the application well, select the pressure wave data of the reference well under approximately the same well condition from the pressure wave database. The well condition of the application well is approximately 4000 meters in well depth, perforation test combined process, well temperature 70℃, bottom hole pressure 100MPa, and shot thickness 40 meters.

[0054] Step 4: Obtain the time domain pressure curve according to the pressure wave data selected in step 3, and obtain the frequency domain pressure curve through frequency spectrum analysis;

[0055] Specifically, the time domain pressure curve obtained by extracting the pressure wave data is shown in Figure 2 . Then the frequency domain pressure curve is generated by using the frequency spectrum analysis method, as shown in Figure 3 .

[0056] Step 5: Process the frequency domain pressure curve to obtain the key frequency:

[0057] Specifically, extract the frequency data between the maximum pressure value P max = 39.6psi and 50% P max = 19.8psi as the key frequency.

[0058] Step 6: Determine the design reference frequency of the perforation shock absorbing spring according to the key frequency;

[0059] Specifically, the lowest frequency f min = 53.7Hz in the key frequency is determined as the design reference frequency f o of the perforation shock absorbing spring.

[0060] Step 7: Determine the natural frequency of the perforation shock absorbing spring according to the best shock isolation frequency ratio.

[0061] Specifically, the shock isolation frequency ratio f s is the natural frequency of the perforation shock absorbing spring. When λ < 1, f o (f min ) is less than f s , the perforation shock absorbing spring will not absorb the pressure wave energy of frequency f o , and will not have a shock absorbing effect; when λ = 1, f o (f min ) is equal to f s , the perforation shock absorbing spring will resonate and intensify the damage to the perforation string; when λ > 1, f o (f min) greater than f s f s Enter the seismic isolation zone;

[0062] In this embodiment 1, the optimal seismic isolation ratio λ = 5 is determined, and f can then be determined. s =10.74Hz;

[0063] Step 8: Determine the relationship between the spring wire diameter, spring mean diameter, and effective number of coils based on the natural frequency of the perforation damping spring.

[0064] Specifically, by Sure G is the shear modulus of the spring, d is the spring wire diameter, D is the spring mean diameter, n is the effective number of coils of the spring, and ρ is the density of the spring material.

[0065] Step 9: Determine the values ​​of spring wire diameter, spring mean diameter, and effective number of coils based on the structural constraints of the damping tool.

[0066] Specifically, the constraint is D. i -d>D>D o +d,D i =68mm is the constraint value of the perforation damping spring on the major diameter inside the damping tool, D o =42mm is the constraint value of the perforation damping spring on the minor diameter inside the damping tool;

[0067] From D = 5d, we can determine that D = 55mm, d = 11mm, and n = 16.

[0068] As can be seen, the overall effect of the manufacturing process according to the method of this invention fully meets the technical requirements. The shock-absorbing spring made according to Embodiment 1 can effectively absorb the pressure wave during perforation, preventing the tubing and testing tools from being subjected to low-frequency impacts. Through actual field application, the perforation tubing did not suffer damage or breakage, confirming the good effect of this technology.

[0069] Example 2

[0070] like Figure 1 As shown, the method for determining the parameters of a perforation damping spring based on pressure wave spectrum analysis according to the present invention is implemented in accordance with the following steps:

[0071] Step 1: Collect a large amount of pressure wave data during perforation of different reference oil and gas wells using downhole pressure gauges.

[0072] Step 2: Establish a pressure wave database for different well conditions, specifically involving parameters such as well depth, process, temperature, pressure, and injection thickness.

[0073] Step 3: According to the well condition of the application well, select the pressure wave data of the reference well under approximately the same well condition from the pressure wave database. The well condition of the application well is approximately 6000 meters in depth, perforation test joint operation process, well temperature 85℃, bottom hole pressure 120MPa, and shot thickness 25 meters.

[0074] Step 4: Obtain the frequency domain pressure curve through frequency spectrum analysis according to the time domain pressure curve of the pressure wave;

[0075] Specifically, the time domain pressure curve is extracted from the pressure wave data, see Figure 4 , and the frequency domain pressure curve is generated through frequency spectrum analysis, see Figure 5 .

[0076] Step 5: Process the frequency domain pressure curve to obtain the key frequency:

[0077] Specifically, the frequency data of the maximum pressure value P max =128.6psi to 50% P max =64.3psi of the pressure wave is taken as the key frequency.

[0078] Step 6: Determine the design reference frequency of the perforation shock absorption spring according to the key frequency;

[0079] Specifically, the lowest frequency f min =76.2Hz in the key frequency is determined as the design reference frequency f o of the perforation shock absorption spring.

[0080] Step 7: Determine the natural frequency of the perforation shock absorption spring according to the optimal shock isolation frequency ratio.

[0081] Specifically, the shock isolation frequency ratio f s is the natural frequency of the perforation shock absorption spring. When λ<1, f o (f mon ) is less than f s , the perforation shock absorption spring does not absorb the pressure wave energy of frequency f o , and does not play a shock absorption role; when λ=1, f o (f min ) is equal to f s , the perforation shock absorption spring resonates and intensifies the damage to the perforation string; when λ>1, f o (f min ) is greater than f s , f s enters the shock isolation zone. By determining the optimal shock isolation ratio λ=5, f s =15.24Hz can be determined.

[0082] Step 8: Determine the relationship among the spring wire diameter, spring diameter, and effective number of turns according to the natural frequency of the perforation shock absorption spring.

[0083] Specifically, by Sure G is the shear modulus of the spring, d is the spring wire diameter, D is the spring mean diameter, n is the effective number of coils of the spring, and ρ is the density of the spring material.

[0084] Step 9: Determine the spring wire diameter, spring mean diameter, and effective number of coils based on the structural constraints of the damping tool.

[0085] Specifically, D i -d>D>D o +d,D i =76mm perforation damping spring, the constraint value D on the major diameter of the damping tool. o =54mm perforation damping spring is constrained within the minor diameter of the damping tool. From D=6.5d, the final values ​​are determined as D=65mm, d=10mm, and n=18.

[0086] As can be seen, the overall effect of the manufacturing process according to the method of this invention fully meets the technical requirements. The shock-absorbing spring manufactured according to Embodiment 2 can effectively absorb the pressure wave during perforation, preventing the tubing and testing tools from being subjected to low-frequency impacts. Through actual field application, the perforation tubing did not suffer damage or breakage, confirming the good effect of this technology.

[0087] Example 3

[0088] like Figure 1 As shown, the method for determining the parameters of a perforation damping spring based on pressure wave spectrum analysis according to the present invention is implemented in accordance with the following steps:

[0089] Step 1: Collect a large amount of pressure wave data during perforation of different reference oil and gas wells using downhole pressure gauges.

[0090] Step 2: Establish a pressure wave database for different well conditions, specifically involving parameters such as well depth, process, temperature, pressure, and injection thickness.

[0091] Step 3: Based on the well conditions of the application well, select pressure wave data from a reference well with approximately the same conditions from the pressure wave database. The application well's conditions are approximately: depth 8000 meters, perforation testing combined with other processes, well temperature 100℃, bottom hole pressure 140MPa, and perforation thickness 30 meters.

[0092] Step 4: Obtain the frequency domain pressure curve based on the time domain pressure curve of the pressure wave through spectral analysis;

[0093] Specifically, pressure wave data is extracted to obtain the time-domain pressure curve, see... Figure 6 Frequency domain pressure curves were generated through spectral analysis, see... Figure 7 .

[0094] Step 5: Process the frequency domain pressure curve to obtain the key frequency:

[0095] Specifically, extract the maximum pressure value P of the pressure wave. max =255.6psi to 50%P max The frequency data of 127.8 psi is used as the key frequency.

[0096] Step 6: Determine the design reference frequency of the perforation damping spring based on the key frequency;

[0097] Specifically, the lowest frequency f in the key frequency range min =84.6Hz was determined as the design reference frequency f for the perforation damping spring. o .

[0098] Step 7: Determine the natural frequency of the perforation damping spring based on the optimal vibration isolation frequency ratio.

[0099] Specifically, the isolation frequency ratio f s When f is the natural frequency of the perforation damping spring, and λ < 1, o (f min (less than f) s The perforation damping spring will not absorb frequency f. o The pressure wave energy has no damping effect; when λ=1, f o (f min ) equals f s The perforation damping spring will resonate, exacerbating the damage to the perforation string; when λ>1, f o (f min ) greater than f s f s Enter the seismic isolation zone. Determine the optimal seismic isolation ratio λ = 5, and obtain f. s =16.92Hz;

[0100] Step 8: Determine the relationship between the spring wire diameter, spring mean diameter, and effective number of coils based on the natural frequency of the perforation damping spring.

[0101] Specifically, by Sure G is the shear modulus of the spring, d is the spring wire diameter, D is the spring mean diameter, n is the effective number of coils of the spring, and ρ is the density of the spring material.

[0102] Step 9: Determine the spring wire diameter, spring mean diameter, and effective number of coils based on the structural constraints of the damping tool.

[0103] Specifically, D i -d>D>D o +d,D i =66mm perforation damping spring, the constraint value D on the major diameter of the damping tool. oD = 44 mm is the constraint value of the small diameter of the shock absorbing spring in the shock absorbing tool. According to D = 7d, it can be determined that D = 56 mm, d = 8 mm, and n = 20.

[0104] It can be seen that the overall effect of the manufacturing process according to the method of the application fully meets the technical requirements. The shock absorbing spring manufactured according to the third embodiment can effectively absorb the pressure wave during perforation, thereby avoiding low-frequency impact on the pipe string and the testing tool. Through actual field application, the perforation pipe string has not been damaged or broken, which confirms that the technology has good effects.

Claims

1. A method for determining parameters of a perforation shock absorbing spring based on pressure wave spectral analysis, characterized by, The following steps are implemented: Step 1: Collect pressure wave data of different reference oil and gas well perforation by using downhole pressure gauge; Step 2: Establish pressure wave database under different well condition parameters, which specifically involves well depth, technology, temperature, pressure and shot thickness parameters; Step 3: According to the well condition of the target application well, select the pressure wave data corresponding to the reference well under the approximately same well condition from the pressure wave database; Step 4: Obtain time domain pressure curve according to the pressure wave data selected in step 3, and obtain frequency domain pressure curve through frequency spectrum analysis; Step 5: Process the frequency domain pressure curve to obtain the key frequency; Step 6: Determine the perforation shock spring design reference frequency f based on the key frequency o ; Step 7: Determine the natural frequency f of the perforation shock absorbing spring based on the best isolation frequency ratio s ; Step 8: According to the natural frequency f of the perforation shock absorbing spring s , get the function relationship of spring wire diameter d, spring diameter D, and effective number of turns n; Step 9: According to the structure constraint of the shock absorption tool, finally determine the values of spring wire diameter d, spring diameter D and effective number of turns n.

2. The method of claim 1, wherein: In step 1, the collection method refers to that for multiple reference oil and gas wells, each reference oil and gas well is collected only once.

3. The method of claim 1, wherein: In step 2, the parameter of technology refers to drill pipe transmission, perforation test combination, segmentation and detonation mode.

4. The method of claim 1, wherein: In step 4, The frequency domain pressure curve generated by the frequency spectrum analysis method refers to the signal processing method of Fourier transform, wavelet transform or Hilbert transform.

5. The method of claim 1, wherein: In step 5, the maximum pressure value P of the pressure wave is extracted max between 0 and 50% P max as the key frequency.

6. The method of claim 1, wherein: In step 6, the lowest frequency f min The design reference frequency f o is determined for the perforating shock absorbing spring 7. The method of claim 1, wherein: In step 7, Isolation frequency ratio f s The natural frequency of the perforation shock-absorbing spring, λ < 1, f o < f s , the perforation shock-absorbing spring does not absorb the pressure wave energy of frequency f o , and does not play a shock-absorbing role; λ = 1, f o = f s , the perforation shock-absorbing spring will resonate and intensify the damage to the perforation string; λ > 1, f o > f s , f s enters the isolation zone; determining the optimal isolation ratio λ can determine f s .

8. The method of claim 7, wherein: The value range of the shock isolation frequency ratio λ is 2.5-5.

0.

9. The method of claim 1, wherein: In step 8, By It is possible to determine Wherein, G is the shear modulus of the spring, d is the spring wire diameter, D is the spring diameter, n is the effective number of turns of the spring, ρ is the density of the spring material, P is the spring stiffness, and m is the spring mass.

10. The method of claim 1, wherein: In step 9, The constraint condition is D i -d > D > d o +d, D i D is the constraint value of the large diameter of the perforating shock absorbing spring in the shock absorbing tool o D is the constraint value of the small diameter of the perforating shock absorbing spring in the shock absorbing tool; by D=μd, μ∈[5,8], the specific values of the spring medium diameter D, the spring wire diameter d and the effective number of turns n are finally obtained.

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