Methods for measuring downhole drill string vibration

Abstract

This invention relates to the field of oil drilling technology and is a method for measuring downhole drill string vibration. The method comprises the following steps: setting a first vibration measuring point on the central axis of the rotary guide tool of the drill string; setting a second vibration measuring point at an eccentric position of the measurement-while-drilling tool (MWD tool) from the center of the drill string; setting sensors at the first and second measuring points respectively; measuring the lateral and axial vibration acceleration values ​​at the two measuring points; calculating the axial, lateral, and torsional vibrations of the drill string; and qualitatively determining the drill string's motion state and main vibration modes. This invention provides technical support for in-depth understanding of the excitation mechanism and inherent characteristics of downhole drilling tool vibration, comparative analysis of downhole drill string vibration, and in-depth research on drill string vibration patterns, and further provides practical numerical support for drill string dynamics theory research. This method is convenient, effective, flexible in operation, and easy to promote and apply, with broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of oil drilling technology and is a method for measuring downhole drill string vibration. Background Technology

[0002] Oil drilling is a crucial step in oil and gas exploration and development. The drill string is the primary drilling tool, comprising the drill bit, bottom access assembly (BH method for measuring downhole drill string vibration), drill pipe, and stabilizers. Drill string vibration is mainly generated by the drill bit's roller cones pressing against the formation. Simultaneously, the drill string operates in a narrow wellbore filled with drilling fluid or gas, bearing loads such as tension, compression, bending, torsion, and drilling fluid pressure. Furthermore, the heterogeneity of the formation and the dynamic characteristics of drilling pressure and torque often result in various vibrations (axial vibration, lateral vibration, torsional vibration, and vortex vibration, such as…). Figure 1 As shown in the figure, the main manifestation and risk source of torsional vibration is stick-slip vibration. Severe vibration can lead to problems such as drill string breakage, drill pipe disengagement, roller cone breakage, inaccurate downhole measurement data, and damage to measuring instruments, resulting in significant economic losses. Therefore, it is essential to detect and study the vibration of the downhole drill string.

[0003] Drill string vibration data acquisition mainly involves two types: surface measurement systems and downhole measurement-while-drilling (MWD) systems. Due to the high flexibility of the drill string and its frequent contact with the wellbore, surface measurement systems cannot accurately determine the lateral vibration of the downhole drill string. MWD systems are further divided into real-time measurement and storage-based measurement. In practical applications in China, real-time measurement is commonly used, utilizing real-time monitoring of drilling vibration and impact parameters to monitor the condition of the bottom hole. After acquisition and processing, the axial acceleration, radial acceleration, torque, and drill collar rotation speed of the bottom hole are transmitted in real-time to the surface system via mud pulses. After processing by surface software, the working status of the downhole drill string can be identified in a timely manner, providing a reference for adjusting drilling parameters and effectively preventing drill string accidents. This real-time measurement method is limited by the transmission speed of the mud pulse signal, so it can only use a lower sampling frequency, which cannot meet the frequency required by the sampling theorem. Therefore, it cannot perform subsequent spectrum analysis of the signal to understand the natural frequencies and excitation characteristics of the drill string in the lateral, longitudinal, and torsional directions, and thus cannot analyze drill string vibration data and diagnose vibration excitation sources. Chinese patent document CN107229599B discloses a method for monitoring torsional vibration of the drill string, and Chinese patent document CN113076649A discloses a method for analyzing the lateral vibration of a drill string in a complex structure well. Both use a single measurement method to analyze the torsional and lateral vibrations of the drill string, which cannot meet the requirements for subsequent spectrum analysis. Summary of the Invention

[0004] This invention provides a method for measuring downhole drill string vibration, which overcomes the shortcomings of the prior art and effectively solves the problems of existing downhole measurement while drilling systems having a single measurement method and measurement data that cannot meet the needs of subsequent data analysis.

[0005] The technical solution of the present invention is achieved through the following measures: a method for measuring downhole drill string vibration, comprising the following steps: setting a first vibration measuring point on the central axis of the rotary guide drill string, setting a second vibration measuring point at an eccentric position of the measurement while drilling tool from the center of the drill string, setting sensors at the first and second vibration measuring points respectively, measuring the lateral vibration acceleration value and the axial vibration acceleration value of the two vibration measuring points, calculating the axial vibration, lateral vibration, and torsional vibration of the drill string, and qualitatively determining the motion state and main vibration mode of the drill string.

[0006] The following are further optimizations and / or improvements to the above-mentioned technical solution:

[0007] The sensor at the first vibration measurement point consists of three orthogonally distributed accelerometers and a fluxgate magnetometer.

[0008] The sensor at the second vibration measurement point consists of three orthogonally distributed accelerometers.

[0009] The axial and lateral vibration values ​​of the drill string are calculated using Equations 1 and 2 below. Torsional vibration (i.e., stick-slip vibration) is characterized by the stick-slip ratio.

[0010] Axial vibration = a z Formula 1

[0011]

[0012]

[0013] Where: a z The value measured by the axial acceleration sensor at the first vibration measurement point is...

[0014] a x a y These are the measured values ​​from the x-axis and y-axis accelerometers at the first vibration measurement point, respectively.

[0015] StickSlip% is the stickiness / slip ratio.

[0016] averagesurfaceRPM is the average rotational speed of the surface drill string over a period of time, expressed in r / min.

[0017] StickSlip is the difference between the maximum and minimum rotational speeds measured by the magnetometer at the first vibration measurement point over a period of time.

[0018] The above qualitative judgment of the drill string motion state and main vibration modes is based on the following criteria:

[0019] When b zp Axial vibration is obvious when the weight is ≥40g;

[0020] when At the same time b xp ≥30g, b yp When the weight is ≥30g, the drill string mainly vibrates laterally;

[0021] when At the same time b xp ≤90g, b yp When the g is ≤90g, the drill string mainly exhibits stick-slip vibration within torsional vibration;

[0022] when and At the same time b xp >90g, b yp When the g is greater than 90g, the lateral and torsional vibrations of the drill string are coupled into vortex.

[0023] Where g is the acceleration due to gravity, b x b y b z These are the measured values ​​from the three acceleration sensors at the second vibration measurement point. b x b y The average value, b xp b yp b zp b x b y b z The peak value.

[0024] The measurement method for the first vibration measurement point mentioned above is real-time measurement.

[0025] The measurement method for the second vibration measurement point mentioned above is a storage-type measurement.

[0026] This invention addresses the shortcomings of existing single-point real-time measurement systems for downhole drill string vibration by employing a method that sets up two vibration measurement points on the downhole drill string. This combines the real-time vibration detection capabilities of a real-time measurement system, providing a basis for controlling downhole vibration during drilling operations, with the advantages of a storage-based measurement system, which performs frequency domain and time-frequency analysis of the signal. Setting up a second vibration measurement point allows for spectral characteristic analysis of the instantaneous acceleration values ​​obtained from high-frequency acquisition through storage-based measurement, revealing the excitation mechanism and inherent characteristics of downhole drill string vibration. Furthermore, by comparing the data from real-time and storage-based measurements, their vibration data can be cross-validated, and the vibration conditions at different locations on the downhole drill string at the same time can be compared and analyzed, leading to a deeper understanding and study of the drill string's vibration morphology. In addition, by combining drilling log records and well logging data, the changes in drill string vibration caused by variations in drilling parameters can be analyzed in depth. Moreover, this method can provide practical numerical support for drill string dynamics theory research. This method is convenient, effective, flexible in operation, and easy to promote and apply, with broad application prospects. Attached Figure Description

[0027] Appendix Figure 1 This is a schematic diagram of the vibration patterns of the downhole drill string. From left to right, the patterns are axial vibration, lateral vibration, vortex vibration, and torsional vibration.

[0028] Appendix Figure 2 This is a schematic diagram showing the locations of the two vibration measurement points in this invention.

[0029] Appendix Figure 3 This is a schematic diagram showing the location and coordinates of the first vibration measuring point in this invention.

[0030] Appendix Figure 4 This is a schematic diagram showing the location and coordinates of the second vibration measuring point in this invention. Detailed Implementation

[0031] The present invention is not limited to the following embodiments, and the specific implementation can be determined according to the technical solution of the present invention and the actual situation.

[0032] Unless otherwise specified, all equipment and devices used in this invention are existing and commonly known in the art.

[0033] The present invention will be further described below with reference to embodiments:

[0034] Example 1: As Figure 2 As shown, the method for measuring downhole drill string vibration is performed according to the following steps:

[0035] A first vibration measurement point is set on the central axis of the rotary guide drill string, and a second vibration measurement point is set on the measurement-while-drilling tool at an eccentric position away from the center of the drill string. Sensors are set on the first and second vibration measurement points respectively to measure the lateral vibration acceleration and axial vibration acceleration values ​​of the two vibration measurement points. The axial vibration, lateral vibration, and torsional vibration of the drill string are calculated, and the motion state and main vibration mode of the drill string are qualitatively determined.

[0036] In this invention, the bottom drill string assembly consists of a rotary steerable drill string and a measurement-while-drilling (MWD) tool. The second vibration measurement point can be located inside the cover plate of the MWD tool housing.

[0037] Example 2: As an optimization of the above example, the sensor at the first vibration measurement point consists of three orthogonally distributed accelerometers and a fluxgate magnetometer. For example... Figure 3 As shown, O is the wellbore center, and c is the drill string center where the sensor is located. x a y For the lateral vibration acceleration values ​​measured by mutually orthogonal accelerometers, a z The axial vibration acceleration value is measured by an axially arranged accelerometer.

[0038] Example 3: As an optimization of the above embodiment, the sensor at the second vibration measurement point consists of three orthogonally distributed accelerometers. For example... Figure 4 As shown, O is the center of the drill string, and the sensor is located at a distance r from the eccentricity of the drill string axis.

[0039] Measurements b from the three accelerometers x b y b z The expression is:

[0040]

[0041] Where: b xc and b yc These are the lateral and radial acceleration components of the drill string, respectively, b. zc Let r be the axial acceleration of the drill string, and r be the eccentricity of the sensor. Let ω be the angular acceleration of the drill string and ω be the angular velocity of the drill string.

[0042] Example 4: As an optimization of the above examples, the axial and lateral vibration values ​​of the drill string are calculated using Equations 1 and 2 below, and the torsional vibration (i.e., stick-slip vibration) is characterized by the stick-slip ratio:

[0043] Axial vibration = a z Formula 1

[0044]

[0045]

[0046] Where: a z The value measured by the axial acceleration sensor at the first vibration measurement point is...

[0047] a x a y These are the measured values ​​from the x-axis and y-axis accelerometers at the first vibration measurement point, respectively.

[0048] StickSlip% is the stickiness / slip ratio.

[0049] averagesurfaceRPM is the average rotational speed of the surface drill string over a period of time, expressed in r / min.

[0050] StickSlip is the difference between the maximum and minimum rotational speeds measured by the magnetometer at the first vibration measurement point within a certain period of time.

[0051] Example 5: As an optimization of the above examples, the drill string motion state and main vibration modes are qualitatively determined according to the following criteria:

[0052] Axial vibration: when b zp When the force is ≥40g, axial vibration is significant. When axial vibration is significant, the risk of drill jumping is high.

[0053] Lateral vibration: when At the same time b xp ≥30g, b yp When the g is ≥30g, the drill string primarily exhibits lateral vibration. That is, b x When the mean of and by is relatively small, and the peak value is relatively large, the drill string mainly vibrates laterally.

[0054] Torsional vibration: when At the same time b xp ≤90g, b yp When the g is ≤90g, the drill string exhibits predominantly stick-slip vibration within torsional vibration. That is, b x and b y When the mean difference is large and the peak value is in the middle to lower range, the drill string mainly exhibits stick-slip vibration in torsional vibration.

[0055] Eddy: When and At the same time b xp >90g, b yp When the g > 90g, the lateral and torsional vibrations of the drill string couple into eddy currents. That is, b x and b y When the mean values ​​are roughly equal and the peak values ​​are at high values, the lateral vibration and torsional vibration of the drill string are coupled into eddy currents.

[0056] Where g is the acceleration due to gravity, b x b y b z These are the measured values ​​from the three acceleration sensors at the second vibration measurement point. b x b y The average value, b xp b yp b zp b x b y b z The peak value.

[0057] Example 6: As an optimization of the above example, the measurement method of the first vibration measuring point is real-time measurement.

[0058] Example 7: As an optimization of the above example, the measurement method of the second vibration point is a storage measurement.

[0059] In this invention, the second vibration measurement point employs a storage-type vibration measurement system for post-drilling analysis, which can record long-term vibration data using a high sampling frequency. Therefore, in addition to time-domain analysis, more importantly, frequency-domain and time-frequency analysis are also possible. Frequency-domain analysis describes the distribution of different frequency components of the signal across the frequency band, using Fast Fourier Transform (FFT) or wavelet analysis methods. Frequency-domain analysis can determine the frequency distribution of the drill string vibration signal and the strength of each frequency component's energy. Time-frequency analysis reflects both time-domain and frequency-domain characteristics, typically using Short-Time Fourier Transform. Through frequency-domain and time-frequency analysis of the drill string vibration signal, a deeper understanding and revelation of the excitation characteristics of downhole drill string vibration can be achieved.

[0060] This invention addresses the shortcomings of existing single-point real-time measurement systems for downhole drill string vibration by employing a method that sets up two vibration measurement points on the downhole drill string. This combines the real-time vibration detection capabilities of a real-time measurement system, providing a basis for controlling downhole vibration during drilling operations, with the advantages of a storage-based measurement system, which performs frequency domain and time-frequency analysis of the signal. By setting up a second vibration measurement point and using storage-based measurement, the spectral characteristics of the instantaneous acceleration values ​​obtained from high-frequency acquisition can be analyzed, revealing the excitation mechanism and inherent characteristics of downhole drill string vibration. Furthermore, by comparing the data from real-time and storage-based measurements, their vibration data can be cross-validated, and the vibration conditions at different locations of the downhole drill string at the same time can be compared and analyzed, leading to a deeper understanding and study of the drill string's vibration morphology. In addition, by combining drilling log records and well logging data, the changes in drill string vibration caused by changes in drilling parameters can be analyzed in depth. Finally, this provides practical numerical support for research on drill string dynamics theory.

[0061] In summary, the method for measuring downhole drill string vibration of this invention employs two vibration measurement points on the downhole drill string, combining the advantages of real-time vibration measurement systems and storage-based measurement systems. This provides technical support for in-depth understanding of the excitation mechanism and inherent characteristics of downhole drill string vibration, comparative analysis of downhole drill string vibration, and in-depth research on the vibration patterns of the drill string. Furthermore, it provides practical numerical support for theoretical research on drill string dynamics. This method is convenient, effective, flexible in operation, and easy to promote and apply, possessing broad application prospects.

[0062] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. A method of measuring downhole drill string vibrations, characterized by The following steps are performed: a first vibration measurement point is set on the central axis of the rotary guide drill string, and a second vibration measurement point is set at an eccentric position of the measurement while drilling tool from the center of the drill string. Sensors are set at the first and second vibration measurement points respectively to measure the lateral vibration acceleration and axial vibration acceleration values ​​of the two vibration measurement points. The axial vibration, lateral vibration, and torsional vibration of the drill string are calculated, and the motion state and main vibration mode of the drill string are qualitatively determined. The sensor at the first vibration measurement point consists of three orthogonally distributed accelerometers and a fluxgate magnetometer; The sensor at the second vibration measurement point consists of three orthogonally distributed accelerometers; The axial and lateral vibration values ​​of the drill string are calculated using Equations 1 and 2 below, and the torsional vibration is characterized by the viscosity-slip ratio: in: The value measured by the axial acceleration sensor at the first vibration measurement point is... The lateral vibration acceleration at the first vibration measurement point is... These are the measured values ​​from the x-axis and y-axis accelerometers at the first vibration measurement point, respectively. The viscosity-slip ratio, The average rotational speed of the ground drill string over a period of time. , The difference between the maximum and minimum rotational speeds measured by the magnetometer at the first vibration measurement point over a certain period of time; The qualitative judgment of the drill string motion state and main vibration mode is based on the following criteria: when At that time, axial vibration was obvious; when ,at the same time At that time, the drill string mainly vibrates laterally; when ,at the same time At that time, the drill string mainly exhibits stick-slip vibration within torsional vibration; when ,and ,at the same time At this time, the lateral vibration and torsional vibration of the drill string are coupled into vortex. Where g is the acceleration due to gravity. These are the measured values ​​from the three acceleration sensors at the second vibration measurement point. They are respectively The average value, They are respectively The peak value.

2. The method for measuring downhole drill string vibration according to claim 1, characterized in that... The first vibration measurement point was measured in real time.

3. The method for measuring downhole drill string vibration according to claim 1 or 2, characterized in that... The second vibration measurement point is measured using a storage-type measurement method.

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