Anti-Vibration Method for the Near-Bit Measurement While Drilling of Pneumatic Down-the-Hole Hammer Drilling

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The drilling process is associated with the occurrence of vibrations loads, which adversely affect the technical and economic indicators of the production process. Based on these considerations, the topic of the study can be considered relevant.

The work submitted for review proposes a new approach to the design of a vibration suppression system based on parameter optimization using a genetic algorithm. This makes the research original, as such methods are rarely used in the field of drilling. The authors also propose a design that includes parts adapted to the specific conditions of pneumatic drilling, which emphasizes the novelty of their approach.

The research results have prospects for practical application. The developed vibration suppression system can improve stability and accuracy of measurement-while-drilling, which, in turn, will improve drilling efficiency. The proposed innovations can be useful in the fields of geothermal energy and geological exploration, where measurement accuracy is critical.

Overall, the manuscript is a completed scientific study developing the field of vibration suppression in measurement-while-drilling systems. It demonstrates original approaches and offers practical solutions to improve drilling efficiency.

There are comments and recommendations to the text of the manuscript.

 1. In the first chapter "1. Introduction" it is necessary to significantly expand the literature review. Pay attention to recent research that has been conducted over the past three years. In particular, it would be good to pay attention to: the use of smart controllers to assessment the vibrations of the drill string; application of dry friction dampers with open shells for drilling shock absorbers; sensor systems with feedback, etc.

 2. The experiments were carried out on a vibration bench, which is a classical approach to the study of vibrations. However, it should be taken into account that real drilling conditions may be drastically different, which may significantly affect the results.

 3. The authors provide a detailed analysis of the data, which allows a deeper understanding of the effectiveness of the proposed system. However, it is worth considering the use of additional statistical methods for a more accurate interpretation of the results. Or explain in the text of the paper why such methods are not needed here.

 4. Your study focuses heavily on longitudinal vibrations, ignoring transverse and torsional vibrations, which can have a significant impact on system performance. This limitation should be discussed in detail in the manuscript.

 5. How effectively can the proposed vibration suppression system reduce the risk of damage to other elements of the drilling equipment, and is there a trade-off between cost and effectiveness?

 6. How can the results of your experimental studies be adapted to other types of drilling rigs, other drilling modes, and different geological structures?

Comments for author File: Comments.docx

Author Response

Comments 1: In the first chapter "1. Introduction" it is necessary to significantly expand the literature review. Pay attention to recent research that has been conducted over the past three years. In particular, it would be good to pay attention to: the use of smart controllers to assessment the vibrations of the drill string; application of dry friction dampers with open shells for drilling shock absorbers; sensor systems with feedback, etc.

 

Response 1: Thanks for you meaningful comments. We have updated the literature review with the latest research articles. The added references are as follows:

 

Line 70 to 72:

Riane et al. [15] eliminated the severe stick-slip vibrations that appear along the drill string of the rotary drilling system according to the LQG observer-based controller approach.

Line 90 to 92:

Shatskyi and Velychkovych [23] presented a new dry friction shell shock absorber de-sign. Such shell shock absorbers are projected to be used in the mining, oil and gas industries.

 

References:

[15] Riane R , Doghmane MZ, Kidouche M, et al. Stick-Slip Vibration Suppression in Drill String Using Observer-Based LQG Controller. Sensors, 2022, 22.

[23] Shatskyi I, Velychkovych A. Analytical Model of Structural Damping in Friction Module of Shell Shock Absorber Connected to Spring. Shock and Vibration, 2023.

 

Comments 2: The experiments were carried out on a vibration bench, which is a classical approach to the study of vibrations. However, it should be taken into account that real drilling conditions may be drastically different, which may significantly affect the results.

 

Response 2: Thanks for the reviewer's advice. Vibration table test is a classical method to study vibration characteristics. It provides a controlled environment that allows us to precisely simulate and quantify the system response under different vibration conditions. This method is of great significance for the preliminary verification of the performance of the shock absorber. Within a short period of time, there is no suitable DTH hammer drilling rig available for our experiment. We hope for the experts' understanding in this matter.

 

Since we were not able to perform downhole testing, we did functional testing to ensure the validity of the results.

1. Prototype Test

The pressure measurement function was verified by applying some mechanical pressure to the measurement of the short section pressure detection. The system was configured for continuous sampling mode and a handheld pressure test tester was used to apply a pressure of 10N to the detection port through a rigid column of 2.5mm diameter. The pressure was calculated to be 2.04 MPa. Comparison with the tester data after testing showed an average error of less than 0.2%, indicating that the system function was basically realised.

 

2. High Temperature Stability Test

Place the measurement system, the sensor and the battery in a thermostatic test chamber. The temperature was set to 80°C by adjusting the control panel of the chamber and the test was continued at this temperature for 2.5 days as shown in the figure. At the end of the test, the measurement system was removed and connected to the host computer to read the pressure measurement data. After inspection, the output value of the pressure measurement system remained relatively stable throughout the test, with no obvious drift, and the pressure measurement system worked normally and the measurement accuracy was not affected. Therefore, the designed measurement system has good stability.

Comments 3: The authors provide a detailed analysis of the data, which allows a deeper understanding of the effectiveness of the proposed system. However, it is worth considering the use of additional statistical methods for a more accurate interpretation of the results. Or explain in the text of the paper why such methods are not needed here.

 

Response 3: Thank you for the insightful suggestion. The main statistical methods used in this study include four parameters: peak difference, peak attenuation rate, fluctuation rate, and system stability enhancement rate to quantitatively analyse the damping effect of the damping device. These parameters were chosen to provide a comprehensive assessment of the performance of the damping device under different vibration conditions. They are specified below:

1. Peak Difference

    By comparing the peak size of the two curves before and after damping, the peak difference between the vibration signals before and after damping is visually reflected, and the damping effect of the damping device is quantitatively illustrated.

2. Peak Attenuation Rate

    Reflects the degree of attenuation of the amplitude of the damping device, the higher the value, the higher the energy dissipation efficiency of the damping device, the better the damping effect.

3. Fluctuation Rate

The degree of dispersion or instability of the vibration signal is measured by calculating the standard deviation of the vibration data. The lower fluctuation rate after damping indicates that the device not only has good vibration damping performance, but also has high stability.

4. System Stability Enhancement Rate

    By comparing the fluctuation rate of vibration signals before and after damping, it indicates the degree of enhancement of system stability by the damping device, the larger the value, the greater the enhancement of system stability by the damping device, and the more stable the system is.

 

The reason for not using other statistical methods to interpret the experimental results is that these parameters already provide a more comprehensive picture of the performance of the damping device. The peak difference and peak attenuation rate directly reflect the degree of attenuation of the amplitude, while the fluctuation rate and system stability improvement rate focus on evaluating the stability of the system. Taken together, these metrics provide a more comprehensive assessment of the effectiveness of the vibration-damping device, and therefore there is no need to introduce additional statistical methods. We have included this explanation and additional details in the revised manuscript.

 

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These parameters were chosen based on their generality and validity in vibration analysis. The peak difference and attenuation rate visualise the changes before and after vibration damping, while the fluctuation rate and system stability enhancement rate further help to understand the stability and reliability of the device. Therefore, the combination of these parameters can provide powerful data to support the design of vibration damping devices.

 

Comments 4: Your study focuses heavily on longitudinal vibrations, ignoring transverse and torsional vibrations, which can have a significant impact on system performance. This limitation should be discussed in detail in the manuscript.

 

Response 4: Thank you for your insightful advice. The vibration damping system in this study is designed for the special working condition of DTH hammer drilling. The main focus of this study is on the longitudinal vibration characteristics of the drill string and its effect on the pressure measurement system. This is based on the following reasons:

1. Significant Effect of Longitudinal Vibrations：

It is mentioned in the study that the longitudinal vibration of the drill string is one of the most significant forms of vibration in the process of submerged hammer drilling, and its vibration magnitude can reach up to 40 g, with a fundamental frequency of 5-25 Hz. The longitudinal vibration has the greatest impact on the performance and stability of the measurement circuit, so the research mainly focuses on how to effectively mitigate the impact of longitudinal vibration.

2. Scope and Objectives of the Study：

The research objective of the study is to design a pressure measurement system with high vibration resistance to solve the problems of measurement accuracy and component life caused by the strong longitudinal vibration during pneumatic submerged hammer drilling. Given that longitudinal vibration has the most direct impact on measurement accuracy. It makes sense to give priority to solving the longitudinal vibration problem.

3. Existing Research Base：

Relatively few studies have been conducted on longitudinal vibration and its effect on the measurement system under pneumatic DTH conditions. Therefore, this study fills this gap and provides a basis for subsequent more comprehensive studies. After solving this problem, other types of vibration problems can be further studied on this basis

 

Nonetheless, the study should indeed mention this limitation and indicate directions for future research to ensure that the reader understands the completeness of the study and the potential range of applications. We have included this explanation and additional details in the revised manuscript.

 

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Although the focus of this study is on longitudinal vibration, it is worth noting that transverse and torsional vibration in the drill string system can similarly affect the performance of the system. Although these forms of vibration were not explored in depth in this study, their presence cannot be ignored. Future research efforts will be directed towards the development of more comprehensive vibration damping solutions to cover all types of vibration. This will further improve the reliability and measurement accuracy of the system.

Line 459 to 461:

Further studies are needed to investigate the interference of torsional vibration of the drill string and its coupling with transverse vibration on the damping device.

 

Comments 5: How effectively can the proposed vibration suppression system reduce the risk of damage to other elements of the drilling equipment, and is there a trade-off between cost and effectiveness?

 

Response 5: Thank you for your insightful advice. The proposed vibration damping system effectively reduces the risk of damage to other components of the drilling equipment through a variety of measures, while taking into account the balance between cost and effectiveness. In this study, a flexible connection scheme based on spring damping elements is proposed. Through the elastic deformation of the spring element and the energy dissipation effect of the damping element, the longitudinal vibration of the drill string is effectively isolated and the measurement circuit is protected. This design not only reduces the impact of vibration on the circuit, but also extends the service life of the equipment. A limiting mechanism is designed to limit the lateral displacement of the circuit unit, thus avoiding its collision friction with the cylinder wall.

 

In this study, cost considerations were taken into account when designing the vibration damping system.For example, a roller design was used to reduce friction in the design of the local limiting device, rather than limiting the device by increasing machining accuracy over a large area, which would have increased the cost considerably.

 

The stiffness damping parameters of the damping system were optimised using the Non-dominated Sorting Genetic Algorithm (NSGA II) to ensure the best performance of the system in practical applications. By optimising the parameters, the damping system is able to achieve the desired damping effect at a controllable cost. Each spring-damping element parameter calculated in this study is non-standard and needs to be customised independently. In order to reduce the cost, standard parts with close stiffness and damping coefficients are chosen in this study.

 

In summary, the vibration damping system proposed in this study is designed with full consideration of the balance between cost and effectiveness. Through reasonable vibration damping design, parameter optimisation and experimental verification, the effectiveness of the system is ensured, while the cost is controlled through optimisation measures such as limiting mechanism. The risk of damage to other components of the drilling equipment can be effectively reduced.

 

Comments 6: How can the results of your experimental studies be adapted to other types of drilling rigs, other drilling modes, and different geological structures?

 

Response 6: Thank you for your insightful advice. The results of the experimental studies described focus on the pneumatic DTH hammer drilling and its specific drilling patterns. It can guide the design of vibration damping of the measuring elements in any DTH hammer drilling, it can reproduce the characteristics of the process, and it can be tailored to any stratigraphic situation. However, its research methods and technical paths are also adaptable and valuable for other types of drilling rigs, drilling modes and different geological structures. The following are some specific adaptation paths:

 

1. Other Types of Drilling Rigs：

Although this study focuses on pneumatic DTH hammer drilling, the principles and techniques of vibration damping system design can be applied to other types of drilling rigs. For example, hydraulic submerged hammer drilling rigs or conventional rotary drilling rigs can be designed in a similar manner for vibration dampening to reduce the vibration problems encountered during drilling.

2. Other Drilling Modes：

Vibration damping technology is a universal requirement for both underbalanced and conventional drilling. The design of vibration damping devices can be adapted to the characteristics of different drilling modes, for example by adjusting the parameters of the damping elements to suit the vibration characteristics under different operating conditions.

3. Different Geological Structures：

Although the study investigates the drilling of geothermal wells, the diversity of geological structures means that vibration damping needs to be considered in other types of drilling operations. By adjusting the parameters of the damping system, such as spring stiffness and damping coefficients, it is possible to better adapt the damping device to different geological conditions.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The paper is very well written and presented.  No major issues detectd, only the question:  Will application of the damping system affect the drilling rate significantly.  Obviously the damping will also affect the response characterisitcs of the bit.

Author Response

Comments 1: Will application of the damping system affect the drilling rate significantly.  Obviously the damping will also affect the response characterisitcs of the bit.

 

Response 1: Thank you for your valuable comments. This damping mechanism has little relevance to shock excitation, and the main rock fragmentation process is vibratory shock fragmentation. In this study, the damping structure does not target the vibration excitation source of rock fragmentation, but mainly suppresses the vibration of the measurement module. The vibration of the measurement module is mainly caused by the reaction force of the impact rock fragmentation.

 

Firstly, vibration damping systems are designed to reduce the harmful vibrations generated during the drilling process. These vibrations not only reduce the drilling rate, but can also lead to premature damage to the drill bit. By damping the vibrations during the drilling process, this reduces the vibrations and thus improves the stability and measurement accuracy of the system.

 

In addition, the effect of damping on the response characteristics of the drill bit is taken into account. If the damping of the damping system is too large, the power transmitted to the drill bit may be weakened, thus indirectly affecting the drilling rate. However, by optimising the stiffness and damping coefficients of the damping system in the study, a better damping effect is ensured without sacrificing the drilling efficiency. For example, by using the NSGA-II algorithm to find the optimal stiffness and damping parameters, the vibration damping system achieves a theoretical vibration damping effect of 90.78% at an operating frequency of 10 Hz, and ensures that the peak vibration attenuation rate of the circuit unit is above 86.446%, and the system vibration stability enhancement rate is above 75.214%. This shows that the optimised vibration damping system can guarantee the vibration damping effect without significantly affecting the drilling rate.

 

Therefore, based on the findings in the study, it can be concluded that the application of damping system does not significantly affect the drilling rate. Proper damping may not only increase the drilling rate, but also extend the life of the drill bit and reduce maintenance. This may also have a positive impact on the overall drilling efficiency. This is important for industrial applications.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

The Authors presented the results of research on the elimination of vibrations in pneumatic percussive drilling technology in their work. The authors correctly diagnosed that one of the main disadvantages of the technology is the high vibrations generated by the working system. This adversely affects the durability of machines, people in the vicinity and the surroundings. Therefore, in order to improve the working conditions during drilling, the Authors propose a new method of designing a vibration damping system, which is based on the optimization of the parameters of the nondominated sorting genetic algorithm II (NSGA-II). The obtained research results indicate that the applied method can significantly reduce the vibrations generated by working arrangement.

The subject of the manuscript is interesting and current, and the presented algorithm can be applied in other areas of the economy.

Important notes:

1.       Does the presented algorithm take into account the heterogeneity of the rock formations in which the holes are drilled? There is a risk that inhomogeneity of conditions may negatively affect the effectiveness of vibration damping.

2.       A number of simplifications have been assumed in the proposed algorithm. What effect can they have on the operation of the damping system, which was developed according to the presented algorithm, in real conditions?

3.       The frequency of vibrations depends, among other things, on the stiffness of the system, while during drilling the length of the drill changes. Does the proposed algorithm take into account the change in the tool length?

4.       The final conclusions should be supplemented.

Author Response

Comments 1: Does the presented algorithm take into account the heterogeneity of the rock formations in which the holes are drilled? There is a risk that inhomogeneity of conditions may negatively affect the effectiveness of vibration damping.

 

Response 1: Thank you for your valuable advice. As the vibration frequency is dependent on the structure of the DTH hammer, the frequency of the DTH hammer mainly depends on the drilling fluid and the structure of the drilling tools. The authors consider for different rock formations will only lead to the amplitude of the shock wave. This study is to quantify the shock wave frequency for peak suppression.

 

The design of the damping system in this study is based on the analysis of the forced vibration full response function of the circuit unit. And the optimal stiffness and damping coefficients are determined by a multi-objective optimisation algorithm (NSGA-II). This optimisation approach focuses on how to achieve the best damping effect by adjusting the parameters of the damping system for a given vibration frequency. Although the effect of the non-homogeneity of the rock formation on the vibration damping effect is not directly addressed in the study, the vibration damping system can achieve a better vibration damping performance under specific conditions through reasonable parameter optimisation.

 

In practice, the non-homogeneity of the rock formation may indeed have an impact on the damping effect. This is because different rock formation properties can lead to variations in the external excitation to which the drill string is subjected, which in turn affects the performance of the vibration damping system. However, the focus of the study is on the development of a generic vibration damping solution. In particular, it addresses the longitudinal vibrations generated during the drilling process. The scheme can provide reliable vibration damping under different vibration conditions. Therefore, although the study does not specifically address rock formation non-homogeneity, the proposed vibration damping system design is flexible and adaptable. This can cope with the challenges posed by rock formation variations to a certain extent.

 

In summary, although the algorithms proposed in the study mainly focus on the optimisation of vibration damping under specific vibration conditions, and do not directly consider the effect of the non-homogeneity of the rock formation. However, the vibration damping system designed through optimisation has good adaptability and can provide reliable vibration damping effect under different working conditions. If the performance of the damping system in non-homogeneous rock formations needs to be further improved, dynamic monitoring of the change of rock formation properties can be included in future research. And the parameters of the damping system can be adjusted accordingly to achieve better damping effect.

 

Comments 2: A number of simplifications have been assumed in the proposed algorithm. What effect can they have on the operation of the damping system, which was developed according to the presented algorithm, in real conditions?

 

Response 2: Thank you for your valuable feedback. In this study, several simplifying assumptions are made to facilitate the analysis of the vibration characteristics of the circuit unit and the design of an effective damping system. These simplifying assumptions may have an impact on the operation of the damping system developed based on the proposed algorithm in practical applications. The details are as follows:

 

1. Influence of Simplified Modelling of Drill strings:

In the actual drilling process, the drill pipe is not a simple homogeneous slender rod, and its material properties, geometry, etc. may vary with its length. Therefore, the simplified model may lead to the deviation of the actual vibration damping effect from the theoretical model prediction. Nevertheless, through experimental verification, it is found that the vibration damping system can still achieve the expected vibration damping effect under actual conditions, indicating that the simplified model is reasonable to some extent.

2. Influence of Neglecting Transverse Deformation:

In actual working conditions, the drill string not only vibrates in the longitudinal direction, but also accompanied by transverse vibration. Neglecting the transverse deformation may underestimate the real vibration condition of the system, which in turn affects the performance of the damping system. However, by optimising the vibration damping parameters, the study enables the system to be effectively damped even if the longitudinal vibration is mainly considered.

3. Impact of Drill Bit Simplification:

The simplification of the drill bit to a mass block ignores its specific geometry and dimensions, which may affect the accurate description of the actual dynamic behaviour of the drill bit. However, the study is concerned with the vibration damping design of the circuit unit rather than the drill bit itself, so this simplification has less impact on the vibration damping effectiveness of the circuit unit.

4. Influence of Boundary Conditions:

Although it is assumed that both ends of the drill string are free, the boundary conditions of the column will be more complicated in the actual drilling process. However, through experimental verification, it is found that the vibration damping system can still perform its proper function even under actual working conditions.

 

Overall, despite the simplifying assumptions, the effectiveness of the proposed vibration damping system under real conditions is experimentally verified in the study. The experimental results show that, in the range of vibration frequency of 5-20Hz and vibration magnitude of 10-40g, the damping device can guarantee the peak vibration attenuation rate of the circuit unit to be above 86.446% and the vibration stability enhancement rate of the system to be above 75.214%. This indicates that, despite the simplifying assumptions, the developed damping system is still able to achieve good vibration damping effects in practical applications.

 

 

Comments 3: The frequency of vibrations depends, among other things, on the stiffness of the system, while during drilling the length of the drill changes. Does the proposed algorithm take into account the change in the tool length?

 

Response 3: Thanks for the reviewer's valuable advice. During the drilling process, the distance of the measuring structure from the bit remains essentially unchanged, and the vibrations generated by impact do not change significantly as the drilling depth increases.

 

The design of the damping system mentioned in this study focuses on how the damping performance of the system can be improved by optimising the damping parameters under specific conditions (e.g. vibration frequencies of 5-15 Hz, which are common during pneumatic DTH hammer drilling). In fact, the variation of the bit length does have an effect on the intrinsic frequency of the system because the system stiffness varies with the increase of the bit length. The Non-dominated Sorted Genetic Algorithm (NSGA-II) used in the study is a method capable of handling multi-objective optimisation problems to find a set of near-optimal solutions. This means that if the effect of a change in bit length needs to be taken into account, the optimisation process can be re-run to obtain new optimal stiffness and damping coefficients by adjusting the input parameters of the algorithm (e.g. bit length).

 

The performance of the damping system was verified by shaker experiments, which were conducted at different frequencies and vibration magnitudes. The experimental results show that the vibration damping system is still able to provide stable vibration damping within a certain range (e.g., frequency of 5-20 Hz, vibration magnitude of 10-40 g). This shows that even if the length of the drill bit changes during the actual drilling process, the vibration damping system is still able to function as long as the change is within a certain limit.

 

Therefore, from the flexibility of the optimisation algorithm as well as the experimental validation results, the system is able to adapt to the length change in the actual drilling process to a certain extent. Future research can further explore how to incorporate factors such as drill length changes into the optimisation model to improve the adaptability and robustness of the damping system.

 

Comments 4: The final conclusions should be supplemented.

 

Response 4: Thanks for the reviewer's advice. We have included this explanation and additional details in the revised manuscript.

 

Line 459 to 461:

Further studies are needed to investigate the interference of torsional vibration of the drill string and its coupling with transverse vibration on the damping device.

 

Line 488 to 492:

The experimental results show that the vibration damping device attenuates the peak vibration of the circuit unit by 94.8165% and improves the system vibration stability by 84.053% under normal drilling operations. Under extreme conditions, the vibration peak attenuation rate is 90.9384%, and the system vibration stability enhancement rate is 89.413%.

 

Author Response File: Author Response.docx