High-Temperature Degradation of Throttling Performance in While-Drilling Jars Induced by Thermal Expansion and Fluid Rheology

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1. Figure 2 shows the physical photo and cross-sectional geometric diagram of the throttle valve. However, in order to provide readers with a clearer and more intuitive understanding of the structure and working principle of the throttle valve, it is advisable for the author to add a cross-sectional view of the three-dimensional geometric model in Figure 2 and annotate some key details (names, dimensions) in Figure 2.  
2. On page 10, it is mentioned that simulation is divided into two stages: thermal mechanical analysis and flow field simulation. After completing the thermal mechanical coupling analysis of the throttle body, the FORTRAN program is used to automatically extract the node coordinates of the internal flow field of the throttle valve, thereby obtaining the geometric information of the thermal deformation throttling channel. It is obvious that the simulation in this manuscript is based on sequential coupling analysis. However, the three processes of heat transfer, flow, and stress change occur simultaneously, and the rationality of the research methodology based on sequential coupling needs to be verified or explained.  
3. The effective implementation of numerical simulation requires geometric or mathematical models, boundary conditions, initial conditions, basic parameters, etc. Fortunately, the author provided detailed mathematical and geometric models in this study. However, the author did not provide boundary conditions, loads, initial conditions, and basic parameters. Without these parameters, it is difficult for readers to obtain effective information because research results are combined and corresponding to experimental conditions, and do not exist in isolation.
4. During the drilling process of unconventional oil and gas reservoirs, there will be many complex accidents, such as equipment problems and geological disasters. Therefore, the last sentence of the first paragraph of the introduction needs to be supported by the following research and work:- Sediment Instability Caused by Gas Production from Hydrate-bearing Sediment in Northern South China Sea by Horizontal Wellbore: Sensitivity Analysis; -Settling behavior and mechanism analysis of kaolinite as a fracture proppant of hydrocarbon reservoirs in CO2 fracturing fluid.  
5. The author should have used the ABAQUS platform to simulate and analyze the thermal mechanical coupling, and then conducted heat transfer analysis using ANSYS or FLUENT. The author said that the data exchange in the middle was implemented through Fortran language encoding. Can the author provide a specific methodology for implementing this process in the manuscript? This detail is crucial for conducting the simulation in this manuscript, for example, which specific data was exchanged during this process? What are the methods, ideas, or processes for implementing data exchange?  
6. An extremely important aspect of this study is the analysis related to heat (temperature), but there are not many statements and discussions about temperature in the research. Therefore, the reviewer believes that the author needs to add some content related to temperature or heat appropriately.
7. This manuscript is essentially divided into two main sections: experiments and simulations. However, the authors do not clearly explain or even hint at the relationship between the two. Therefore, the authors should include a statement in the introduction or abstract that briefly explains the logical connection between the experiments and simulations.

Author Response

Review #1

[1] Comment: Figure 2 shows the physical photo and cross-sectional geometric diagram of the throttle valve. However, in order to provide readers with a clearer and more intuitive understanding of the structure and working principle of the throttle valve, it is advisable for the author to add a cross-sectional view of the three-dimensional geometric model in Figure 2 and annotate some key details (names, dimensions) in Figure 2.

Author Response: Reviewer’s suggestion is very accurate and reasonable. As the reviewer suggested, we have revised Figure 2 by adding a cross-sectional view of the three-dimensional geometric model of the throttle valve and some key details (component names, representative dimensions) to enhance clarity and facilitate better understanding of the valve’s structure and working principle. (see “Figure 2” in the revised manuscript)

 

[2] Comment: On page 10, it is mentioned that simulation is divided into two stages: thermal mechanical analysis and flow field simulation. After completing the thermal mechanical coupling analysis of the throttle body, the FORTRAN program is used to automatically extract the node coordinates of the internal flow field of the throttle valve, thereby obtaining the geometric information of the thermal deformation throttling channel. It is obvious that the simulation in this manuscript is based on sequential coupling analysis. However, the three processes of heat transfer, flow, and stress change occur simultaneously, and the rationality of the research methodology based on sequential coupling needs to be verified or explained.

Author Response: Thank you for the reviewer’s comments. As a downhole drilling tool, the while-drilling hydraulic jar enters the wellbore together with the drill string during the drilling process. At this stage, the hydraulic jar remains in an inactive state, and its throttling components are unconstrained, allowing them to undergo free thermal expansion due to the high-temperature wellbore environment. However, due to differences in the material properties of structural components, geometric variations in the throttling channel occur even before the jar is activated. When a stuck pipe incident occurs, the driller applies an axial force to the drill string, gradually increasing the load until it reaches the preset triggering force of the jar. At this point, the central valve moves into contact with the metal sealing surface on the cylinder sleeve, forming an effective seal and dividing the internal cavity into upper and lower hydraulic chambers with different pressures. Driven by the resulting pressure differential, hydraulic oil flows through the needle-type throttling orifice inside the central valve body into the lower chamber. Under the extrusion effect of the high-pressure fluid, both the needle-type throttle and the valve seat experience further deformation, causing the geometry of the throttling passage to continuously evolve during the jarring process. Hence, we divided the simulation into two stages: thermal–mechanical analysis and flow field simulation, and a sequential coupling strategy was deliberately adopted based on the actual working characteristics of the while-drilling hydraulic jar. Given this operational sequence, it is physically reasonable to perform the thermal–mechanical analysis first, in a quasi-static manner, to capture the geometry changes caused by thermal expansion. Then, based on the thermally deformed geometry, the flow field under jarring conditions is simulated. This sequential approach achieves a balance between computational efficiency and physical fidelity, and it effectively captures the key features influencing throttling performance under realistic downhole conditions.

[3] Comment: The effective implementation of numerical simulation requires geometric or mathematical models, boundary conditions, initial conditions, basic parameters, etc. Fortunately, the author provided detailed mathematical and geometric models in this study. However, the author did not provide boundary conditions, loads, initial conditions, and basic parameters. Without these parameters, it is difficult for readers to obtain effective information because research results are combined and corresponding to experimental conditions, and do not exist in isolation.

Author Response: Reviewer’s suggestion is very accurate and reasonable. As the reviewer suggested, we have added detailed descriptions of the boundary conditions, loads, initial conditions, and basic parameters to enhance the clarity and reproducibility of our numerical simulations. (see “5.1 Simulation Model” in the revised manuscript)

[4] Comment: During the drilling process of unconventional oil and gas reservoirs, there will be many complex accidents, such as equipment problems and geological disasters. Therefore, the last sentence of the first paragraph of the introduction needs to be supported by the following research and work:- Sediment Instability Caused by Gas Production from Hydrate-bearing Sediment in Northern South China Sea by Horizontal Wellbore: Sensitivity Analysis; -Settling behavior and mechanism analysis of kaolinite as a fracture proppant of hydrocarbon reservoirs in CO2 fracturing fluid.

Author Response: Thank you for the reviewer’s comments, In response, we have supplemented the last sentence of the first paragraph in the introduction with relevant references that support the occurrence of complex accidents during the drilling of unconventional oil and gas reservoirs.

[5] Comment: The author should have used the ABAQUS platform to simulate and analyze the thermal mechanical coupling, and then conducted heat transfer analysis using ANSYS or FLUENT. The author said that the data exchange in the middle was implemented through Fortran language encoding. Can the author provide a specific methodology for implementing this process in the manuscript? This detail is crucial for conducting the simulation in this manuscript, for example, which specific data was exchanged during this process? What are the methods, ideas, or processes for implementing data exchange?

Author Response: Thank you for the reviewer’s comments. We agree that the data exchange process between the thermal–mechanical simulation and the flow field analysis is critical to ensuring the accuracy and reliability of the coupled simulation. In our study, the thermal–mechanical analysis was conducted using the ABAQUS platform, and a user-defined Fortran script was developed to extract the deformed nodal coordinates from the ABAQUS output database (ODB file). Specifically, the script accessed the node sets corresponding to the throttling components and retrieved their updated spatial positions after thermal deformation. These nodal data were saved in a structured ASCII text format compatible with CAD and mesh reconstruction software, and the deformed geometry was subsequently imported into CAD software to reconstruct the three-dimensional flow channel for the subsequent fluid field simulation.

 

[6] Comment: An extremely important aspect of this study is the analysis related to heat (temperature), but there are not many statements and discussions about temperature in the research. Therefore, the reviewer believes that the author needs to add some content related to temperature or heat appropriately.

Author Response: Reviewer’s suggestion is very accurate and reasonable. The wellbore temperature plays a critical role in the performance of the while-drilling hydraulic jar, particularly in relation to the thermal expansion of throttling components and the subsequent influence on the flow channel geometry and throttling performance. As the reviewer suggested, we have added more detailed discussions and descriptions related to temperature effects in the revised manuscript to better highlight the significance of thermal effects in this study. (see “Figure 10 and Figure 11” in the revised manuscript)

 

[7] Comment: This manuscript is essentially divided into two main sections: experiments and simulations. However, the authors do not clearly explain or even hint at the relationship between the two. Therefore, the authors should include a statement in the introduction or abstract that briefly explains the logical connection between the experiments and simulations.

Author Response: We appreciate the reviewer’s valuable comment. As the reviewer suggested, we have revised the Introduction and Abstract to briefly explain this relationship. Specifically, the experimental work provides foundational parameters and boundary conditions for the numerical simulations, while the simulation results help further interpret and generalize the observed experimental phenomena. This complementary approach ensures both accuracy and comprehensive understanding in evaluating the thermal–fluid–structural coupling behavior of the throttling components. (see “Abstract and Introduction” in the revised manuscript)

We tried our best to improve the manuscript and made some changes in the manuscript. These changes will not influence the content and framework of the paper. And here we did not list the changes but marked in red in revised paper.

Reviewer 2 Report

Comments and Suggestions for Authors

Paper: machines-3791455-v1

Title: High-Temperature Degradation of Throttling Performance in While-Drilling Jars Induced by Thermal Expansion and Fluid Rheology

 

The theory, application and results were satisfactorily presented and discussed. However, the original manuscript needs of some improvement; and I have four comments as follow below.

Comment 1: The first one is related with the references. Most of them are outdated. Please use / add more up to date references (in fact, the manuscript needs of more citations).

Comment 2: Can the authors further explain their motivation for application of the linkage integrating the thermo mechanical coupling of the valve body with flow field simulations? It would be better if a baseline method is available and compared with the present model. The purpose is to demonstrate the new features, benefits, and advantages of the present approach.

Comment 3: It would be desirable to show the limitations of the present methodology. Also, it would be useful to discuss about their drawbacks as well as the ways to solve them.

Comment 4:  In “Conclusion”, it is required to include technical discussion related to the present results behaviour as compared as previous works, when possible. More sense of physics in conclusions is recommended too. In closing, it is important to complete the section with perspectives for a future research. Finally, the main contribution of the present manuscript should be clarified aiming to justify its publication in Machines.

End.

Author Response

Review #2

 

[1] Comment: The first one is related with the references. Most of them are outdated. Please use / add more up to date references (in fact, the manuscript needs of more citations).

Author Response: Thank you for the reviewer’s valuable suggestion. We have added more up-to-date references to enhance the relevance and rigor of our manuscript. (see “1.Introduction” in the revised manuscript)

 

[2] Comment: Can the authors further explain their motivation for application of the linkage integrating the thermo mechanical coupling of the valve body with flow field simulations? It would be better if a baseline method is available and compared with the present model. The purpose is to demonstrate the new features, benefits, and advantages of the present approach.

Author Response: Reviewer’s suggestion is very accurate and reasonable. The motivation for integrating the thermo-mechanical coupling of the valve body with flow field simulations arises from the need to accurately capture the evolution of throttling performance under high-temperature and high-pressure downhole conditions. In such extreme environments, thermal expansion and stress-induced deformation significantly affect the geometry of the throttling channel, especially in the valve region where the flow area is extremely small. If these deformations are not considered, the simulated flow field may deviate considerably from actual conditions, leading to inaccurate predictions of pressure drop, flow resistance, and overall tool performance. In this study, we adopted a sequentially coupled simulation strategy to address the challenges of fully-coupled thermo-fluid-structure interaction, which are difficult to implement due to mesh size discrepancies and extreme geometric gradients in the throttling region. Specifically, the thermal–mechanical simulation was performed in ABAQUS, and a custom-developed FORTRAN script was used to extract the deformed nodal coordinates of the valve body. These coordinates were then used to reconstruct the flow domain geometry for subsequent fluid simulations. This workflow ensures high consistency between structural deformation and fluid domain, minimizes manual errors, and enhances simulation efficiency.

 

[3] Comment: It would be desirable to show the limitations of the present methodology. Also, it would be useful to discuss about their drawbacks as well as the ways to solve them.

Author Response: Thank you for the reviewer’s valuable comment. We fully agree that a critical evaluation of the methodology’s limitations and potential improvements can enhance the scientific rigor and transparency of the study. In response to the reviewer’s suggestion, we have revised the manuscript to include a more comprehensive discussion of the current method’s limitations, outlined its potential drawbacks, and proposed feasible solutions or future directions to address these issues. (see the third paragraph in “1. Introduction” of the revised manuscript)

 

[4] Comment: In “Conclusion”, it is required to include technical discussion related to the present results behaviors as compared as previous works, when possible. More sense of physics in conclusions is recommended too. In closing, it is important to complete the section with perspectives for a future research. Finally, the main contribution of the present manuscript should be clarified aiming to justify its publication in Machines.

Author Response: We appreciate the reviewer’s constructive suggestion regarding the enhancement of the "Conclusion" section. In response, we have thoroughly revised the conclusion section as follows:

“In this paper, the high-temperature degradation of the throttling performance of a hydraulic-while-drilling jar was systematically investigated by considering both the thermal expansion of structural components and the high-temperature rheological behavior of hydraulic oil. The geometric variation of the throttling passage was treated as a coupling mechanism that integrates the thermo-mechanical deformation of the valve body with the evolution of the internal flow field. Simulation results show that during up and down-jarring operations, the fluid pressure continuously decreases along the flow direction, while the velocity sharply increases upon entering the throttling passage and exhibits slight fluctuations due to shear effects within the channel. Compared to ambient conditions, the viscosity of hydraulic oil significantly decreases with increasing temperature, and thermal expansion of the throttling components leads to enlarged flow areas. As a result, both flow velocity and mass flow rate increase markedly under high-temperature conditions, leading to a significant reduction in throttling performance. Moreover, while the free thermal expansion of the valve body generally enlarges the throttling passage area, pressure-induced deformation during jarring also alters the geometric distribution of the throttling passage. To improve the throttling performance of HWD jars under high-temperature conditions, temperature-sensitive or low-expansion materials should be considered in the structural design to control geometric variations and offset the adverse effects of fluid rheological degradation, thereby ensuring more reliable jarring tool performance for downhole high-temperature operations.”

We tried our best to improve the manuscript and made some changes in the manuscript. These changes will not influence the content and framework of the paper. And here we did not list the changes but marked in red in revised paper.

Reviewer 3 Report

Comments and Suggestions for Authors

High-Temperature Degradation of Throttling Performance in While-Drilling Jars Induced by Thermal Expansion and Fluid Rheology

 

The authors studied the high-temperature degradation of the throttling performance of a  hydraulic-while-drilling jar by incorporating both the thermal expansion of structural components and the high-temperature rheological behavior of the fluid.  The work is relevant and employs a combined experimental-numerical approach.

 

Overall, the paper is well written. However, the lack of experimental validation for the core integrated model and its predictions is a fundamental flaw that severely undermines the quantitative conclusions. Without validation against physical tests (e.g., a high-pressure, high-temperature flow loop with instrumented prototype valves), either by themselves or from the literature, the quantitative results and conclusions lack credibility.

 

-In addition, No mesh sensitivity analysis is presented.

- Better justification for RNG k-ε, including near-wall treatment (y+) is needed

-The use of FORTRAN program needs to be justified and explained

 

Other minor issues:

-In line 258, please check “As shown as that the viscosity of the hydraulic oil decreases significantly with increasing temperature.”

-"Noether thrusting valve" (Fig 2 caption), "dimension l" (should be "dimensionless"? Page 6, λ definition), inconsistent formatting in some equations.

-Fig 4: The curve is mentioned, but only a table is shown in the provided text. Ensure the figure includes the actual curve.

-Caption of figure 4 should start with capital letter, the same thing happens with other figures

-4.2 should start with capital letter

-Thermos-physical or thermophysical

 

-In figure 8, Mises stress does not seem to reach 345.59 MPa during up-jarring, and 178.24 MPa during down-jarring.

-Figure 13. the variation in fluid velocity, however, the y-axis of the graph says channel cross sectional area. Also, can you please explain why the data in figure 13, does not increase  or decrease in accordance with the temperature.

-Please check that the figure numbers in the text correspond to the figure you are talking about, such as figure 13 and 14.

 

-The number of references is small, please adda few more

Author Response

Review #3

Overall: The authors studied the high-temperature degradation of the throttling performance of a hydraulic-while-drilling jar by incorporating both the thermal expansion of structural components and the high-temperature rheological behavior of the fluid. The work is relevant and employs a combined experimental-numerical approach.

Overall, the paper is well written. However, the lack of experimental validation for the core integrated model and its predictions is a fundamental flaw that severely undermines the quantitative conclusions. Without validation against physical tests (e.g., a high-pressure, high-temperature flow loop with instrumented prototype valves), either by themselves or from the literature, the quantitative results and conclusions lack credibility.

Author Response: Thank you very much for your valuable feedback and positive evaluation of our work. We fully acknowledge the reviewer’s concern regarding the lack of experimental validation for the core integrated model. Due to the significant challenges and high costs associated with replicating downhole high-temperature and high-pressure conditions—particularly for jarring operations—direct validation through full-scale physical testing is not currently feasible within the scope of this study. However, to partially address this limitation, we have conducted separate experimental characterizations of key components and processes, including the thermal expansion behavior of structural materials and the rheological properties of the fluid at elevated temperatures, and these results have been incorporated into the simulation framework. We agree that full-scale experimental validation would significantly enhance the credibility of the numerical predictions, and as part of our future work, we plan to carry out flow loop experiments under controlled high-temperature and high-pressure conditions using instrumented jar prototypes.

 

[1] Comment: In addition, No mesh sensitivity analysis is presented.

Author Response: Thank you for reviewer’s comment. We acknowledge that a mesh sensitivity analysis is essential to ensure the reliability and accuracy of numerical results. As the reviewer suggested, we have added mesh sensitivity analysis to evaluated the influence of mesh density on key simulation outputs. The results demonstrate that the selected mesh resolution offers a good balance between accuracy and computational efficiency. (see “5.1 Simulation Model” in the revised manuscript)

[2] Comment: Better justification for RNG k-ε, including near-wall treatment (y+) is needed

Author Response: Thank you for reviewer’s comment. As the reviewer suggested, we have added a detailed justification for employing the RNG k-ε turbulence model. This model was selected due to its enhanced capability in capturing flow separation, recirculation, and strong shear effects, which are typical in the throttling passages of hydraulic-while-drilling jars. Compared with the standard k-ε model, the RNG variant provides improved accuracy for flows with high strain rates and streamline curvature. in additional, for near-wall treatment, we adopted the standard wall function approach, which is appropriate for high-Reynolds-number simulations. Grid resolution near the walls was carefully designed to maintain y⁺ values within the recommended range (typically between 30 and 300), ensuring the validity of the wall-function-based treatment. (see “3.3. RNG k- ε Model” in the revised manuscript)

 

[3] Comment: The use of FORTRAN program needs to be justified and explained

Author Response: Thank you for the reviewer’s insightful comment. Due to the extremely small flow channel at the throttling valve position compared to other regions, there is a significant difference in mesh size, which makes fully coupled thermo-fluid-structural simulations difficult to achieve. To address this challenge, we adopted a sequential coupling strategy. Specifically, we developed a custom FORTRAN program to automatically extract the updated nodal coordinates of the inner surface of the throttle body from the thermal–mechanical simulation results. This program enables accurate reconstruction of the thermally deformed throttling channel geometry and its transfer into the fluid simulation environment. The use of the FORTRAN script ensures consistent geometric mapping between simulations, reduces manual intervention and associated errors, and enhances the efficiency and reliability of the overall simulation workflow. To verify the accuracy of the extracted data, we added Figures 9 and 10 in the revised manuscript, which present the cross-sectional area of the throttling channel at the initial state. The extracted results show good agreement with those calculated directly from the geometric parameters, confirming the reliability of the FORTRAN-based extraction method. (see “Figure 10 and Figure 11” in the revised manuscript)

 

[4] Comment: In line 258, please check “As shown as that the viscosity of the hydraulic oil decreases significantly with increasing temperature.”

Author Response: Thank you for the reviewer’s comments. We have carefully revised the sentence to correct the grammatical issue. The revised sentence follow as: “It is shown that the viscosity of the hydraulic oil decreases significantly with increasing temperature.”

 

[5] Comment: "Noether thrusting valve" (Fig 2 caption), "dimension l" (should be "dimensionless"? Page 6, λ definition), inconsistent formatting in some equations.

Author Response: We thank the reviewer for pointing out these issues. The terminology errors have been corrected and the inconsistent equation formatting has been revised. We have also thoroughly checked the entire manuscript for grammatical and typographical mistakes. (see the revised manuscript)

[6] Comment: Fig 4: The curve is mentioned, but only a table is shown in the provided text. Ensure the figure includes the actual curve. Caption of figure 4 should start with capital letter, the same thing happens with other figures

Author Response: Thank you for the reviewer’s valuable comment. Upon careful review, we confirm that Figure 4 does include the experimental curve as described in the text. We have clarified the presentation to avoid any misunderstanding. In addition, we have revised the caption of Figure 4 to begin with a capital letter, as well as checked and corrected the captions of all other figures to ensure consistency with formatting guidelines.

 

[7] Comment: 4.2 should start with capital letter

Author Response: We are very sorry for these formatting errors. We have corrected the heading of section 4.2 to ensure it starts with a capital letter, and we have checked all other section titles to maintain consistent formatting throughout the manuscript.

 

[8] Comment: In figure 8, Mises stress does not seem to reach 345.59 MPa during up-jarring, and 178.24 MPa during down-jarring.

Author Response: Thank you for the reviewer’s comment. Due to geometric features, the fluid pressure during jarring operations causes stress concentration on the inner wall of the plug. This is reflected in the red-colored region in Figure 9 of the revised manuscript. The peak Mises stress values do reach 345.59 MPa during up-jarring and 178.24 MPa during down-jarring at these localized zones, although the overall stress distribution may appear lower in other areas.

 

[9] Comment: Figure 13. the variation in fluid velocity, however, the y-axis of the graph says channel cross sectional area. Also, can you please explain why the data in figure 13, does not increase or decrease in accordance with the temperature.

Author Response: We sincerely appreciate the reviewer’s careful observation. The y-axis label in the original figure was indeed incorrect — it should represent fluid velocity, not channel cross-sectional area. This labeling error has been corrected in the revised manuscript (see “Figure 14” in the revised manuscript).

 

[10] Comment: Please check that the figure numbers in the text correspond to the figure you are talking about, such as figure 13 and 14.

Author Response: Thank you for the reviewer’s careful reading. We have thoroughly checked the manuscript to ensure that all figure numbers in the text correctly correspond to the respective figures.

 

[11] Comment: The number of references is small, please adda few more

Author Response: Thank you for the reviewer’s valuable suggestion. In response, we have conducted a thorough literature review and added several recent and relevant references to better support the context and findings of our study. The updated reference list in the revised manuscript now includes these additional citations, which we believe enhance the comprehensiveness and academic rigor of the paper.

We tried our best to improve the manuscript and made some changes in the manuscript. These changes will not influence the content and framework of the paper. And here we did not list the changes but marked in red in revised paper.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

accepted

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have considered my comments. The paper can be published in its present form.

Reviewer 3 Report

Comments and Suggestions for Authors

The issues have been addressed satisfactorily