The Whole-Aperture Pore Structure Characteristics and Their Controlling Factors of the Dawuba Formation Shale in Western Guizhou

Round 1

Reviewer 1 Report

Yuan et al. provided an interesting study regarding aperture structure characteristics in dawuba shale. Substantial experimental work and analysis have been given in this work. Minor revision is suggested at this stage. Detailed comments are given below for the authors’ consideration.

1. The geological setting of the given formation is suggested to be described with more information.
2. In addition to the pore structure, which is relatively static, permeability measurement is sometimes more important for reservoir characterization. The article below is suggested to be added as a starting point in the introduction part. Permeability measurement of the fracture-matrix system with 3D embedded discrete fracture model. Petroleum Science. 2022.
3. Kindly add the description what is GB / T3723-1999 in line 121.
4. It is suggested to use scientific writing of numbers in this manuscript like in Table 4.
5. It is suggested to add more discussion regarding the relationship between pore structure and mineral analysis and other experiment results if any.

Author Response

Yuan et al. provided an interesting study regarding aperture structure characteristics in dawuba shale. Substantial experimental work and analysis have been given in this work. Minor revision is suggested at this stage. Detailed comments are given below for the authors’ consideration.

 

1. The geological setting of the given formation is suggested to be described with more information.

Responses: thank you for your comments. We have added more descriptions about geological setting.

2. In addition to the pore structure, which is relatively static, permeability measurement is sometimes more important for reservoir characterization. The article below is suggested to be added as a starting point in the introduction part.

Permeability measurement of the fracture-matrix system with 3D embedded discrete fracture model. Petroleum Science. 2022.

Responses: thank you for your comments. We have added descriptions about permeability.

3. Kindly add the description what is GB / T3723-1999 in line 121.

Responses: thank you for your comments. It is an acknowledged industrial standard. All the relative measurements follows it.

4. It is suggested to use scientific writing of numbers in this manuscript like in Table 4.

Responses: thank you for your comments. We have revised it

5. It is suggested to add more discussion regarding the relationship between pore structure and mineral analysis and other experiment results if any.

Responses: thank you for your comments. We have added discussions about pore structure and mineral analysis.

Reviewer 2 Report

Dear Authors,

I have reviewed your paper titled “The whole-aperture pore structure characteristics and its controlling factors of the Dawuba Formation shale in western Guizhou”.

The paper discusses an important topic in relation to understanding the pore structure characteristic of shale and the enrichment mechanism of shale gas in formations within Qianxi area. To achieve this, the authors conducted qualitative and quantitative studies of the formations.

Nine (9) shale samples were selected from cores of different layers in well QSA-1. Such samples we selected for high pressure mercury injection experiment and low temperature gas adsorption experiment.

The high pressure mercury injection and low temperature gas adsorption enabled to obtain the pore pressure characteristics of shale from nano to micros scale. This helped to quantify the full aperture distribution characteristics of the individual members of Dawuba formation.

The study provided the description of micropores, mesopores and macropores of the studied shale formation. It showed that the pore development characteristics are different in the various members in Dawuba formation. In addition, the study concluded that the organic carbon content and clay mineral content of shale has influence on the adsorption capacity of shale by affecting its pore structure.

This is a very good, structured manuscript. The research work that has been conducted has great value in shale gas application. The paper is well written. The authors described the aim, methodology, execution, results and conclusions clearly.

Based on my review, I conclude that the paper is a good one. Hence, I recommend its publication and I look forward to reading it in its published version.

Yours Sincerely,

 

Author Response

Dear Authors,

 

I have reviewed your paper titled “The whole-aperture pore structure characteristics and its controlling factors of the Dawuba Formation shale in western Guizhou”.

 

The paper discusses an important topic in relation to understanding the pore structure characteristic of shale and the enrichment mechanism of shale gas in formations within Qianxi area. To achieve this, the authors conducted qualitative and quantitative studies of the formations.

 

Nine (9) shale samples were selected from cores of different layers in well QSA-1. Such samples we selected for high pressure mercury injection experiment and low temperature gas adsorption experiment.

 

The high pressure mercury injection and low temperature gas adsorption enabled to obtain the pore pressure characteristics of shale from nano to micros scale. This helped to quantify the full aperture distribution characteristics of the individual members of Dawuba formation.

 

The study provided the description of micropores, mesopores and macropores of the studied shale formation. It showed that the pore development characteristics are different in the various members in Dawuba formation. In addition, the study concluded that the organic carbon content and clay mineral content of shale has influence on the adsorption capacity of shale by affecting its pore structure.

 

This is a very good, structured manuscript. The research work that has been conducted has great value in shale gas application. The paper is well written. The authors described the aim, methodology, execution, results and conclusions clearly.

 

Based on my review, I conclude that the paper is a good one. Hence, I recommend its publication and I look forward to reading it in its published version.

 

Yours Sincerely,

Responses: thank you for you comments

Reviewer 3 Report

This paper presents an experimental methodology to assess whole-aperture pore structure and its characteristics in shale formations. It also provides specifics on the controlling factors affecting the pore development in shale. The research and experiments are well articulated. The paper is well structured and aligns with the processes journal after incorporating the following comments:

The literature part in the introduction needs to be improved. For instance, the following references can be included in the paper to enhance the introduction:

This book chapter reference provides comprehensive details on the pore-structure characterization and associated experiments

Mudunuru, M. K., J. W. Carey, L. Chen, Q. Kang, S. Karra, V. V. Vesselinov, R. S. Middleton, P. A. Johnson, and H. S. Viswanathan. "Subsurface energy: Flow and reactive-transport in porous and fractured media." In HANDBOOK OF POROUS MATERIALS: Synthesis, Properties, Modeling and Key Applications Volume 4-Porous Materials for Energy Conversion and Storage, pp. 323-395. 2021.

The following two papers provide how to transfer experimental knowledge of pore structure and its data to field-scale and data-driven models

Mudunuru, M.K., O'Malley, D., Srinivasan, S., Hyman, J.D., Sweeney, M.R., Frash, L., Carey, B., Gross, M.R., Welch, N.J., Karra, S. and Vesselinov, V.V., 2020. Physics-Informed Machine Learning for Real-time Reservoir Management. In AAAI Spring Symposium: MLPS.

Srinivasan, Shriram, Daniel O’Malley, Maruti K. Mudunuru, Matthew R. Sweeney, Jeffrey D. Hyman, Satish Karra, Luke Frash et al. "A machine learning framework for rapid forecasting and history matching in unconventional reservoirs." Scientific Reports 11, no. 1 (2021): 1-15.

2. Figure-7 needs to be improved as it is difficult to read the difference between the lines micropore and macropore.

Author Response

This paper presents an experimental methodology to assess whole-aperture pore structure and its characteristics in shale formations. It also provides specifics on the controlling factors affecting the pore development in shale. The research and experiments are well articulated. The paper is well structured and aligns with the processes journal after incorporating the following comments:

 

The literature part in the introduction needs to be improved. For instance, the following references can be included in the paper to enhance the introduction:

 

This book chapter reference provides comprehensive details on the pore-structure characterization and associated experiments

 

Mudunuru, M. K., J. W. Carey, L. Chen, Q. Kang, S. Karra, V. V. Vesselinov, R. S. Middleton, P. A. Johnson, and H. S. Viswanathan. "Subsurface energy: Flow and reactive-transport in porous and fractured media." In HANDBOOK OF POROUS MATERIALS: Synthesis, Properties, Modeling and Key Applications Volume 4-Porous Materials for Energy Conversion and Storage, pp. 323-395. 2021.

 

The following two papers provide how to transfer experimental knowledge of pore structure and its data to field-scale and data-driven models

 

Mudunuru, M.K., O'Malley, D., Srinivasan, S., Hyman, J.D., Sweeney, M.R., Frash, L., Carey, B., Gross, M.R., Welch, N.J., Karra, S. and Vesselinov, V.V., 2020. Physics-Informed Machine Learning for Real-time Reservoir Management. In AAAI Spring Symposium: MLPS.

 

Srinivasan, Shriram, Daniel O’Malley, Maruti K. Mudunuru, Matthew R. Sweeney, Jeffrey D. Hyman, Satish Karra, Luke Frash et al. "A machine learning framework for rapid forecasting and history matching in unconventional reservoirs." Scientific Reports 11, no. 1 (2021): 1-15.

Responses: thank you for your comments.

 

2. Figure-7 needs to be improved as it is difficult to read the difference between the lines micropore and macropore.

Responses: thank you for your comments. We have revised figure 7.

Reviewer 4 Report

Line 88. Indicate and describe techniques used for quantitative assessment of porosity.

Line 90. Indicate the time, angles, current, and probe size used during argon ion polishing.

Sections 2.3 and 2.4 more details on what samples were used in term of geometry and the size of probes. Details on possible errors and limitations are necessary.

XRD method description is missed. 

Figure 2. Indicate the epoch. 

Figure 3. The diagram is obscure, try to find clear way to visualize mineral composition.

What do you mean by micro- , meso- and macro- pore? Clear indication of the terminology in the introduction is needed, only within the discussion part the real meaning was revealed.

Regarding the "conclusion" part.

1. 10%+89%=99%, where is 1%? Reading conclusion apart from discussion part is not relevant, which must be corrected. I don't understand what meso-, micro- and macro- pores mean.
2. Very general conclusion, any shale contains many types of pores. And why do you suggest that "micro-fractures and interlayer pore fractures of clay minerals" provide "good reservoir space"?
3. Very ambiguous conclusion, not clear. No pore sizes, no relevant information on association with mineral or organic part.
4. It is widely known that "The organic carbon content and clay mineral content of shale affect the adsorption 349 capacity of shale", whats new here?

 

Author Response

Line 88. Indicate and describe techniques used for quantitative assessment of porosity.

Responses: Thank you for your comments. We added descriptions about techniques used for quantitative assessment of porosity.

Line 90. Indicate the time, angles, current, and probe size used during argon ion polishing.

Responses: Thank you for your comments. We added descriptions about Ar-ion polishing information.

Sections 2.3 and 2.4 more details on what samples were used in term of geometry and the size of probes. Details on possible errors and limitations are necessary.

Responses: Thank you for your comments. We added descriptions about samples, possible errors and limitations.

XRD method description is missed.

Responses: Thank you for your comments. We added descriptions about XRD.

Figure 2. Indicate the epoch.

Responses: Thank you for your comments. We have indicated it “the Dawuba formation was formed in Carboniferous period”.

Figure 3. The diagram is obscure, try to find clear way to visualize mineral composition.

Responses: Thank you for your comments. We added values on the top of each histogram column.

What do you mean by micro- , meso- and macro- pore? Clear indication of the terminology in the introduction is needed, only within the discussion part the real meaning was revealed.

Responses: Thank you for your comments. We added descriptions about pore size in introduction part.

Regarding the "conclusion" part.

 

1. 10%+89%=99%, where is 1%? Reading conclusion apart from discussion part is not relevant, which must be corrected. I don't understand what meso-, micro- and macro- pores mean.

Responses: Thank you for your comments. According to the data in Table 3, the value should be 89.78% and 10.22%.

2. Very general conclusion, any shale contains many types of pores. And why do you suggest that "micro-fractures and interlayer pore fractures of clay minerals" provide "good reservoir space"?
3. Very ambiguous conclusion, not clear. No pore sizes, no relevant information on association with mineral or organic part.

Responses to 2 and 3: Thank you for your comments. The organic matter mainly provided more micropores, which will affect the adsorbed gas. But the volume of micropores is less than the mesopores and macropores, which was related to minerals and contained more free-state shale gas.

4. It is widely known that "The organic carbon content and clay mineral content of shale affect the adsorption 349 capacity of shale", what`s new here?

Responses: Thank you for your comments. The Dawuba formation in this research area. The new point lies more in localization.

Round 2

Reviewer 4 Report

Please, provide corrections according  two comments regarding conclusions. There are no corrections or eleboration in the revised version. The questions are important.

Point 2 in conclusion: Very general conclusion, any shale contains many types of pores. And why do you suggest that "micro-fractures and interlayer pore fractures of clay minerals" provide "good reservoir space"?

Point 3 in conclusion: Very ambiguous conclusion, not clear. No pore sizes, no relevant information on association with mineral or organic part.

 

Author Response

Please, provide corrections according two comments regarding conclusions. There are no corrections or eleboration in the revised version. The questions are important.

 

Point 2 in conclusion: Very general conclusion, any shale contains many types of pores. And why do you suggest that "micro-fractures and interlayer pore fractures of clay minerals" provide "good reservoir space"?

Responses: Thank you for your comments. We added descriptions and figure 12 to show the reason why "micro-fractures and interlayer pore fractures of clay minerals provides good reservoir space".

Point 3 in conclusion: Very ambiguous conclusion, not clear. No pore sizes, no relevant information on association with mineral or organic part.

Responses: Thank you for your comments. We added more detailed descriptions in conclusion section.