Investigation on the Injection Pattern of Intermittent Natural Gas Flooding in Ultra-Low Permeability Reservoirs
Round 1
Reviewer 1 Report
The manuscript provides an investigation on the oil displacement in ultra-low permeable reservoir by means of natural gas injected with an intermittent mode (IGI) to control gas finger and enhance oil recovery. The work is well organized, but the Authors should address the following issues before publishing.
Remarks:
- In the introduction, please revise the sentences from lines 60-64. They are not very clear and some further details are necessary to make clear which are the operational problems of IGI and why there are no ’’successful experience’’.
- The Authors should describe with more details the experimental setup employed and the protocol used to perform the experiments.
- In Figure 2, the time scale of the graphs (c) and (d) should be made clearer.
- Could the Authors define how they were calculated the recovery improvement and the gas-liquid ratio?
- Could the Author define the stress sensitivity mentioned at line 150?
- The sentence reported on lines 131-132, ‘‘The problem…application.’’ needs to be made clearer.
- It is not clear to me if the cycle index goes form 1 cycle to 7 cycles as reported at line 104 or can achieves 11 cycles as reported in table 2 or can reaches 12 cycles as reported at line 151.
- Finally, it is recommended to improve the discussion of the results comparing the findings related to the IGI methods to those related to the employment of continuous natural gas flooding technique.
Some formatting and misprint issues should be addressed, such as:
- ‘Charactristics’at line 25
- In general, a space between number and unit is missing
- the formatting of table 1 should be revised
- At line 151 some spaces are missing between the numbers of cycles.
Author Response
Dear Editor and Reviewers,
Thanks very much for taking your time to review this manuscript. We really appreciate all your comments and suggestions. Please find our itemized responses in below and our revisions in the re-submitted files.
Thanks again!
The reviewers’ comments and our responses are listed below.
Comment 1: The main findings with important opinions should be mentioned in the Abstract section. The authors need to consider these points in the revision stage.
Response 1: The Abstract section is improved by adding the main findings with important opinions.
Comment 2: Please use more recent references (for the last 3-4 years ago) to better present the literature review and the importance of the topic.
Response 2: We have cited the recent references related to the topic，especially for the last 3-4 years. Shown in the REFERENCES section.
Comment 3: Barring a few sentences in the text, the English language is fair. However, the text is not free from grammar errors. Ensure that your English manuscript is guaranteed free of language issues. In addition, the manuscript should be thoroughly checked for English corrections as there are some colloquial terms being used.
Response 3: We have improved the English writing all of the paper.
Comment 4: The Introduction section needs to be extended by describing the cause, fatality, novelty of the work, advantages, and disadvantages of the present study.
Response 4: The Introduction section is rewritten. The cause, fatality, novelty of the work, advantages and disadvantages of the present study are added.
Comment 5: In the Introduction section (first paragraph), it is recommended to add a sentence about other technologies (such as asphaltene control) that can improve production performance. The following references in the revision stage can be used, in which the recovery improvement was evaluated:
- Petroleum Science and Technology, Volume 36, Issue 14, 2018, pp. 1030-1036.
- Journal of Petroleum Science and Engineering, Volume 206, 2021, 109066.
Response 5: The other technologies (such as profile control, asphaltene control) that can improve production performance is added in the Introduction section. And the references recommended are cited.
Comment 6: The aims of the work should be mentioned in detail in the last paragraph of the Introduction section.
Response 6: The aims of the work is mentioned in the last paragraph of the Introduction section.
Comment 7: Please add the photo of the used experimental apparatus.
Response 7: The photo of the used experimental apparatus is added.
Comment 8: More descriptions of the studied field (Fuyu oilfield) should be presented.
Response 8: We have added some descriptions of the studied field. Fuyu oilfield has the serious water channeling after a long term water flooding, Thus, gas flooding to enhance oil recovery is necessary for this oilfield. It is meaningful for this oilfield to study the adaption of IGI.
Comment 9: The obtained results should be supported by references.
Response 9: The obtained results are all concluded from the experiment. There is no references about the experiment of technical parameters discussion of IGI in ultra-low permeability reservoir. Thus, we can’t provide the reference to support this result.
Comment 10: More discussion on oil recovery for each cycle of IGI is needed.
Response 10: We have added more discussion on oil recovery for each cycle of IGI.
Comment 11: The conclusion also needs to be rewritten. Include the following: new concepts and innovations demonstrated in this study, a summary of findings, a comparison with findings by other workers, and concluding remarks.
Response 11: The conclusion is rewritten according to the comments.
Author Response File: 
Author Response.doc
Reviewer 2 Report
The review of the manuscript entitled: “Investigation on the Injection Pattern of Intermittent Natural Gas Flooding in Ultra-low Permeability Reservoir”. By responding to the following comments and questions, the work can be improved:
1. The main findings with important opinions should be mentioned in the Abstract section. The authors need to consider these points in the revision stage.
2. Please use more recent references (for the last 3-4 years ago) to better present the literature review and the importance of the topic.
3. Barring a few sentences in the text, the English language is fair. However, the text is not free from grammar errors. Ensure that your English manuscript is guaranteed free of language issues. In addition, the manuscript should be thoroughly checked for English corrections as there are some colloquial terms being used.
4. The Introduction section needs to be extended by describing the cause, fatality, novelty of the work, advantages, and disadvantages of the present study.
5. In the Introduction section (first paragraph), it is recommended to add a sentence about other technologies (such as asphaltene control) that can improve production performance. The following references in the revision stage can be used, in which the recovery improvement was evaluated:
- Petroleum Science and Technology, Volume 36, Issue 14, 2018, pp. 1030-1036.
- Journal of Petroleum Science and Engineering, Volume 206, 2021, 109066.
6. The aims of the work should be mentioned in detail in the last paragraph of the Introduction section.
7. Please add the photo of the used experimental apparatus.
8. More descriptions of the studied field (Fuyu oilfield) should be presented.
9. The obtained results should be supported by references.
10. More discussion on oil recovery for each cycle of IGI is needed.
11. The conclusion also needs to be rewritten. Include the following: new concepts and innovations demonstrated in this study, a summary of findings, a comparison with findings by other workers, and concluding remarks.
Author Response
Dear Editor and Reviewers,
Thanks very much for taking your time to review this manuscript. We really appreciate all your comments and suggestions. Please find our itemized responses in below and our revisions in the re-submitted files.
Thanks again!
The reviewers’ comments and our responses are listed below.
Comment 1: In the introduction, please revise the sentences from lines 60-64. They are not very clear and some further details are necessary to make clear which are the operational problems of IGI and why there are no ’’successful experience’’.
Response 1: The introduction section is rewritten, including the sentences from lines 60-64. There is little application of this technology because the applicability and the technical parameters of IGI in ultra-low permeability reservoir are little studied.
Comment 2: The Authors should describe with more details the experimental setup employed and the protocol used to perform the experiments.
Response 2: The experimental processes, devices and materials are described, and the conditions of the experiments, including the temperature and pressure, are given. Some experimental apparatus and the protocol used to perform the experiments are added.
Comment 3: In Figure 2, the time scale of the graphs (c) and (d) should be made clearer.
Response 3: We have reset the time scale of the graphs (c) and (d) in Figure 2 to make them clearer.
Comment 4: Could the Authors define how they were calculated the recovery improvement and the gas-liquid ratio?
Response 4: The oil recovery improvement is the difference between the oil recovery after the experiment and the one before the experiment.
The gas-liquid ratio is the ratio between the output liquid and the output gas, it can be used to describe the degree of gas channelling.
Comment 5: Could the Author define the stress sensitivity mentioned at line 150?
Response 5: The stress sensitivity can be defined as the permeability change with the affecting under different pressures.
Comment 6: The sentence reported on lines 131-132, ‘‘The problem…application.’’ needs to be made clearer.
Response 6: From the research, the IGI has the good abilities of controlling gas finger and enhancing oil recovery. However, in the practical application, the ultimate aim is make the benefit maximization. Thus, the further experiment is to find the optimal technical parameters of IGI to make the degree of controlling gas finger and enhancing oil recovery maximum.
Comment 7: It is not clear to me if the cycle index goes form 1 cycle to 7 cycles as reported at line 104 or can achieves 11 cycles as reported in table 2 or can reaches 12 cycles as reported at line 151.
Response 7: We have unified the cycle index of IGI in the paper, which goes form 1 cycle to 11 cycles.
Comment 8: Finally, it is recommended to improve the discussion of the results comparing the findings related to the IGI methods to those related to the employment of continuous natural gas flooding technique.
Response 8: We have improve the discussion of the results both from the cycle index of IGI and the conclusions section.
Comment 9: Some formatting and misprint issues should be addressed, such as: - ‘Charactristics’at line 25
- In general, a space between number and unit is missing
- the formatting of table 1 should be revised
- At line 151 some spaces are missing between the numbers of cycles.
Response 9:
- The “charactristics” is misprint, and it is corrected.
- The space between number and unit is deleted in the paper.
- The formatting of table 1 is revised.
- We have rewritten the expression of different cycles.
Author Response File: Author Response.doc
Round 2
Reviewer 1 Report
The Authors carefully revised and improved the manuscript.
Reviewer 2 Report
The work was revised based on the comments. It is ready for publication.
