Dear Dr. zhao,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please submit your revised manuscript by Sep 17 2025 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org . When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

• A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
• A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
• An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols . Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols .

We look forward to receiving your revised manuscript.

Kind regards,

Lisong Zhang

Academic Editor

PLOS ONE

Journal Requirements:

When submitting your revision, we need you to address these additional requirements.

1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf

2. We note that this submission includes NMR spectroscopy data. We would recommend that you include the following information in your methods section or as Supporting Information files:

1) The make/source of the NMR instrument used in your study, as well as the magnetic field strength. For each individual experiment, please also list: the nucleus being measured; the sample concentration; the solvent in which the sample is dissolved and if solvent signal suppression was used; the reference standard and the temperature.

2) A list of the chemical shifts for all compounds characterised by NMR spectroscopy, specifying, where relevant: the chemical shift (δ), the multiplicity and the coupling constants (in Hz), for the appropriate nuclei used for assignment.

3)The full integrated NMR spectrum, clearly labelled with the compound name and chemical structure.

We also strongly encourage authors to provide primary NMR data files, in particular for new compounds which have not been characterised in the existing literature. Authors should provide the acquisition data, FID files and processing parameters for each experiment, clearly labelled with the compound name and identifier, as well as a structure file for each provided dataset. See our list of recommended repositories here: https://journals.plos.org/plosone/s/recommended-repositories

3. We note that your Data Availability Statement is currently as follows: All relevant data are within the manuscript and its Supporting Information files.

Please confirm at this time whether or not your submission contains all raw data required to replicate the results of your study. Authors must share the “minimal data set” for their submission. PLOS defines the minimal data set to consist of the data required to replicate all study findings reported in the article, as well as related metadata and methods (https://journals.plos.org/plosone/s/data-availability#loc-minimal-data-set-definition).

For example, authors should submit the following data:

- The values behind the means, standard deviations and other measures reported;

- The values used to build graphs;

- The points extracted from images for analysis.

Authors do not need to submit their entire data set if only a portion of the data was used in the reported study.

If your submission does not contain these data, please either upload them as Supporting Information files or deposit them to a stable, public repository and provide us with the relevant URLs, DOIs, or accession numbers. For a list of recommended repositories, please see https://journals.plos.org/plosone/s/recommended-repositories.

If there are ethical or legal restrictions on sharing a de-identified data set, please explain them in detail (e.g., data contain potentially sensitive information, data are owned by a third-party organization, etc.) and who has imposed them (e.g., an ethics committee). Please also provide contact information for a data access committee, ethics committee, or other institutional body to which data requests may be sent. If data are owned by a third party, please indicate how others may request data access.

4. Thank you for stating the following financial disclosure:

This research is supported by the National Natural Science Foundation of China�No.52174031�and the Youth Innovation Team of Shaanxi Universities.

Please state what role the funders took in the study. If the funders had no role, please state: "The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript."

If this statement is not correct you must amend it as needed.

Please include this amended Role of Funder statement in your cover letter; we will change the online submission form on your behalf.

5. Thank you for stating the following in the Acknowledgments Section of your manuscript:

This research is supported by the National Natural Science Foundation of China�No.52174031�and the Youth Innovation Team of Shaanxi Universities.

We note that you have provided funding information that is not currently declared in your Funding Statement. However, funding information should not appear in the Acknowledgments section or other areas of your manuscript. We will only publish funding information present in the Funding Statement section of the online submission form.

Please remove any funding-related text from the manuscript and let us know how you would like to update your Funding Statement. Currently, your Funding Statement reads as follows:

This research is supported by the National Natural Science Foundation of China�No.52174031�and the Youth Innovation Team of Shaanxi Universities.

Please include your amended statements within your cover letter; we will change the online submission form on your behalf.

6. Please amend your authorship list in your manuscript file to include author jinsheng zhao.

7. Please amend the manuscript submission data (via Edit Submission) to include author Li JInfeng.

8. If the reviewer comments include a recommendation to cite specific previously published works, please review and evaluate these publications to determine whether they are relevant and should be cited. There is no requirement to cite these works unless the editor has indicated otherwise. 

Additional Editor Comments :

Reviewer 1

This manuscript focuses on the study of the displacement efficiency of fracturing fluid on crude oil in tight sandstone reservoirs, conducting relevant experiments, and exhibiting certain innovativeness and practicality. However, there are some deficiencies need to be checked out and revised:

1. In Introduction section, author mentioned imbibition, but there is a lack of the relevance of imbibition to the main work of this manuscript. It is recommended that author should clarify this relevance to enhanced the readability of the manuscript.

2. The relationship of imbibition and the flowback of fracturingfluid should be clarified in introduction (for example, the flowback of fracturingfluid may be achieved through imbibition).

3. The case of letters in table 1 needs to be consistent.

4. It is recommended that other physical parameters of experimental cores such as length, diameter and porosity should be shown in table 1.

5. Is the method that converting theabscissa of the NMR T₂ spectrum to pore-throat radius commonly used in the industry? Author should appropriately cite some relevant literatures to demonstrate its rationality.

6. Introduction section mentioned that the study revealed the main factors affecting oil-water displacement during the flowback process of tightoil fracturing, but the discussions of main factorsin Section 2 and 3 is not enough, which is confused.

7. The manuscript only reviewed the effect of capillary force on imbibition, while gravity also plays an important role in affecting imbibition. To better explain the background and relevant theoriesof this study, it is recommended to cite the following literatures:

a) https://doi.org/10.1016/j.geoen.2024.213071.

b) https://doi.org/10.2118/224403-PA.

c) https://doi.org/10.1080/01932691.2023.2177670.

d) https://doi.org/10.1016/j.geoen.2024.213057.

Reviewer 2

The paper is lacking with the several important results. The present form of the manuscript is not acceptable for possible publication in the journal. The comments that need to be addressed as follows:

1. While the authors have applied the tight sandstone method in their study, it would be beneficial to provide a brief introduction to this method for a clearer understanding by readers. Very few manuscripts have been considered to address the issues which is not sufficient.

2. The inclusion of Table 1, comparing results across various studies, is appreciated. However, the novelty of the study could be better emphasized. Strengthening the content related to the novelty would enhance the paper.

3. Although the introduction section offers a comprehensive overview, it would be beneficial to include more recent works in the field to further contextualize the study.

4. Full methodology section is incomplete such as sample preparation, testing and error analysis.

5. Authors could add more explanation for this statement. 'Fig. 4 - Fig. 6 were sketched to portrayed the streamline graphs for the signal amplitude problems under discussion for distinct values of pores. They stated that increasing in the pores, the graphs of streamline more presiding.'

6. Many of the study's results are presented without thorough explanation. Adding citations in the results and discussion section would help properly convey the significance of each finding and provide a more comprehensive analysis.

7. Several minor typographical errors are present in the paper. Correcting these errors is essential for improved readability and credibility.

8. The axes labels and tick labels in the figures are too small, affecting clarity. Enhancing the font sizes of these labels would significantly improve readability.

9. The conclusion section is not thoroughly presented.

Reviewer 3

Hello, Author. Thank you for submitting this manuscript for review. I want to commend the thoroughness of the research; however, I have highlighted its strengths and some areas where it could be improved.

1. This study addresses relevant practical problems like long flowback in tight reservoirs. It employs suitable experimental methods such as coreflooding and NMR T2 analysis to examine the displacement efficiency of different fracturing fluid gel-breakers. The experimental design controls key variables such as permeability through core pairs, interfacial tension, and viscosity to isolate their effects. Using NMR for pore-level displacement measurement is a strength. The conclusions about pore size impact, viscosity, interfacial tension, and time dependency are reasonable extensions of the experimental data.

Tables 2, 3, and 4 and Figures 4, 5, and 6 generally support the main conclusions regarding the effects of viscosity (Table 2), surfactants/interfacial tension (Table 3), and displacement time (Table 4) on overall and pore-specific displacement efficiency. The data support the observation of negative efficiency in micropores and plausibly explained.

However, the main weakness is the lack of replication. The study uses only one core per condition (e.g., one core for guanidine gum, one for cross-linked gum, one for slickwater, one for slickwater+surfactant). Although cores from longer samples were used for some comparisons (cores 1-2, 3-4), this does not constitute true replication. Natural heterogeneity within a single long core means results from one sample may not be representative. Without replicates, the reliability and general applicability of the efficiency values (e.g., 23.25% vs 18.31%, 13.11% vs 16.73%) are significantly reduced. While the directions of effects (e.g., lower viscosity increases efficiency) are probably valid due to controlled comparisons, the effect magnitudes and absolute efficiency values lack solid statistical support since n=1 per condition. The time-dependent study (Core 5) also involved only one core sequentially.

2. The manuscript reports no statistical analysis at all. Results are presented as single measurements (e.g., displacement efficiencies in tables) without any variance measures (standard deviation, error bars), significance tests (t-tests, ANOVA), or discussion of uncertainty. Given that only one core per condition was used (n=1), rigorous statistical comparison of treatments is impossible. The lack of acknowledgment of this limitation or attempts to quantify uncertainty (such as repeated measurements if feasible) means the analysis is not rigorous or appropriate.

3. The manuscript does not specify that raw data (like NMR T2 spectra, core properties beyond permeability, fluid measurements) have been deposited in a public repository or provided as supplementary material. While summary results are shown in figures and tables, raw data necessary for reproduction or re-analysis are not explicitly available in the manuscript or declared as accessible elsewhere.

4. The manuscript is generally clear and follows the conventional structure (Abstract, Intro, Methods, Results, Discussion, Conclusion). Technical terminology is appropriate. However, there are some instances of non-standard English and grammatical errors that slightly hinder readability but do not obscure the meaning:

a. "There usually have a long backflow period" (Abstract - should be "is").

b. "produced by the well soak" (Abstract - phrasing is awkward).

c. "reservoir reservoirs" (Abstract - redundant)

d. Inconsistent capitalization (e.g., "Guanidine gum" vs "guanidine gum").

e. Sentences are often lengthy and would benefit from concise rewriting and professional copyediting.

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

Reviewer #1: Yes

Reviewer #2: No

Reviewer #3: Partly

**********

2. Has the statistical analysis been performed appropriately and rigorously? -->?>

Reviewer #1: Yes

Reviewer #2: No

Reviewer #3: No

**********

3. Have the authors made all data underlying the findings in their manuscript fully available??>

The PLOS Data policy

Reviewer #1: Yes

Reviewer #2: No

Reviewer #3: No

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English??>

Reviewer #1: Yes

Reviewer #2: No

Reviewer #3: No

**********

Reviewer #1: This manuscript focuses on the study of the displacement efficiency of fracturing fluid on crude oil in tight sandstone reservoirs, conducting relevant experiments, and exhibiting certain innovativeness and practicality. However, there are some deficiencies need to be checked out and revised.

Reviewer #2: The paper is lacking with the several important results. The present form of the manuscript is not acceptable for possible publication in the journal. The comments that need to be addressed as follows:

1. While the authors have applied the tight sandstone method in their study, it would be beneficial to provide a brief introduction to this method for a clearer understanding by readers. Very few manuscripts have been considered to address the issues which is not sufficient.

2. The inclusion of Table 1, comparing results across various studies, is appreciated. However, the novelty of the study could be better emphasized. Strengthening the content related to the novelty would enhance the paper.

3. Although the introduction section offers a comprehensive overview, it would be beneficial to include more recent works in the field to further contextualize the study.

4. Full methodology section is incomplete such as sample preparation, testing and error analysis.

5. Authors could add more explanation for this statement. 'Fig. 4 - Fig. 6 were sketched to portrayed the streamline graphs for the signal amplitude problems under discussion for distinct values of pores. They stated that increasing in the pores, the graphs of streamline more presiding.'

6. Many of the study's results are presented without thorough explanation. Adding citations in the results and discussion section would help properly convey the significance of each finding and provide a more comprehensive analysis.

7. Several minor typographical errors are present in the paper. Correcting these errors is essential for improved readability and credibility.

8. The axes labels and tick labels in the figures are too small, affecting clarity. Enhancing the font sizes of these labels would significantly improve readability.

9. The conclusion section is not thoroughly presented.

Reviewer #3: Hello, Author. Thank you for submitting this manuscript for review. I want to commend the thoroughness of the research; however, I have highlighted its strengths and some areas where it could be improved.

1. This study addresses relevant practical problems like long flowback in tight reservoirs. It employs suitable experimental methods such as coreflooding and NMR T2 analysis to examine the displacement efficiency of different fracturing fluid gel-breakers. The experimental design controls key variables such as permeability through core pairs, interfacial tension, and viscosity to isolate their effects. Using NMR for pore-level displacement measurement is a strength. The conclusions about pore size impact, viscosity, interfacial tension, and time dependency are reasonable extensions of the experimental data.

Tables 2, 3, and 4 and Figures 4, 5, and 6 generally support the main conclusions regarding the effects of viscosity (Table 2), surfactants/interfacial tension (Table 3), and displacement time (Table 4) on overall and pore-specific displacement efficiency. The data support the observation of negative efficiency in micropores and plausibly explained.

However, the main weakness is the lack of replication. The study uses only one core per condition (e.g., one core for guanidine gum, one for cross-linked gum, one for slickwater, one for slickwater+surfactant). Although cores from longer samples were used for some comparisons (cores 1-2, 3-4), this does not constitute true replication. Natural heterogeneity within a single long core means results from one sample may not be representative. Without replicates, the reliability and general applicability of the efficiency values (e.g., 23.25% vs 18.31%, 13.11% vs 16.73%) are significantly reduced. While the directions of effects (e.g., lower viscosity increases efficiency) are probably valid due to controlled comparisons, the effect magnitudes and absolute efficiency values lack solid statistical support since n=1 per condition. The time-dependent study (Core 5) also involved only one core sequentially.

2. The manuscript reports no statistical analysis at all. Results are presented as single measurements (e.g., displacement efficiencies in tables) without any variance measures (standard deviation, error bars), significance tests (t-tests, ANOVA), or discussion of uncertainty. Given that only one core per condition was used (n=1), rigorous statistical comparison of treatments is impossible. The lack of acknowledgment of this limitation or attempts to quantify uncertainty (such as repeated measurements if feasible) means the analysis is not rigorous or appropriate.

3. The manuscript does not specify that raw data (like NMR T2 spectra, core properties beyond permeability, fluid measurements) have been deposited in a public repository or provided as supplementary material. While summary results are shown in figures and tables, raw data necessary for reproduction or re-analysis are not explicitly available in the manuscript or declared as accessible elsewhere.

4. The manuscript is generally clear and follows the conventional structure (Abstract, Intro, Methods, Results, Discussion, Conclusion). Technical terminology is appropriate. However, there are some instances of non-standard English and grammatical errors that slightly hinder readability but do not obscure the meaning:

a."There usually have a long backflow period" (Abstract - should be "is").

b."produced by the well soak" (Abstract - phrasing is awkward).

c."reservoir reservoirs" (Abstract - redundant)

d.Inconsistent capitalization (e.g., "Guanidine gum" vs "guanidine gum").

e.Sentences are often lengthy and would benefit from concise rewriting and professional copyediting.

**********

what does this mean? ). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy

Reviewer #1: No

Reviewer #2: No

Reviewer #3: Yes:  Adeniyi Adebayo

**********

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/ . PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org . Please note that Supporting Information files do not need this step.

Attachments

Attachment

Submitted filename: Review-PONE-D-25-35735.docx

Study on crude oil displacement efficiency by fracturing fluid in tight sandstone reservoir

PONE-D-25-35735R1

Dear Dr. zhao,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice will be generated when your article is formally accepted. Please note, if your institution has a publishing partnership with PLOS and your article meets the relevant criteria, all or part of your publication costs will be covered. Please make sure your user information is up-to-date by logging into Editorial Manager at Editorial Manager®  and clicking the ‘Update My Information' link at the top of the page. For questions related to billing, please contact billing support .

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Lisong Zhang

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

Reviewer #1: All comments have been addressed

Reviewer #3: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions??>

Reviewer #1: Yes

Reviewer #3: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously? -->?>

Reviewer #1: Yes

Reviewer #3: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available??>

The PLOS Data policy

Reviewer #1: Yes

Reviewer #3: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English??>

Reviewer #1: Yes

Reviewer #3: Yes

**********

Reviewer #1: (No Response)

Reviewer #3: Hello Author, I am pleased with your responses and the actions taken to address the issues I raised in the first submission.

**********

what does this mean? ). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy

Reviewer #1: No

Reviewer #3: No

**********