Experimental and EOR Mechanism Study of Water Shutoff Effects on Fractured Tight Sand Gas Reservoirs Using Fuzzy Ball Fluids

Round 1

Reviewer 1 Report

The paper discusses the water shut-off effect of fuzzy ball fluids in fractured tight sandstone gas reservoirs. The authors conducted experiments using Linxing He-2 reservoir matrix cores and cores with artificial fractures to simulate interlayer water, artificial fractures and water output channels from side and bottom. They used simulated formation water and nitrogen as the two-phase flow phase. The breakthrough pressure of the air and water phases were tested after plugging with fuzzy ball fluid.

The results showed that the fuzzy ball fluid can block the small-scale water output channels such as matrix pores through the polymer film-forming structure and plug the artistic cracks and the large-scale water output channels of the water flowing into the sides and bottom through the accumulation of many fuzzy balls. This greatly increases the flow resistance of water.

The authors concluded that the amount of fuzzy ball fluid should be carefully adjusted with the consideration of the water output and the formation conditions. For large-scale water output channels and side and bottom water shut-off operations, it is recommended to increase the number of fuzzy balls and increase the number of fuzzy balls in the system, to increase the breakthrough pressure of water, and achieve air stable and water control.

 

The text is well-written and easy to understand. The experimental methods are sound, and the results are presented clearly. The conclusions are supported by the data.

Author Response

Thanks for your review and comments on our work, which has given us great courage and strength.

Reviewer 2 Report

The paper “Experimental and EOR mechnism study on water shut-off effects on fractured tightsand gas reservoirs by Fuzzy ball fluids” focuses on the overcome fractured tight sandstone gas reservoir. The experimental methodology is not well explained in my opinion, how they conduct experiments or how the setup. Because I'm not an expertise in this field my comments are below

-line 69 the authors use double parenthesis

-In all Figures, it's better to use a dot after a number of figures

- Please follow the journal pattern for writing an equation such as, aligning left or right

-In line 267 ''formation water and the fuzzy ball fluid is 28°'' Please give a detailed explanation of how the authors measure the degree.

- In line 351 the authors write 3 after a dot, does it correct?

- Why do authors make points after Figure 8.? 

-In reference, the authors should follow the journal template, such as you don't need to add the abbreviation J for the journal

Author Response

Thanks for your review and comments on our work, which has given us great courage and strength. We have carefully revised the manuscript and marked in red, and responded to the reviewer's comments one by one.  We have referred to the english language editing by MDPI, to checked for correct use of grammar and common technical terms, and edited to a level suitable for reporting research in a scholarly journal.  The details for your good comments is uploaded as a file.

Author Response File: Author Response.pdf

Reviewer 3 Report

The authors present a study to test the efficacy of fuzzy-ball additives in fractured tight sandstone reservoirs. They design a laboratory experiment that reveals that the water breakthrough pressure gradient is greater than that of gas and that the difference between the two is more pronounced depending on the fractures present. In addition, the authors present field data that is relatively unconvincing of the potential of fuzzy-ball additives.

This article reads as if it perhaps was not ready for submission. There are numerous errors such as misplaced numbers in the text, erroneous figure numbers, and a lack of proper spaces between elements.

In my opinion, what this article lacks is clarity. For instance, it was not until I saw (mislabeled) Figure 9 that I had an understanding of the implications of fuzzy-ball technology. Also, the figure captions, especially in the three figures that display data need to be improved such that the reader can more readily draw the information out of them.

 

 

A few more specific thoughts:

In the title, you mention EOR, but I am not sure if that is what we are dealing with. Isn't LX-Y a production well?

Explain with great care what the mechanism and implications of fuzzy-ball technology are in the introduction. I think this is missing at present. It is not readily apparent why we would want "plugging". Wouldn't that decrease permeability?

Figure 1: Needs a scale bar

Figure 2: This is entirely up to you, but I'm not sure this figure adds anything.

Section 2.3: I think this is a little awkward at present. Perhaps you could elaborate on the testing procedure, or just move these sentences into section 3.1.3.

I am unfamiliar with a "cashmere bag," so other readers may not know about it either. It would be nice to give an explanation.

On Figure 8, you need a clear explanation of why the phenomenon seen in section D indicates the success of the fuzzy-balls. I believe that the second numbered point is attempting this, but the link is not drawn sufficiently.

(mislabeled) Figure 9: I like this figure, but many of the details are obscured by scale. It might be possible to put the two subfigures on the righthand side on the bottom and expand the size of everything. Also, to the best of my knowledge, MDPI allows for figures to expand into the margin on the left. In addition, this figure contains a typo, "sealaplugged"

 

My final thought: I think you need to tie the laboratory studies into the discussion more explicitly. In the introduction, you state that the knowledge gap is systematic laboratory studies, and yet, it seems like most of the discussion and conclusion is related to the field data and the theory of fuzzy-balls. I guess the field, the theory, and the laboratory all just feel disparate at the moment.

The English is quite rough in places. This is not necessarily a matter of grammar, although there were a few places where I saw such errors. It is more about using phrases appropriately and flowing from idea to idea.

You should double-check all the units in the text because I saw a number of errors there.

I am not sure, but I believe "fuzzy-ball" should be hyphenated. There are a couple times when you do use a hyphen, but most of the time you don't.

Also I saw a few capital letters in the wrong place.

I think you need to really carefully "fly-speck" this document. There are too many easily catchable errors.

Author Response

Thanks for your review and comments on our work, which has given us great courage and strength. We have carefully revised the manuscript and marked in red, and responded to the reviewer's comments one by one. Due to our inadequate language skills, we have referred to the english language editing by MDPI, to checked for correct use of grammar and common technical terms, and edited to a level suitable for reporting research in a scholarly journal. The details for your good comments is uploaded as a file.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Thank you for your careful revisions. I think the key element here is the description of the fuzzy ball mechanism early in the paper.

This reads much better now, good job!