Study on Calculation Method for Wellbore Pressure in Gas Wells with Large Liquid Production

Round 1

Reviewer 1 Report

 I have read with interest the article,,Study on calculation method of wellbore pressure in gas wells with large liquid production”. The article provides useful information on calculation method of wellbore pressure in gas wells with large liquid production. The result can be useful in the context of the wellbore. 

I recommend the publication of the article. 

Author Response

We gratefully thanks for the precious time the reviewer spent making constructive remarks.

Thank you for your recognition of this article.

Reviewer 2 Report

Please see attachment for detailed comments to the manuscript.

In general, the quality of the text and the images must be improved.

A list of symbols with unit should be added.

Comments for author File: Comments.rtf

Author Response

We gratefully thank you for your time spend making the constructive remarks and useful suggestions, which has significantly raised the quality of the manuscript and has enable us to improve the manuscript. Each suggested revision and comment, brought forward by the reviewers was accurately incorporated and considered.Below the comments of the reviewers are response point by point and the revisions are indicated.
1.Comment: line 47: "... Duns Ros" citation needed
1.Reply: References have been cited in the article
2.Comment: line 93: "is not rigorous in logic" this statement should be justified
2.Reply: The original intention of the article is "that the means of verifying the accuracy of the empirical model obtained through the experiment with CFD model is not rigorous, and that the experiment is more accurate than CFD simulation". There is a misunderstanding in the expression in the article, so the sentence has been corrected again.
3.Comment: line 105: missing premise location
3.Reply: Location has been added
4.Comment: lines 114-116: missing the reference temperature for the used values.In general, here should be provided a comprehensive table including also the oil
4.Reply: During the indoor experiment, the ambient temperature of 20 ℃ is maintained for a long time, so it is considered that the pipeline temperature is also about 20 ℃. The indoor experiment environment is normal temperature and pressure. To save space, no additional tables have been added.
5.Comment: figures 4-5: missing legends for the axis quantities and units
5.Reply: The meaning represented by the XY axis in Figure 4 and figure 5 has been updated and explained in the article. It is the dimensionless standard number of speed, which can also be queried from references.
6.Comment: equation 1-3: spcify units for v and theta
6.Reply: The unit of V is meters per second,m/s; The unit of theta is °.
7.Comment: line 165: is a repetition of line 161
7.Reply: Duplicate sentences have been deleted from the latest manuscript
8.Comment: figures 12-13: the x and y axis quantites are not readable
8.Reply: The x-axis represents the number of iterations, and the y-axis represents the value of the result
9.Comment: table 2: wrong caption
9.Reply: The table name of Table 2 is omitted when modifying the article format. After correction, the name of Table 2 is "Parameters of the newly established liquid-holdup-calculation model"
10.Comment: line 227 and others: "slippage" correct to "slip" missing definition of "El"
10.Reply: Corrected
11.Comment: figure 18-19-20: caption is not understandable, missing axes legends
11.Reply: 
figure18 :XYZ axis represents v_sg, gas–liquid ratio and pressure drop (kPa), respectively
figure19:XYZ axis represents v_sg, Froude number and pressure drop (kPa), respectively
figure20:XYZ axis represents v_sg, Reynolds number and pressure drop (kPa), respectively
12.Comment: equation 14: not clear the meaning of "esin"
12.Reply: it means e*sin theta
13.Comment: lines 305-308: revise the english form of the text
13.Reply: The article has been polished by professionals

Reviewer 3 Report

The paper presents an experimental study in gas injection to enhance the liquid production within the oil and gas production tubing by improving the wellbore pressure. Below are comments for authors' attention:

• The abstract needs to be reviewed and rewritten. There are some typos. Also, what is the MB method and the BB method?
• Authors should review the models' names again. These should be:
  • Aziz and Govier model
  • Begss and Brill model
  • Hasan model --- ???? not sure about this, please check
  • Mukherjee and Brill model
  • Pattern model --- ??? please check
• Lines 114-116
  • authors should state at what temperature the surface tension of water is 37 mN/m. at 20 degrees, the surface tension is about 72.8 mN/m.
  • Also, in line 116, these values are not surface tension. They are viscosity and authors should use "mPa.s" not "MPa.s" or they can easily use cP (centipoise)
• Figure 2:
  • what is the condition (liquid flow and air flow) and also the angle and pipe diameter? is it the same for both pipe diameters?
  • what is Churn area?
  • Furthermore, use different colour for Mukherjee model or authors can use different line shapes
  • What are Vsg and Vs

The above comments are applicable to other Figures as well.

Lines 314-318: although authors' claimed that their extracted model is more accurate, however, they should also, again, argue that scientifically. Why other methods are not accurate and have a large difference from real data.

English grammar needs to be reviewed.

Are references 5 and 6 identical? if Yes, remove one of them.

Same for references 11 and 12

Author Response

We gratefully thank you for your time spend making the constructive remarks and useful suggestions, which has significantly raised the quality of the manuscript and has enable us to improve the manuscript. Each suggested revision and comment, brought forward by the reviewers was accurately incorporated and considered.Below the comments of the reviewers are response point by point and the revisions are indicated.

1.comment: The abstract needs to be reviewed and rewritten. There are some typos. Also, what is the MB method and the BB method?

Authors should review the models' names again. These should be:

Aziz and Govier model

Begss and Brill model

Hasan model --- ???? not sure about this, please check

Mukherjee and Brill model

Pattern model --- ??? please check.

1. Reply: Thank you for your comments. The article has been retouched by professional people. The name of each model has been corrected to make it more accurate. The Pattern model was proposed by Ruiquan Liao, an expert in multiphase flow direction in China. In China, we call it Pattern model.
2. Comment: Lines 114-116

authors should state at what temperature the surface tension of water is 37 mN/m. at 20 degrees, the surface tension is about 72.8 mN/m.

Also, in line 116, these values are not surface tension. They are viscosity and authors should use "mPa.s" not "MPa.s" or they can easily use cP (centipoise)

2. Reply: During the indoor experiment, the ambient temperature of 20 ℃ is maintained for a long time, so it is considered that the pipeline temperature is also about 20 ℃. The indoor experiment environment is normal temperature and pressure. So at 20 degrees, the surface tension is about 72.8 mN/m. The error in the value has been corrected in the latest manuscript.

Line 116, where the surface tension is changed to viscosity.

3. Comment: Figure 2:

what is the condition (liquid flow and air flow) and also the angle and pipe diameter? is it the same for both pipe diameters?

3. Reply: The purpose of the picture is to show the different patterns of gas-liquid two-phase flow in the experiment.. The 60mm plexiglass tube is used, and the figure is observed when the included angle with the horizontal angle is 60 °..
4. Comment: what is Churn area?
5. Reply: Change the Churn area to transition flow.
6. Comment: Furthermore, use different colour for Mukherjee model or authors can use different line shapes.
7. Reply: The color of Mukherjee model lines in the picture has changed.
8. Comment: What are Vsg and Vsl.
9. Reply: Vsg ——superficial gas velocity ;vsl——superficial liquid velocity
10. Comment: Lines 314-318: although authors' claimed that their extracted model is more accurate, however, they should also, again, argue that scientifically. Why other methods are not accurate and have a large difference from real data.
11. Reply: The reason the error of these models is too large is that the water production of the Donghai gas field is huge, and the daily liquid production of a single well can reach 300 square meters. As the influence of the gas–liquid ratio on the pressure drop was not considered, the calculation of the above pressure-drop model will be inaccurate.

In the latest manuscript, this part is supplemented according to your suggestions.

8. Comment: English grammar needs to be reviewed.

Are references 5 and 6 identical? if Yes, remove one of them.Same for references 11 and 12.

8.Reply: The article has been polished by professionals and the references have been adjusted.

Thank you for your valuable advice.