Characterization of Extra Low-Permeability Conglomerate Reservoir and Analysis of Three-Phase Seepage Law
Round 1
Reviewer 1 Report
This study analyzes the three-phase seepage law of low permeability. The essay is poorly written. The methodology lacks specificity. My suggestion is extensive revision. Here are my thoughts:
1. “Therefore, it is particularly important to study the non-linear seepage law of low permeability [19].” If the significance of the non-linear seepage law of low permeability was discussed in [19], then why did the authors exert so much effort to conduct the same analysis? What is the current status of your research? Please describe the novelty of the research and its distinction from similar previously published works.
2. The graphical scheme of three-phase relative permeability curve test must be added.
3. “The mathematical model method is based on two basic assumptions: one liquid phase strongly wets rocks, the gas phase is the non-wetting phase, and the other liquid phase is the intermediate wetting phase;” Which of the mathematical models is it? No mathematical equations are present in the manuscript.
4. Before the method is explained in detail, the validity of the results presented is very questionable.
Author Response
Reply
- At present, the research work on conglomerate reservoirs mainly focuses on reservoir description, reservoir formation mechanism, seismic interpretation, and logging interpretation based on geological methods, while the research on the characterization of conglomerate reservoirs and three-phase seepage law is less [17]. The existing experimental research methods of seepage law are mainly aimed at medium-high-permeability reservoirs [18]. For low permeability reservoirs, rocks have complex physical properties and abnormal seepage laws, and problems in the development of many low permeability reservoirs need to be solved urgently [19]. Therefore, it is necessary to study the characterization of ultra-low permeability conglomerate reservoirs and three-phase seepage laws. The purpose of this paper is to establish a laboratory test method for the three-phase permeability of extra-low permeability conglomerate reservoirs and a three-phase seepage simulation method based on the pore network model and to obtain extra-low permeability conglomerate reservoirs in the Lower Wuerhe Formation in Block 8.
- The graphical scheme of three-phase relative permeability curve test has been added to the subsection “Three-phase relative permeability curve test”.
- The description here is wrong. It is correct that the mathematical model method is based on the following basic assumptions: the water phase strongly wets the rock, the gas phase is the non-wetting phase, and the oil phase is the intermediate wetting phase. The calculation formula is a common relative permeability formula, which is not listed in this paper.
- Relevant details have been updated.
Reviewer 2 Report
The results look good but many figures are without legends and difficult to interpret. Put more effort into explaining the figures in the text
Units of permeability should be checked at various places
The methodology should be explained in detail. Very casual approach is followed to explain the method.
Line 38 Bring more clarity in explaining "current production capacity construction"..
line 42 from pore structure directly jumping to actual development, sentence linking is missing difficult to understand
Line 43 to 50 too big sentence, difficult to understand. shorten it
Line 53 to 55 reference required
Line 87, unit is not proper standard unit should be used
Line 109, Methodology should be used instead of research method,
Research method subsections 1 2 and 3, detailed methodology is required, should be presented in the form of flow chart
Line 124 " the stable state of the three-phase fluid is judged by CT scanning technology, and the saturation of the three-phase fluid is tested 125 online" Explain how??
Line 138 "An experimental test method is established, and the CT online saturation test is used 138 to obtain the unsteady oil-water and oil-gas phase permeability curves" should be explained
mercury intrusion and micro-CT (make and place is not described)
Line 156-158 "An adaptive model is established, and a unitized three-phase seepage simulation is carried out based on the pore network model. An algorithm is established to calculate the three-phase relative permeability, oil displacement efficiency, and other parameters, and use the experimental data for correction". No model is shown nor elaborated. Please discuss elaborately
Figure quality must be improved
Figure 2 and 3 no legend is provided
Line 195- 98, provide reference to support the arguement.
Table 1,
|
T01251 |
T07252 |
T14251 |
T23251 |
T28252 |
T36251 |
Not detailed, what are these numbers
English is clear but difficult to understand technically in various places
Author Response
- Comments and Suggestions for Authors
The results look good but many figures are without legends and difficult to interpret. Put more effort into explaining the figures in the text
Reply: The legend of the relevant figures has been supplemented.
Units of permeability should be checked at various places
Reply: The units of permeability have been checked and modified.
The methodology should be explained in detail. Very casual approach is followed to explain the method.
Reply: The methodology section has been supplemented with schematic diagrams and experimental procedures.
Line 38 Bring more clarity in explaining "current production capacity construction".
Reply: The current production capacity construction specifically includes geological surveys, logging and other process technologies for low-permeability oil reservoirs, construction work in pipelines, pumping stations, sewage discharge, safety, as well as comprehensive information management and digital oilfield construction.
line 42 from pore structure directly jumping to actual development, sentence linking is missing difficult to understand
Reply: Thank you very much for your suggestion. The following is the revised sentence: Due to the unique pore structure of low permeability reservoirs, they exhibit characteristics such as high-water injection pressure, slow oil well performance, rapid increase in water content after water breakthrough, and rapid decrease in liquid production and oil recovery index in actual development. These characteristics are closely related to their pore structure, as the complexity of pore structure brings great difficulties to water injection and oil recovery, leading to increased development difficulty.
Line 43 to 50 too big sentence, difficult to understand. shorten it
Reply: The following is the revised sentence: The physical properties of the rock surface in low-permeability conglomerate reservoirs vary greatly. The capillary and interfacial forces in pores are significantly different from those in medium and high permeability reservoirs. Therefore, the distribution mechanism of residual oil in sandy conglomerate reservoirs is different from that of conventional reservoirs with medium and high permeability. This makes some techniques and comprehensive adjustment methods suitable for residual oil in the later stage of development of medium and high permeability conventional reservoirs unusable in low permeability reservoirs.
Line 53 to 55 reference required
Reply: The reference has been supplemented.
Kang, W.-L., Zhou, B.-B., Issakhov, M., & Gabdullin, M. (2022). Advances in enhanced oil recovery technologies for low permeability reservoirs. Petroleum Science, 19(4), 1622–1640. https://doi.org/10.1016/j.petsci.2022.06.010
Line 87, unit is not proper standard unit should be used
Reply: The unit has been adjusted.
Line 109, Methodology should be used instead of research method,
Reply: Methodology has replaced research method.
Research method subsections 1 2 and 3, detailed methodology is required, should be presented in the form of flow chart
Reply: Relevant details have been updated.
Line 124 " the stable state of the three-phase fluid is judged by CT scanning technology, and the saturation of the three-phase fluid is tested 125 online" Explain how??
Reply: Specifically, by placing the sample in a CT scanner for scanning, information such as the density and absorption coefficient of the three-phase fluid in the sample can be obtained, thereby analyzing the distribution and saturation of the three-phase fluid.
Line 138 "An experimental test method is established, and the CT online saturation test is used 138 to obtain the unsteady oil-water and oil-gas phase permeability curves" should be explained
Reply: The experimental process has been supplemented.
mercury intrusion and micro-CT (make and place is not described)
Reply: The nitrogen adsorption method and gasoline quality evaluation method pretest parameters such as porosity and permeability, and then send the Intrusion Porosimeter to the laboratory for testing according to ASTM D4404-84 standard. The three-dimensional structure of conglomerate core samples was characterized using the MicroXCT-400 micro-CT scanner produced by Xtek Company in Finland.
Line 156-158 "An adaptive model is established, and a unitized three-phase seepage simulation is carried out based on the pore network model. An algorithm is established to calculate the three-phase relative permeability, oil displacement efficiency, and other parameters, and use the experimental data for correction". No model is shown nor elaborated. Please discuss elaborately
Reply: The experimental process has been supplemented.
Figure quality must be improved
Reply: Figure quality has been adjusted.
Figure 2 and 3 no legend is provided
Reply: Legends for Figures 2 and 3 have been provided.
Line 195- 98, provide reference to support the argument.
Reply: Liu, C., Yin, C., Lu, J., Sun, L., Wang, Y., Hu, B., & Li, J. (2020). Pore structure and physical properties of sandy conglomerate reservoirs in the Xujiaweizi depression, northern Songliao Basin, China. Journal of Petroleum Science and Engineering, 192, 107217. https://doi.org/10.1016/j.petrol.2020.107217
Not detailed, what are these numbers
Reply: These figures are core numbers, and I have revised Table 1.
- Comments on the Quality of English Language
English is clear but difficult to understand technically in various places
Reply: The text has been checked and edited.
Reviewer 3 Report
Interesting content, although it has scientific value, and covers all most all the aspects of the topic. Nevertheless, it lacks of important analysis and explanation, and the scientific significance of the article needs to be strengthened. I have a few general comments which can be considered constructive feedback to improve the quality of the work. Please review my feedback and try to incorporate them.
Abstract
The abstract is lengthy and lacks conciseness. It would be beneficial to shorten it. Additionally, in the results section of the abstract, it is recommended to emphasize only the key findings of the paper, rather than including all the results at the abstract level
Introduction
· Line 35 “According to incomplete statistics” . First why it is not completed , second , please add a reference here if possible
· Line 37 , please add between parenthesis the value of the permeability in Darcy or millidarcy
· Line 53: To clarify the meaning of "home and abroad," you can replace it with "domestically and internationally" or "in China and other countries." If you have specific references for the average recovery rate of low permeability reservoirs, it would be helpful to include the
· Line 67 to 69 “At present, the research work on conglomerate reservoirs mainly focuses on reservoir description, reservoir formation mechanism, seismic interpretation, and logging interpretation based on geological methods, while the research on the characterization of conglomerate reservoirs and three-phase seepage law is less..” Please try to rephrase this paragraph, improve the language . here is my suggestion “Currently, research on conglomerate reservoirs primarily concentrates on describing the reservoir, investigating the formation mechanism, conducting seismic interpretation, and performing logging interpretation using geological methods. However, there is relatively less research dedicated to characterizing conglomerate reservoirs and understanding the three-phase seepage law”
· Please try to add a few citations which have done similar works, just share their main findings
· From line 76 to line 108, the part which is covered here is mainly related to the field and the objectives of the study , therefore I would recommend you to create a new header called Studied filed and research objectives , for the mentioned part. It will be great if you can have the figures which shows the location of the field and the simple figure shows the stratigraphy of the field
RESEARCH METHODS
· Please change the title to Methodology
· Please provide a brief overview of the methodology, including the steps involved. Additionally, it would be helpful to include a figure illustrating the workflow of the methodology
· Line 119 “summarized and summarized”, it is a typo mistake I guess , please remove the second summarized
· Please for each experiment mention in this part try to give a short detail regarding the procedures, test condition, applied parameters and assumptions
RESULTS AND DISCUSSION
· Line 181 “ we selected Well T85722” what are the main response behind selecting this well ? Can you please clarify it.
· Line 186 “presents an inverse rhythm pattern distribution with the horizon depth”, Please add the depth to the points showing in fig 1 , so that we can understand the relation better
· Did you use drilling, cutting to measure the porosity and permeability or you used real cores
· For fig 2 please add legend which shows the difference between the 3 color lines
· Please for permeability stick with one unit do not change , either use Darcy or mD
· Please add more analyses to the data shown in fig 2 and 3, 4,5 to 12 . Try to use extra citation to strengthen your judgment
· In Table 1, could you please provide more details about the relationship between the measured parameters and depth? Specifically, identify which parameter exhibits a strong correlation with depth, either positively or negatively.
· Fig 4 and 5 , can you please define which k ?
· For all the figures , please add more discretion of the fig at the figure title
· Same as for fig 8 and 9 , what does PV mean? Is the pressure value is it delta pressure, please make it clear?
· Please add at the end of the paper, list of abbreviation
CONCLUSION
The conclusion is short and does not cover all the findings of the work
NA
Author Response
The abstract is lengthy and lacks conciseness. It would be beneficial to shorten it. Additionally, in the results section of the abstract, it is recommended to emphasize only the key findings of the paper, rather than including all the results at the abstract level
Reply: The abstract has been rewritten.
Introduction
- Line 35 “According to incomplete statistics” . First why it is not completed , second , please add a reference here if possible
Reply: The following is the revised sentence: According to preliminary statistics, 58% of China's existing proven unutilized oil-in-place reserves are oil reservoirs with a permeability of less than 50×10-3μm2 [1].
- Line 37 , please add between parenthesis the value of the permeability in Darcy or millidarcy
Reply: According to preliminary statistics, 58% of China's existing proven unutilized oil-in-place reserves are oil reservoirs with a permeability of less than 50×10-3μm2 (50×10-6 mD) [1].
- Line 53: To clarify the meaning of "home and abroad," you can replace it with "domestically and internationally" or "in China and other countries." If you have specific references for the average recovery rate of low permeability reservoirs, it would be helpful to include the
Reply: According to statistics, the average recovery rate of low permeability reservoirs in China and other countries is only about 20%, and most of the crude oil is retained in the reservoir and cannot be recovered [7].
- Line 67 to 69 “At present, the research work on conglomerate reservoirs mainly focuses on reservoir description, reservoir formation mechanism, seismic interpretation, and logging interpretation based on geological methods, while the research on the characterization of conglomerate reservoirs and three-phase seepage law is less..” Please try to rephrase this paragraph, improve the language . here is my suggestion “Currently, research on conglomerate reservoirs primarily concentrates on describing the reservoir, investigating the formation mechanism, conducting seismic interpretation, and performing logging interpretation using geological methods. However, there is relatively less research dedicated to characterizing conglomerate reservoirs and understanding the three-phase seepage law”
Reply: Thank you for your kindly suggestion.
- Please try to add a few citations which have done similar works, just share their main findings
Reply: There are two main methods for studying three-phase relative seepage problems: mathematical modeling method and physical simulation method. Stone statistical model is often used in mathematical model method, that is, two-phase relative permeability curve is used to calculate three-phase relative permeability curve [17]. This method is fast, simple, and widely used, but it is too idealized with multiple assumptions and is only applicable to water wet rock cores [18]. In some cases, the calculation results deviate from the experimental values. The actual flow process of the reservoir can be simulated by using the physical simulation method to test the three-phase relative permeability curve [19]. This method is relatively straightforward and can also provide experimental data under up to 13 saturation process conditions for the actual situation of oil and gas migration and production [20]. However, due to some limitations of laboratory instruments and measurement methods, the three-phase saturation cannot be measured synchronously and accurately, and there are some problems such as end effect, which restrict the study of measuring three-phase relative permeability curve by physical simulation method.
- From line 76 to line 108, the part which is covered here is mainly related to the field and the objectives of the study , therefore I would recommend you to create a new header called Studied filed and research objectives , for the mentioned part. It will be great if you can have the figures which shows the location of the field and the simple figure shows the stratigraphy of the field
Reply: Thank you for your suggestion. Considering the structure of the article, I did not add a new header. I have restructured the introduction. I have added a figure of the location of the oil field in the introduction.
RESEARCH METHODS
- Please change the title to Methodology
Reply: Modified as required.
- Please provide a brief overview of the methodology, including the steps involved. Additionally, it would be helpful to include a figure illustrating the workflow of the methodology
Reply: The method steps and the figure have been supplemented.
- Line 119 “summarized and summarized”, it is a typo mistake I guess , please remove the second summarized
Reply: Modified as required.
- Please for each experiment mention in this part try to give a short detail regarding the procedures, test condition, applied parameters and assumptions
Reply: Relevant details have been supplemented.
RESULTS AND DISCUSSION
- Line 181 “ we selected Well T85722” what are the main response behind selecting this well ? Can you please clarify it.
Reply: Well T85722 is the main well for the current mining target and has important engineering significance. The core and geological data are relatively complete and easy to obtain and utilize. This will provide convenience for developing scientific and reasonable experimental plans and analysis.
- Line 186 “presents an inverse rhythm pattern distribution with the horizon depth”, Please add the depth to the points showing in fig 1 , so that we can understand the relation better
Reply: Figure 1 is a typical structural diagram, and the depth of each horizon cannot be marked on Figure 1.
- Did you use drilling, cutting to measure the porosity and permeability or you used real cores
Reply: Standard experimental cores are obtained through drilling, cutting, and grinding.
- For fig 2 please add legend which shows the difference between the 3 color lines
Reply: The legend has been supplemented.
- Please for permeability stick with one unit do not change , either use Darcy or mD
Reply: Modified as required.
- Please add more analyses to the data shown in fig 2 and 3, 4,5 to 12 . Try to use extra citation to strengthen your judgment
Reply: I have added other references to my paper.
- In Table 1, could you please provide more details about the relationship between the measured parameters and depth? Specifically, identify which parameter exhibits a strong correlation with depth, either positively or negatively.
Reply: Secondary intergranular dissolved pores are negatively correlated with depth, average throat width is positively correlated with depth, and average pore throat ratio is positively correlated with depth, while other parameters are not obviously correlated with depth. I have added it to my paper.
- Fig 4 and 5 , can you please define which k ?
Reply: k represents the permeability of the core.
- For all the figures , please add more discretion of the fig at the figure title
Reply: Modified as required.
- Same as for fig 8 and 9 , what does PV mean? Is the pressure value is it delta pressure, please make it clear?
Reply: PV is the pore volume.
The conclusion is short and does not cover all the findings of the work
Reply: The conclusion has been rewritten.
The attachment is the list of abbreviation.
Author Response File: 
Author Response.pdf
Round 2
Reviewer 1 Report
Comments for author File: 
Comments.docx
Reviewer 2 Report
changes are incorporated.
Reviewer 3 Report
No further comments
No further comments
