Quantitative Evaluation and Evolution of Overpressure in the Deep Layers of a Foreland Basin: Examples from the Lower Cretaceous Bashijiqike Formation in the Keshen Area, Kuqa Depression, Tarim Basin, China

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript attempts to quantify overpressure in the deep layers of the Kuqa Foreland Basin and evaluate its evolution, with a focus on the Bashijiqike Formation. While the paper covers a crucial aspect of overpressure in foreland basins, the novelty and methodology require substantial improvement. Below are specific comments to help enhance the manuscript.

1. The manuscript presents multiple sources of overpressure, but the distinction between disequilibrium compaction, tectonic compression, and fracture transfer remains unclear. A more comprehensive explanation of how these overpressure types interact and contribute to the overall pressure system is necessary.

2. The quantitative evaluation model for overpressure, although suitable for deep formations, is not clearly justified as a novel contribution. Comparing your model's performance against existing models or methodologies from recent studies would clarify its advantages and innovations.

3. The use of PetroMod software is well-noted; however, there is a lack of details on the specific settings, assumptions, and calibration data used for the simulations. More technical insight into the modeling process, particularly how geological uncertainties were managed, is needed to replicate the study.

4. The manuscript refers to seismic and well log data but does not thoroughly describe how these data were integrated into the overpressure evaluation. Clarifying how the seismic attributes and well logs specifically contributed to your modeling would be beneficial.

5. Figures showing results of pressure evolution and geological settings, such as Figure 10 and Figure 11, are highly complex. Adding simpler explanatory diagrams or enhancing captions to highlight key points in each figure would improve comprehension.

6. The methodology section is brief in explaining the selection of the Bashijiqike Formation as the study area. A clearer explanation of why this specific formation is representative or unique within the Kuqa Depression is needed to justify the study’s focus.

7. The validation of the overpressure model is insufficient. There should be more robust evidence comparing the model predictions with actual measured data, such as DST and mud weight, to prove the accuracy and applicability of the model to the Keshen gas field.

 

8. A major concern is that the paper largely relies on established geological concepts and lacks a clear statement of novelty. A detailed explanation of how this study advances current knowledge of overpressure in foreland basins is needed. Without a strong statement of novelty, the contribution to the field is not clear.

9. The model’s assumptions (e.g., steady-state conditions, homogeneity) are not fully addressed. Discussing these assumptions and their potential impacts on the results would provide a better understanding of the model's limitations.

10. The geological setting section contains extensive background but lacks specificity on how it directly impacts overpressure distribution. Reorganizing this section to emphasize its relevance to the main focus of the manuscript would improve its coherence.

11. The acoustic transit-vertical effective stress crossplots (Section 3.3) lack a clear explanation of their relevance to the main objectives of the study. More detail on how these crossplots were interpreted and their significance in the context of overpressure evaluation is required.

12. The transfer overpressure calculation is based on the work of previous models, but it is not clear how this model improves upon or differs from those. Justifying why an improved version was needed and what enhancements were made would strengthen the methodology.

13. The manuscript references tectonic compression as a key factor but does not sufficiently explain how the timing and magnitude of tectonic events were determined. Including a timeline of tectonic evolution and its correlation with overpressure development would clarify this relationship.

14. The chemical and mechanical impacts of acidic gas reservoirs are not considered in your overpressure evolution discussion. Considering the potential effects of geochemical reactions on the rock properties and pressure distribution would enhance the model's comprehensiveness.

15. The practical implications of the overpressure study are underexplored. Adding a discussion on how the findings might influence drilling strategies, well safety, or resource management in similar geological contexts would add value to the study.

16. The novelty of the methodology is questionable, as many of the approaches and models applied are well-established in existing literature. More emphasis on how your specific approach offers a new perspective or solution to overpressure evaluation in deep basins is required.

 The manuscript, while comprehensive in its scope of overpressure evaluation, lacks a clear statement of novelty, thorough validation of its model, and sufficient methodological rigor. Due to these major concerns, rejection is suggested until significant improvements are made to address the novelty, methodology, and application of the study.

Comments on the Quality of English Language

The manuscript is generally understandable, but the quality of English requires improvement. There are instances of awkward phrasing, grammatical errors, and technical terms that are inconsistently used throughout the text. A thorough language review focusing on sentence structure, proper use of technical terminology, and overall coherence would enhance readability and ensure clarity in conveying the study’s objectives and results. It may be beneficial to consider professional language editing to improve the manuscript's quality.

Author Response

1. The manuscript presents multiple sources of overpressure, but the distinction between disequilibrium compaction, tectonic compression, and fracture transfer remains unclear. A more comprehensive explanation of how these overpressure types interact and contribute to the overall pressure system is necessary.

Mudstone disequilibrium compaction overpressure

Disequilibrium compaction is essentially due to the imbalance between compaction and drainage.Previous studies have shown that the main factors affecting the disequilibrium compaction compaction are deposition rate and mud content. The greater the deposition rate, the less favorable the directional arrangement of mudstone particles, and the more likely it is to lead to the imbalance between compaction and drainage, resulting in disequilibrium overpressure.In the sand-mudstone interlayer, the high sandstone content makes the overpressure in mudstone easy to transfer upward and downward, and the drainage is smooth, which is not conducive to the formation of unbalanced compaction type overpressure. However, in principle, as long as the factors that can cause the imbalance between compaction and drainage can produce disequilibrium compaction type overpressure.

Transfer overpressure

When two pressure systems are connected by an open fault, the fluid pressure quickly adjusts to reach hydrostatic equilibrium, and a new pressure system is formed, which is caused by the spatial realignment of the fault into a fault-transmitted overpressure.

Tectonic compression overpressure

Tectonic extrusion type overpressure is lateral compaction caused by tectonic extrusion.

The interaction of various overpressures

It must be admitted that the interaction between different types of overpressure exists, but it is relatively small, and the contribution of different types of overpressure is mainly different in different geological historical periods. Before 2.48Ma: It is mainly based on disequilibrium compaction type overpressure. 1.75-2.48mA due to the influence of tectonic extrusion, it is mainly tectonic extrusion type overpressure. After 1.75Ma, the fracture opens, which is mainly caused by fracture transfer overpressure and tectonic extrusion overpressure.

2. The quantitative evaluation model for overpressure, although suitable for deep formations, is not clearly justified as a novel contribution. Comparing your model's performance against existing models or methodologies from recent studies would clarify its advantages and innovations.

The fracture transfer overpressure model is compared with the existing model:

The original fracture transfer overpressure model was exponential, and it was found that it could not fully fit the acoustic velocity effective stress template in the deep foreland basin during fitting. Therefore, if the previous method was used for calculation, the error would be large.The new model is logarithmic and has a good fit with the acoustic velocity and effective stress in the deep background of foreland basin. Higher calculation accuracy.

 

 

Fig13.Sonic-velocity effective-stress(SV-ES)schematic obtained by calculation in the well KS201,fitting the original and newly established loading curves.The original loading curve is in the form of quasi-exponential,it cannot be fitted to the actual situation of well KS201.The.newly established loading curves is log-like morphology,it is more in line with the actual situation of well KS201.

 

Advantages of model

 

Comparison between the structural extrusion overpressure model and the existing model:

A lot of work has been done on the relationship between rock structural stress and pore abnormal fluid pressure, and the corresponding quantitative evaluation model of tectonic compression and pressurization has been proposed.It includes: quantitative evaluation of the upper limit of the contribution of structural extrusion to overpressure based on plane stress field, quantitative evaluation of the contribution of structural extrusion based on plane stress field to overpressure in semi-closed system, quantitative evaluation of the contribution of numerical simulation based on three-dimensional stress state to overpressure, etc.However, these models have many solving parameters, are easily affected by human factors, or lack consideration of rock deformation process, deformation mechanism and pressure evolution, which limits the applicability and operability of the models to a certain extent.

 

3. The use of PetroMod software is well-noted; however, there is a lack of details on the specific settings, assumptions, and calibration data used for the simulations. More technical insight into the modeling process, particularly how geological uncertainties were managed, is needed to replicate the study.

 

The parameters required by the software are listed in the following table: Appendix in this document.

Table 1 Parameters required for the burial simulation

Category	Pressure
	Mudstone disequilibrium compaction overpressure		Tectonic compression overpressure	Fracture transfer overpressure
Basic data	Elements	Porosity		The shape and distribution characteristics of the fracture	The opening time of the fracture
	Methods or values	Calculated by the equivalent depth method after the compaction curve compiled by the logging curve(Fig. 3b)			2.48–1.75
	References			Tarim Oilfield Company, PetroChina.	Jia and Li, 2008; Guo et al., 2016a; Guo et al., 2016c
Adjusted data				Permeability of the fault
Calibration data	Elements	The amount of mudstone disequilibrium compaction overpressure	The amount of tectonic compression overpressure	The amount of fault transfer overpressure
	Methods or values.	Calculated using the equivalent depth method after the compaction curve compiled by the logging curve.	See the Appendix for the quantitative evaluation model.	See the Appendix for the quantitative evaluation model.
	References

 

 

 

 

Table 2 Parameters required for the litholog (porosity) simulation

Table 3 Parameters required for the pressure simulation

 

 

Category	Burial
Basic data	Elements	The top and bottom depth of each layer	Formation deposition time of each layer	Erosion thickness	Erosion time
	Methods or values
	References	Tarim Oilfield Company, PetroChina.
Adjusted data	Geological framework generated during the simulation
Calibration data	Elements	Actual geological situation
	Methods
	References	Tarim Oilfield Company, PetroChina

 

Category	Litholog (porosity)
Basic data	Elements	Sedimentary facies distribution	Well Lithology information	Porosity	Effective stress
	Methods  or values			Calculated by Wiley formula after the compaction curve compiled by logging curve (Figure 3c)	Subtracting the pore pressure (calculated by the equivalent depth method after the compaction curve compiled by the log) from the overburden (S = ρgh) (Figure 3b)
	References	Tarim Oilfield Company, PetroChina.
Adjusted data	Porosity–Effective stress relationship
Calibration data	Elements	Measured porosity
	Methods
	References	Tarim Oilfield Company, PetroChina.

4.The manuscript refers to seismic and well log data but does not thoroughly describe how these data were integrated into the overpressure evaluation. Clarifying how the seismic attributes and well logs specifically contributed to your modeling would be beneficial.

Seismic data are not used in this paper. The application of log data is mainly reflected in the evaluation of unbalanced compaction and fracture transfer overpressure. The compaction curve is compiled using the effective point of log data, which is described in detail in the method. The sound velocity effective stress chart is also prepared using points from the logging data, which are described in detail in the method

5. .Figures showing results of pressure evolution and geological settings, such as Figure 10 and Figure 11, are highly complex. Adding simpler explanatory diagrams or enhancing captions to highlight key points in each figure would improve comprehension.

Figures 10 and 11 are indeed complex, but because the information in them is critical, they cannot be simplified. Therefore, the key parts of the map are marked as detailed

 

 

 

6. The methodology section is brief in explaining the selection of the Bashijiqike Formation as the study area. A clearer explanation of why this specific formation is representative or unique within the Kuqa Depression is needed to justify the study’s focus.

The Bashijiqik Formation is the main reservoir in Kesen area, and is also the key area of exploration at present. At the same time, the depth is between 6500 and 8000m, which accords with the characteristics of deep foreland basin.

7. The validation of the overpressure model is insufficient. There should be more robust evidence comparing the model predictions with actual measured data, such as DST and mud weight, to prove the accuracy and applicability of the model to the Keshen gas field.

At present, the quantitative methods that can directly reflect the pressure of deep formation are mainly DST and mud data. In order to further verify the pressure data, this paper uses inclusion data for further constraint, as shown in Figure 10.

8.A major concern is that the paper largely relies on established geological concepts and lacks a clear statement of novelty. A detailed explanation of how this study advances current knowledge of overpressure in foreland basins is needed. Without a strong statement of novelty, the contribution to the field is not clear.

The novelty of this study lies in the quantitative evaluation of the pressure in the deep foreland basin and the coupled evolution of the multi-genetic pressure in the deep foreland basin. Previous studies mainly focused on the evolution of pressure from a single origin, which coupled to promote the evolution of deep pressure in foreland basins. This explanation is supplemented in the introduction..

9. The model’s assumptions (e.g., steady-state conditions, homogeneity) are not fully addressed. Discussing these assumptions and their potential impacts on the results would provide a better understanding of the model's limitations.

PM does not assume this setting in the simulation process, only geological conditions, pore and pressure Settings, boundary conditions and oil and gas migration and accumulation conditions.

10. The geological setting section contains extensive background but lacks specificity on how it directly impacts overpressure distribution. Reorganizing this section to emphasize its relevance to the main focus of the manuscript would improve its coherence.

The geological background has been reorganized and rewritten.split the geological setting into two (2) section: 1) the structural system, and 2) petroleum system including source and reservoir intervals and its interval characteristics.

11. The acoustic transit-vertical effective stress crossplots (Section 3.3) lack a clear explanation of their relevance to the main objectives of the study. More detail on how these crossplots were interpreted and their significance in the context of overpressure evaluation is required.

Section 3.3 adds that the sonic-effective stress chart is mainly used to identify the causes of overpressure. The causes of pressure on the loading curve are mainly unbalanced compaction type overpressure, those on the unloading curve are mainly caused by fluid expansion, and the pressure points in sandstone are generally fracture transfer type overpressure.

12.The transfer overpressure calculation is based on the work of previous models, but it is not clear how this model improves upon or differs from those. Justifying why an improved version was needed and what enhancements were made would strengthen the methodology.

The improvement of the model can be seen in question 2. The previous quantitative evaluation model of fault transfer is similar to exponential form, and it is found in the process of fitting that it is not suitable for deep layer under the structural geological background and cannot be fitted, while the new model is similar to logarithmic form, which can better perform sound velocity - effective stress chart, so as to quantitatively evaluate fault transfer overpressure.

13.The manuscript references tectonic compression as a key factor but does not sufficiently explain how the timing and magnitude of tectonic events were determined. Including a timeline of tectonic evolution and its correlation with overpressure development would clarify this relationship.

Structural compression is a key factor. To determine this relationship, a tectonic evolution timeline is added in this paper. The magnitude of tectonic compression is mainly determined by the constrained simulation results of acoustic emission experiments. See Method (3.4) for details.

14.The chemical and mechanical impacts of acidic gas reservoirs are not considered in your overpressure evolution discussion. Considering the potential effects of geochemical reactions on the rock properties and pressure distribution would enhance the model's comprehensiveness.

At present, chemical compaction is indeed the frontier research in the field of pressure, but it is still blank in the Kuqa region. Due to the complex causes of pressure in this region, the role of chemical compaction is rarely mentioned, and the research is very difficult, and the Kuqa region is currently limited by data, and the study cannot be realized. Chemical compaction is not the main factor in the cause of pressure in the Kuqa Depression, and it is often ignored. At present, the study of chemical compaction mainly focuses on basins with relatively simple pressure origin, which can fully reflect the importance of chemical compaction, such as Xihu Depression.

15.The practical implications of the overpressure study are underexplored. Adding a discussion on how the findings might influence drilling strategies, well safety, or resource management in similar geological contexts would add value to the study.

The main significance of overpressure research is that it has an important impact on oil and gas migration and accumulation as well as drilling safety. This paper only studies the genesis and evolution of pressure, and my main research direction is oil and gas migration and accumulation direction. If this part needs to be supplemented, please see the following statement.

Overpressure is the driving force of oil and gas migration, and the source-reservoir pressure difference is the driving force of vertical oil and gas migration, and the source-reservoir pressure difference refers to the pressure difference between source rock and reservoir. The greater the source-reservoir pressure difference, the greater the driving force of vertical oil and gas migration. Fluid potential is the driving force of oil and gas lateral migration. Oil and gas migrate at high momentum gradient and accumulate at low momentum gradient. According to this principle, the direction of oil and gas migration and the area of oil and gas accumulation can be studied.

Combined with the hydrocarbon accumulation event, the hydrocarbon migration and accumulation in Keshen area can be described as follows: the evolution characteristics of the source-reservoir pressure difference in Keshen area are as follows: the source-reservoir pressure difference was about 5-10MPa before the tectonic extrusion, increased to 50-60MPa after the tectonic extrusion, and decreased to about 30MPa after the fault transmission. The characteristics of momentum gradient evolution in Keshen area are as follows: the momentum gradient is 600m/km before tectonic extrusion, decreases to 500m/km after tectonic extrusion, and increases to 500m/km after fault transmission. Therefore, the Keshen area is not a strong area of vertical migration of oil and gas because of insufficient vertical migration power before tectonic compression. It is a high momentum gradient area, not a favorable accumulation area for lateral migration of oil and gas. There are sufficient vertical migration forces after tectonic compression, and it is a favorable accumulation area for vertical migration of oil and gas. It is a low momentum gradient area and a favorable accumulation area for lateral migration of oil and gas. The vertical migration force is sufficient after fault transmission, and it is a favorable accumulation area for vertical migration of oil and gas. It is a low momentum gradient area and a favorable accumulation area for lateral migration of oil and gas.

16. The novelty of the methodology is questionable, as many of the approaches and models applied are well-established in existing literature. More emphasis on how your specific approach offers a new perspective or solution to overpressure evaluation in deep basins is required.

The method is improved in the existing literature, the original method is not suitable for this area, and the improved method is more suitable, which is a kind of progress and innovation.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This paper mainly studies the mechanism and evolution of deep high pressure in Kuqa foreland basin, Tarim Basin, China, and its impact on oil and gas exploration, and obtains a more accurate pressure prediction model through numerical simulation and geological data analysis.

(1) The introduction section is relatively weak and does not fully reflect the content of quantitative evaluation and evolution. It is hoped that the author can revise and strengthen the introduction and research in this regard.

(2) The article uses models to quantitatively evaluate and simulate the process of pressure evolution, but the advantages and quantitative evaluation effects of this method have not been reflected compared to other models.

(3) How is the identification method and contribution of pressure from different sources calculated, and how are existing methods such as log combination valves, Bowers method, porosity comparison, and comprehensive analysis used to identify the types of pressure caused by various reasons and evaluate their respective degrees of impact.

(4) I hope to provide a clearer concept of the "multi-genetic pressure" mentioned in the paper, and at the same time, I hope to provide deeper reasons for the "disequilibrium compaction".

(5) The author takes the Kuche Depression in Tarim Basin as an example to investigate the universality of the methods used in this article for different basins.

(6) I hope the language can be further modified.

Comments on the Quality of English Language

Moderate editing of English language required.

Author Response

• The introduction section is relatively weak and does not fully reflect the content of quantitative evaluation and evolution. It is hoped that the author can revise and strengthen the introduction and research in this regard.

The introduction has been rewritten as follows:

There are obvious differences in the identification and quantitative evaluation methods of overpressure under different geological backgrounds.At present, the cause and quantitative evaluation of pressure are mainly concentrated in the middle and shallow reservoirs and under the background of relatively single pressure cause

( Zeng,2010;Fan,2016;Luo,2007 ;Li,2021).The pressure formation and quantitative evaluation methods, especially quantitative evaluation methods, in the deep background of foreland basins are very lacking.

At present, there are two main methods to study paleo-fluid pressure, which are fluid inclusions and numerical simulation by using basin simulation software, among which petromode simulation software is widely used(Aplin et al., 2000;Gutierrez et al., 2005).Most studies on the evolution of overpressure focused on single origins, such as the evolution of the tectonic compressive stress field and the instantaneous flow field in fracture propagation (Zeng et al., 2010; Wang et al., 2022). The coupling of overpressure caused by multi-genetic pressure and analysing its evolution remains a weak link in the study of overpressure.

• The article uses models to quantitatively evaluate and simulate the process of pressure evolution, but the advantages and quantitative evaluation effects of this method have not been reflected compared to other models.

The fracture transfer overpressure model is compared with the existing model:

The original fracture transfer overpressure model was exponential, and it was found that it could not fully fit the acoustic velocity effective stress template in the deep foreland basin during fitting. Therefore, if the previous method was used for calculation, the error would be large.The new model is logarithmic and has a good fit with the acoustic velocity and effective stress in the deep background of foreland basin. Higher calculation accuracy.

 

 

Fig13.Sonic-velocity effective-stress(SV-ES)schematic obtained by calculation in the well KS201,fitting the original and newly established loading curves.The original loading curve is in the form of quasi-exponential,it cannot be fitted to the actual situation of well KS201.The.newly established loading curves is log-like morphology,it is more in line with the actual situation of well KS201.

 

Comparison between the structural extrusion overpressure model and the existing model:

A lot of work has been done on the relationship between rock structural stress and pore abnormal fluid pressure, and the corresponding quantitative evaluation model of tectonic compression and pressurization has been proposed.It includes: quantitative evaluation of the upper limit of the contribution of structural extrusion to overpressure based on plane stress field, quantitative evaluation of the contribution of structural extrusion based on plane stress field to overpressure in semi-closed system, quantitative evaluation of the contribution of numerical simulation based on three-dimensional stress state to overpressure, etc.However, these models have many solving parameters, are easily affected by human factors, or lack consideration of rock deformation process, deformation mechanism and pressure evolution, which limits the applicability and operability of the models to a certain extent.

• How is the identification method and contribution of pressure from different sources calculated, and how are existing methods such as log combination valves, Bowers method, porosity comparison, and comprehensive analysis used to identify the types of pressure caused by various reasons and evaluate their respective degrees of impact.

This part has been discussed in detail in the results and discussion. The recognition of overpressure of unbalanced compaction type is mainly based on the compaction curve method, the recognition of overpressure of fracture transfer type is mainly based on the Bowers curve method, and the recognition of overpressure of structural extrusion type is mainly based on the relationship of ground stress. The quantitative evaluation of disequilibrium compaction is mainly based on equivalent depth method, the quantitative evaluation of fracture transfer overpressure is mainly based on the calculation of Bowers curve by mathematical model, and the quantitative evaluation of tectonic extrusion overpressure is mainly based on in-situ stress simulation calculation combined with mathematical model.

• I hope to provide a clearer concept of the "multi-genetic pressure" mentioned in the paper, and at the same time, I hope to provide deeper reasons for the "disequilibrium compaction".

Multi-genetic overpressure

Multi-cause pressure means that the cause of pressure is not a single, but in the process of geological evolution has appeared different causes of pressure, or at the same time there are two kinds of pressure simultaneously.

Mudstone disequilibrium compaction overpressure

Disequilibrium compaction is essentially due to the imbalance between compaction and drainage.Previous studies have shown that the main factors affecting the disequilibrium compaction compaction are deposition rate and mud content. The greater the deposition rate, the less favorable the directional arrangement of mudstone particles, and the more likely it is to lead to the imbalance between compaction and drainage, resulting in disequilibrium overpressure.In the sand-mudstone interlayer, the high sandstone content makes the overpressure in mudstone easy to transfer upward and downward, and the drainage is smooth, which is not conducive to the formation of unbalanced compaction type overpressure. However, in principle, as long as the factors that can cause the imbalance between compaction and drainage can produce disequilibrium compaction type overpressure.

• The author takes the Kuche Depression in Tarim Basin as an example to investigate the universality of the methods used in this article for different basins.

The method presented in this paper is not applicable to different basins, but is suitable for deep foreland basins. Because the pressure causes of different basins are different, the methods used in this paper are very different. Therefore, I cannot discuss the generality in different basins, except to say that the method presented in this paper is suitable for deep foreland basins.

(6)I hope the language can be further modified.

This article has been retouched.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Figures--------

Figures 6 (a) and (b) text too small to read. need englargement. 

Figure 9 (a) and (b) in-diagram text isn't readable. Perhaps white color or text box would help. 

Figure 11 y -axis text too small to read. needs enlargement. 

Manuscript text------

1)  The introduction could better clarify the practical applications, such as for drilling safety or hydrocarbon extraction.

2) The analysis of overpressure mechanisms (disequilibrium compaction, tectonic compression, fracture transfer) is thorough, but lacks detailed discussion on how each mechanism affects drilling operations. Suggest adding a table to summarize how each mechanism impacts drilling. 

3) The use of multiple data sources (DST data, well logs, mud weights) is thorough, but technical details in some sections are dense. Summarizing more effectively would make the paper more accessible to a broader audience.

4) A clear summary of model strengths, assumptions and limits to applicability needs to be provided near the conclusion. 

5) The formal and technical language are hindering accessibility for a broader audience. Simplifying sentences and reducing jargon would improve readability. Or give a table (serving as dictionary) at the beginning which introduces the more esoteric terms used in the manuscript. 

6) Including comparisons with similar studies from regions outside China would better contextualize findings and assess their general applicability.

 

Author Response

1)Figures 6 (a) and (b) text too small to read. need englargement. 

Figure 9 (a) and (b) in-diagram text isn't readable. Perhaps white color or text box would help. 

Figure 11 y -axis text too small to read. needs enlargement. 

Re:The text in Figures 6(a) and 6(b) has been enlarged as follows:

 

Figure 9 (a) and (b) text has been changed:

 

Figure 11 The map has been changed as follows:

 

2) The introduction could better clarify the practical applications, such as for drilling safety or hydrocarbon extraction.

The introduction section has been improved as follows:

The existence of overpressure is common in petroliferous basins. Understanding their distribution characteristics,origins and quantitative characteristics is fundamental for predicting pore pressure and for studying the migration and accumulation of petroleum. The accuracy of pressure prediction depends on accurate quantitative evaluation of different origins of pressure(Zhang et al.2013;Hao et al., 2007).

3）The analysis of overpressure mechanisms (disequilibrium compaction, tectonic compression, fracture transfer) is thorough, but lacks detailed discussion on how each mechanism affects drilling operations. Suggest adding a table to summarize how each mechanism impacts drilling. 

The main significance of overpressure research is that it has an important impact on oil and gas migration and accumulation as well as drilling safety. This paper only studies the genesis and evolution of pressure, and my main research direction is oil and gas migration and accumulation direction. If this part needs to be supplemented, please see the following statement.

Overpressure is the driving force of oil and gas migration, and the source-reservoir pressure difference is the driving force of vertical oil and gas migration, and the source-reservoir pressure difference refers to the pressure difference between source rock and reservoir. The greater the source-reservoir pressure difference, the greater the driving force of vertical oil and gas migration. Fluid potential is the driving force of oil and gas lateral migration. Oil and gas migrate at high momentum gradient and accumulate at low momentum gradient. According to this principle, the direction of oil and gas migration and the area of oil and gas accumulation can be studied.

Combined with the hydrocarbon accumulation event, the hydrocarbon migration and accumulation in Keshen area can be described as follows: the evolution characteristics of the source-reservoir pressure difference in Keshen area are as follows: the source-reservoir pressure difference was about 5-10MPa before the tectonic extrusion, increased to 50-60MPa after the tectonic extrusion, and decreased to about 30MPa after the fault transmission. The characteristics of momentum gradient evolution in Keshen area are as follows: the momentum gradient is 600m/km before tectonic extrusion, decreases to 500m/km after tectonic extrusion, and increases to 500m/km after fault transmission. Therefore, the Keshen area is not a strong area of vertical migration of oil and gas because of insufficient vertical migration power before tectonic compression. It is a high momentum gradient area, not a favorable accumulation area for lateral migration of oil and gas. There are sufficient vertical migration forces after tectonic compression, and it is a favorable accumulation area for vertical migration of oil and gas. It is a low momentum gradient area and a favorable accumulation area for lateral migration of oil and gas. The vertical migration force is sufficient after fault transmission, and it is a favorable accumulation area for vertical migration of oil and gas. It is a low momentum gradient area and a favorable accumulation area for lateral migration of oil and gas.

4）The use of multiple data sources (DST data, well logs, mud weights) is thorough, but technical details in some sections are dense. Summarizing more effectively would make the paper more accessible to a broader audience.

The use of DST data, logging data and mud gravity is summarized:

DST data: The most direct and accurate pressure data, but the amount of data is small

Mud specific gravity data: the accuracy is low, the amount of data is large, and it needs to be screened and used, but the longitudinal distribution of pressure can be described. The screening method is to select the points with relative error within 10% of the DST data.

Logging data: An indirect means of extracting useful data points. The extraction standard is: the thickness of mudstone is more than 20m, and the content of mud is more than 75%. There is no obvious expansion and shrinkage phenomenon.

5）A clear summary of model strengths, assumptions and limits to applicability needs to be provided near the conclusion. 

The fracture transfer overpressure model is compared with the existing model:

The original fracture transfer overpressure model was exponential, and it was found that it could not fully fit the acoustic velocity effective stress template in the deep foreland basin during fitting. Therefore, if the previous method was used for calculation, the error would be large.The new model is logarithmic and has a good fit with the acoustic velocity and effective stress in the deep background of foreland basin. Higher calculation accuracy.

Limitations: This model is only suitable for deep foreland basins

 

 

 

Fig13.Sonic-velocity effective-stress(SV-ES)schematic obtained by calculation in the well KS201,fitting the original and newly established loading curves.The original loading curve is in the form of quasi-exponential,it cannot be fitted to the actual situation of well KS201.The.newly established loading curves is log-like morphology,it is more in line with the actual situation of well KS201.

 

Comparison between the structural extrusion overpressure model and the existing model:

A lot of work has been done on the relationship between rock structural stress and pore abnormal fluid pressure, and the corresponding quantitative evaluation model of tectonic compression and pressurization has been proposed.It includes: quantitative evaluation of the upper limit of the contribution of structural extrusion to overpressure based on plane stress field, quantitative evaluation of the contribution of structural extrusion based on plane stress field to overpressure in semi-closed system, quantitative evaluation of the contribution of numerical simulation based on three-dimensional stress state to overpressure, etc.However, these models have many solving parameters, are easily affected by human factors, or lack consideration of rock deformation process, deformation mechanism and pressure evolution, which limits the applicability and operability of the models to a certain extent.

Limitations: This model is only suitable for deep foreland basins.

 

 

6）The formal and technical language are hindering accessibility for a broader audience. Simplifying sentences and reducing jargon would improve readability. Or give a table (serving as dictionary) at the beginning which introduces the more esoteric terms used in the manuscript. 

Mudstone disequilibrium compaction overpressure

Disequilibrium compaction is essentially due to the imbalance between compaction and drainage.Previous studies have shown that the main factors affecting the disequilibrium compaction compaction are deposition rate and mud content. The greater the deposition rate, the less favorable the directional arrangement of mudstone particles, and the more likely it is to lead to the imbalance between compaction and drainage, resulting in disequilibrium overpressure.In the sand-mudstone interlayer, the high sandstone content makes the overpressure in mudstone easy to transfer upward and downward, and the drainage is smooth, which is not conducive to the formation of unbalanced compaction type overpressure. However, in principle, as long as the factors that can cause the imbalance between compaction and drainage can produce disequilibrium compaction type overpressure.

Transfer overpressure

When two pressure systems are connected by an open fault, the fluid pressure quickly adjusts to reach hydrostatic equilibrium, and a new pressure system is formed, which is caused by the spatial realignment of the fault into a fault-transmitted overpressure.

Tectonic compression overpressure

Tectonic extrusion type overpressure is lateral compaction caused by tectonic extrusion.

Multi-genetic overpressure

Multi-cause pressure means that the cause of pressure is not a single, but in the process of geological evolution has appeared different causes of pressure, or at the same time there are two kinds of pressure simultaneously.

Pressure evolution

It refers to the change of pressure over time in geological history.

7) Including comparisons with similar studies from regions outside China would better contextualize findings and assess their general applicability.

Similar studies at home and abroad have been described in a new and improved introduction. For the overpressure caused by unbalanced compaction, the equivalent depth method is a general and universal technique in the quantitative evaluation of fracture transfer overpressure. Fan,2016 adopted the quantitative calculation of Bowers curve, which is also one of the most widely used methods at present. However, this method has some problems in the process of application in the deep foreland basin, so this paper has improved it. The improved technology has a certain range of application and is only applicable to the deep foreland basin. At present, there are many quantitative evaluation models of tectonic extrusion type overpressure, including quantitative evaluation of the upper limit of contribution of tectonic extrusion to overpressure based on plane stress field, quantitative evaluation of contribution of tectonic extrusion to overpressure in semi-closed system based on plane stress field, quantitative evaluation of contribution of numerical simulation to overpressure based on three-dimensional stress state, etc. The quantitative evaluation model in this paper mainly considers the characteristics of tectonic compression and brittle plasticity in deep layers, so it has a certain range of application, but is not universal.

For the study of overpressure evolution, PM software has always been widely used, but the current software research is usually related to the study of pressure with a single cause, and the coupling study of multi-cause pressure in deep foreland basin is rarely involved. In this paper, the coupling study of multi-cause overpressure is carried out, so this method also has a range of application and is only suitable for the specific geological background of foreland basin. It's not universal.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript presents an in-depth study on the evolution of overpressure mechanisms in the Kuqa Depression, focusing on disequilibrium compaction, tectonic compression, and fracture transfer in the Bashijiqike Formation. While the research is comprehensive and makes use of multiple data sources, several critical areas need improvement. Below are a few comments:

The novelty of the study needs to be further articulated. Although the research addresses multiple overpressure mechanisms, a clearer distinction from previous studies is essential to emphasize the novel contributions and theoretical advancements.

The methodology section lacks adequate detail on data preprocessing steps. For example, there is minimal discussion of how erroneous data points were filtered and how these choices may impact the results.

The study integrates mud weight data to complement drill stem test (DST) measurements, but the paper does not discuss the possible biases or limitations of relying on mud weight as a proxy for pressure data.

There is a need for further validation of the simulation models. Specifically, the methodology should describe whether and how the results were benchmarked against field data or other established modeling frameworks.

The coupling of different overpressure mechanisms is a central component of the study, yet the assumptions underlying this coupling are not sufficiently explained. A sensitivity analysis exploring the interplay between different overpressure sources would strengthen the study’s findings.

The study mentions Rhino and Ansys Workbench software for stress field simulation but does not provide enough technical detail about model construction, mesh generation, or boundary conditions, which are crucial for reproducibility.

While the acoustic log data is used to derive the compaction curve, additional information on the quality control of these logs would be helpful. Were any log calibration or correction methods employed?

The fracture transfer overpressure model is an important aspect of the paper. However, the assumptions regarding fracture permeability and connectivity should be elaborated upon, especially since these parameters can significantly influence the results.

The Earth stress field simulation methodology could be improved by including a more thorough description of the assumptions regarding stress anisotropy and their implications for the results.

The discussion section does not critically assess potential discrepancies between modeled and observed pressure values. A more detailed evaluation of the limitations of the modeling approach would improve the paper.

The figures depicting stress distribution and overpressure evolution are useful but could benefit from additional annotations. Clearer labeling of key trends and data points would aid readers in interpreting the results.

The manuscript could enhance its clarity by defining technical terms more precisely. For instance, the distinction between brittle and plastic deformation processes could be more explicit.

While the study focuses on the Kuqa Depression, a discussion on the broader applicability of the findings to other basins would increase the impact of the research.

The mathematical equations used for overpressure calculation are provided, but their derivation and underlying assumptions are not fully explained. This limits the accessibility of the methodology for readers unfamiliar with these models.

The paper’s language is generally clear but could benefit from minor revisions to improve consistency and technical precision. Some terms are used interchangeably, which could confuse readers.

The references section is comprehensive, but the manuscript should ensure all citations are correctly matched to their corresponding text mentions. Cross-checking the references for accuracy is recommended.

While the manuscript addresses a relevant topic and presents valuable findings, there are several critical areas requiring further clarification, expansion, and validation. The issues with methodological detail, the need for clearer articulation of novelty, and incomplete discussions on limitations and assumptions necessitate a major revision. Addressing these points will enhance the rigor and impact of the study, bringing it closer to publication.

Comments on the Quality of English Language

The quality of the English language is generally adequate, but there are some areas where clarity could be improved. A few sentences are awkwardly phrased, and some technical terms are used inconsistently throughout the manuscript. A careful review for grammatical correctness, sentence structure, and word choice would enhance readability and precision. 

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Round 3

Reviewer 1 Report

Comments and Suggestions for Authors

The revised manuscript shows a clear effort to address the comments from the previous round of review, and the improvements made have significantly enhanced the quality of the work. The authors have taken meaningful steps to clarify the methodology, add more details to the experimental setup, and provide better contextual explanations of their approach. The response to previous comments is commendable, but there are still a few areas that need further attention to reach full clarity and robustness. Below are a few additional suggestions.

• The calibration results from the Keshen area are well-detailed, but reliance on data from a single region may limit generalizability. Adding justification for how findings in this specific region can be applied more broadly would help address this limitation.
• The assumptions regarding isotropic stress conditions in the Keshen area are mentioned but require further empirical support. Adding direct data or references to back up the claim that "no obvious anisotropy" is present would lend more credibility to this assertion.
• While the limitations of the study are acknowledged, a more thorough discussion on the potential impacts of these limitations on broader applications could provide a more critical evaluation, enhancing the discussion section.
• The revised section on the relationships between acoustic velocity and effective stress is clearer and easier to follow. Adding a practical example to illustrate the application of this model could make it more accessible for readers less familiar with the topic.

 

The revised manuscript shows considerable improvement in terms of clarity, methodological transparency, and addressing previous comments. However, there are still areas that need additional enhancement, particularly with regard to empirical validation and broader applicability of findings. I recommend a minor revision to further improve these aspects and ensure that the manuscript meets a high standard of rigor and generalizability.

Comments on the Quality of English Language

Minor editing of English language required.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf