Well Testing of Fracture Corridors in Naturally Fractured Reservoirs for an Improved Recovery Strategy^†

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This work presents a well testing technique to detect and identify fracture corridors based on a simplfied continuous-media model. the authors also present diagnosis plots and equations to invert the reservoir and corridors parameters. I have the following technique comments for the authors' reference.

1. The model establishment is missing. Please add the corresponding content.
2. Please detail clarify how to get Fig. 4 and Fig. 5. why it's not smooth.
3. Diagnosis plot is not usually used now because complete flow regimes cannot be tested in field cases. the practicability of pressented method should be considered.
4. Why the authors not consider the non-linear fitting.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

1. The abstract of the manuscript should include the purpose and background of the research, the content and methods of the research, the main results of the research, and the discussion. However, although the abstract of this study provides a very detailed explanation of the research content and background, the discussion of the main research results is clearly insufficient. The author needs to improve the abstract to attract readers' interest and ensure the standardization of the research paper.
2. Table 1 shows the impact of well placement on the recovery rate of corridor type oil-free bottom water reservoirs, although this is the result of other studies. However, it is not appropriate for the author to display only such a table here, as the impact of well layout also depends on factors such as the model. It is recommended that the author also provide the reservoir model on which Table 1 is based, in order to be targeted.
3. Appropriate assumptions are necessary for building models and conducting numerical simulations of oil reservoirs. Moreover, the implementation of model solving and simulation requires appropriate simplification. For this reason, “2.2. Simplified Well-testing Model for Corridor-Type Naturally Fractured Reservoirs” What are the partial premises and assumptions? Furthermore, how can the accuracy of the simplified model proposed in this section of the manuscript be guaranteed? 
4. Oil and gas from unconventional reservoirs (such as shale gas, fractured reservoirs and hydrate layers) are bound to be the future source of oil and gas. Therefore, the first sentence of the introduction section of the manuscript needs to be supported by the following papers: Settling behavior and mechanism analysis of kaolinite as a fracture proppant of hydrocarbon reservoirs in CO2 fracturing fluid; Sediment Instability Caused by Gas Production from Hydrate-Bearing Sediment in Northern South China Sea by Horizontal Wellbore: Sensitivity Analysis.
5. The characteristic parameters that affect reservoir permeability (mainly permeability and porosity) have significant stress sensitivity. This characteristic was not taken into account in this study. What impact will ignoring this factor have on the well test results?
6. The characteristic parameters that affect reservoir permeability (mainly permeability and porosity) have significant stress sensitivity. This characteristic was not taken into account in this study. What impact will ignoring this factor have on the well test results? In addition, the author's description of the model in Figure 2 is not clear and detailed enough. Additionally, what are the boundary and initial conditions of the research model? It is important for simulation.
7. Figure 14 shows the diagnostic diagram of bilinear flow. The author presented the data to you as a linear curve. However, when t is greater than 9, it is obvious that it has deviated from the fitted line. And afterwards, the data will continue to deviate further from the straight line. Is it appropriate for the author to fit as a straight line?
8. In the manuscript, many simulation results are not mentioned, such as Figure 13 and Figure 14, which are common and confusing for readers and reviewers.
9. The title of the fourth part is inappropriate, the summary and conclusion should be similar.
10. It is recommended to use International Units (SI units) for all parameters in the manuscript.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Manuscript ID energies-3701312

Brief summary:

The manuscript provides a comprehensive investigation into well testing as a diagnostic and predictive tool for identifying fracture corridors in corridor-type naturally fractured reservoirs (NFRs). The topic is highly relevant given the complexity of flow behaviors in NFRs and the significant share of global hydrocarbon reserves they represent. The authors have made a valuable contribution by presenting a simplified, yet effective, modeling approach that balances analytical clarity and computational practicality.

Comments on the article:

• The manuscript is generally clear, detailed, and well-organized.
• Most of the Figures and tables are clear and support the discussion effectively.
• The study clearly outlines its objective to develop and validate a simplified model for well testing in corridor-type NFRs. It highlights a practical method to distinguish between fracture and matrix wells and to optimize well placement accordingly.
• The simplification of the flow model by integrating local heterogeneities and treating distant fracture corridors as part of the matrix is novel and well-justified.
• The manuscript outlines explicit formulas for permeability, radius of investigation, conductivity, and corridor length enhancing reproducibility.
• The plots in Figures 4 to 12 are effectively used to distinguish between flow regimes in matrix and fracture wells.
• The cumulative logit model adds a robust statistical dimension to estimate the probability of corridor detection errors under varying conditions.
• The manuscript requires professional English editing. There are several grammatical errors, and unclear statements throughout.
• The references are relevant and recent and include a good mix of peer-reviewed papers, conference proceedings, and technical reports.
• DOIs are provided, which is excellent, but they must follow the same format.

Final recommendation: Accept after minor revisions.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

The authors presented and discussed two examples of using pattern recognition to analyze diagnostic plots of the fracture and matrix wells in a simulated corridor-type NFR. Also, they estimated the accuracy of finding the well’s location from the test. The study showed that well testing and good reservoir description were critical for better oil recovery in corridor-type NFRs. I have some comments about the proposed work:
1. Effective well installation requires understanding fracture corridor shape and spatial distribution, according to the study. These traits are difficult to characterize, especially in complex geological environments. If fracture pathways are misidentified, the offered techniques may not promote recovery.
2. The methods and findings may not apply to all NFRs. Future research should validate the proposed methodologies using field data from diverse reservoir types and geological contexts, suggesting that the current findings may be limited to specific situations.
3. If fracture spacing or matrix permeability are too high or low, sweep efficiency may decrease, the report finds. These factors may affect the effectiveness of the offered techniques, which the study may not examine.
4. How fluids interact with fracture corridors determines the success of enhanced oil recovery (EOR) technologies like waterflooding or gas injection. The paper acknowledges this complexity but does not go into detail about fluid dynamics, which may restrict its practical applicability.
5. The paper promotes a shift toward integrated, multidisciplinary methodologies that include geological, geophysical, and engineering data. Implementing such extensive methods might be resource-intensive and not necessarily practical.
6. The paper recommends extending statistical models to include uncertainties in seismic interpretation and other measures, but it does not outline how to do so. This may limit the application of the offered methods in actual life.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

I have check the reply made by the authors, and they have been carefully replied. Therefore, I think this paper can be accepted for publication now.