Numerical Simulation of the Effect of Injected CO₂ Temperature and Pressure on CO₂-Enhanced Coalbed Methane

Round 1

Reviewer 1 Report

Author replied with all recommended changes.

Reviewer 2 Report

The comments are well covered with the revised manuscript.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

The research paper represents the modeling of replacing CH4 using CO2 in coal.

The manuscript needs to answers following questions.

Author needs to put all the abbreviation in the beginning such as what is difference between K and k in equation 2 and 10

Reviewer 2 Report

The authors conducted a numerical study on the productivity of coalbed methane when CO2 is injected. The focus is on the impact of CO2 pressure and temperature on the processes in the reservoir.

Minor comments read:

 

1. The last paragraph in the introduction should give the contents, meaning it should be mentioned what is presented in the following sections. Currently it describes a methodology such that it reads as an abstract.

 

2. The heading of section 3. is weird. The section does not describe a numerical model, but a setup.

 

3. The setup in Fig.2 needs justification. It seems to be a section of a multi-well system, in fact infinite wells, because of symmetry.

 

4. The section 5. “conclusions” gives only rough information on the results. Specific numbers should be given. Also implications should be elaborated.

Reviewer 3 Report

There are many articles related to ECBM by CO2 injection. Some of them are pure modeling and others experimental. Anyway, the assumptions for the proposed model are not sound and are proved only by software modeling. The following assumptions are wrong:

CO2 will definetely have a rock mass temperature and changes in the CO2 injection temperature will not last for 30 years as in the proposed model. The CO2 will equilibrate with the coal seam temperature and any assumption that the effect of CO2 injection temperature will have a long lasting effect is wrong. How can you assume ideal gas law for CO2 in pressure regimes existing in coal seams? This will lead to enormous errors.

This study is just a modeling study with no prove in experimental research and therefore cannot be published in Applied Sciences.