Modelling Methane Adsorption Isotherms on Shale at Different Temperatures
Round 1
Reviewer 1 Report
The present work tries to use the classical adsorption theories to describe the behavior of methane adsorption under high temperature conditions from classical models in shales. It is important to specify that the theories of Polanyi, Langmuir and in a complementary way the Clausius-Clapeyron equation of capillary systems have been used in a complementary way rather than as different methodologies as the author comments.
I consider that the article can be considered for publication but with major corrections, for example:
1. Reorder the ideas in the introduction, for example, it is mentioned that: “the prediction of the adsorption curve under different temperature conditions can be divided into two ways: Polanyi and Clausiuis-Clapeyron” and at the end of the nothing comes out that Lagmuir's theory will be used, perhaps it would be convenient to add a paragraph also on the special conditions of this theory, in the introduction section one.
2. Correct grammatically mistakes, for example in line 22 change adoption for adsorption, in line 71-72 change gravitational field for potential adsorption, be carefully with the number of the equations. In line 232 change the word absorption for adsorption. Line 261 change the word "isometric heat of adsorption for Isosteric heat of adsorption.
3. In line 15 use the word: Isosteric heat of adsorption instead adsorption heat, I recommend the IUPAC technical report, Pure Apple. Chem. 2015.
4. In line 16 use the word Clausius-Clapeyron equation of capillary systems instead, only Clausius-Clapeyron, it has different meaning.
5. The determination of k-value in the specific case of shale it will be valid for other kind of shales? it will be convenient to express the value with its respective uncertainty.
6.
Author Response
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Reviewer 2 Report
In this manuscript the author introduces a new methane adsorption isotherm prediction method on shales by combining Polanyi’s adsorption potential theory with Langmuir adsorption theory. Polanyi’s theory is applicable for condensable gases below their critical point, while actual shale reservoir temperature is usually much higher than the critical temperature of methane. The author cleverly introduces a virtual vapour pressure calculated based on a referenced work and continues to develop the new isotherm. The advantage of the author’s method is that it can predict adsorption isotherms at geologic relevant high temperatures by using only one isotherm at at low-temperature. The author validated his approach with existing published adsorption experimental measurements.
The manuscript is well written, albeit in need of some English editing, and presents a newly developed adsorption prediction methodology for methane in shale and as such is worth publishing.
Author Response
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Reviewer 3 Report
In this submission to Atmosphere, the authors present a method to predict adsorption isotherms at different temperatures. In this method, the authors quantify the relationship between Langmuir pressure and temperature. Using this method, the authors predict adsorption isotherms of Long-maxi shale from 45℃ to 120℃. The authors also predicted the adsorption capacity of Long-maxi shale at geologic depths. The authors conclude that their study provides theoretical foundations for the efficient evaluation of adsorbed gas content in shale gas reservoirs under geologic conditions
I consider this manuscript to be of interest to researchers on methane adsorption as well as readers of this journal. As such, I am somewhat in favor of publication with a few minor comments that should be incorporated into the manuscript before acceptance. While the authors use a very coarse-grained Clausius-Clapeyron approach for methane adsorption, there has been much prior work using classical DFT calculations for methane adsorption and surfaces, which should be noted as related work:
AIChE J. 2015, 61, 3012-3021
J. Chem. Theory Comput. 2012, 8, 2012–2022
In particular, these prior works showed that classical DFT calculations give deeper insight into methane adsorption to give more accurate predictions of these processes. Of course, I am not necessarily asking the authors to carry out classical DFT calculations of their system, but the authors should note these related computational investigations in this area. With this minor modification, I would be willing to re-review this manuscript for Atmosphere.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
After reviewing the latest version of the manuscript, I would like to express my approval towards it's the publication.
