Geological Formation Mechanism and Thermal Resources Assessment of Geothermal Spring in Lushan County, China

Round 1

Reviewer 1 Report

The paper under review concerns an interesting subject – the geological mechanisms underlying geothermal resources and their evaluation. The research is based on a large volume of diversified information, ranging from remote sensing and hydrochemistry to geophysical methods and geological mapping and interpretation.

The paper needs a major revision before being considered for publication. There has clearly not been a careful revision of this paper, both in what concerns form (text, figures, tables, English, style) and content. The paper is now a little more than a catalogue of the methods used in geothermal exploration in the area in question. A clear conceptual geologic global model of the geothermal field is needed (water sources, water circulation, energy sources, flows). A more detailed assessment is needed – was an internationally recognized standard used? – e.g.  the “Specifications for the application of the United Nations Framework Classification for Fossil Energy and Mineral Reserves and Resources 2009 (UNFC-2009) to Geothermal Energy Resources” or “The Australian Code for Reporting of Exploration Results, Geothermal Resources and Geothermal Reserves”.

I have the following comments, just some examples of the extensive deep revision needed:

Geothermal resources are an important energy source. The knowledge and use of naturally occurring hot water (or hot rock formations) are not new, as the paper claims in its first sentence (abstract). The importance of geothermal energy (and the interest of this paper’s subject) need not be overemphasized. Please review the text removing exaggerated claims. Line 86 -87: “The stratigraphic division of the research area belongs to Mianchi-Queshan district and Xiongershan district in the west of Henan Province”. What does this mean? Figures 1 and 2 should have same scale, orientation and area. Figure 3: Layout of geological technical means and working methods in the geothermal. fields of (a) Shangtang; (b) Zhongtang & Wentang; (c) Xiatang; (d) Jianchang: What geological technical means? Use the same font in the legend. Table 1: the river water has a mineralization of 173 g/l (Shangtang river) and 225 g/l (Xiatng river; shouldn’t it be Xiatang, by the way). These are errors, for sure. Format error in the last line. What is “watery type”? Line 280: Table 3. Does this table refers to a single borehole? Line 288: Table 4: What is “Observation interval (Days)”: is it the moment (day) at which the reading was done? If so, it is an interval… . I would also question the usefulness ofa table with immutable  measures along the year. Extensive editing of English language and style is required The text frequently includes subjective, unsubstantiated affirmations such as: Lines 41b- 43: “And compared with solar energy, wind energy, water energy and other renewable energy, geothermal energy has the advantages of stability, high utilization rate, safety, low operation cost, comprehensive utilization and so on”. In addition to the highlighted expression, hard data should support this affirmation. The authors needlessly repeat the same idea in consecutive sentences: Lines 54 – 63. Line 66: “50 km” instead of “half hundred kilometres”. Simple is always better than needlessly complicated. Lines 89-90: “The fold structure was not very developed, the fault structure was very developed, the deformation was strong, and the main structural line direction is north-west-west near east-west.” What does this mean? What do the next sentences mean? Please restructure and rewrite all this section – lines 86-97. Line 133: “An exploration holes were completed in Shentang geothermal field.” Concordance error – how many exploration holes were drilled? Where? What were the results? Line 137: Pumping tests to measure air temperature? Line 139: Long-term observation: for only one year? Line 254: Figure and its caption in separated pages. Line 288: Table separated in two pages. Line 320: Figure 6 – the legend lacks colour. Line 378: Figure 9: photos lack legend. Line 411: Figure 11: Lacks scale and orientation. The same applies to Figure 12, Figure 17 (which is also lacking units). Line 494: Figure 18: lacks scale and legend: what are (a) , (b) and (c)?

Comments for author File: Comments.pdf

Author Response

Response to Reviewer 1

Reviewer 1: The paper under review concerns an interesting subject – the geological mechanisms underlying geothermal resources and their evaluation. The research is based on a large volume of diversified information, ranging from remote sensing and hydrochemistry to geophysical methods and geological mapping and interpretation.

The paper needs a major revision before being considered for publication. There has clearly not been a careful revision of this paper, both in what concerns form (text, figures, tables, English, style) and content. The paper is now a little more than a catalogue of the methods used in geothermal exploration in the area in question. A clear conceptual geologic global model of the geothermal field is needed (water sources, water circulation, energy sources, flows). A more detailed assessment is needed – was an internationally recognized standard used? – e.g. the “Specifications for the application of the United Nations Framework Classification for Fossil Energy and Mineral Reserves and Resources 2009 (UNFC-2009) to Geothermal Energy Resources” or “The Australian Code for Reporting of Exploration Results, Geothermal Resources and Geothermal Reserves”.

 

Reply: Thank you very much for your suggestion and for giving us the opportunity to revise the article. I will then revise the paper thoroughly, including form (text, figures, tables, English, style) and content.

The research program was financial supported by the Geological Exploration Fund of Henan Province in China, so the analysis process and assessment work implemented China's domestic standards and the main factors of geothermal field (water sources, water circulation, energy sources, flows) were all described in Section 4.1 of the article.

 

I have the following comments, just some examples of the extensive deep revision needed:

Geothermal resources are an important energy source. The knowledge and use of naturally occurring hot water (or hot rock formations) are not new, as the paper claims in its first sentence (abstract). The importance of geothermal energy (and the interest of this paper’s subject) need not be overemphasized.

Please review the text removing exaggerated claims.

 

Reply: Thanks for your good suggestion. This paper was submitted for the Special Issue "Techniques for Sustainable Processing of Natural Resources" of Applied Sciences, so in response to the theme of the Special Issue, I wrote those sentences “… and promote the development of techniques for sustainable processing of natural resources” which has now been deleted. (see L19-23).

 

Line 86 -87: “The stratigraphic division of the research area belongs to Mianchi-Queshan district and Xiongershan district in the west of Henan Province”. What does this mean?

 

Reply: Thank you for reminding us. This passage is really ambiguous and We’ve rewritten it. See L 77-81 and L94-107.

 

Figures 1 and 2 should have same scale, orientation and area.

 

Reply: Thank you for your suggestion. Figures 1 has been revised and now it has same scale, orientation and area with Figure 2 (see L108).

 

Figure 3: Layout of geological technical means and working methods in the geothermal fields of (a) Shangtang; (b) Zhongtang & Wentang; (c) Xiatang; (d) Jianchang: a. What geological technical means? b. Use the same font in the legend.

 

Reply: Geological technical means and working methods include drilling, geophysical exploration, in-situ test, in-situ dynamic observation, water quality sampling and analysis. They’ve been marked in Figure 3 and the fonts in the legend have been adjusted (see L136).

 

Table 1: the river water has a mineralization of 173 g/l (Shangtang river) and 225 g/l (Xiatng river; shouldn’t it be Xiatang, by the way). These are errors, for sure. Format error in the last line. What is “watery type”?

 

Reply: Thank you for your careful reminder.

a: It’s our mistake. The units used for different batches of test results were different, and we did not convert the units when we inputted them. Xiatng is a spelling mistake and the correct name is indeed Xiatang. The errors have been revised.

b: In this research, the water hydrochemical types were classified by Shoka Lev (CAЩукалев) classification Method .

c: “watery type” is a spelling mistake of “water type” and the correct one should be “Hydrochemical Type”. The error has been revised.

Please see Table 1 (L192-193).

 

Line 280: Table 3. Does this table refers to a single borehole?

 

Reply: Yes, the data in Table 3 were came from a single borehole which was drilled in Shangtang geothermal field during previous exploration and our study referenced to previous research data (see L277).

 

Line 288: Table 4: What is “Observation interval (Days)”: is it the moment (day) at which the reading was done? If so, it is an interval… . I would also question the usefulness of a table with immutable measures along the year.

 

Reply: Thank you for your reminder. We made a wrong description. It should be not "Observation interval (Days)" but "Days from the first measurement".

After consideration, We also feel that the table is really useless, so we deleted it and changed it to text description (see L300-309).

 

Extensive editing of English language and style is required

 

Reply: Thanks a lot! According to the requirements of you and other reviewers, we’ve polished the whole article.

 

The text frequently includes subjective, unsubstantiated affirmations such as: Lines 41b- 43: “And compared with solar energy, wind energy, water energy and other renewable energy, geothermal energy has the advantages of stability, high utilization rate, safety, low operation cost, comprehensive utilization and so on”. In addition to the highlighted expression, hard data should support this affirmation.

 

Reply: Some data have been supplemented into the article, which shows many advantages of geothermal energy. See L42-51.

 

The authors needlessly repeat the same idea in consecutive sentences: a. Lines 54 – 63.

 

Reply: It was really a lengthy and wordy passage, and we've simplified and rewritten it. See L60-65.

 

Line 66: “50 km” instead of “half hundred kilometres”. Simple is always better than needlessly complicated.

 

Reply: Thank you for your suggestion. “half hundred kilometres” is a common usage in Chinese and here it looks like Chinglish. It has been revised. See L68-69.

 

Lines 89-90: “The fold structure was not very developed, the fault structure was very developed, the deformation was strong, and the main structural line direction is north-west-west near east-west.” What does this mean? What do the next sentences mean? Please restructure and rewrite all this section – lines 86-97.

 

Reply: This section has been reorganized and rewritten. See L95-107.

 

Line 133: “An exploration holes were completed in Shentang geothermal field.” Concordance error – how many exploration holes were drilled? Where? What were the results?

 

Reply: Two exploration holes were actually completed: one in Shentang geothermal field (results see section 3.2.4 d) and the other in geothermal prospect investigation area Matang geothermal field (Matang geothermal field was mentioned in L91-92). Because Matang geothermal field belongs to the prospective area and is not the main research content of this study, the borehole in Matang was not mentioned.

As for the borehole data of Shangtang geothermal field mentioned in Table 3 of this article (L277), in fact it was drilled in previous exploration research of Shangtang geothermal field and this study referenced to previous research data.

 

Line 137: Pumping tests to measure air temperature?

 

Reply: Thank you for your careful reminder. This is our mistake. The purpose of pumping test was to observe the water level, water volume and water temperature. The temperature measurement was done separately. This section has been revised. See L142-144.

 

Line 139: Long-term observation: for only one year?

 

Reply: Yes, the observation period is one year. The main purpose of Long-term observation is to observe the changes of water level, water volume and water temperature of hot springs within one year. In fact, these items change within one year, but there is little change between different years. In addition, the research was financial supported by the Annual Geological Exploration Fund of Henan Province in China, so all the field work must be completed in one year.

 

Line 254: Figure and its caption in separated pages.

 

Reply: My original submission was properly edited and typeset; as the editorial office made formatting changes to it, Figure and its caption appear in separated pages. Before official publication, the editorial office will typeset it again to correct version.

 

Line 288: Table separated in two pages.

 

Reply: The same reason like above one. My original submission was properly edited and typeset; as the editorial office made formatting changes to it, Table was separated in two pages. Before official publication, the editorial office will typeset it again to correct version.

 

Line 320: Figure 6 – the legend lacks colour.

 

Reply: Thank you for your suggestion. Color has been supplemented in the legend. See Figure 6 (L327).

 

Line 378: Figure 9: photos lack legend.

 

Reply: Figure 9 has been revised. See Figure9 (L384-389).

 

Line 411: Figure 11: Lacks scale and orientation. The same applies to Figure 12, Figure 17 (which is also lacking units).

 

Reply: Figures 7, 11, 12 and 17 have been revised. See L342, L418, L440 and L489 .

 

Line 494: Figure 18: lacks scale and legend: what are (a) , (b) and (c)?

 

Reply: Figure 18 has been revised. See L507-509.

Reviewer 2 Report

The manuscript requires major restructuring to ensure that its study objective, methods, result and conclusion are presented coherently.

The methods need to be discussed to allow for clear independent evaluation of their soundness and also allow for repeatability. E.g. the geophysics session did not present how the geophysical data were acquired. What electrode configurations were used? Also, the pumping test does not present any information on pumping test which leave one in doubt if pumping test were done.

Avoid discussing details already presented in tables.

I will recommend merging the results of all the hot spring highlighting what is different and how they are related instead of discussing them separately.

There is also need for improving on the use of English.

Comments are also made in the body of the manuscript - see attached - which could help in improving the manuscript.

 

Comments for author File: Comments.pdf

Author Response

All the comments have been replied in the PDF document.

Author Response File: Author Response.pdf

Reviewer 3 Report

In this manuscript, the author presented a case-study on the geological formation mechanism of geothermal spring in Lushan. The work analysis is supported with ample data and and the interpretation is convincing. Overall the paper is written in an orderly manner and will be interested to the audience in the geothermal community. The reviewer has several comments that need to be addressed before the manuscript can be published.

1) Geochemical analysis is relatively weak in this work. It is clear to the reviewer that there is an extensive mixing of deep geothermal fluid and shallow groundwater in the studied area. The question is, how much percentage of mixing is it? Is the isotope method available to the author? The author mentioned in line 194 that some H/O isotope info is available. If that is the case, it should be possible to get an H/O isotope ratio curve for the local precipitation water. When combined with the isotope fractionation in the geothermal fluid, it should be possible to estimate an quantitative mixing ratio. This estimation should then be compared with the K-N geothermometry estimation, which will lead to more affirmative conclusion on the temperature of deep geothermal resources.

2) Line 233-234. Here the units are clearly wrong. The permeability has a unit of length squared，while the hydraulic conductivity should have a unit of length over time.

3) Line 269-273. Instead of introducing the layering info in the text, a more commonly approach is to present a well logging result including casing, screening information, lithology interpretation of stratification, as well as any pressure-temperature-spin (PTS) logging result. It seems like the author has not conducted any PTS logging in both static (shut-in) or dynamic (producing) conditions. If that's true, it's recommended to do that. PTS is standard for geothermal wells.

4) Line 338, Figure 7. The 2D resistivity profile is helpful only in a limited way. The general purpose of a geothermal survey is to target deep, high-enthalpy geothermal fluid (for production), as well as high-permeability conduits (for injection). The standard procedure is to employ very high density meganetic-telluric (for > 1km depth) or CSAMT survey (< 1 km), and also using the data to perform 3D inversion on apparent resistivity. In many geothermal reservoirs, this has been proved to be very effective in identify the location of geothermal reservoir and the pathway for fluids. From this work, the reviewer feels that it has not been widely applied yet in China. Just a recommendation for the future work.

5) Section 4.2.3. The reviewer recommend to re-write this section completely. To be honest, such kind of quantification of exploitable geothermal resources has little practical value. First, please make clear what is the utilization approach? Is it for electricity production or is it for heating? For the temperature presented so far electricity production will not be likely. Then it is better to calculated, how many sqm of heating space can be supported by the geothermal resources.

Author Response

Response to Reviewer 3

Reviewer 3: In this manuscript, the author presented a case-study on the geological formation mechanism of geothermal spring in Lushan. The work analysis is supported with ample data and and the interpretation is convincing. Overall the paper is written in an orderly manner and will be interested to the audience in the geothermal community. The reviewer has several comments that need to be addressed before the manuscript can be published.

 

1) Geochemical analysis is relatively weak in this work. It is clear to the reviewer that there is an extensive mixing of deep geothermal fluid and shallow groundwater in the studied area. The question is, how much percentage of mixing is it? Is the isotope method available to the author? The author mentioned in line 194 that some H/O isotope info is available. If that is the case, it should be possible to get an H/O isotope ratio curve for the local precipitation water. When combined with the isotope fractionation in the geothermal fluid, it should be possible to estimate an quantitative mixing ratio. This estimation should then be compared with the K-N geothermometry estimation, which will lead to more affirmative conclusion on the temperature of deep geothermal resources.

 

Reply: Thank you very much for your suggestion. Geochemical analysis is indeed weak in this study. Due to the limited funds support, only water quality analysis has been done in this study. The H / O isotopic information mentioned in this article was from the collected the research data in the 1950s, while the K-Na geothermometer data came from 1997 in the last century. The Geological Exploration Fund of Henan Province in China focuses on engineering application rather than scientific research, so there is no detailed study on the mixing percentage of geothermal fluid and shallow groundwater.

 

2) Line 233-234. Here the units are clearly wrong. The permeability has a unit of length squared，while the hydraulic conductivity should have a unit of length over time.

 

Reply: Thank you for your reminding. It should be our wrong description. Here “permeability coefficient” should be “hydraulic conductivity”, and “water conductivity coefficient” should be “coefficient of transmissivity”. See L240-241.

 

3) Line 269-273. Instead of introducing the layering info in the text, a more commonly approach is to present a well logging result including casing, screening information, lithology interpretation of stratification, as well as any pressure-temperature-spin (PTS) logging result. It seems like the author has not conducted any PTS logging in both static (shut-in) or dynamic (producing) conditions. If that's true, it's recommended to do that. PTS is standard for geothermal wells.

 

Reply: Thank you for your advice. The well logging method PTS you recommended is what we need. In future research, we will try to use the technology.

 

4) Line 338, Figure 7. The 2D resistivity profile is helpful only in a limited way. The general purpose of a geothermal survey is to target deep, high-enthalpy geothermal fluid (for production), as well as high-permeability conduits (for injection). The standard procedure is to employ very high density meganetic-telluric (for > 1km depth) or CSAMT survey (< 1 km), and also using the data to perform 3D inversion on apparent resistivity. In many geothermal reservoirs, this has been proved to be very effective in identify the location of geothermal reservoir and the pathway for fluids. From this work, the reviewer feels that it has not been widely applied yet in China. Just a recommendation for the future work.

 

Reply: Thank you very much for your guidance and suggestions. Before this geophysical exploration and research, the depth and location of geothermal occurrence could not be determined accurately, so conventional methods were used for research. It turns out that 2D resistivity profile have indeed limited effect and we are interest in the method you proposed. In the further study of the geothermal group, it may be used and we hope it can play a role.

 

5) Section 4.2.3. The reviewer recommend to re-write this section completely. To be honest, such kind of quantification of exploitable geothermal resources has little practical value. First, please make clear what is the utilization approach? Is it for electricity production or is it for heating? For the temperature presented so far electricity production will not be likely. Then it is better to calculated, how many sqm of heating space can be supported by the geothermal resources.

 

Reply: Thank you for your reminder. Obviously, the temperature of these hot springs can not be used for power generation. At present, they can only be used for heating, bathing, breeding, etc. The area available for heating has been estimated (see L656-659).

Round 2

Reviewer 1 Report

Dear authors,

I acknowledge the additional effort put into this paper; it has now improved the initial version. I still feel the English language and style can be improved; perhaps the journal editors may help in this regard.

Notwithstanding the improvements needed, these are now mostly of style and language (and having a sound English is a barrier we all have to overcome in time).

In conclusion, the paper may accepted after an additional thorough format and language review).

Congrats on the work done so far.

Reviewer 3 Report

none.