Integration of Geophysical and Geospatial Techniques to Evaluate Geothermal Energy at Siwa Oasis, Western Desert, Egypt
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsI think it's ok for this paper to be accepted in present form. Thanks!
Author Response
No Comments - The reviewer stated that this paper can be accepted in its present form.
Reviewer 2 Report
Comments and Suggestions for AuthorsThe entire discussion of “treatment” of bottom hole temperatures estimated from drilling records is quite troubling. The approximation methods to “correct” for cooling form drilling fluids is fraught with massive errors. The authors admit that “There are limitations to these 208 methods, including a reliance on assumptions because there is a lack of documentation of 209 drilling procedures, as documentation is time consuming and requires great resources. 210 The actual duration of mud circulation in the well is an example of one of these limitations”. And then to take the bottom “temperature” and make that into a geothermal gradient is flimsy.
How is the change in lithology from surface to bottom of drill hole taken into account? One layer with drastically different conductivity, for example, could throw off all calculations without the authors having any knowledge.
SRTM data have an inherent bias due to the illumination geometry. So derived lineaments are similarly significantly biased. Discuss this factor in detail. How do you determine that “dense lineament zones have high permeability”? Did you perform the required field verification of each lineament to determine its origin?
In order to make use of the nighttime temperature data, you must calculate the thermal inertia of each pixel. This takes into account the conductivity, density, diffusivity of the materials. It is absolutely necessary in order to make any sense of the surface temperature data.
How does the surface geology have any bearing on the magnetic susceptibility? They are “measuring” two disparate spatial attributes. One is just the surface, the other integrates in a general way, several hundred meters to kilometers of subsurface material.
Figure 8: there is NO correlation between the two variables. The plot should never have been presented.
I am “astounded” if you had not found an area of high geothermal potential that also has hot springs. The springs alone are all you needed to find this area, and you could have dispensed with all your computer work.
~line 433: how does the Qattara Depression “…while to the south and west, it grades into the Great Sand Sea, which further supports its high geothermal potential.”? I don’t understand this. Explain
Figure 10 needs to be at the beginning of the paper, not buried at the end. The entire discussion of lithology properties is meant to support claims of geothermal potential. So they need to be integrated early in the introduction of the geology of the area.
Author Response
Please see the attached file
The authors would like to extend their thanks and appreciation to the esteemed reviewer for his/her positive reply and hope that after its publication, this point of view will spark a lively debate on the subject.
Author Response File: 
Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThis paper utilizes integration of geophysical and geospatial techniques to evaluate geothermal energy at Siwa Oasis, Western Desert, Egypt, and provide an overview of Egypt's geothermal resource potential. However, there are still some problems in the current edition. The following eight important aspects should be improved in this manuscript.
1. The formatting is very poor, and this deserves a full-manuscript-wide major revision, mainly in the citation format of references, the contextualization of physical quantities in formulas, the incorrect use of units of physical quantities, the inconsistency of units throughout the manuscript, the incorrect use of geothermal terminology, the absence of quite a few references, and so on. It is hoped that the authors can set the right attitude and take the writing of scientific and technical papers seriously.
2. Figure 1. The whole manuscript revolves around the assessment of geothermal potential, and the geothermal heat flow is one of the most basic and important parameters. Therefore, it is very important to give the heat flow measurement points and the magnitude of the heat flow in the study area as a reference in Figure 1 (in addition to the information of the hot springs), please give the labeling in the figure and describe it briefly in the Geothermal regime in Egypt chapter.
3. Section 2. Geothermal regime in Egypt. This paragraph about the listing of previous research needs extensive revision. First, the citation formatting is problematic and really strange; second, you list what this person did and what that person did, but it's all direct quotes. The author should consider brief citation, that is, summarize the core idea of the original author in your own words and put the citation after; third, the structure of juxtaposition between these previous results is mainly based on juxtaposition structure, and the logical relationship between before and after is not strong, which needs to be revised by the author properly.
4. Line 252-254. In fact, there is a quantitative equation for the relationship between the mean annual temperature and the temperature in the thermostatic zone, with different parameters in different regions. There are two points to note here, first, the depth of the thermostatic zone, and second, the study of the relationship between mean annual temperature and the thermostatic zone. Please elaborate on the background to this.
5. Line 263-266, I'm curious as to how you got the parameter thermal conductivity, first, you used thermal conductivity when you calculated heat flow, and here you've reversed it to calculate thermal conductivity? Second, is your Q here the heat flow? What should the units be? Did you use the thermal conductivity to calculate the value of the heat flow, and then later used the value of the heat flow to calculate the thermal conductivity? It is also very important that you recount the exact source of each parameter in this section.
6. Line 387-390, The authors believe that this result is negatively correlated, but why is it more clearly positively correlated from the trend in the graph? Could the authors please elaborate on the process of analyzing the data and what it represents geologically?
7. Section 4.5, Please provide details of the criteria for categorization, as well as the process of categorization. Only after that do you start using the categorization.
8. Section 6, The discussion section is slightly thin, and the authors could consider combining their strengths, such as the rationalization of remotely sensed data (in conjunction with other measured data), a top to down discussion of thermal anomaly zones; e.g., the calculation of two-dimensional temperature field profiles passing through zones of geothermal potential, and so on.
Overall, this manuscript has an interesting and pioneering work in Egypt, however, given its current state, it is not suitable for publication. For the above reasons, I would suggest a "Major Revision".
Some specific comments are as follows:
Line 18, Environmental degradation reduces crop yields, that's fine, but the question here is whether unsustainable surface water discharges are also "environmental degradation" as you put it. Moreover, unsustainable surface water discharge not only leads to soil salinization, but also to surface water depletion. The logic of these sentences is a bit confusing, so please reorganize the language.
Line 22, Before presenting the ideal exploration areas for geothermal, you should emphasize why geothermal is important in renewable and sustainable energy.
Line 26-27, Strange formulation, why is Siwa suitable for power generation with the above characteristics? Is this temperature high enough? The resource is large enough? You don't express any of these, but you use the expression "as a result of". This is very confusing.
Line 31, GTP first appeared here, but the connection between this sentence and the next is poorly done, please rewrite or merge these two sentences.
Line 48, Lack of references.
Line 54, Please pay attention to the writing format, CO2? The same below.
Line 56-57, It should not be a simple statement, there should be a brief description of the construction background and labeled references.
Line 61, 64, 65, [2], [3], [4], Pay attention to the format and specification of the citation! The same below.
Line 84-87. It is important to note that temperature measurements and heat flow studies remain the most direct and reliable methods, but the limitation is the difficulty of obtaining reliable heat flow values in a given area. Multi-parameter constraints such as geophysical, geochemical, and remote sensing techniques are good, but measured temperatures are the ultimate test. Please reorganize this sentence logically.
Line 89, This unit (mW·m-2) is written incorrectly, please revise throughout; Besides, as mentioned before, having a map of the distribution of heat flow points is a good way to solve the problem, rather than just a textual description.
Line 92, Sandstones, please explain the use of capitalization here.
Line 94, There should be the necessary spaces between numerical and physical units.
Line 100, The presentation of such references is irregular.
Line 115, Please define the high or low ground temperature gradient before using it, as we do not have a standardized standard.
Line 121, Please pay attention to the writing code, it's odd that the units are expressed inconsistently.
Line 133, Temperature data from 116 drilled wells, and from 30 m depth, should be listed in a table and made available to the reader as important raw data. If the amount of data is large, the authors may consider placing this data in an appendix, or in Github.
Line 184-185, The title of figure 4 should be renamed.
Line 194, It is not necessarily low, for example, in the shallow part, it is on the high side.
Line 199-206, unsteady-state BHT correction is important, but this formulation is too wordy, please reorganize.
Line 215-217, The format is not right, please correspond with formula 1, also the format of subscripts should be standardized, not randomly arranged.
Line 234, table 1, Please also list the original measured temperature.
Line 237, Just use the expression crystalline basement directly.
Line 238, precambrian is ok, same below.
Line 257, It should be thermal conductivity.
Line 259, What does this mean? What does the unit of heat flow mean?
Line 268, The location map of the wells is not clear, please redraw the location of the wells.
Line 271, Fig. 5 (f), What is the significance of this? Is it the temperature at the same depth?
Line 284-286, The two sentences should be combined into one.
Line 349, Please provide details of the criteria for categorization, as well as the process of categorization.
Line 392, And 5.2?
Line 440-460, The presentation in this section seems to have little to do with the results, please consider putting it in another section.
Line 486, Please explain in detail why you put this figure here, as it should have gone in the Geologic Background section.
Comments on the Quality of English Language1. The formatting is very poor, and this deserves a full-manuscript-wide major revision, mainly in the citation format of references, the contextualization of physical quantities in formulas, the incorrect use of units of physical quantities, the inconsistency of units throughout the manuscript, the incorrect use of geothermal terminology, the absence of quite a few references, and so on. It is hoped that the authors can set the right attitude and take the writing of scientific and technical papers seriously.
Author Response
Please see the attached file
The authors would like to extend their thanks and appreciation to the esteemed reviewer for his/her positive reply and hope that after its publication, this point of view will spark a lively debate on the subject.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for Authorsthank you for your revisions
Author Response
Please see the attached file
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe authors submitted a revised manuscript. However, no changes are shown (I cannot find it), only highlighted in the final. This is not the way people do when submitting a revision. Please consult the journal editor or any senior researchers who have done this before. Moreover, the response to reviewers is far from enough and therefore not useful. You should always explain in detail how you addressed the concerns and suggestions, point by point. For example, if there are three points listed in one major concern, you should address each of them in detail, instead of writing just three words like saying "R / Agree and done" after the multiple points. You should inform the reviewers where exactly the changes were made (i.e., line numbers), instead of shifting all the efforts to reviewers to find where the changes are. Again, please ask some experienced authors how one should make a revision.
I will review the manuscript once the authors follow the conventions and resubmit a qualified revision. Thank you.
Comments on the Quality of English LanguageNo
Author Response
Please see the attached file
Author Response File: Author Response.pdf
Round 3
Reviewer 3 Report
Comments and Suggestions for AuthorsI am happy to see the changes made by the authors in the new version of the manuscript, the current version is a great improvement in quality. There is still one problem concerning the technical aspects that I would like to ask the authors to explain in detail (the main problem 5 in the previous version and Fig. 6).
It is mainly in the following three areas:
1 Line 272, "Heat flow measures how much energy is transferred from the Earth's core to its surface." There is a major problem with this formulation; heat flow is the amount of heat dissipated from the Earth's interior to space through the surface per unit area of the Earth's core. Heat flow can be used as a calculation, but it is problematic to express it directly in this way, so please correct it.
2 Regarding the mixing of units, for example, heat flow, you say it is flow of the geothermal heat (Line 276), and then you say "flow of geothermal energy", which is actually " heat flow". What is the point of changing the name? What is the point of changing the name? What is the author trying to say? Another example is the unit of thermal conductivity, you use "W/m/K" (276) and "W/m°C" (277, wrong), which makes readers question the author's professionalism.
3 I am still not convinced by the author's explanation in his reply. How did you map the heat flow over such a large area using only the localized 27 boreholes? I think the author left out a lot of details and explanations. you used thermal conductivity to calculate the heat flow, and then later used the value of the heat flow to calculate the thermal conductivity? How is it???
I would like to ask the author to consider the above comments and continue to revise them in the text. I don't want readers to have similar confusion.
Comments on the Quality of English LanguageFine
Author Response
1 Line 272, "Heat flow measures how much energy is transferred from the Earth's core to its surface." There is a major problem with this formulation; heat flow is the amount of heat dissipated from the Earth's interior to space through the surface per unit area of the Earth's core. Heat flow can be used as a calculation, but it is problematic to express it directly in this way, so please correct it.
Response,1: Thank you so much for this comment, we modified it in the line 272 to 273, page no.8, the last paragraph in that page, and added a reference.
Burton-Johnson, A.; Dziadek, R.; Martin, C. Review Article: Geothermal Heat Flow in Antarctica: Current and Future Directions. The Cryosphere 2020, 14, 3843–3873, doi:10.5194/tc-14-3843-2020.
2 Regarding the mixing of units, for example, heat flow, you say it is flow of the geothermal heat (Line 276), and then you say "flow of geothermal energy", which is actually " heat flow". What is the point of changing the name? What is the point of changing the name? What is the author trying to say? Another example is the unit of thermal conductivity, you use "W/m/K" (276) and "W/m°C" (277, wrong), which makes readers question the author's professionalism.
Response 2: Thank you so much for this comment, we modified the heat flow to be flow of geothermal heat, according to (Burton-Johnson, A.; Dziadek, R.; Martin, C. Review Article: Geothermal Heat Flow in Antarctica: Current and Future Directions. The Cryosphere 2020, 14, 3843–3873, doi:10.5194/tc-14-3843-2020). You can find it in the line 284, page no.9, the second paragraph in that page.
Also, we modified the unit of thermal conductivity coefficient in the line 278, page no.9, first paragraph in the page, it was a mistake in writing.
3 I am still not convinced by the author's explanation in his reply. How did you map the heat flow over such a large area using only the localized 27 boreholes? I think the author left out a lot of details and explanations. you used thermal conductivity to calculate the heat flow, and then later used the value of the heat flow to calculate the thermal conductivity? How is it???
Response 3: At the first, thank you so much for this comment.
The response for first part of this comment.
- Most oil companies and oil wells are concentrated around the Gulf of Suez region, because most of the oil and natural gas presence is in this region and the Mediterranean Sea. Therefore, the data available for oil wells is largely present in this region, while in the Western Desert region, specifically in the Siwa Oasis, oil wells are very few and unavailable. Consequently, only 27 wells were available in this area, and we dealt with. In addition, this data for the wells is secret, specific to oil companies, and is difficult to obtain.
- A study was conducted to evaluate the geothermal energy around the Gulf of Suez region in 2020, Fahil, A.S.; Ghoneim, E.; Noweir, M.A.; Masoud, A. Integration of Well Logging and Remote Sensing Data for Detecting Potential Geothermal Sites along the Gulf of Suez, Egypt. Resources 2020, 9, 109, doi:10.3390/resources9090109, and a large thermal zone was discovered extending between the Hammam Faraun region and the Ayun Moussa region, in addition to the southwestern part of the Gulf of Suez near the Ras Gharib region and the El Gouna region. Therefore, the authors were thinking to conduct geothermal study to make a comparison between the evaluation of the geothermal energy in the Gulf of Suez region and the Siwa Oasis region in the Western Desert.
- Siwa Oasis is considered one of the most promising places for discovering the geothermal energy, and it is also one of the areas that the Egyptian government seeks to work on developing it to attract people to live there because it is considered a tourist area that tourists visit for the purpose of medical tourism, but it has some problems such as high salinity in agricultural lands and water, and it was necessary to researchers searching for a solution to these problems and searching for a source of energy in this region. The solution was the geothermal energy, which can be used to generate electricity and a source of energy. It can also be used to desalinate salt water, which has affected the agricultural lands in the study area.
- There are not many recent studies to evaluate the geothermal energy in the Western Desert, specifically in the Siwa Oasis.
- We specifically need to interpolate for 27 oil wells points, by using the IDW (Inverse Distance Weighting) function in ArcGIS to generate rasters sounds good to use in this research. Interpolation is a method to predict an unknown from known values. From the definition, we need some known values to do an interpolation using any interpolation method. The known values which are commonly called sampling point, can be gathered from some measurements and site investigation like drilling, surveying, etc. Using the known value from some locations, we are trying to predict a value of other neighborhood location that is close to the known location. Inverse Distance Weighted interpolation is a deterministic spatial interpolation approach to estimate an unknown value at a location using some known values with corresponding weighted values. As shown in page no.8, the second paragraph, line 261 to 264 and in page no.9, the caption of figure 6, line 287 and 288. https://www.geodose.com/2019/03/spatial-interpolation-inverse-distance-weighting-idw.html.
- The 27 oil well almost cover large part of the Siwa Oasis region which our study are focused on the assessment of the geothermal energy along Siwa Oasis in the Western Desert.
- All these evidences were taken into consideration and the authors attempted to conduct a preliminary study to know and evaluate the geothermal temperature of the Earth’s interior in this region. Only 27 oil wells were available to the research team, which were studied and benefited from. Geophysical and remote sensing data were also used to strengthen the study.
I think the author left out a lot of details and explanations. you used thermal conductivity to calculate the heat flow, and then later used the value of the heat flow to calculate the thermal conductivity? How is it???
The response for second part of this comment.
At the first, when we get the raw data of oil wells, it was in the form of temperatures at different depths and the bottom hole temperature data.
Second, we should correct these data by using Horner method and Gulf of Mexico method.
(http://www.zetaware.com/utilities/bht/horner.html), Now, we have corrected temperature bottom hole data at known depth.
Third, we can use the following equation to calculate the Geothermal Gradient (GG)
Where T is the corrected bottom hole temperature, TS is the mean annual surface temperature which is 26.7 oC (Morgan, P.; Boulos, F.K.; Swanberg, C.A. REGIONAL GEOTHERMAL EXPLORATION IN EGYPT*. Geophys Prospect 1983, 31, 361–376, doi:10.1111/j.1365-2478.1983.tb01059.x.)
Fourth, by knowing the thermal conductivity coefficient which suggest values of the stratigraphic section (1.8–2.6 W/m/K) in the NW Desert that estimated by (Morgan, P.; Boulos, F.K.; Swanberg, C.A. Regional Geothermal Exploration In Egypt. Geophys. Prospect 1983, 31, 361–376, doi:10.1111/j.1365-2478.1983.tb01059.x.) Where is 1.3 W/m/k for limestone and 1.84 W/m/k for sandstone formations and most of the formations in the study area are limestone and sandstone rocks, also by knowing the value of the Geothermal Gradient , We can calculate the Heat Flow (Q) value by using the following equation.
Finally, we can calculate the Thermal Conductivity (K) by using the value of Heat Flow (Q), A which means the body's surface area, ΔT is the temperature differential throughout the body. So, we can use the following equation to calculate the Thermal Conductivity.
where K (W/m/K) is thermal conductivity, Q (mW/m2) is flow of geothermal energy, A (m2) is the body's surface area, ΔT is the temperature differential throughout the body. The thermal conductivity in the study area ranges from 1.3–2.65 W/m/k.
At the first, thank you very much for taking the time to review this manuscript and for your valuable comments that made great improvement in our manuscript.
Author Response File: Author Response.pdf
