the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 13 Jun 2023
Multiple phase rifting and subsequent inversion in the West Netherlands Basin: implications for geothermal reservoir characterization
Abstract. The tectonic evolution of rift basins can strongly influence the petrophysical properties of its sedimentary infills at various scales and, therefore, influence the characteristics of present resources. Understanding the tectonic evolution of a rift basin is therefore decisive, as it can have consequences for the parameters that influence the planning of geothermal doublets. In this framework, this study gives a detailed interpretation of the syn- and post-rift episodes in the West Netherlands Basin, since Jurassic times. Despite multiple studies on the geotectonic setting of the West Netherlands Basin, a detailed understanding of its syn- and post-rift phases in the context of geothermal exploration is still fundamentally lacking. With a renewed interpretation of a seismic 3D cube, covering a large portion of the onshore section of the basin, we identified two important Jurassic rifting episodes and one Cretaceous inversion event. Rifting caused compartmentalisation of the main producing geothermal target in the area; the Late Jurassic Nieuwerkerk Formation. Yet, the central portions of the half-grabens show good potential for geothermal exploration. Subsequent inversion could have caused local breaching of the aquifer, forming a potential risk. Therefore, only non to moderately inverted areas should be considered for geothermal exploration. This study provides a better understanding of the multi-phase rifting history in the West Netherlands Basin, providing important constraints on the reservoir-seal integrity and with that, the amount of heat that can be safely produced from a geothermal reservoir rock. Aiming to contribute to the energy transition, this study provides an integrated picture of the West Netherlands Basin and shows how a basin’s geological history can affect its geothermal resources.
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RC1: 'Comment on egusphere-2023-1126', Anonymous Referee #1, 17 Jul 2023
Dear authors,
Thank you very much for sharing this work. I very much enjoyed reading it and appreciate your effort to unravel the WNB puzzle further to support geothermal development in the basin. Your described the structural setting in a very detailed way that I have not seen in previous prublications on this area.
My main reccomendation for revisions is that I suggest to more clearly explain how your work enhances insights in facies architecture in the basin. I did not see a clear comparison with previously published conceptual geological models on the regional sst disctribution. your figure 7 is your main outcome on this, but for example Den Hartog Jager published very similar figures isnt that right? (if not please highlight the differences)
You warn that future exploration should stay away from strongly inverted areas, can you indicate on the maps which blocks are in such areas? (maybe even plot current geothermal wells in fig (6-h, for example?). geothermal wells are dotted all over the place, did any of these already target strongly inverted areas? do their performance support your statements? (can you link your work to recent geological observations in geothermal developements, or to data from oil and gas wells)? also the hydrocarbon wells target such strongly inverted areas, yet they have good reservoir performance and no (significant?) seismic events. I had all these questions while reading your work and I wrote them here as examples of how you could link your work better to well performance data and practical impact. This could highlight what your new insights are and make you story stronger.
Please also find a list of questions and comments below. if something is not clear I would be happy to discuss this further. I hope this is all constructive and usefull in further tuning your manuscript.
Questions:
From the abstract it is not directly clear to me what you are doing: giving a detailed interpretation of the syn and post rift episodes” do you mean more detailed than before, and can you specify already here what new details you discovered?
line 24-26: "This study provides a better understanding of the multi-phase rifting history in the West Netherlands Basin, providing important constraints on the reservoir-seal integrity and with that, the amount of heat that can be safely produced from a geothermal reservoir rock".
few questions on this sentence:
- why is the seal integrity important in a geothermal reservoir?
- I dont understant what you mean: you provide a better understanding..., by providing important constraints on the reservoir-seal integrity and the amount of heat that can be produced. that is quite a big step, can you be a bit more concrete?Figure 2: inside mega sequence 5 is a big unconformity, why is this not megasequence boundary? (inside the Northsea Group is a similar unconfromity right, and this is included in your megasequnces, or are these different?) How do you define a mega sequence? In this figure it also seems to me as if the entire Nieuwerkerk Formation is Early Cretaceous.
From the intro and geological framework section it is not clear to me what the problem is that you are trying to solve. can you explain that more clearly, please? being the advocate of the devil: exploitation is going quite alright, is it not?
You state that higher N/G is expected in the core of the half grabens, but is that always the case? In these locations there is more accommodation for deposition, but also less erosion, and so more preservation of fines and hence lower N/G could also happen... The ratio of accomodation space increase and sediment supply is key, but we don’t quite know that and there is no hard data on this. How should I see this and how is this recognised in data (wells/seismic?)
Line 430: “we can identify areas suitable for further investigation within the L3NAM2012AR seismic 3D cube” : what do you mean with suitable? Are not all areas already being investigated? can you specify what you expect in these areas?
you state that there is difference in degree of inversion between areas, is this reflected in the performance of the 14 active doublets? or in future seismic risk or is there any other potential practical impact? explaining this would enhance practical use and impact of your work. (I asked this before, so ignore if you already adress this above)
Line 426: could fracturing not also enhance performance of the reservoir?
Final sentence of the discussion: you suggest that a new deep attribute analysis could disclose information on facies architecture. Can you be more specific? It would be great if there is a suitable attribute, but if no-one did this yet, I think that the big question is on how to image these things and then this statement deserves a bit more speculation/discussion.
Figure 7: how do you explain the high N/G oil/gas reservoirs at the structural highs with this model? Other models that people presented before include one where a single high N/G sand layer ( the Delft Sst) is deposited on top of the lower N/G Alblasserdam Mbr, probably also covering the highs.( Out of curiosity: why did you not differentiate between the Delft and Alblasserdam Mbrs?) how do other models describe regional sandstone distribution?
you describe the main faults in the basin: I was curious if you have any ideas on sub-seismic structures around these major faults?
Comments/corrections:
start of intro: perhaps slightly rephrase into a structure like this:
tectonic evolution is important and explain why. Then introduce the problem you are trying to solve: something is lacking, and then: in this framework this study did that… this is a more logical order. (hopefuly this is clear)
line21: ‘…the rifting produced the geothermal target”. im not sure if this is the correct way to phrase this. The target is formed by sedimentary processes, the rifting compartimentalised it, affected properties maybe, but didn’t create it, right?
Line 20: can you already state whether its when in the Cretaceous, I was curious straightaway.
Line 21: ‘yet’ suggests a contradiction, but which one is not clear to me.
Line 22: “subsequent inversion… a potential risk.” is this a new problem statement. Or one of your new insights, or a hypothesis? And is breaching the right word? And perhaps explain why this is a potential risk.
Line 24: second time that you state that the study gives more insight in tectonic evolution of the basin.
Maybe also good to explain briefly why you focus on the Jurassic-Cretaceous for readers that are not familiar with this basin. Final sentence is also quite repetitive.
Line 53-55: you state that inversion and the rifting history could have controlled the architecture of the rift phase. What do you mean with that rift phase, structural architecture/structural setting? Or sedimentary architecture of the Jurassic tectono-sedimentary sequence?
Line57: could you add a statement before the listing of your focus on what is missing in current knowledge more clearly. You had something on it in th abstract, but it makes sense to make that extra clear here.
Line123: why is it relevant to mention that you used a guided approach, and even more specifically name the Petrel terminology? Do you doubt accuracy, otherwise maybe loose it to make it more generic.
Citation: https://doi.org/10.5194/egusphere-2023-1126-RC1 - AC1: 'Reply on RC1', Annelotte Weert, 17 Aug 2023
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RC2: 'Comment on egusphere-2023-1126', Conor O'Sullivan, 03 Aug 2023
Dear authors,
I appreciate the invitation to review your manuscript and read your work on the West Netherlands Basin (WNB), it seems like an interesting place with more work to come to unlock its geothermal potential. You give a detailed overview of the interpreted horizons and the structural evolution and comment on the role this has in the distribution of geothermal reservoirs in the WNB. This will be a useful resource for people exploring this region for geothermal resources.
However, there are three main things that can be added which will make this an even more relevant reference for this basin and geothermal exploration in general:
- In the introduction and conclusion, make it clearer what is new about your work when compared to previous studies. This will allow your reader to understand what to expect and focus on.
- Add a brief section which outlines the different types of geothermal energy and which ones are applicable to the WNB. Some mention is made throughout the manuscript to different projects currently active in the basin, so this will help provide some context.
- Frequent mention is made to the large well database which was available; if this includes porosity or net-to-gross data, then this could be included to support the interpretations presented in the manuscript. Something like a net-to-gross map, or a porosity depth chart with inverted and non-inverted sandstones highlighted could go a long way to supporting the findings of the manuscript.
All the points above will make a good manuscript even better. I would be very happy to discuss any of the points above, or my comments below, further if the authors would find it helpful. Best of luck with resubmission!
Comments:
15: just geothermal doublets? Maybe consider expanding to include other geothermal developments as well to widen the scope of the paper.
44-45: it would be interesting to hear how many projects targeted each of these three reservoirs.
46-49: Is there any data available about the success rate of geothermal exploration in the WNB? If so, it would be good to include it here to give context to these statements.
48-49: As this is a key statement and related to your outcomes, it might be worth explaining how thickness and heterogeneity is important here i.e. a thicker and more homogenous reservoir is better than a thin and heterogenous reservoir.
Introduction: this provides a good overview of the geothermal scene in the WNB, however its unclear what your study is doing differently. I think a few lines in the final paragraph which differentiate your work from previous studies would be great.
Figure 1 caption: a) The white lines on a light blue background are not the easiest to see. I would suggest either changing the colour of the inversion markers or adding a boundary line around the zones. b) It is unclear why the wells are coloured the way they are. I assume this is the deepest formation encountered in each well? Please add a line in the caption explaining this to help the reader.
93: What does the Zechstein Group consist of in the study area? It’s not shown in Figure 2 so mention the lithology here to help your reader. Probably worth checking each unit there to make sure you are consistently describing them (e.g. age, stratigraphic name, broad lithological overview).
113-115: This is a very large well database but no mention is made here as to what these wells were used for. Expand on this here to help the reader. I assume just formation tops, as the cube was depth converted. Were there any mismatches between formation tops and the depth converted cube?
153-154: Always good to include the uninterpreted lines so your reader can understand what features and reflectors you are interpreting, nice one!
152-153: It would be good to describe these active geothermal projects in a bit more detail (e.g. are these closed-loop, open-loop, etc.), given the scope of this paper. There location relative to inverted structures will allow the reader to see your results in action.
159: I would call this the ‘youngest’ megasequence (or just megasequence 1) as, strictly speaking, the ‘first’ megasequence will be the oldest in terms of geological evolution.
175: Like the comment above, use of ‘first’ here could be confusing for the reader. Additionally, to avoid confusion ‘3’ should be spelled out (i.e. three) as it is referring to the three megasequences and not megasequence 3.
217-218: I would caveat the use of horizon flattening to describe thickness changes, particularly in more deeply buried units. Horizon flattening is a useful ‘quick-and-dirty’ technique to get broad ideas of unit variation across a section, but doesn’t account for things like differential compaction due to thickness variations in shallower units, which can be particularly important in high porosity rocks like the Nieuwerkerk Formation.
Strikeline 3415: I’m unsure if having this strike line is particularly helpful for showcasing the WNB. Structural interpretation on a line parallel to the structural trend will give a false sense of the structures and is best done on lines parallel to the direction of principle movement. It might be worth including one more dip-line, perhaps to the south of the dataset, to give the reader an indication of change along the length of the basin.
Figure 5: If we are imaging a normal fault (fault i) this obliquely, we would expect the apparent dip to much shallower than the very high angles interpreted here. Additionally, should the absence of megasequence 6 on the Lansingerland High be explained in-text (no mention is made currently)? It is different to the other three sections seen so far.
267-268: As you mention changes in seismic facies, does this relate to changing sedimentology and possibly reservoir quality? Can these be used as indicators for geothermal explorers working in this basin?
332-334: While you’re correct the North Sea Dome likely doesn’t have much impact on the WNB, it is important to realise that this far from the epicentre of this event, the effects likely to be relatively subtle, and possibly overprinted by later structural evolution. Maybe worth mentioning this as a caveat.
337-338: As this is the first mention of igneous activity, it’s worth expanding on this a bit more here: does this impact the geothermal prospectivity of the basin? There are no igneous structures interpreted on the sections or shown in the strat column, where do they occur?
338-340: Why are we considering these faults are sealed? Is it the lithology towards the top of megasequence 5? Worth clarifying this here to help your reader. Also, do we have evidence of this? Are there any fault-seal studies that be referenced, or are they hydrocarbon accumulations trapped in tilted fault blocks to demonstrate seal effectiveness?
383: Attributing deformation to the Laramide seems a bit unrealistic here, given several other events occurring much closer to the WNB at this time, including the incipient Alpine Orogeny, the opening of the North Atlantic, and the development of the North Atlantic Igneous Province to think of a few.
389-399: I wonder is it worth talking about the Triassic at all here, as it is not mapped and is not the focus of the study? I leave this to the authors’ discretion.
407: As you state these values are depth and not elevation, they do not need the negative symbol in front of them.
408-409: I think it might be useful to have a short introductory section earlier in the manuscript, probably between the intro and geological framework sections, which briefly explains the different types of geothermal energy, and highlight which ones are active or planned in the Netherlands.
422-423: As there is such a large well database to support this manuscript, would it not be possible to produce a net-to-gross map for each reservoir unit, to validate these claims?
426-427: Is there any published data or interpretations to support this? If not, perhaps include a general reference which states the degree of fracturing in inverted structures. Breached hydrocarbon accumulations might also support this supposition.
436-439: As with the comment above, perhaps a porosity vs depth plot could be made from available well data? Comparing the inverted and non-inverted reservoirs will likely show that the inverted areas will have poorer porosity due to deeper burial and greater mechanical compaction prior to inversion when compared to non-inverted areas. This could help support your findings in this study.
441-446: I would highlight what new findings you have here, to make your work stand out from existing literature. Similar to what has been suggested for the introduction above.
Grammer and language:
13: as you are referring to multiple rift basins, it should be ‘their sedimentary infill’ rather than ‘its’.
15: I feel decisive is not the right word here. Consider changing to something like crucial, essential, or imperative.
22: ‘Yet’ can be removed here as there is no counterstatement in contradiction to the sentence.
46: ‘hardly affordable’ feels awkward here. Maybe change to something like ‘more critical than in hydrocarbon exploration’.
47: again ‘decisive’ feels out of place. Considering rewording as in comment above.
47: remove ‘mentioned’.
55-56: ‘Not straightforward’ reads awkwardly, particularly at the end of a paragraph. Maybe change with something like ‘more complex’.
78-80: These sentences feel like they should be one single sentence.
81: remove ‘Yet,’.
81: Reword the first half to ‘Despite the tectonic phases mentioned above, …’.
84: ‘wherefore’ is pretty archaic, consider changing to ‘therefore’.
85-87: pulses of what? I’m assuming extension/rifting?
153: Flattened ‘to’ the base of the Rijnland Group.
178: ‘Last’ should be replaced by ‘Lastly’ or ‘Finally’.
183: ‘basically’ comes across as a little informal. I would remove it here as megasequences 1-3 are unfaulted.
194: ‘semi-graben’ should be ‘half-graben’?
195: ‘binding’ should be ‘bounding’.
213: this short sentence feels weird and should be combined with the preceding sentence.
217: ‘even better visible’ reads awkwardly. Change to something like ‘even more clearly visible’.
230 and 237: ‘bind/binding’ should be ‘bound/bounding’.
239: check spelling of ‘reflectors’.
282: I would reword this slightly to say ‘megasequence 3 was deposited during inversion’.
364: sedimented sounds a little odd here. Perhaps reword to ‘was deposited during’.
Citation: https://doi.org/10.5194/egusphere-2023-1126-RC2 - AC2: 'Reply on RC2', Annelotte Weert, 17 Aug 2023
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EC1: 'Comment on egusphere-2023-1126', Patricia Cadenas Martínez, 05 Sep 2023
Dear authors,
I went over and checked all the clarifications and replies you provided to comments posted during the interactive discussion. You addressed and clarified all the points highlighted by the reviewers and I think you can revise the manuscript and continue with the required procedures.
The only remark I would like to highlight for the review process is that it may be useful including and displaying in the manuscript a dip NE-SW trending seismic line in the southern half of the studied zone, and also delineating the location of displayed 2610, 3410, and 3415 seismic lines in figure 6, particularly figure 6h.
Thanks for the interactive discussion and all your work with the manuscript
Sincerely,
Patricia
Citation: https://doi.org/10.5194/egusphere-2023-1126-EC1 -
AC3: 'Reply on EC1', Annelotte Weert, 06 Sep 2023
Dear Editor,
We thank you for your response and the useful suggestions.
Within the revised manuscript, we will include a NE-SW trending seismic line in the southern half of the studied zone and include the locations of the seismic sections in Figure 6.Citation: https://doi.org/10.5194/egusphere-2023-1126-AC3
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AC3: 'Reply on EC1', Annelotte Weert, 06 Sep 2023
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2023-1126', Anonymous Referee #1, 17 Jul 2023
Dear authors,
Thank you very much for sharing this work. I very much enjoyed reading it and appreciate your effort to unravel the WNB puzzle further to support geothermal development in the basin. Your described the structural setting in a very detailed way that I have not seen in previous prublications on this area.
My main reccomendation for revisions is that I suggest to more clearly explain how your work enhances insights in facies architecture in the basin. I did not see a clear comparison with previously published conceptual geological models on the regional sst disctribution. your figure 7 is your main outcome on this, but for example Den Hartog Jager published very similar figures isnt that right? (if not please highlight the differences)
You warn that future exploration should stay away from strongly inverted areas, can you indicate on the maps which blocks are in such areas? (maybe even plot current geothermal wells in fig (6-h, for example?). geothermal wells are dotted all over the place, did any of these already target strongly inverted areas? do their performance support your statements? (can you link your work to recent geological observations in geothermal developements, or to data from oil and gas wells)? also the hydrocarbon wells target such strongly inverted areas, yet they have good reservoir performance and no (significant?) seismic events. I had all these questions while reading your work and I wrote them here as examples of how you could link your work better to well performance data and practical impact. This could highlight what your new insights are and make you story stronger.
Please also find a list of questions and comments below. if something is not clear I would be happy to discuss this further. I hope this is all constructive and usefull in further tuning your manuscript.
Questions:
From the abstract it is not directly clear to me what you are doing: giving a detailed interpretation of the syn and post rift episodes” do you mean more detailed than before, and can you specify already here what new details you discovered?
line 24-26: "This study provides a better understanding of the multi-phase rifting history in the West Netherlands Basin, providing important constraints on the reservoir-seal integrity and with that, the amount of heat that can be safely produced from a geothermal reservoir rock".
few questions on this sentence:
- why is the seal integrity important in a geothermal reservoir?
- I dont understant what you mean: you provide a better understanding..., by providing important constraints on the reservoir-seal integrity and the amount of heat that can be produced. that is quite a big step, can you be a bit more concrete?Figure 2: inside mega sequence 5 is a big unconformity, why is this not megasequence boundary? (inside the Northsea Group is a similar unconfromity right, and this is included in your megasequnces, or are these different?) How do you define a mega sequence? In this figure it also seems to me as if the entire Nieuwerkerk Formation is Early Cretaceous.
From the intro and geological framework section it is not clear to me what the problem is that you are trying to solve. can you explain that more clearly, please? being the advocate of the devil: exploitation is going quite alright, is it not?
You state that higher N/G is expected in the core of the half grabens, but is that always the case? In these locations there is more accommodation for deposition, but also less erosion, and so more preservation of fines and hence lower N/G could also happen... The ratio of accomodation space increase and sediment supply is key, but we don’t quite know that and there is no hard data on this. How should I see this and how is this recognised in data (wells/seismic?)
Line 430: “we can identify areas suitable for further investigation within the L3NAM2012AR seismic 3D cube” : what do you mean with suitable? Are not all areas already being investigated? can you specify what you expect in these areas?
you state that there is difference in degree of inversion between areas, is this reflected in the performance of the 14 active doublets? or in future seismic risk or is there any other potential practical impact? explaining this would enhance practical use and impact of your work. (I asked this before, so ignore if you already adress this above)
Line 426: could fracturing not also enhance performance of the reservoir?
Final sentence of the discussion: you suggest that a new deep attribute analysis could disclose information on facies architecture. Can you be more specific? It would be great if there is a suitable attribute, but if no-one did this yet, I think that the big question is on how to image these things and then this statement deserves a bit more speculation/discussion.
Figure 7: how do you explain the high N/G oil/gas reservoirs at the structural highs with this model? Other models that people presented before include one where a single high N/G sand layer ( the Delft Sst) is deposited on top of the lower N/G Alblasserdam Mbr, probably also covering the highs.( Out of curiosity: why did you not differentiate between the Delft and Alblasserdam Mbrs?) how do other models describe regional sandstone distribution?
you describe the main faults in the basin: I was curious if you have any ideas on sub-seismic structures around these major faults?
Comments/corrections:
start of intro: perhaps slightly rephrase into a structure like this:
tectonic evolution is important and explain why. Then introduce the problem you are trying to solve: something is lacking, and then: in this framework this study did that… this is a more logical order. (hopefuly this is clear)
line21: ‘…the rifting produced the geothermal target”. im not sure if this is the correct way to phrase this. The target is formed by sedimentary processes, the rifting compartimentalised it, affected properties maybe, but didn’t create it, right?
Line 20: can you already state whether its when in the Cretaceous, I was curious straightaway.
Line 21: ‘yet’ suggests a contradiction, but which one is not clear to me.
Line 22: “subsequent inversion… a potential risk.” is this a new problem statement. Or one of your new insights, or a hypothesis? And is breaching the right word? And perhaps explain why this is a potential risk.
Line 24: second time that you state that the study gives more insight in tectonic evolution of the basin.
Maybe also good to explain briefly why you focus on the Jurassic-Cretaceous for readers that are not familiar with this basin. Final sentence is also quite repetitive.
Line 53-55: you state that inversion and the rifting history could have controlled the architecture of the rift phase. What do you mean with that rift phase, structural architecture/structural setting? Or sedimentary architecture of the Jurassic tectono-sedimentary sequence?
Line57: could you add a statement before the listing of your focus on what is missing in current knowledge more clearly. You had something on it in th abstract, but it makes sense to make that extra clear here.
Line123: why is it relevant to mention that you used a guided approach, and even more specifically name the Petrel terminology? Do you doubt accuracy, otherwise maybe loose it to make it more generic.
Citation: https://doi.org/10.5194/egusphere-2023-1126-RC1 - AC1: 'Reply on RC1', Annelotte Weert, 17 Aug 2023
-
RC2: 'Comment on egusphere-2023-1126', Conor O'Sullivan, 03 Aug 2023
Dear authors,
I appreciate the invitation to review your manuscript and read your work on the West Netherlands Basin (WNB), it seems like an interesting place with more work to come to unlock its geothermal potential. You give a detailed overview of the interpreted horizons and the structural evolution and comment on the role this has in the distribution of geothermal reservoirs in the WNB. This will be a useful resource for people exploring this region for geothermal resources.
However, there are three main things that can be added which will make this an even more relevant reference for this basin and geothermal exploration in general:
- In the introduction and conclusion, make it clearer what is new about your work when compared to previous studies. This will allow your reader to understand what to expect and focus on.
- Add a brief section which outlines the different types of geothermal energy and which ones are applicable to the WNB. Some mention is made throughout the manuscript to different projects currently active in the basin, so this will help provide some context.
- Frequent mention is made to the large well database which was available; if this includes porosity or net-to-gross data, then this could be included to support the interpretations presented in the manuscript. Something like a net-to-gross map, or a porosity depth chart with inverted and non-inverted sandstones highlighted could go a long way to supporting the findings of the manuscript.
All the points above will make a good manuscript even better. I would be very happy to discuss any of the points above, or my comments below, further if the authors would find it helpful. Best of luck with resubmission!
Comments:
15: just geothermal doublets? Maybe consider expanding to include other geothermal developments as well to widen the scope of the paper.
44-45: it would be interesting to hear how many projects targeted each of these three reservoirs.
46-49: Is there any data available about the success rate of geothermal exploration in the WNB? If so, it would be good to include it here to give context to these statements.
48-49: As this is a key statement and related to your outcomes, it might be worth explaining how thickness and heterogeneity is important here i.e. a thicker and more homogenous reservoir is better than a thin and heterogenous reservoir.
Introduction: this provides a good overview of the geothermal scene in the WNB, however its unclear what your study is doing differently. I think a few lines in the final paragraph which differentiate your work from previous studies would be great.
Figure 1 caption: a) The white lines on a light blue background are not the easiest to see. I would suggest either changing the colour of the inversion markers or adding a boundary line around the zones. b) It is unclear why the wells are coloured the way they are. I assume this is the deepest formation encountered in each well? Please add a line in the caption explaining this to help the reader.
93: What does the Zechstein Group consist of in the study area? It’s not shown in Figure 2 so mention the lithology here to help your reader. Probably worth checking each unit there to make sure you are consistently describing them (e.g. age, stratigraphic name, broad lithological overview).
113-115: This is a very large well database but no mention is made here as to what these wells were used for. Expand on this here to help the reader. I assume just formation tops, as the cube was depth converted. Were there any mismatches between formation tops and the depth converted cube?
153-154: Always good to include the uninterpreted lines so your reader can understand what features and reflectors you are interpreting, nice one!
152-153: It would be good to describe these active geothermal projects in a bit more detail (e.g. are these closed-loop, open-loop, etc.), given the scope of this paper. There location relative to inverted structures will allow the reader to see your results in action.
159: I would call this the ‘youngest’ megasequence (or just megasequence 1) as, strictly speaking, the ‘first’ megasequence will be the oldest in terms of geological evolution.
175: Like the comment above, use of ‘first’ here could be confusing for the reader. Additionally, to avoid confusion ‘3’ should be spelled out (i.e. three) as it is referring to the three megasequences and not megasequence 3.
217-218: I would caveat the use of horizon flattening to describe thickness changes, particularly in more deeply buried units. Horizon flattening is a useful ‘quick-and-dirty’ technique to get broad ideas of unit variation across a section, but doesn’t account for things like differential compaction due to thickness variations in shallower units, which can be particularly important in high porosity rocks like the Nieuwerkerk Formation.
Strikeline 3415: I’m unsure if having this strike line is particularly helpful for showcasing the WNB. Structural interpretation on a line parallel to the structural trend will give a false sense of the structures and is best done on lines parallel to the direction of principle movement. It might be worth including one more dip-line, perhaps to the south of the dataset, to give the reader an indication of change along the length of the basin.
Figure 5: If we are imaging a normal fault (fault i) this obliquely, we would expect the apparent dip to much shallower than the very high angles interpreted here. Additionally, should the absence of megasequence 6 on the Lansingerland High be explained in-text (no mention is made currently)? It is different to the other three sections seen so far.
267-268: As you mention changes in seismic facies, does this relate to changing sedimentology and possibly reservoir quality? Can these be used as indicators for geothermal explorers working in this basin?
332-334: While you’re correct the North Sea Dome likely doesn’t have much impact on the WNB, it is important to realise that this far from the epicentre of this event, the effects likely to be relatively subtle, and possibly overprinted by later structural evolution. Maybe worth mentioning this as a caveat.
337-338: As this is the first mention of igneous activity, it’s worth expanding on this a bit more here: does this impact the geothermal prospectivity of the basin? There are no igneous structures interpreted on the sections or shown in the strat column, where do they occur?
338-340: Why are we considering these faults are sealed? Is it the lithology towards the top of megasequence 5? Worth clarifying this here to help your reader. Also, do we have evidence of this? Are there any fault-seal studies that be referenced, or are they hydrocarbon accumulations trapped in tilted fault blocks to demonstrate seal effectiveness?
383: Attributing deformation to the Laramide seems a bit unrealistic here, given several other events occurring much closer to the WNB at this time, including the incipient Alpine Orogeny, the opening of the North Atlantic, and the development of the North Atlantic Igneous Province to think of a few.
389-399: I wonder is it worth talking about the Triassic at all here, as it is not mapped and is not the focus of the study? I leave this to the authors’ discretion.
407: As you state these values are depth and not elevation, they do not need the negative symbol in front of them.
408-409: I think it might be useful to have a short introductory section earlier in the manuscript, probably between the intro and geological framework sections, which briefly explains the different types of geothermal energy, and highlight which ones are active or planned in the Netherlands.
422-423: As there is such a large well database to support this manuscript, would it not be possible to produce a net-to-gross map for each reservoir unit, to validate these claims?
426-427: Is there any published data or interpretations to support this? If not, perhaps include a general reference which states the degree of fracturing in inverted structures. Breached hydrocarbon accumulations might also support this supposition.
436-439: As with the comment above, perhaps a porosity vs depth plot could be made from available well data? Comparing the inverted and non-inverted reservoirs will likely show that the inverted areas will have poorer porosity due to deeper burial and greater mechanical compaction prior to inversion when compared to non-inverted areas. This could help support your findings in this study.
441-446: I would highlight what new findings you have here, to make your work stand out from existing literature. Similar to what has been suggested for the introduction above.
Grammer and language:
13: as you are referring to multiple rift basins, it should be ‘their sedimentary infill’ rather than ‘its’.
15: I feel decisive is not the right word here. Consider changing to something like crucial, essential, or imperative.
22: ‘Yet’ can be removed here as there is no counterstatement in contradiction to the sentence.
46: ‘hardly affordable’ feels awkward here. Maybe change to something like ‘more critical than in hydrocarbon exploration’.
47: again ‘decisive’ feels out of place. Considering rewording as in comment above.
47: remove ‘mentioned’.
55-56: ‘Not straightforward’ reads awkwardly, particularly at the end of a paragraph. Maybe change with something like ‘more complex’.
78-80: These sentences feel like they should be one single sentence.
81: remove ‘Yet,’.
81: Reword the first half to ‘Despite the tectonic phases mentioned above, …’.
84: ‘wherefore’ is pretty archaic, consider changing to ‘therefore’.
85-87: pulses of what? I’m assuming extension/rifting?
153: Flattened ‘to’ the base of the Rijnland Group.
178: ‘Last’ should be replaced by ‘Lastly’ or ‘Finally’.
183: ‘basically’ comes across as a little informal. I would remove it here as megasequences 1-3 are unfaulted.
194: ‘semi-graben’ should be ‘half-graben’?
195: ‘binding’ should be ‘bounding’.
213: this short sentence feels weird and should be combined with the preceding sentence.
217: ‘even better visible’ reads awkwardly. Change to something like ‘even more clearly visible’.
230 and 237: ‘bind/binding’ should be ‘bound/bounding’.
239: check spelling of ‘reflectors’.
282: I would reword this slightly to say ‘megasequence 3 was deposited during inversion’.
364: sedimented sounds a little odd here. Perhaps reword to ‘was deposited during’.
Citation: https://doi.org/10.5194/egusphere-2023-1126-RC2 - AC2: 'Reply on RC2', Annelotte Weert, 17 Aug 2023
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EC1: 'Comment on egusphere-2023-1126', Patricia Cadenas Martínez, 05 Sep 2023
Dear authors,
I went over and checked all the clarifications and replies you provided to comments posted during the interactive discussion. You addressed and clarified all the points highlighted by the reviewers and I think you can revise the manuscript and continue with the required procedures.
The only remark I would like to highlight for the review process is that it may be useful including and displaying in the manuscript a dip NE-SW trending seismic line in the southern half of the studied zone, and also delineating the location of displayed 2610, 3410, and 3415 seismic lines in figure 6, particularly figure 6h.
Thanks for the interactive discussion and all your work with the manuscript
Sincerely,
Patricia
Citation: https://doi.org/10.5194/egusphere-2023-1126-EC1 -
AC3: 'Reply on EC1', Annelotte Weert, 06 Sep 2023
Dear Editor,
We thank you for your response and the useful suggestions.
Within the revised manuscript, we will include a NE-SW trending seismic line in the southern half of the studied zone and include the locations of the seismic sections in Figure 6.Citation: https://doi.org/10.5194/egusphere-2023-1126-AC3
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AC3: 'Reply on EC1', Annelotte Weert, 06 Sep 2023
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