Brief statement from the LFZG on the seismic hazardDrilling phase of the geothermal project of Deutsche Erdwärme in Graben-Neudorf 1st draft - status 20.8.2021 Prof. Dr. F.R. Schilling, Dr. B. Müller, Technical Petrophysics, KITAugust 2021
Evaluation of the "Seismic Hazard Study for the Geothermal Project Graben-Neudorf" (Q-Con, 14.05.2020) in the mining approval procedure for theMain Operating Plan of the Deutsche Erdwärme GmbH (short: DEW) Summary: This statement refers to the seismic hazard during the execution of drilling and borehole tests in GrabenNeudorf in the context of the geothermal project applied for by Deutsche ErdWärme (DEW) in the permit "Graben-Neudorf" on May 20, 2020 .
Taking into account the experiences from neighboring boreholes (e.g. Huttenheim field, Hofwiese 1), the densities for mud and cementation should be selected in such a way that unintentional damage to the formations is avoided. formations is avoided. The data to be obtained during drilling can provide further information for the selection of mud and cement densities, and can be used for subsequent use of the well (as a production or injection well).
In our consideration, we assume that the completion is designed according to the state of the art is designed. It is assumed that the well will be drilled and completed in accordance with the generally accepted and dismantled in accordance with the generally recognized rules of safety engineering and that the technical parts of the plant are regularly checked for their functionality.
In addition to the documents provided by DEW, the opinion is based on theavailable observations of other drilling projects (worldwide) and model calculations (DEW's own and and expert opinions on other drilling projects ) for other wells in the Rhine Graben, which have been prepared according to the state of the art.
Accordingly, the planned drilling project, the borehole tests and the production tests can be expected tothe occurrence of damage-relevant seismicity can be virtually ruled out according to currentruled out.
... Conclusion and Recommendation: The expert opinion of Q-Con "Seismic hazard study for the geothermal project GrabenNeudorf" (14.05.2020, DEW002_200514) was carried out according to the state of the art and did not assess the seismic risk based on all data available to date. The drilling phase can be considered analogous to oil and gas wells. From our point of view, there is no reason In our view, there is nothing to prevent the approval of the drilling and the borehole tests with regard to the seismic risk, incl. production test.
For a more detailed appraisal and evaluation of the seismic hazard during thephase, the acquisition of drilling data is essential. Only then can the parameter data available can be narrowed down and verified.
The LFZG has already given hints for useful additional measurements in advance in order to parameters on which the hazard study is based. This was taken into account by the This was taken into account by the mining authority in the approval. For the operating phase, we see the necessity to verify the parameters assumed in the risk study and, if necessary, to adjust the models. and have made corresponding recommendations. Our assessment is explicitly only "step by step" in accordance with the mining approval - not across the board for an overall project.
A detailed analysis and risk assessment, as stipulated in the mining permits, is only to be carried out is only possible with the data obtained during drilling. Before intensive hydraulic tests, we believe the seismic hazard study must be compared with the data obtained and then and then evaluated and possibly updated. In doing so, it may may be advisable, depending on the data situation and the resulting situation, to consult to consult further experts. We would consider this if requested by the LBD in due course. LBD at the appropriate time in a safety-oriented manner in exchange with the authority. with the authority.
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