Abstract
AbstractThere are many successful geothermal projects that exploit the Upper Jurassic aquifer at 2–3 km depth in the German Molasse Basin. However, up to now, only P-wave seismic exploration has been carried out. In an experiment in the Greater Munich area, we recorded S-waves that were generated by the conventional P-wave seismic survey, using 3C receivers. From this, we built a 3D volume of P- to S-converted (PS) waves using the asymptotic conversion point approach. By combining the P-volume and the resulting PS-seismic volume, we were able to derive the spatial distribution of the vp/vs ratio of both the Molasse overburden and the Upper Jurassic reservoir. We found that the vp/vs ratios for the Molasse units range from 2.0 to 2.3 with a median of 2.15, which is much higher than previously assumed. This raises the depth of hypocenters of induced earthquakes in surrounding geothermal wells. The vp/vs ratios found in the Upper Jurassic vary laterally between 1.5 and 2.2. Since no boreholes are available for verification, we test our results against an independently derived facies classification of the conventional 3D seismic volume and found it correlates well. Furthermore, we see that low vp/vs ratios correlate with high vp and vs velocities. We interpret the latter as dolomitized rocks, which are connected with enhanced permeability in the reservoir. We conclude that 3C registration of conventional P-wave surveys is worthwhile.
Funder
Bundesministerium für Wirtschaft und Energie
Publisher
Springer Science and Business Media LLC
Subject
Economic Geology,Geotechnical Engineering and Engineering Geology,Renewable Energy, Sustainability and the Environment
Reference71 articles.
1. Allen PA, Crampton SL, Sinclair HD. The inception and early evolution of the North Alpine Foreland Basin. Switzerland Basin Res. 1991;3(3):143–63. https://doi.org/10.1111/j.1365-2117.1991.tb00124.x.
2. Anselmetti FS, Eberli GP. Sonic velocity in carbonate sediments and rocks. In: Palaz I, Marfurt KJ, editors. Carbonate seismology. Geophysical Developments Series 6. Tulsa: Society of Exploration Geophysicists; 1997.
3. Bachmann GH, Müller M, Weggen K. Evolution of the Molasse Basin (Germany, Switzerland). Tectonophysics. 1987;137:77–92.
4. Bale R, Gratacos B, Mattocks B, Roche S, Poplavskii K, Li X. Shear wave splitting applications for fracture analysis and improved imaging; some onshore examples. First Break. 2009;27:73–83.
5. Behle A, Dohr G. Converted waves in exploration seismics. In: Dohr G, editor. Seismic shear waves. Part B: Applications. Handbook of Geophysical Exploration 15B. London/Amsterdam: Geophysical Press; 1985.
Cited by
7 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献