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Main Title: Wireline distributed acoustic sensing allows 4.2 km deep vertical seismic profiling of the Rotliegend 150 °C geothermal reservoir in the North German Basin
Author(s): Henninges, Jan
Martuganova, Evgeniia
Stiller, Manfred
Norden, Ben
Krawczyk, Charlotte M.
Type: Article
Abstract: We performed so-far-unprecedented deep wireline vertical seismic profiling at the Groß Schönebeck site with the novel method of distributed acoustic sensing (DAS) to gain more detailed information on the structural setting and geometry of the geothermal reservoir, which is comprised of volcanic rocks and sediments of Lower Permian age. During the survey of 4 d only, we acquired data for 61 source positions using hybrid wireline fiber-optic sensor cables deployed in two 4.3 km deep, already existing wells. While most of the recorded data have a very good signal-to-noise ratio, individual sections of the profiles are affected by characteristic coherent noise patterns. This ringing noise results from incomplete coupling of the sensor cable to the borehole wall, and it can be suppressed to a large extent using suitable filtering methods. After conversion to strain rate, the DAS data exhibit a high similarity to the vertical component data of a conventional borehole geophone. We derived accurate time–depth relationships, interval velocities, and corridor stacks from the recorded data. Based on integration with other well data and geological information, we show that the top of a porous and permeable sandstone interval of the geothermal reservoir can be identified by a positive reflection event. Overall, the sequence of reflection events shows a different character for both wells explained by lateral changes in lithology. The top of the volcanic rocks has a somewhat different seismic response in both wells, and no clear reflection event is obvious at the postulated base of the volcanic rocks, so that their thickness cannot be inferred from individual reflection events in the seismic data alone. The DAS method enabled measurements at elevated temperatures up to 150 ∘C over extended periods and led to significant time and cost savings compared to deployment of a conventional borehole geophone string. This wireline approach finally suggests significant implications for observation options in old wells for a variety of purposes.
Subject(s): acoustic sensing
North German Basin
seismic profiling
Issue Date: 25-Feb-2021
Date Available: 26-Apr-2021
Language Code: en
DDC Class: 550 Geowissenschaften
Sponsor/Funder: BMWi, 0324065 TIB, Rissdominierte Erschließung eines tiefen geothermischen Reservoirs zur Stromerzeugung im Norddeutschen Becken - seismische Erkundung, Konzeption und bohrtechnische Planung am Standort Groß Schönebeck
EC/H2020/691728/EU/Demonstration of soft stimulation treatments of geothermal reservoirs/DESTRESS
EC/H2020/676564/EU/EPOS Implementation Phase/EPOS IP
Journal Title: Solid Earth
Publisher: Copernicus
Volume: 12
Issue: 2
Publisher DOI: 10.5194/se-12-521-2021
Page Start: 521
Page End: 537
EISSN: 1869-9529
ISSN: 1869-9510
TU Affiliation(s): Fak. 6 Planen Bauen Umwelt » Inst. Angewandte Geowissenschaften » FG Angewandte Geophysik
Appears in Collections:Technische Universität Berlin » Publications

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