The seismic conversion log and its application to vertical seismic profiling at the German Continental Deep Drilling Site (KTB)

The conversion of compressional to shear waves in a vertical seismic profile (VSP), recorded in 1999 between 3-8.5 km depth at the German Continental Deep Drilling Site (KTB) was quantified with the newly developed conversion log method and analyzed in detail. The experiment yielded high quality seismic data in terms of signal bandwidth, signal-to-noise ratio, amplitude reference, and stability of the source signal. Important facts were obtained: The source signal proved to be simple. Its multi-phase signature is a result of multi-pathing within the crust. The determination of attenuation values in a complicated crustal environment is hampered by the structural features. In a scattering environment the wave conversion log method is not only capable of determining the conversion amplitude from the direct vicinity of the borehole but also from distant conversion points. The conversion in the field data as well as in model data is frequency dependent in an unusual manner; intermediate frequency signals (30-60 Hz) convert less than low (15-30 Hz) and high frequency signals (60-240 Hz). In the crust at the KTB site only about 10% - 50% of the conversion originates from the variation of the mineral composition of the rocks. Wave conversion depends on the fracture density. However, wave conversion is also highly dependent on chlorite content that seems to 'heal' the influence of cracks and fissures. This is important for crustal surface seismic experiments aiming at the reflection analysis of fault zones

Near‐surface fault detection using high‐resolution shear wave reflection seismics at the CO2CRC Otway Project site, Australia

High‐resolution, near‐surface, shear wave reflection seismic measurements were carried out in November 2013 at the CO2CRC Otway Project site, Victoria, Australia, with the aim to determine whether and, if so, where deeper faults reach the near subsurface. From a previous P wave 3‐D reflection seismic data set that was concentrated on a reservoir at 2 km depth, we can only interpret faults up to 400 m below sea level. For the future monitoring in the overburden of the CO2 reservoir it is important to know whether and how the faults continue in the subsurface. We prove that two regional fault zones do in fact reach the surface instead of dying out at depth. Individual first‐break signatures in the shot gathers along the profiles support this interpretation. However, this finding does not imply perforce communication between the reservoir and the surface in the framework of CO2 injection. The shear wave seismic sections are complementary to existing P wave volumes. They image with high resolution (better than 3 m vertically) different tectonic structures. Similar structures also outcrop on the southern coast of the Otway Basin. Both the seismic and the outcrops evidence the complex youngest structural history of the area.BMBF, 03G0797A, Verbundprojekt UR VI: PROTECT; Vorhersage von Deformation für eine abgesicherte Speicherung von Kohlenstoff (PRediction Of deformation To Ensure Carbon Traps); Vorhaben: Subseismische Deformationsvorhersage potentieller Wegsamkeiten und ihre seismische Validierung - Sonderprogramm GEOTECHNOLOGIE

Near-surface fault detection using high-resolution shear wave reflection seismics at the CO2CRC Otway Project site, Australia

High-resolution, near-surface, shear wave reflection seismic measurements were carried out in November 2013 at the CO2CRC Otway Project site, Victoria, Australia, with the aim to determine whether and, if so, where deeper faults reach the near subsurface. From a previous P wave 3-D reflection seismic data set that was concentrated on a reservoir at 2 km depth, we can only interpret faults up to 400 m below sea level. For the future monitoring in the overburden of the CO2 reservoir it is important to know whether and how the faults continue in the subsurface. We prove that two regional fault zones do in fact reach the surface instead of dying out at depth. Individual first-break signatures in the shot gathers along the profiles support this interpretation. However, this finding does not imply perforce communication between the reservoir and the surface in the framework of CO2 injection. The shear wave seismic sections are complementary to existing P wave volumes. They image with high resolution (better than 3 m vertically) different tectonic structures. Similar structures also outcrop on the southern coast of the Otway Basin. Both the seismic and the outcrops evidence the complex youngest structural history of the area

Einsatz von 3D-Seismik zur Reduzierung des Fündigkeitsrisikos bei Geothermieprojekten : Endbericht ; Laufzeit des Vorhabens: 01.11.2006 - 30.06.2011

[no abstract available