Reeck, Konstantin, Jegen, Marion , Elger, Judith and Berndt, Christian (2021) Joint integration of velocity and resistivity to improve gas hydrate estimates - A case study from SO227/266. [Poster] In: 81. Jahrestagung der Deutschen Geophysikalischen Gesellschaft (DGG). , 01.03.-05.03.2021, Kiel (online) .

Abstract

Gas hydrate dynamics may impact the global carbon cycle and global warming. They may be used as a possible future energy source, but their dynamics may also influence slope stability. Therefore, their occurrence, formation, dissociation, and mobilization are of high interest. The quantification of gas hydrates in continental margins, either by drilling or geophysical methods, is the bases to understanding gas hydrate dynamics. To provide estimates of the gas hydrate saturation the common methodology reaches from the simple detection of gas hydrates by seismic imaging to more sophisticated approaches using the combination of geological, geochemical and geophysical methods. While most geophysical experiments use empirical relationships like Archie’s Law to derive saturations from remotely sensed data, a coupling of rock physics and geophysics by effective medium modeling offers new perspectives to directly invert for porosity, gas and gas hydrate saturations. We apply a joint elastic and electric approach by using a self-consistent approximation/differential effective medium model (SCA-DEM) on data from downhole P-wave velocity and induction sensors, recorded in a sedimentary setting at Formosa Ridge south-westoff Taiwan. In a first step, we construct a background model and derive porosity distributions from the data. Subsequently, we invert the complete borehole dataset for gas and gas hydrate saturations. A sensitivity analysis shows how the joint elastic andelectric approach is able to distinguish between gas and gas hydrate saturations and thereby overcomes the widely observed disagreement in saturation levels between seismic and electromagnetic methods. This approach lays the foundation to directly derive saturation levels from an existing joint geophysical electromagnetic and seismic dataset at Formosa Ridge.

Actions (login required)

View Item