| Title | Identification of Fluid Zone Using Vp/Vs Ratio Structure Derived from Micro-Seismic Tomography in Geothermal Exploration |
|---|---|
| Authors | Andri Dian Nugraha, ,Ahmad Syahputra, Sri Widiyantoro, Rachmat Sule, Dody Astra |
| Year | 2013 |
| Conference | Indonesian Geothermal Association Conference |
| Keywords | |
| Abstract | Micro-seismic events are routinely observed due to hydraulic fracturing, fluid injection, and signature normal earthquakes from local fault activities during geothermal exploration. A micro-seismic event generates and propagates seismic waves (P-and Swaves) through the medium beneath subsurface recorded by receivers on the surface or in a borehole (seismograph or geophone). Vp/Vs ratio is one of physical properties that can be used to determine fluid-filled rock zone. In this study, we used data catalog of micro-seismic events including P-and Swave arrival times, origin times, source and receiver locations to invert for seismic velocities structure especially for Vp/Vs ratio structure using tomographic inversion method in a geothermal field. Our tomographic inversion results show a prominent feature of high Vp/Vs ratio a depth of about 0.25 km to 1.25 km (beneath the Mean Sea level) around injection wells. This high Vp/Vs value coincides with low Vp and low Vs values as indication of high pore fluid pressure. Our interpretation is that high Vp/Vs with low Vp, and low Vs may be related to fluidfilled rock zone from the injection well. From this study, we can show that seismic tomography inversion represents one of powerful methods to delineate the subsurface structure, especially for reservoir characterization. |