Identification of reservoir characteristics based on seismic velocity tomography using microearthquake method in "x" geothermal field

This research studies microearthquake (MEQ) data analysis in "X" geothermal field. The data was recorded in two phases; before and during drilling, with a total number of 2863 events recorded. The quality assessment method was applied using wadati diagram analysis in order to select the best quality data for advance processing. The result shows that the MEQ events are having trend of Vp/Vs ratio around 1.76. The MEQ data then processed using tomography inversion technique to obtain the image of subsurface seismic velocity structure. The results of seismic tomography inversion shows anomaly pattern which consistent with the lithology and geological structure. The results also shows a good agreement with the interpretation of resistivity section from magnetotelluric (MT) data, as well as from geochemical data. The region infered as reservoir zone are observed with dominantly high Vp/Vs anomaly which indicates incompressible characteristics that may relate to existence of water content, while the low Vp/Vs anomaly which indicates steam cap existence are not observed in this region. This pattern of anomaly leads to inference that the reservoir characteristics are dominated with liquid phase of fluid.