oa Heuristic Model of Hydrocarbon Reservoir Related Microtremors

A number of surveys over different oil and gas fields throughout the world have reported the presence<br>of spectral anomalies in the passive seismic wavefield (between about 1 Hz and 6 Hz), with a high<br>degree of correlation to the location of hydrocarbon reservoirs. If these microtremors originate from<br>the reservoirs, they can be used as a reservoir indicator and for reservoir characterization. A<br>preliminary model is presented to explain the potential source mechanism of microtremors generating<br>the spectral anomalies. Poroelastic effects due to wave induced fluid flow and oscillations of different<br>fluid phases are significant processes in the low-frequency range which can modify the earth’s<br>omnipresent seismic background spectrum. These processes only occur in partially saturated rocks. We<br>assume that hydrocarbon reservoirs are partially saturated whereas the surrounding rocks are fully<br>saturated. Real data observations are in general agreement with this conceptual model.