| Simultaneous extraction of oil and sand during cold production of heavy oil generates high-porosity channels termed "wormholes". The development of wormholes causes reservoir pressure to fall below the bubble point, resulting in dissolved-gas coming out of solution to form foamy oil. Amplitude anomalies in the vicinity of the borehole observed in time-lapse seismic surveys are possibly a result of the presence of foamy oil and wormholes. These results can be used to image the drainage pattern, which reflects the foamy oil and wormhole footprints, for infill drilling designs. The use of time-lapse reflection seismology for detecting the presence of foamy oil and wormholes is discussed here. This thesis presents one of the first comprehensive seismic modeling studies of these cold production phenomena.; The presence of small amounts of gas within the foamy oil can dramatically decrease the fluid bulk modulus, reducing the P-wave velocity of saturated sands. Elastic moduli and velocities, under gas influence, have been modeled to an in-situ reservoir in a Western Canadian heavy oil field. 2D numerical seismic responses of foamy oil zones show amplitude anomalies and traveltime delays when pre- and post-production results are compared. (Abstract shortened by UMI.)... |
