4D地震探査によるオイルサンド貯留層の動的挙動把握

抄録

Time-lapse three-dimensional (3D) seismic monitoring study was conducted in the JACOS Hangingstone steam assisted gravity drainage (SAGD) operation area, Alberta, Canada. The objective of the study was to delineate steam-affected areas using differences between two 3D seismic data acquired at different production stages for efficient reservoir management.
The time-lapse surveys were acquired in February, 2002 and in March, 2006. As repeatability is important for the time-lapse seismic surveys, the two 3D seismic surveys were recorded with nearly identical field acquisition parameters and the data sets of both surveys were processed with identical processing flows.
P-wave and S-wave velocities of oil sands core plugs from the field were also measured under various pressure and temperature conditions to understand the relationship between seismic velocities and reservoir conditions. The laboratory measurement results were combined and a rock physics model was proposed to predict velocity changes of the oil sands under reservoir conditions expected during SAGD operations.
The two seismic volumes show significant differences in seismic character within the reservoir and time delays below the reservoir around the active SAGD well pairs. Synthetic seismic data based on the rock physics model were analyzed to evaluate seismic response changes of the time-lapse 3D seismic survey. From our analysis, the differences of the seismic responses between the two 3D seismic volumes can be quantitatively explained by P-wave velocity decrease of the oil sands layers due to the steam-injection. In addition, our result suggests that a larger area would be influenced by pressure than by temperature.
In conclusion, the time-lapse 3D seismic monitoring along with the rock physics model is useful for qualitative and quantitative estimate of the rock property changes of the interwell reservoir sands in the field.