Timelapse Seismic Modelling of CO2 Fluid Substitution in the Redwater Leduc Reef, Alberta

摘要

Ray tracing and finite difference modeling were undertaken to evaluate the variations in seismic response of the Redwater reef along a 2D line across the reef with 40% CO2 saturation in upper-Leduc zone. The input geological model was based on well data. Ray tracing and finite difference synthetic seismic sections demonstrate similar seismic attributes for all formations. Cooking Lake and Beaverhill Lake formations display positive structure below the reef in time sections due to the lateral velocity change from on-reef to off-reef, but corrected in the depth sections. Terminations of the Upper and Middle Leduc events are obvious on the pre-stack time and depth-migrated sections. Higher amplitudes at the base of Upper-Leduc member are evident near the reef margin due to the higher porosity of the foreslope facies in the reef rim compared to the lagoonal facies within the center of the reef. Time-lapse seismology proved an enormous amplitude difference for the seismic data before and after 40% CO2 saturation. A high amplitude reflection at the top of upper-Leduc, top of the rim, and base of upper-Leduc near the reef edge was strong evident to monitor the CO2 saturation seismically.