Some key challenges in thermal heavy oil recovery include how to monitor steam flood effectiveness and cap-rock integrity. Kuwait Oil Company acquired baseline 3D VSP surveys in January 2016 as geophysical surveillance projects for a steam flood pilot. This paper presents a technical approach of 3D VSP acquisition design, data processing, seismic inversion, quantitative interpretation and its application for the monitoring of steam movement.
Applying pressured steam to a reservoir can lead to damage of overlying cap-rock and could cause energy leakage through fractures. The technique of baseline 3D VSP and future time-lapsed 4D VSP are designed to image steam flood movement within the reservoirs. The possible applications of 3D/4D VSP technology include imaging the steam chamber size of a 30-day steam cycle, reservoir characterization and investigating integrity of the sealing cap shale.
Extensive planning and immaculate execution of the 3D VSP operations resulted in timely completion of survey acquisitions with high quality data. Because of the optimized acquisition parameters, the frequencies attained in these surveys were more than 30% higher than previously achieved in this same area. Extensive modeling enabled innovative customization of the acquisition design, optimized parallel processing, and interpretation techniques have allowed for a time effective acquisition-to-results turnaround that may affect the second cycle of the steam injection program. Resulting analysis on processed data clearly indicate the steam flow shape and direction. These significant results are providing important input for development decisions.
The reduction of the bin size from high fold and tight source / receiver distribution proven to be an effective and high quality method for imaging shallow geological target reservoirs. The resulting high frequencies obtained allowed for better vertical and spatial resolution, which enabled steam chamber size estimation and study of cap-rock integrity.