Application of Borehole-to-Surface Electromagnetic Method in Evaluating Remaining Oil Distribution in Ultra-deep Carbonate Reservoirs

This paper presents the application of the differential borehole-to-surface electromagnetic method to evaluate the distribution of remaining oil in ultra-deep carbonate reservoirs in western China. The method involves multiple excitations within the target formation, followed by differential processing of phase parameters to obtain a 3D data volume of differential phase anomalies. These anomalies are used to analyze the spatial distribution of residual oil, with a theoretical resolution of 5 meters vertically and ±12.5 meters laterally. The study, conducted in a reservoir at depths of 6,100 to 6,500 meters, demonstrates the method’s ability to distinguish fluid properties and effectively evaluate remaining oil distribution. Results from production wells validate the reliability of the electromagnetic predictions, highlighting the method’s high resolution and precision in ultra-deep oil exploration.