Comparison of Detection Capability by the Controlled Source Electromagnetic Method for Hydrocarbon Exploration

Abstract

Marine controlled-source electromagnetic (CSEM) is an efficient offshore hydrocarbon exploration method that has been developed during the last 18 years. Sea Bed Logging (SBL) and towed streamer electromagnetic (TSEM) are two different data acquisition systems. We compared these two methods by using 1D sensitivity modeling and 2D Occam’s inversion. Based on this research, we tested the effect of frequency, offset range, water depth, reservoir size, and reservoir depth on the detection capability of the two acquisition methods in terms of sensitivity. In order to test the methodology clearly and simply, the geological model was extremely simplified for the inversion. The effect of these parameters on resolution was checked as another purpose. To easily evaluate our inversion results, a simple quantity was employed that we called the anomaly transverse resistance ratio. In the shallow water environment, both the SBL and the TSEM systems had a good sensitivity to the high resistivity targets. However, in the deep water environment, the SBL system had a low noise floor. Then, it could provide better detectability to the deep target. The TSEM had the advantage in terms of the horizontal resolution because of the dense in-line sampling of the electric field.