Joint 3D Inversion of BSEM and TFEM Data

The borehole-to-surface electromagnetic method (BSEM) and the time-frequency electromagnetic method (TFEM) are two controlled-source electromagnetic methods (CSEM) for identifying oil and gas reservoirs in the sub-surface. For both methods, oil and gas targets are predicted by making use of resistivity and polarization parameters of sub-surface reservoirs, and desirable outcomes have already been achieved. Each method has its own advantages and disadvantages respectively. In order to further improve the results of the BSEM and TFEM in detecting hydrocarbons and delineating the oil-water boundary, we propose a joint BSEM and TFEM exploration technique. This paper focuses on 3D joint inversion of BSEM data and TFEM data. First, we describe a 3D joint inversion algorithm of the BSEM and TFEM based on the quasi-analytical approximation (QA) algorithm and re-weighted conjugate gradient (RRCG) algorithm. We then test the inversion algorithm for its effectiveness by using synthetic data. The inversion results of synthetic data show that the joint inversion results derived from the data of two methods are better than those from using only BSEM or TFEM. Therefore, our results illustrate that the joint exploration can improve processing and interpretation accuracy of the CSEM method.