2-D Pixel-Based Inversion for Simultaneous Reconstruction of Resistivity and Dielectric Constant From Electromagnetic Logging-While-Drilling Measurements

The dielectric effects are significant in certain circumstances in hydrocarbon exploration and production. Neglecting these effects can result in an inaccurate description of subsurface structure in terms of resistivity estimation and boundary location. However, almost all existing research has ignored the dielectric effects in the inversion process for ultradeep electromagnetic logging-while-drilling (LWD) measurements. As a complement, this article aims to investigate the impact of the dielectric constant on the inversion performance. In this study, we present the possible causes of the appearance of large dielectric constant in formations and discuss the influence of dielectric constant on one set of measurements via the sensitivity study. Besides, a 2-D pixel-based inversion algorithm is introduced for simultaneous determination of resistivity and dielectric constant. Also, the gradient of measurements with respect to interested parameters using the adjoint method is provided and validated. In addition, the capability of the inversion approach is demonstrated with several numerical examples. It is found that accounting for the dielectric constant in the inversion can help to improve the interpretation of electromagnetic measurements in some scenarios, thus enhancing the understanding of the subsurface structures.