The effects of near well heterogeneities on single-well imaging: numerical studies

Abstract

Single-well imaging plays an increasingly important role in the exploration and production of hydrocarbon in horizontal wells. Depending on the scattering strength, reflections from lateral sections below heterogeneous regions around the borehole suffer signal distortion and amplitude loss, which complicates the imaging of deeper structures. Thus, the understanding of scattering phenomena and their impact on single-well imaging is of significant interest for hydrocarbon exploration. This paper establishes a complex horizontal well numerical model with which the effects of heterogeneous overburden on deep reflection imaging are studied using dipole acoustic logging. Synthetic data were analyzed with respect to the observed reflectivity in the heterogeneous layer and along the deep reflection. The results show that strong velocity fluctuations increase the severity of the scattering effect when correlation distances are in the order of the dominant wavelength. The reflection images migrate and reveal additional structural details of the medium. Low frequency band imaging enables the extraction of undistorted real reflectors by using the Reflection Image Spectroscopy method. The results explain the influence of the heterogeneous overburden on single-well imaging results and provide theoretical guidance for logging interpretation.