Multi-mode seismic source for underground application

Abstract

A new multi-mode downhole acoustic source has been designed to fulfill requirements of oil business. Three acoustic modes of radiation, i.e., monopole, dipole, and quadruple modes, respectively, are considered to assess the properties of the oil reservoir. Because of the geometry of the well it is challenging to design an efficient and effective powerful device. This new source uses an apparatus to convert the axial motion of the four motors distributed on the azimuth into a radial one. In order to make this conversion effective, the axial motion transformation into a radial one is performed thanks to a rod rolling on a cone; this conversion minimizes the loss by friction and is very effective. The conversion apparatus is also exploited to match the acoustic impedance of the surrounding medium. This new design is described in this paper as well as intensive modeling which allowed optimizing this multi-mode source device. Experimental data is in a good agreement with numerical modeling.