A real-time borehole correction of electromagnetic wave resistivity logging while drilling

Abstract

The response of electromagnetic wave logging while drilling is influenced greatly by borehole and drilling fluid resistivity when the size of borehole is relatively large and drilling fluid resistivity is low. Borehole radius and drilling fluid resistivity were introduced to obtain more accurate transformed resistivity on the basis of the commonly used resistivity transformation model. The influence of borehole was considered in the newly established three dimensional transformation model, and a new borehole correction method was proposed. The resistivity transformation database can be established by calculation according to a certain instrument, and the true resistivity is obtained by three dimensional interpolation search technology of real-time correction in practical use. The results of numerical simulation and modeling verification show that the transformed resistivity by real-time correction coincides with the resistivity corrected by charts. The method can eliminate the borehole influence, reduce calculation dimension, and improve the inversion efficiency of highly deviated and horizontal wells logging data. Key words: electromagnetic wave logging while drilling, resistivity, borehole influence correction, resistivity transformation model