A Study On Calibration And Borehole Effect Of Three-dimensional Induction Logging

Induction logging is one of the most important methods in the areas of resistivity measurement. Resistivity is a key parameter to analysing the lithology, reservoir hydrocarbon saturation, and the oil and gas evaluation. The three-dimensional (3D) induction logging is the newest induction logging tool at home and abroad. It not only can simultaneouslly measure the horizontal resistivity and vertical resistivity, but also obtain the dip and azimuth information. It is a significant method to identify shale, thin interactional low resistivity reservoir and suitable for the vertical, deviated and horizontal wells. The3D induction logging instrument design, measurement theory and data processing are very compliated. There are many problems to be solved. The thesis studies the basic theory of the3D induction logging, calibration method and the characteristics of the borehole effect. The results provide the theoretical guidance for the development of3D induction logging tool. It has a theoretical and practical importance.Firstly, the thesis discusses the basic theory of the3D induction logging. The electromagnetic field calculation formula, tensor voltage formula, tensor conductivity formula, and the transform relations of tensor conductivity and axis conductivity in the isotropic and anisotropic formations are derived and build. They are the foundation of the study on3D induction logging theory.Moreover, we studies one-dimensional, two-dimensional and three-dimensional geometric factors of the3D induction logging. These geometric factors are programmed by the MATLAB language. The response characteristics of geometrical factor s are calculated and analysed. The results show that the borehole effect on the horizontal component and cross-component of the measurements is more serious than that on the vertical component.Secondly, the calibration methods of3D induction logging are studied. Formulas of the nine calibration factors are derived and programmed. The code can calculate the calibration factor of given position of three transimitters and three receivers. It considers the effects of the calibration ring position, azimuth and inclination change and the location. The program can be used to calculate and analysis the calibration factors, determine the scale ring size and the best scale position, explain the variations of the measured signal with the scale central location, azimuth and inclination changes. It is an essential tool in the calibration of3D induction logging instruments.Finally, we study the3D numerical modeling of the borehole effect on measurements of the3D induction logging. It is calculated and analysed that the borehole effect generated by factors such as the borehole diameter, mud resistivity, boundary of the interface formation, formation dip, and azimuth. It uses the COMSOL software. The results show that the3D induction tool is more sensitive on the dip and azimuth, and the conductivity of borehole mud.