The Research On Electromagnetic Logging Response In Anisotropic Formation Using Finite Difference Time Domain Method

Along with the continuous development of petroleum industry, and the continuous improvement of drilling technology and logging technology, high angle well, multilateral well and horizontal well gradually become the oil-gas field exploratory and exploitation technology of high efficiency and high benefit; and its proportion becomes bigger. Then,anisotropic oil-gas field is 20% in the proportion of all discovered oil-gas fields. Moreover, in the anisotropic formation, these logging responses are very different from those responses of traditional vertical borehole in isotropic formation. So, researching electromagnetic logging response in anisotropic formation has important signification to the explanation of log information and geological evaluation.In the thesis, the response of three species electromagnetic logging in anisotropic formation was researched using the three-dimensional finite different time domain (FDTD) method in cylindrical coordinate system, including electromagnetic logging while drilling, high frequency electromagnetic logging and electromagnetic pulse logging. And the achievements are obtained as following: (1) the basic theory formulas of three-dimensional cylindrical coordinate system finite different time domain method in anisotropic formation are developed. The rotation formulas of conductivity tensor and the iterative formulas of electric field component difference are deduced particularly. Then, this method programme is compiled on the Matlab7.01 software, and the validity of programme is validated. (2) Using finite different time domain method, the influencing regularity of electromagnetic logging response while drilling are simulated in inhomogeneous isotropic formation and complex formation considering drilling collar, mud, invasion and permittivity. (3) Using finite different time domain method, the influencing regularity of high frequency electromagnetic logging are simulated in uniform anisotropic formation and complex anisotropic formation considering mud, shoulder, invasion and other factors. (4) Using finite different time domain method, the influencing regularity of electromagnetic pulse logging are simulated in uniform anisotropic formation and complex anisotropic formation considering mud, shoulder, invasion and other factors. The results provide definite theory support to the development of electromagnetic pulse logging instrument and the log interpretation in anisotropic formation.