Simultaneous determination of relative angles and anisotropic resistivity using multicomponent induction logging data

摘要

Modem induction tools with multicomponent transmitter-receiver configuration provide direct measurements to derive both horizontal and vertical resistivity that is essential in delineating low resistivity reservoirs frequently encountered in hydrocarbon exploration. The multicomponent induction data are unfocused and nonlinear functions of resistivity structures and geometric factors such as relative dip and azimuth angles. Previous inversion techniques assume the knowledge of relative dip and azimuth. In reality, however, we do not always have accurate a priori information about this angle information. Inappropriate assumption about relative dip and azimuth angles can lead to incorrect inversion results. It is necessary, therefore, to appropriately treat relative dip and azimuth angles in the inversion. In this paper, we first investigate how relative dip and azimuth angles affect multicomponent induction logging data by performing sensitivity analysis. We then explore possible means to extract relative dip and azimuth information from multicomponent induction logging data from inversion. We design a simultaneous 1D inversion method to recover relative dip, relative azimuth, horizontal resistivity, and vertical resistivity. The objective function used in our inversion algorithms assigns the same importance to each inversion parameter. The inversion process is constrained with outside penalty functions. Numerical data tests indicate that our new inversion algorithm can effectively extract information about formation dip as well as anisotropic resistivity structure from multi-component induction logging data.