Efficient inversion systems and methods for directionally-sensitive resistivity logging tools

摘要

Various resistivity logging tools, systems, and methods are disclosed. At least some tool embodiments include transmit and receive antennas that measure the electromagnetic response of the formation, at least one of which is tilted to provide a directional sensitivity. A processor converts the response (measured as a function of the tool's rotation angle) into a set of inversion parameters, which are then used to estimate the anisotropic properties of the formation. The set of inversion parameters includes at least one parameter based on an antipodal sum of the response signal, and may further include parameters based on an antipodal difference and an average of the signal response. Antipodal sum and difference values at different rotational orientations can be included in the set of inversion parameters, and they may be normalized to reduce environmental effects. Some tool embodiments collect the relevant formation measurements using parallel or perpendicular tilted antennas.

主权项

1. A system comprising:
a logging tool having a tool axis, the tool comprising: at least one transmit antenna to transmit an electromagnetic wave into a formation; and at least one receive antenna to receive an electromagnetic wave from the formation, wherein at least one of the transmit and receive antennas is tilted with respect to the tool axis; the system further comprising at least one processor coupled to the at least one receive antenna to convert the receive antenna's response, as a function of a rotational angle of the tool about its axis, into at least one antipodal sum value for a given position of the tool in a borehole in the formation, wherein the at least one processor serves to determine one or more anisotropic formation parameters based at least in part on said at least one antipodal sum value.