T.S. Schroeder, J.Q. Wu, and L.R.B. Hammons
Teleco Oilfield Services Inc., Meriden, CT
ABSTRACT
A model of the response of a 2 MHz MWD propagation resistivity tool indicates that the two resistivity measurements, amplitude ratio resistivity (Rar) and phase difference resistivity (Rpd), will separate when highly dipping thin beds are encountered. Several other environmental and tool related factors may also cause the curves to separate, and these must be considered when evaluating the dipping thin bed effect in field data.
The model has been used to construct charts for determining thin bed resistivities for given tool measurements and dips relative to the logging tool. Examples cited from the Gulf of Mexico demonstrate how these charts can be used with 2 MHz propagation resistivity data to evaluate geologic conditions, determine whether tool or calibration problems exist, and assess which of the two resistivity measurements best represents true formation resistivity.