Method for determining a wellbore position with respect to an earth formation layer boundary

摘要

Methods for determining a position of a wellbore with respect to layer boundaries in earth formations include projecting a trajectory of the wellbore onto an initial model of the earth formations, selecting a segment of the trajectory and calculating along the segment expected responses of a well logging instrument. Differences between the expected responses and responses measured by the instrument along the segment are determined. The model is adjusted, the expected responses are recalculated and the differences are again determined. These are repeated until the differences fall below a selected threshold. In one embodiment, the trajectory of the wellbore can be adjusted to remain within a selected distance of a selected one of the layer boundaries.