Directional measuring device for use in oil or gas exploration, has transmission and receiving coils some of which are wound on screen with slit(s) or element(s) inclined to borehole axis

摘要

A directional measuring device has transmission coil(s) and receiving coil(s) mounted on a support suitable for going down a borehole. Each coil can emit or receive energy in azimuth, axial and radial directions. At least one of each type of coil is wound around a screen having slit(s) or conductor element(s) inclined to the longitudinal axis of the support. Independent claims are included for the following: (a) a device similar to that above, where the screen interacts with the coils to attenuate selectively the energy field in at least one of the directions; (b) a directional measuring system for a directional drilling system having a first sub-assembly at the bottom of the drill string and adjacent to it, a second sub-assembly including a drill bit, where each assembly has antenna(e) with coils wound on a screen as above; (c) directional measurement of a subterranean formation surrounding a borehole using a device as above, where energy is emitted alternately from a screened coil and an unscreened coil and the reflected energy by both types of coil, and the screened coils are then rotated 180 deg about the borehole axis and the signals are emitted and received as before; and (d) directional measurement of a subterranean formation surrounding a borehole using a device as above, where energy is emitted from a screened coil and received by a unscreened coil or emitted from an unscreened coil and received by a screened coil. Preferred Features: The device measures the resistivity of the surrounding formation.