| 摘要 |
A diagraph in a borehole is arranged so at least one of its antennae is inclined to the instrument axis to have a magnetic dipole corresponding to an azimuth angle. While the diagraph is rotated in the borehole, electromagnetic energy is emitted and the resulting voltage signals measured directionally as a function of the azimuth orientation of the diagraph. The diagraph is equipped with at least first emitting and receiving antennae separated by a first distance, at least one of the first antennae having a magnetic dipole inclined relative to the longitudinal axis of the instrument, the antennae being oriented around the axis of the instrument so at least one inclined magnetic dipole corresponds to a first azimuth angle. The azimuth variation of the first signals is adjusted by approximation functions. The adjusting stage is executed while the first voltage signals are measured and the adjustment is stopped when a convergence is reached. The adjustment functions are sinewaves defined by the coupling components of the magnetic dipoles of the first emitting antennae and the orientation vectors of the first receiving antennae. The adjustment functions are functions of the rock formation parameters including the resistivity of the rock layers, the position of the diagraph, the deviation of the probe, the azimuth angle at the diagraph position or a combination of the above. The adjustment coefficients are terms of constants, sinphi, cosphi, sin2phi and cos2phi which define an iterative adjustment algorithm to determine the azimuth proportion of the directional vectors. The adjustment algorithm is used to select directional measurements in real time to be used as guidance. The diagraph also has second emitting and receiving antennae spaced from the first and arranged so the second azimuth angle is 90degrees from the first. The second antennae are arranged and operated like the first. The dephasing and attenuation between the two sets of voltage measurements are calculated and combined to generate a symmetrical or asymmetrical measurement. Only one of the first antennae has an inclined magnetic dipole and the noise of the first and second voltage signals is measured using the second harmonic coefficients. Alternatively, all the first antennae have inclined magnetic dipoles and the adjustment coefficients and noise are measured using the third harmonic coefficients. An Independent claim describes the equipment for carrying out this method, using a diagraph with first and second pairs of emitting/receiving antennae and data handling and recording equipment.
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