| 摘要 |
<p>A method and apparatus is provided for measurement-while-drilling utilizing improved antennas. An elongated tubular member (39) is provided with an outer peripheral surface having a contoured portion (45) defining a plurality of discrete communication regions of (47) reduced radial dimension. An antenna pathway (91) is defined in the elongated member substantially transverse to the plurality of discrete communication regions. An antenna member is partially disposed in the antenna pathway with portions of the antenna member extending out of the elongated member at the plurality of discrete communication regions to facilitate communication of electromagnetic energy. In a reception mode of operation, the antenna member detects electromagnetic energy in the wellbore and generates a current corresponding thereto. If operated in a transmission mode of operation, the antenna member emits electromagnetic energy in the wellbore in response to an energizing current. Preferably, the plurality of discrete communication regions are circumferentially disposed about the elongated member. Means is provided for preferentially communicating electromagnetic energy with particular portions of the antenna member which are disposed in the plurality of discrete communication regions. In one particular embodiment, a plurality of electrically-operable magnetic circuit elements are provided for communicating with particular ones of the plurality of discrete communication regions of the antenna member, for altering antenna gain in response to at least one control signal.</p> |
