| 摘要 |
The invention relates to a ranging system (1) for controlling a drilling process downhole. The ranging system has a longitudinal direction and comprises a drilling tool (2) for drilling a first borehole (3), the drilling tool having a tool axis (4) and comprising a magnetic field source (5) in the form of an electromagnet generating a magnetic field (6) and having a magnetic field source axis (7) which is substantially parallel to the tool axis. Moreover, the ranging system comprises a sensing tool (8) arranged in a second borehole (9) for measuring the magnetic field by means of at least two sensor units (10), which sensor units are arranged at a distance (D) from each other along an axis of the sensing tool.
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