| 摘要 |
<p>A method for creating a second borehole 2 in an earth formation 4 at a selected orientation relative to a first borehole 1, wherein a position parameter represents a position of the first borehole 1. The method comprises: a) providing a borehole element 14 that generates a magnetic field and is adapted to be arranged in the first borehole 1; b) measuring at least one component of the magnetic field at a selected distance from the borehole element 14; c) installing the borehole element 14 in the first borehole 1; d) measuring the magnetic field in the second borehole 2 using magnetometer means 28; e) providing a finite element model of the magnetic field using each component of the magnetic field measured in step (b) as a boundary condition for the finite element model; f) calculating the magnetic field in the second borehole 2 using the finite element model, and determining a difference between the calculated magnetic field in the second borehole 2 and the measured magnetic field in the second borehole 2; g) adjusting the position parameter so as to minimise said difference; and h) determining a selected direction dependent on the adjusted position parameter and further drilling the second borehole 2 in the selected direction.</p> |
