| 摘要 |
A method for operating an earth formation drilling device arranged to supply a jet of abrasive fluid for the purpose of providing a borehole by removing earth formation material through abrasion, comprises a drill string and a drilling assembly connected to the drill string. Said drilling assembly comprises a jetting device with a mixing space, a drilling fluid, a particle inlet, an abrasive fluid outlet for discharging a mixture of drilling fluid and magnetic particles, and a magnetic particle circulation system comprising a supporting surface which is exposed to a return stream along the drilling assembly. Furthermore, a magnetic device is provided for attracting the magnetic particles onto the supporting. Said method is characterized buy the steps of : -fixing the magnetic device with respect to the supporting surface, -selecting a magnetic field density which increases along the sloping supporting surface towards the entrance, -attracting magnetic particles onto the supporting surface under the influence of the fixed magnetic device, -making the magnetic particles move over the sloping supporting surface (under the influence of the magnetic field of the magnetic device. |
