Method and device for directional down-hole drilling
The invention concerns a method and a device for directional drilling of a hole, in particular when drilling curved holes for mining, drift mining or similar, whereby a drill support is used in the form of a flexible continuous drill tube with a proximal end and a distal end, that at the end of the drill support distal end is connected a down hole assembly comprising a drill bit for forming a drill string, which is fed into the gradually forming hole. To avoid and minimize the occurrence of “stick slip” during directional drilling, according to the method, the drill support while drilling is taking place is held fixed at its proximal end against rotation outside the borehole and the rotating motion for indexing the drill bit around an axis extending in the direction of drilling is performed in the area between the drill support's distal end and the drill bit while drilling is in progress.
1. Method of directional drilling of a hole, for which is used a drill support in the form of a flexible continuous drill tube with proximal end and distal end, that at the end of the drill support's distal end is connected a bottom hole assembly comprising a drill machine and a percussion tool acting on a drill bit for forming a drill string, which is fed into the gradually formed hole, the method including:
indexing the drill bit while drilling is in progress by gradually rotating around its axis between each blow of the drill bit,
performing the indexing in the area between the drill support's distal end and the drill bit, the indexing taking place when the drill bit is moving away from a rock surface or being in its retracted position,
carrying out the indexing using a rotatable fluid activated motor, a liquid driving fluid for which is fed via a passage that extends through the drill support; and
controlling the direction of the drill bit relative to the drill support using a controller including a motor adjustable joint, said bottom hole assembly including said controller.
2. Method according to claim 1 , whereby the drill bit rotates around the drill axis in defined steps by the fluid activated motor.
3. Method according to claim 1 , whereby the bottom hole assembly is of the type that allows some of the drive flow used to activate the drill bit action to be alternately diverted for rotating and indexing the drill bit.
4. Device for directional drilling of a hole, comprising a drill support in the form of a flexible continuous drill tube with a proximal end and a distal end and a bottom hole assembly comprising a drill machine and a percussion tool acting on a drill bit also allowing the drill bit to be rotated while drilling is in process the assembly being connected at the end of the drill support's distal part for forming a drill sting, and a means of feeding the drill string into the gradually forming borehole, wherein the bottom hole assembly comprises a fluid activated means for indexing and rotating the drill bit around an axis extending in the direction of drilling while drilling is in progress, the indexing means being so synchronized to the percussion tool that the indexing taking place when the drill bit is moving away from a rock surface or being in its retracted position, a passage extended through the drill support for supporting the indexing means with a liquid driving fluid, and wherein the bottom hole assembly comprises a controller including a motor adjustable joint to control the direction of the drill bit relative to the drill support.