Application of Steering Downhole Motor

Directional drilling is a way to drill the target along with the designed axial line. To do this, except for applying downhole motor, it is required to use a complete system, combined with float sub, bent sub, steel collar, non-magnetic collar, stabilizer, bit as well as MWD system. Our downhole motor is one ofthe drilling tools to perform this operation.

1. Our downhole motor meets the demands of directional drilling.

2. Bent sub is composed of bent nipples, with its male thread onto the top of the drill. The top of bent nipple is connected with collar. Thus, there forms an angle between collar and the drill. This angle plays a key role in determining directional oblique angle. The angle degree of bent sub ranges from 0° to 3° which is decided by the customers. The factors of change of hole size, hole deviation angle and footage rate shall be considered in selection of bent subs. The angle of bent sub may directly affect the hole deviation angle and inclination change (See Table-4).

If the bent nipple has muleshoe key on it, you should examine the alignment between the key and bent sub, to ensure correct directional azimuth. If using magnetic deflection, you should examine the interaction between the alignment line and polarity of the magnet inserted in the collar, and record it befor operation.

3. Influence of Opposite Torque to Directional Driling:

The downhole motor combination will be stripped in with the drill pipe into the scheduled depth of directional deflection, deforming under the reaction of opposite torque from the schedule depth to the platform. When enhancing drilling weight, the drill may output a certain torque. Thus, the opposite torque of same force and reverse direction will react on the combination, causing torsion deformation. This will, of course, affect the directional azimuth.

During the period of directional drilling, the opposite torque shall be considered to ensure correct direction. The degree of opposite torsion angle caused by the opposite torque depends upon:

• Drilling weight
• Type and length of drill pipe
• Size of deviation angle
• Type and length of collar and heavy drill pipe
• The quantity and length of centralizer, when completed with centralizer for the opposite torsion angle of drill string, refer the data in Table-5.

If deviation of scheduled direction occurs, during on-going deflection with the planed deviation angle, it is advised to refer Table-6 to obtain effective azimuth change, which is less affecting the deviation angle.