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When selecting PDM for operations, it is necessary to take into account the size of well holes, drilling trajectory required, bottom temperature, drill requirements, water eye pressure drop, flow, stratigraphic configuration and other factors to select the specifications of drills for developing operational plans. The onsite construction must be strictly in accordance with the operating plan having been formulated.

Carry out ground check before sending PDM down to the well
1. Check the connecting threads to see whether all the threads are applied with thread pastes except the connecting threads between the lifting pipe nipples and the bypass valves, to prevent the screw from getting loose.
2. Check the bypass valve: connect the drill bit to the spindle of the drill and put the drill into a position on the dial suitable for observing the bypass valve; lock it with slips; remove the lifting nipples, and press the spool to the lower dead point with a wooden stick; inject water from the top. The bypass valve should have no leakage; after releasing the pressure, the spool can automatically reset. This indicates that the bypass valve is normal.
3. Connect the square drill pipe, and remove the slips; lower the drill so that the bypass valve body is at a position under the dial that is easy to be observed; start the mud pump, then there should be mud jetting out from the bypass hole on the bypass valve. Gradually increase in the flow until the bypass valve is closed. Lift the PDM drill to see if the drill is rotating. At this time, the bypass valve should be well closed without mud flowing out.
4. At the end of ground inspection, connect the parts according to the designed combination of drill strings. When lowering the drilling down to the well, it is necessary to control the lowering speed to prevent damages to the drill due to bumping into the sand bridge, stairs on the well walls, tube overshoes and the like. If the drilling is impeded, start the pump for cycling, and have it slowly slide by. In the case that directional drills or PDM with curved joints encounter barriers, it is necessary to rotate the drill string to allow it to pass by slowly to prevent biased movement.
When lowering the drill into an ultra-deep well or a high-temperature well, it is necessary to periodically conduct halfway open-pump cycle to reduce the temperature at the bottom of the well. If the drilling fluid cannot flow quickly into the drill string in the process of drilling down, slow down the drill speed or stop the drill to inject drilling fluid through punch irrigation. Never make percussion drilling or lower the drill seat directly into the bottom of the well.
5. Start the drill: when the drill is 0.3-1 meters from the bottom of the well, start the pump for circulation, and gradually increase the flow to the recommended values. Write down the pole pressure gauge readings and compare them with the calculated pressure value. Fully clean the bottom of the well. Slowly rotate the drill or rotate it in grades (30-45 degrees per time) in the process of cleaning. Clean out the bottom of the well. After the cleanout, lift the drill up for 0.3-1 meters, and re-check the circulating pressure.
6. Drilling in: lower the drill to the bottom of the well, and gradually increase the pressure of drilling; increase the motor torque value, and the values on the pole pressure gauge is increased. The increased pressure value should conform to the voltage drop of the motor required by the drill. As the PDM adopts the positive displacement motor, the display on the drill platform of the pole pressure gauge type is an important indicator for indicating whether the drill is in normal work. The increased values on the pressure gauge reflect whether the motor is working normally, and whether the load is appropriate. It can also reflect whether the bit weight is appropriate. The driller can learn about the working conditions of the drill through the drill. Normally, do not drill too fast at the beginning, which is conducive to the wear-in of the internal parts of the drill, and avoid abrupt bit weight to prevent the braking of the drill. Lowering the drill with an even force can ensure the smoothness of the slant hole interval and the accuracy of orientation.
7. Start drilling: the drilling process of the drill is similar to that of conventional drills, during which the bypass valve is in the open status, allowing the drilling fluid to access the annulus.
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