Usage Instructions for Screw Drilling Tools

Before leaving the factory, all threaded connections of screw drilling tools are coated with anaerobic adhesive and tightened according to the specified torque. There is no need to retighten before use.

1. Ground Inspection

Before lowering the screw drilling tool into the well, a ground inspection must be conducted:

1. Lift the tool with a lifting short joint and place it in the turntable slip, ensuring the bypass valve is positioned above the turntable. Attach the safety slip and remove the lifting short joint.
2. Check the flexibility of the bypass valve by pressing down the valve core with a wooden stick, then release it. The valve core should return to its normal position under spring force. Repeat this process 3–5 times to ensure there is no sticking, and the valve moves smoothly.
3. Lower the bypass hole of the drilling tool below the drill floor and start the pump to ensure the bypass hole is closed. Activate the motor and drive the connection joint to rotate. After stopping the pump, the valve core should automatically reset, and mud should flow out from the bypass hole, confirming the tool is working correctly.

2. Lowering the Tool into the Well

When lowering the tool, control the descent speed strictly to avoid the motor reversing, which could cause the internal connections to loosen. Also, avoid damaging the tool by striking sand bridges, casing shoes, etc.

• For deep wells, high-temperature well sections, or sandy formations, periodic mud circulation is recommended to cool the tool, protect the stator rubber, and prevent sand blockage.
• When approaching the bottom of the well, reduce the descent speed and begin circulation at a low flow rate. Once mud returns to the surface, gradually increase the flow rate.
• Avoid sudden stops or placing the tool directly at the bottom of the well.

3. Drilling Operation

1. Prior to drilling, clean the wellbore and measure the circulating pump pressure.
2. Gradually increase the drilling pressure when starting, and the driller can use the following formula to control the operation:

Drilling pump pressure = Circulating pump pressure + Tool load pressure drop

3. In the initial stages of drilling, avoid excessive drilling pressure. The tool and bit may not be fully engaged, and the wellbore may not be cleaned properly, which can cause bit balling.
4. The torque generated by the tool is proportional to the motor’s pressure drop. Increasing drilling pressure will increase the torque.
5. Even and continuous drilling ensures a smooth wellbore curve and maintains good directional accuracy.

4. Pulling the Tool and Checking

1. Use clean water to flush the bypass valve and move the valve core up and down with a wooden stick to ensure it closes smoothly.
2. Secure the tool with a pipe wrench, rotate the drive joint clockwise with a chain wrench, and inject clean water into the tool to flush its internal parts. Finally, inject a small amount of mineral oil into the motor.
3. Pay attention to the pull-out speed to prevent stuck tools or damage.
4. Measure the bearing gap of the tool. If it exceeds the maximum allowable tolerance, the tool should be repaired and the bearings replaced. For workover tools, axial bearing gaps may need to be adjusted.

5. Ground Inspection Before Lowering the Tool

1. Except for the connection between the lifting short joint and bypass valve, all other shell connections of the screw drilling tool should be coated with a locking agent.
2. Use a screw drill bit handler to install the screw drill bit, and only use a chain wrench to rotate the tool’s drive shaft head. Rotation should only be counterclockwise to prevent loosening of internal threads.
3. Lift the short lifting joint and place the tool into the turntable, ensuring the bypass valve is positioned for easy observation. Fix the tool with a slip and remove the lifting short joint.
4. Check the bypass valve by pressing down the valve core with a hammer handle or wooden stick, then adding water to check if the valve leaks. If there is no significant water leakage and the valve core pops back to the original position, the bypass valve is working correctly.
5. While lowering the tool, ensure the bypass valve is positioned for easy observation. Start the drilling pump and gradually increase the flow rate until the bypass valve closes. Lift the screw drilling tool to check if the bit rotates. Ensure the valve is in the “closed” position, and no drilling fluid flows from the bypass hole. After stopping the pump, observe whether the bypass valve opens again and mud flows out of the bypass hole.

6. Lowering the Tool into the Wellbore

When lowering the screw drilling tool, control the speed carefully to avoid damaging the tool due to sand bridges, shoulder formations, or casing shoes. If encountering such well sections, the drilling pump should be activated to gradually enlarge the wellbore for passage.

When using a bent joint or bent casing, the screw drill bit may come into contact with the wellbore’s hard rock or casing shoe. Periodic rotation of the tool is recommended to minimize side drilling impacts.

For deep wells or high-temperature sections, periodic mud circulation is recommended to prevent bit clogging or stator damage due to heat.

If the drilling fluid cannot pass through the bypass valve quickly, slow down the descent or periodically inject more mud. Avoid sticking the tool or placing it directly at the bottom of the well.

7. Activating the Screw Drilling Tool

If the screw drilling tool is at the well bottom, it should be lifted 0.3–0.4 meters and the drilling pump activated. Record the standpipe pressure reading and compare it with the calculated pressure. If the pressure exceeds the hydraulic calculated value, it is usually caused by side drilling by the screw bit.

8. Wellbore Cleaning

Especially in directional wells, the wellbore must be kept clean. Accumulated or settled rock cuttings can affect the rotation speed or cause borehole deviation. It is recommended to clean using the normal drilling fluid circulation. The screw drilling tool can also be rotated intermittently (30°–40° per rotation) to clear debris from the wellbore.

After cleaning, lift the screw drilling tool 0.3–0.4 meters and recheck the pressure.

9. Pulling the Tool

When pulling the tool, the bypass valve should be in bypass mode, allowing drilling fluid to enter the annulus, but the screw drilling tool itself cannot discharge drilling fluid. Typically, heavy-weight drilling fluid is injected above the drilling column before pulling to ensure smooth fluid discharge.

1. After the screw drilling tool is lifted to the bypass valve position, remove the components from the bypass valve and flush it with clean water. Then, press and release the valve core using a wooden stick or hammer handle to ensure it moves freely.
2. After cleaning, reinstall the lifting short joint and lift the screw drilling tool.