Understanding the Tripping Out Process on an Offshore Oil Rig

The tripping out process on an offshore rig is a critical operation in the oil field industry. It involves the removal of the drillstring, including the bit and bottom hole assembly (BHA), from the well bore. This process is essential for activities such as drill bit changes, bottom hole assembly changes, or any other necessary component exchanges. In this article, we will break down the steps involved in this procedure and what occurs after the process is completed.

Steps Involved in Tripping Out

1. Start the Clean Cycle: The process begins by circulating the hole to ensure it is clean. Typically, one bottle up is sufficient. This refers to the amount of mud in the annulus (the space between the drillstring and the wellbore) from the drill bit to the surface.

2. Prepare the Slug: A slug is a controlled volume of drilling mud with a higher ppg (pounds per gallon) weight than the normal drilling mud. This slug is prepared in a slug pit

3. Pump the Slug: The slug is pumped into the drill pipe and displaced out of the surface piping with normal weight mud. The higher density of the slug ensures that the drillstring is empty of mud when it is pulled out of the hole.

4. Break Off and Remove the Drill String: The heavier slug's increased hydrostatic pressure ensures the drillstring is empty when pulled. Once the mud is gone, the last section of the drill string is broken off the J key (ramp) on the rig floor and racked in the Derrick with the help of the derrickman.

5. Unscrew and Rack: The stands (usually a little over 90 feet in length) are unscrewed and racked in the Derrick by tilting the bails and allowing the derrickman to open the elevator and pull the stand back to be racked in the monkey board for vertical storage. This process is repeated until the entire drillstring is removed from the well.

6. Change the Bit or BHA: The last section of the drillstring is often the BHA, which consists of several sections of heavy pipe with a thicker steel wall. This ensures the weight is applied to the drill bit for efficient rock formation penetration. Once the bit or BHA is changed, the process is reversed to lower the new bit back into the wellbore.

Post-Tripping Out Operations

After the tripping out process is completed, the following steps are typically undertaken:

1. Inspection and Maintenance: Once the drillstring is removed, it is inspected for any wear or damage. Any necessary repairs or maintenance are performed before the process is reversed.

2. Bit Reinstallation: The new drill bit is prepared and reattached to the drillstring. This involves aligning the bit with the kelly bushing and tightening the connections to ensure a secure fit.

3. Lowering the Bit: The tripping in process involves lowering the new drill bit back into the wellbore. This is done by adding on and screwing on more stands of drillpipe that had been previously removed.

4. Preparation for Drilling: Once the new bit is securely in place, preparations are made for the next drilling session. This includes setting up the necessary equipment, calibrating the depth, and ensuring the rig is ready to drill.

The tripping out process is a vital part of offshore drilling operations. By understanding the steps involved and the procedures following the completion of the process, rig operators can ensure efficient and safe work conditions.

Frequently Asked Questions

Q: What is the purpose of tripping out?

A: Tripping out is performed to change the drill bit or other components of the drilling assembly, such as the BHA, and to ensure the wellbore is ready for the next phase of drilling.

Q: How does the slug help in the tripping out process?

A: The slug, which has a higher ppg weight, ensures the drillstring is empty of mud when it is pulled out of the well. This prevents any mud from contaminating the new bit or BHA and helps to maintain the cleanliness of the wellbore.

Q: What are the risks associated with tripping out?

A: Risks include hydraulic system failures, connection failures, and the potential for damage to the equipment during the process. Proper training and safety measures are crucial for a successful and safe tripping out operation.