Identifying drill bit failure during oil well drilling is vital to prevent expensive downtime and ensure operational safety. Employing various methods can enhance your ability to identify potential issues as shown below.
Sweep is a mud which has higher rheology and/or more mud weight than current mud property. It is used to carry cutting that set at low side of a wellbore and it is widely used for Sea water drilling.
Bit balling is one of the drilling operational issues which can happen anytime while drilling. This issue can cause several problems such as reduction in rate of penetration and surface torque, increase in stand pipe pressure. Personnel may eventually need to pull out of hole the BHA in order to clear the balling issue at the bit. This article will teach you about the bit balling and how to prevent it in the planning phase and how to effective detect and clear the balled up bit before it becomes a worse problem.
Drilling Torque – Drilling torque will be lower than normal drilling torque since most of the cutters are covered up by cuttings.
Rate of Penetration – The ROP will decrease more than projection. If you drill 100 fph and later on the ROP drops to 50 fph without any drilling parameters changed, this might be this problem.
Standpipe Pressure – Standpipe pressure increases with no changes in flow rates or drilling parameters. Balling up around the bit reduce annular flowing area resulting in increasing pressure.
Mechanical blind back off is the procedure to intentionally break out stuck drill string by applying left hand torque and transmitting down hole. This is the last method to recover drill string because back-off position cannot exactly determine. One situation that I used to do the blind back of is when the perforating gun cannot be run into tubing string.
Procedure to Perform Blind Back Off Operation
1. Determine drilling parameters prior to get stuck if possible.
Pick up weight __ lb
Slack off weight __ lb
Rotating weight __ lb
2. Pick up drill string at 10% over the rotating weight. Apply 50% of make-up torque with left hand turn and lock TDS. Record how many turns. Slowly work string down for 5-10 minutes to transmit surface torque to the bottom. Weight while working should be between pick-up and slack off weight.
3. Repeat step#2 with 70%, 90%, 100%, 110% make up torque
4. The string should be back off while working down.
Note: The concept is to have overpull tension applied at each connection while left hand torque is transmitted into the drillstring. Once the drill string is worked, the torque will be transferred to the bottom connection of the well.
Sometimes drillpipe is accidentally dropped into the well and you need to fish it out of the well. One easy option that may be feasible to perform is to use a drill string to screw into the drill pipe in the well.
Before going into a detailed procedure, you may need to check the following conditions.
• Tight clearance between hole and tool joint
• Tool joint at the top of fish is in a good condition
Data that you need to know before going to fish the drill string
• Fish length
• Top of fish
• Weight of fish in the mud
• Actual turn to fully engage when screw in
Detailed procedure for fishing drill pipe by screwing into the fish
Fish length = xxx ft
Expected TOF = xxx ft
Weight of the fish (BHA + DP) = xx Klb
1. Trip in hole 1 stand
2. Count the actual turn of drill pipe
3. Run in hole to xxx MD (200 ft above the Top Of Fish)
4. Make up top drive
5. Break circulate with 160 GPM using current drilling fluid in the well
• Record pressure
6. Record pick up and slack off weight without rotation
7. Record pick up and slack off weight with 20 RPM
8. Record torque with 20 RPM
– In the steps 5-8, you will get the base line values when the drill string does not engage with another part.
9. Slowly run in hole without rotation
10. Tag top of fish while pumping with 160 GPM
11. Pick up 5 ft
12. Slowly run in hole with 20 RPM
13. Attempt to screw into the top of fish (tool joint)
14. Indicators if the fish is engaged.
– Increase in pumping pressure, torque, weight on bit and pick up weight.
– When picking up drill string, increment of pick up weight should close to buoyed weight of the fish (dropped drill string).
15. Flow check
16. Pull out of hole to surface.
Note: This is the generic guideline. You may need to adapt some parameters/steps to match with your rig operation.
