Factors Affecting Drill Bit Balling Up
▪️Formation – Clay stone and shale has tendency to ball up the bit even though you use highly inhibitive water based mud or oil based mud.

▪️Weight On Bit – High weight on bit will have more chance to create this issue.

▪️Hydrostatic Pressure in Wellbore – High hydrostatic pressure (pressure above 5,000 psi) can induce bit balling issue in water based mud.

▪️Bit Design – Poor bit cutting structure and poor junk slot area in PCD bits contribute to this issue.

▪️Hydraulic – Low flow rate will not be able to clean the cutting around the bit.

Planning To Mitigate The Problem:
🔹Bit Selection – For the rock bits, steel tooth bits are better than insert bits because the steel tooth ones have greater teeth intermesh. For the PCD bits, the larger junk slot area is preferred.

🔹Bit Nozzle Selection – The bits with high flow tube or extended nozzles are not recommended. If the bigger bit size is utilized, don’t block off the center jet. The center jet will flush all cutting more effectively.

🔹Good Hydraulic – Hydraulic horse power per cross sectional area of the bit is the figure which can be utilized for measuring good hydraulic for bit balling mitigation. Hydraulic horse power per square inch (HSI) less than 1.0 will not be able to clean the bits. It is good practice to have more than 2.5 of HSI for good bit cleaning.

🔹Weight On Bit – Don’t try to run a lot of WOB. If you increase WOB but you get lower ROP, you may have bit balling up issue. You should lower the weight and attempt to clean the bit as soon as possible.

🔹Drilling Fluid– Mud chemical additives as PHPA which can prevent clay swelling issue must be added into the water based mud system. If feasible, drilling with oil based fluid will have less chance of balling up bit/BHA.