For drilling engineer have knowledge for chose/select bid type can reduce cost of drilling operation. Drilling process also have more challenge for us to design our well planing and drilling bit selection rules will help you to get best result of your drilling program. Some formation have different characteristic it is make our bit should have ability to penetration the formation with optimum rate. The good drilling bit selection that’ s way why you have to learn it.
Bit selection rules list
• Shale has a better drilling response to RPM.
• Limestone has a better drilling response to bit weight.
• Bits with roller bearings can be run at a higher RPM than bits with journal bearings.
• Bits with sealed bearings can give longer life than bits with open bearings.
• Milled tooth bits with journal bearings can be run at higher weights than milled tooth
bits with roller bearings.
• Diamond bits can run at higher RPM than tri-cone bits.
• Bits with high offset may wear more on gauge.
• Bits with high offset may cause more hole deviation.
• Cost per foot analysis can help you decide which bit to use.
• Examination of used bits can help you decide which bit to use.
• Make the bit up to proper torque.
• Hoist and lower the bit slowly through ledges and dog legs.
• Hoist and lower the bit slowly at liner tops.
• Rock bits are not designed for reaming. If you do ream, do it with light weight and low
• Protect nozzles from plugging with Smith Tool jet plugs.
Establish a bottom hole pattern
• Rotate the bit and circulate when approaching bottom. This will prevent plugged nozzles and clear out fill.
• Lightly tag the bottom with low RPM.
• Gradually increase the RPM.
• Gradually increase the weight.
If the expected penetration rate is not achieved
• Drilling fluid density may be too high with respect to formation pressure.
• Drilling fluid solids may need to be controlled.
• Pump pressure or pump volume may be too low.
• The bit used may be too hard for the formation.
• Formation hardness may have increased.
• RPM and weight may not be the best for bit type and formation — carry out a drill off test.
• Ensure that the bit is stabilised.
Before re-running green bits
• Make sure the bit is in gauge.
• Check any bit for complete cutting structure.
• Check any sealed bearing bit for effective seals .
• Soak any sealed bearing bit in water or diesel to loosen formation packed in the reservoir cap equalisation ports.
• Regrease143/4″ diameter and larger open bearing bits.
Bit selection rules is not only for save drilling cost but also can increase probability of success drilling job, reduce the drilling program, and more benefit.