311.2mm Rock Bit , IADC 515 , Tricone Bit, Oil Well Drilling , HDD Drilling , Pilot Bit

RECOMMENDED DRILLING PARAMETERS FOR APPLICATION

* Lubricants *

High drilling temperatures and high pressures in the lubrication system, together with the potential of exposure to water and chemicals, require high performance from lubricants. Most bit lubricants are specially formulated. Leading bit manufacturers employ scientists to develop and test lubricants. Better drill-bit lubricants are stable to temperatures > 300°F, and many function normally at temperatures down to ≈0°F.

They are hydrophobic (repel water) and retain their stability if water penetrates the bit. Quality lubricants are also resistant to chemicals commonly found in drilling fluids, are environmentally safe, and do not contain the lead additives that have traditionally helped resist high pressures.

- Lubricant supply. Roller-cone bits typically contain one lubricant reservoir in each leg (Fig. 7). Thus, for a three-cone bit, there are three reservoirs. Each must have the capacity for sufficient reserves of lubricant for operation of the bearing assembly it serves throughout the bit’s life.

- Pressure equalization and relief. A column of drilling fluids and cuttings contained in a well exerts very high pressures on a bit operating at the well bottom. These high pressures are applied to the seal system and must be resisted by lubricant in the seal and bearing system. At installation, lubricant is at atmospheric pressure and cannot provide significant resistance to well-bottom pressures. Accordingly, internal lubrication system pressures equalize themselves with external bit pressures to prevent seal failure caused by differential pressure. Equalization is accomplished by a small relief valve installed in the lubricant reservoir system.