Diamond Bit Operating Parameters
Hydraulics
Hydraulic programs for diamond bits must consider circulation rate and
pressure loss. There should be sufficient fluid and pressure to cool and
clean under the bit. Rig hydraulics do not require modification, but a good
optimum flow rate in the range of 4.5 to 7.0 gallons per minute per square
inch of hole area is necessary. It may be more or less if the hole or
operating conditions dictate and if the bit is designed for such conditions.
Each diamond on the bit is continually on bottom, continually doing work,
therefore the entire area must be continually cleaned and cooled. The bit
must be kept clean to prevent balling up, and to keep formations exposed to
the cutting action of the diamonds. The bit must be kept cool; excessive
heat is one of the diamond's worst enemies. Because of the diamond's
cutting action, heat is always being generated and a damage can only be
prevented with adequate flow rates. Other factors being equal, better
performance may be expected with higher rates of fluid flow.
Pressure is required to force the fluid over the face of the bit at velocities
high enough to provide adequate cooling and cleaning. When the bit is off
bottom, the fluid has a nearly unrestricted flow, but on bottom, the fluid
must pass through a small area made up of fluid courses in the bit and the
hole itself (clearance is the space between the bit matrix and the
formation). This results in an off-on bottom pressure difference in a range
of 100 to 1,000 psi depending on the total fluid area and operating
conditions (mud density, bit weight, pump pressure, etc.).
Hydraulics
Hydraulic programs for diamond bits must consider circulation rate and
pressure loss. There should be sufficient fluid and pressure to cool and
clean under the bit. Rig hydraulics do not require modification, but a good
optimum flow rate in the range of 4.5 to 7.0 gallons per minute per square
inch of hole area is necessary. It may be more or less if the hole or
operating conditions dictate and if the bit is designed for such conditions.
Each diamond on the bit is continually on bottom, continually doing work,
therefore the entire area must be continually cleaned and cooled. The bit
must be kept clean to prevent balling up, and to keep formations exposed to
the cutting action of the diamonds. The bit must be kept cool; excessive
heat is one of the diamond's worst enemies. Because of the diamond's
cutting action, heat is always being generated and a damage can only be
prevented with adequate flow rates. Other factors being equal, better
performance may be expected with higher rates of fluid flow.
Pressure is required to force the fluid over the face of the bit at velocities
high enough to provide adequate cooling and cleaning. When the bit is off
bottom, the fluid has a nearly unrestricted flow, but on bottom, the fluid
must pass through a small area made up of fluid courses in the bit and the
hole itself (clearance is the space between the bit matrix and the
formation). This results in an off-on bottom pressure difference in a range
of 100 to 1,000 psi depending on the total fluid area and operating
conditions (mud density, bit weight, pump pressure, etc.).
