Drilling
DRILLING FLUIDS
The key to making the rotary drilling system work is the ability to circulate a fluid continuously down through the drill pipe, out through the bit nozzles and back to the surface.
The drilling fluid can be air, foam (a combination of air and liquid or a liquid.
Liquid drilling fluids are commonly called drilling mud.
All drilling fluids, especially drilling mud, can have a wide range of chemical and physical properties. These properties are specifically designed for drilling conditions and the special problems that must be handled in drilling a well.
Purpose of Drilling Fluids
1. Cooling and lubrication. As the bit drills into the rock formation, the friction caused by the rotating bit against the rock generate heat. The heat is dissipated by the circulating drilling fluid. The fluid also lubricates the bit.
2. Cuttings removal. An important function of the drilling fluid is to carry rock cuttings removed by the bit to the surface. The drilling flows through treating equipment where the cuttings are removed and the clean fluid is again pumped down through the drill pipe string.
3. Suspend cuttings. There are times when circulation has to be stopped. The drilling fluid must have that gelling characteristics that will prevent drill cuttings from settling down at the bit. This may caused the drill pipe to be stuck.
4. Pressure control. The drilling mud can be the first line of defense against a blowout or loss of well control caused by formation pressures.
The hydrostatic head produced by the mud in psi is = 0.052 x G x H where G = density of mud in ppg H = depth of the hole in feet.
This hydrostatic head will counter the formation pressure in order to avoid a blowout while drilling.
For example, Lets say a well is being drilled in a salt-water basin (pressure gradient of 0.465 psi/ft), the pressure in the formation at 10,000 feet
The key to making the rotary drilling system work is the ability to circulate a fluid continuously down through the drill pipe, out through the bit nozzles and back to the surface.
The drilling fluid can be air, foam (a combination of air and liquid or a liquid.
Liquid drilling fluids are commonly called drilling mud.
All drilling fluids, especially drilling mud, can have a wide range of chemical and physical properties. These properties are specifically designed for drilling conditions and the special problems that must be handled in drilling a well.
Purpose of Drilling Fluids
1. Cooling and lubrication. As the bit drills into the rock formation, the friction caused by the rotating bit against the rock generate heat. The heat is dissipated by the circulating drilling fluid. The fluid also lubricates the bit.
2. Cuttings removal. An important function of the drilling fluid is to carry rock cuttings removed by the bit to the surface. The drilling flows through treating equipment where the cuttings are removed and the clean fluid is again pumped down through the drill pipe string.
3. Suspend cuttings. There are times when circulation has to be stopped. The drilling fluid must have that gelling characteristics that will prevent drill cuttings from settling down at the bit. This may caused the drill pipe to be stuck.
4. Pressure control. The drilling mud can be the first line of defense against a blowout or loss of well control caused by formation pressures.
The hydrostatic head produced by the mud in psi is = 0.052 x G x H where G = density of mud in ppg H = depth of the hole in feet.
This hydrostatic head will counter the formation pressure in order to avoid a blowout while drilling.
For example, Lets say a well is being drilled in a salt-water basin (pressure gradient of 0.465 psi/ft), the pressure in the formation at 10,000 feet