Drilling Terms

Drilling Terms
Annulus The space between the drill pipe and hole wall or casing inside surface.
BHA Bottom Hole Assembly.
Bit Breaker The steel plate that locates the bit in the rotary table while it is screwed onto/made up to the drillstring.
BOP Blow Out Preventer, a series of valves that close to seal in the well and prevent it blowing out.
Cavings Formation that has fallen out of the well bore wall down hole.
Drill Collar Heavy drill pipe used in the BHA to add weight.
Fishing Attempting to recover an item out of the well bore to surface.
GPM Gallons Per Minute.
HSE Health, Safety and Environment.
HSI Hydraulic horsepower per Square Inch.
Kelly The heavy steel drive shaft with a square or hexagonal cross section that locks in the rotary table and is connected to the drillstring to transmit torque.
LCM Lost Circulation Material.
LWD Logging While Drilling.
MWD Measurement While Drilling.
OBM Oil Based Mud.
RMS Root Mean Square (a method of averaging a signal).
RoP Rate of Penetration, fph/mph.
Rotary Table Device on the rig floor used to drive/rotate the kelly and support the drillstring.
RPM Combination Revolutions Per Minute.
RSA Rock Strength Analysis.
PDC Polycrystalline Diamond Compact.
POBM Pseudo Oil Based Mud.
PPE Personal Protective Equipment.
PSI Pounds per Square Inch, fluid pressure.
Sliding While directionally drilling with a motor, the rotary drive is switched off so the drillstring does not rotate and is ‘slid’ downhole
SPM Strokes Per Minute.
SPP Stand Pipe Pressure.
Spudding Burying the bit face into material, eg: the hole bottom or casing shoe assemblies.
TFA Total Flow Area, the sum of the cross-sectional areas of the exits of all nozzles in the bit.
Toolface The direction the motor is orientated to in hole while sliding.
Top Drive A torsional motor used to drive the drill string. Usually installed on the bigger rigs and can provide more power than a kelly drive.
WBM Water Based Mud.
WoB Weight on Bit, klbs/tonnes.