Drilling Mud weight

Drilling fluid or mud has the following functions:-
  • Remove the cuttings generated from the hole
  • To contain the formation pressure or pore pressurefor safe drilling.
  • To cool and lubricate the drill bit and drill string
  • Formation of good mud cake to stablize the borehole wall
  • Transmit hydraulic energy to tools and bit
  • Ensure adequate formation evaluation through wireline logging
To accomplish the above functions drilling mud should have some basic properties as per plan.They are:-
  • Mud density
  • Viscosity
  • Yeild point
  • Gel strength
  • PH etc
In this article we are going to focus on Mud density or Mud weight.

Mud density is one of the most important drilling fluid properties.It is the weight of drilling fluid per unit volume and the units are Kg/m3 , gm/cm3,specific gravity and ppg(pounds per gallon) but in field generally ppg or gm/cmis used.
SG= ppg/8.345 = (lb/ft3)/62.3 =gm/cm3
Function of Drilling fluid density is to keep the borehole pressure higher higher than the Formation pressure.This keeps formation fluid from flowing into the wellbore and prevents formation fluid from causing a blow out.

Field measurement of Mud weight

In field fluid density is measured with a mud balance.
Mud weight

Mud density is regularly measured to check if the current mud density is as per plan.If the mud density is to be increased weighting material such as barite is added and if the mud weight is to be reduced water or low density mud can be added
Note:- In field,mud weight is regularly measured. Mud weight into the well is measured by the pump man and mud weight out of the well is measured by shaker man while Mud engineer is responsible for lab test on mud and maintaining the mud properties.

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