Introduction Drilling Mud Function and Performance

DRILLING FLUIDS

Drilling fluids include both gases and liquids, liquids are called drilling mud, where the drilling
mud is one of the most important elements of any drilling operation. The mud has a
number of functions which must all be optimized to ensure safety and minimum hole problems
Failure of the mud to meet its design functions can prove extremely costly in terms of materials
and time, and can also jeopardise the successful completion of the well and may even result in
major problems such as stuck pipe, kicks or blowouts
There are basically two types of drilling mud: water-based and oil-based, depending on whether
the continuous phase is water or oil. the water-base mud is the most commonly used. The use of
oil-base mud is usually limited to drill extremely hot formations or formations that are affected
adversely  by  water-base mud .  Where  the  use  of  gasses  is  limited  to  formations  that  are
competent  (hard)  and  impermeable.  Gas–liquid  mixtures  can  be  used  when  only  a  few
formations  capable  of  producing  water  at significant  rates  are encountered. Then  there  are  a
multitude of additives which are added to either change the mud density or change its chemical
properties

(Drilling mud selection: (Data REQUIREMENTS

The following information should be collected and used when selecting drilling fluid or fluids
for a particular well. It should be noted that it is common to utilize two or three different fluid
types on a single well

1-The  range  of  temperature,  strength,  permeability,  and  pore  fluid  pressure  exhibited  by
formations (Pore pressure /fracture gradient plots to establish the minimum /  maximum mud
weights to be used on the whole well
2- Offset well data (drilling completion reports, mud recaps, mud logs etc.) from similar wells in
the area to help establish successful mud systems, problematic formations, potential hazards,
estimated drilling time etc


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 Types of formations to be drilled

4-Casing design program and casing seat depths. The casing scheme effectively divides the well
into separate sections; each hole section may have similar formation types, similar pore pressure
regimes or similar reactivity to mud
 The water quality available
5-Restrictions that might be enforced in the area i.e. government legislation in the area
environmental concerns, etc

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