الجمعة، 17 نوفمبر 2017

Drilling Fluids Functions

1-Cool the drill bit and lubricate its teeth
2-Lubricate and cool drill string
3-Control formation the pressure
4-Carry cutting to the surface
5-Stabilize the well bore
6-Help in the well logs
7-limitting corrosion
1-Cool bit and lubricate its teeth
Drilling action requires mechanical energy in form of weight on bit, rotation and hydraulic energy
Large part of energy dissipated as heat
A Heat must be removed to allow drilling
Mud helps remove heat
Mud helps remove cutting between the teeth and prevent bit balling

2-Cool and lubricate drill string
Rotating drill string generates heat
Mud help dissipate heat from hole
Mud absorbs heat by convection and release it by radiation
Mud lubricate drill string and reduce friction
 3-Control formation pressure

For safe drilling, high formation pressures must be contained within the hole to 
prevent damage and injury
This achieved by hydrostatic pressure of mud
Mud pressure should be higher than formation pressure
An overbalance of 100-200 psi is used
Pressure overbalance id referred as chip hold down pressure
Penetration rate decreases as CHDP increases
For abnormal pressure CHDP becomes negative and kick will happen

4-Carry cutting to surface
Cutting generated by the bit must be removed
Drilling mud carries cutting form bottom to surface
A Carrying capacity depend on annular velocity, plastic viscosity and yield 
point of mud and slip velocity of generated cutting For power law fluid
 5- Stabilize the wellbore  

Good mud cake stabilize the hole
Differential pressure between mud and formation keep hole stable
Reduce drilling time also help keep hole stable

 6-Help in the evaluation 
and interpretation of the well logs
During logging mud fill the hole
Logs used to detect hydrocarbon, measure porosity, formation ,pressure
Mud should posses properties that help evaluate these properties
Water base -mud  is  better  for  electric  logging  

7-Limiting corrosion
The drilling  fluid in most cases  will have water which contain dissolved salts
This serves as a medium for corrosion
Precautions should be taken  to prevent  damage  of the  equipment
Mud containing oil as the continuous phase may decrease
   or  prevent corrosion  completely

Drilling Fluids Functions Reviewed by الحريف on نوفمبر 17, 2017 Rating: 5 – They   1-Cool the drill bit and lubricate its teeth 2-Lubricate and cool drill string 3-Control formation the pressure 4-C...

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