Drilling FLUID SYSTEMS & Functions

INTRODUCINGDRILLING FLUIDS In geotechnical engineering, drilling fluid is used to aid the Drilling of boreholes into the earth and any composition, which is used to aid in production and removal of cuttings from the well bore, is termed as drilling fluid

Often used while drilling oil and natural gas wells and on exploration drilling rigs, drilling fluids are also used for much simpler boreholes, such as water wells

Liquid drilling fluid is often called drilling mud

The main functions of drilling fluids include providing hydrostatic pressure to prevent formation fluids from entering into the well bore

Cool the bit

carrying out drill cuttings

lubricate the drill string

suspending the drill cuttings while drilling is paused

Control formation pressures

Minimizing formation damage

Primary Functions of a Drilling Fluid

Drilling Fluid can be classified on the basis of principal component :

These components are :

(i) Water

(ii) oil

(iii) gas

Principal Components of Drilling FluidsWater based muds are the most commonly used drilling fluids.

Oil-based muds are generally more expensive and require stringent pollution control measures and use for the down hole drilling

The use of gases as Drilling fluid is limited to the formations which are impermeable Selection of a Drilling Fluid:

Three factors affecting drilling fluid performance are:

The change of drilling fluid viscosity

The change of drilling fluid density

The change of mud pHFactors influencing drilling fluid performanceThe types of Formations to be drilled. Drilling Fluid should be compatible with the formation

The water quality available

The pressure range of Formation Fluids

The range of temperature, strength, and permeability exhibited by the formations

Ecological considerations

Factors to consider when selecting a Drilling Fluid: