funnel
from pete 426 slide notes
Drilling fluid is an essential material to drill a well. The main functions of it are to circulating the rock fragments and exerting enough pressure to the formation. In order to fulfill these requirements, special properties should be met to achieve a successful job.
Some important the fluid properties are list below:
1. Fluid viscosity
2. Density
3. Gel strength
4. Yield point
5. pH value
Density:
The
density
of fluid is primarily related
to the hydrostatic pressure it can provide to stabilize the wellbore.
Either over
or less mud density will result to problems. If the mud density is low,
then it
can¡¯t overcome the formation pressure, blowout may happen. However if
the mud
density is weight out according to the pressure requirement, then
drilling mud
will invade into the reservoir, which is called the fluid loss.
Therefore, it
is crucial to make mud with proper density.
Mud density can be measured by using mud weight balance. (see picture)
Viscosity:
Viscosity has many types. In this case we only focus on the dynamic viscosity, which means we only concern the fluid when it is flowing.
In simple words, the dynamic viscosity is the property of fluid which indicates its flowing behavior. Generally, in daily life, those liquids we call them thick normally have high viscosity, and oppositely liquid like water which is very easy to flow, normally have low viscosity. The easiest method to measure the viscosity is using the funnel, fully fill the funnel with drilling mud, count the time after it entirely leave it. Then a rational viscosity evaluation could be made. Obviously, liquid use longer time shows a higher viscosity comparing to those who leave very quickly. The rule unit for viscosity is called poises, which is the product of pascal and seconds.
funnel
Gel strength & Yield point:
Gel strength measures the required stress to initiate the liquid flow from sedate condition. Yield point indicates the capability of a fluid to suspend the cuttings.
pH:
A
pH
value range from 8-12 is
normally required to allow some mud additives can work.