The developing drilling mud technology follows the industrial needs but in the interest
of reducing formation damage the object is choosing the most suitable mud. It is even
more important question when the pressure and temperature in a well is high. This
paper tries to make this choice easier by measuring static and dynamic filtration
of drilling mud on changing temperature.
Before designing a HPHT well there are two important cases which must be considered,
the margin between the fracture gradient and the pore pressure is small what is critical
in the design of the well and HPHT wells usually have high ECD (Equivalent Circulating
Density) that leads to lost circulation problems that becomes difficult to control.
The choice of accurate mud density is critical due to the narrow margin between the
pore pressure and the fracture gradient. The applied mud has to stay stable under
extreme temperatures and pressures and has to have optimized rheology to minimize
ECD. In our presentation we will show the results and comparison of the experiments
that were conducted using a dynamic HPHT filter press with core sample plugs as filters
both static and dynamic conditions and Fann 90 model (Dynamic Filtration System) to
determine the filtrate and thickness and composition of the filter cake. The quantity
and quality of spurt loss and fluid loss was compared on different temperatures and
core samples. Filtration rate is one of the most complex mud properties because it
may be influenced by almost any change in other properties-rheology, composition and
particle size distribution-and in this way its effect on formation damage. At elevated
temperatures these effects are more significant.