drilling 12 Flashcards
If borehole pressure < F.P.P.
formation fluid influx can occur
BHP > F.F.P
ormation will breakdown, mud losses can occur, primary well control barrier cannot be achieved
A formation will fracture when the pressure in the borehole exceeds
the least of the stresses within the rock structure.
these fractures will propagate in a direction perpendicular to the
least principal stress
To initiate wellbore wall fracture, the pressure in the borehole must be
greater than the least principal stress in the formation.
Drilling practice indicates that when the hydrostatic pressure of the drilling fluid is high enough,
the borehole wall will break.
The pressure of the drilling fluid column is defined as
formation fracture pressure.
A test that determines the fracture pressure of the casing shoe and open formation.
LEAK OFF TEST
used to determine the pressure at which the rock in the open hole section of the well just starts to break down
Leak-off test
Installed between the pressure gauge and pump. Close this valve during shut-in; do not rely on the pump to hold pressure.
Shut-in valve
Installed between shut in valve and pump. Open during shut in to check for leaks in the shut in valve. Also used to bleed off pressure when the test is completed.
Bleed valve
Open while filling drill pipe and test head, close when mud starts to flow out valve.
Purge valve
To identify the minimum horizontal stress 𝜎ℎ
Extended LEAK OFF TEST (XLOT)
