CHAPTER 2 (PART 2) Flashcards
SITUATION 1
Drill within the mud window between the formation pore pressure and the formation fracture because:
if BHP < F.P.P, then _____
formation fluid influx can occur
According to SITUATION 1
How about if BHP > F.P.P, what will happen to the formation
formation will breakdown, mud losses can occur, primary well control barrier cannot be achieved
What means BHP
Borehole Pressure
A formation will fracture when ___
the pressure in the borehole exceeds the least of the stresses within the rock structure
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
To propagate the fracture the pressure must be ___
maintained at a level greater than the least principal stress
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
What are some approaches to calculate fracture pressure based on empirical data analysis and numerical method?
• The Hubbert and Willis Method
• The Matthews and Kelly Method
• The Eaton Method
• The Rongzun Huang Method
• A test that determines the fracture pressure of the casing shoe and open formation.
• It is conducted after drilling out of a new casing shoe to determine the maximum pressure that the open hole can withstand before the fluid in the wellbore will begin to leak off and fracture the formation.
• Traditionally, it is conducted to determine the upper threshold for the mud weight.
• It is 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
The ___ is considered to be the first point that deviates from the usual pressure profile while pumping fluid down hole.
leak off pressure
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
Used to purge air. Open while filling drill pipe and test head, close when mud starts to flow out valve.
Purge valve
Four inches or larger for easy visibility. Liquid filled, mounted away from test line for smoother readings. Lowest range, smallest dial increments possible to minimize uncertainties caused by needle oscillations.
Pressure gauge
LOT operation is terminated when the ___
pressure no longer continues to increase linearly as the mud is pumped into the well
When the pressure no longer increases linearly with an increase in volume pumped, it is assumed that ___
the formation is starting to breakdown
•It is assumed in these tests that the weakest part of the wellbore is the formations which are exposed just below the casing shoe.
•when these tests are conducted, the pressure at surface, and throughout the wellbore, initially increases linearly with respect to pressure.
LOT and FBT
what means ELOT or XLOT
Extended LEAK OFF TEST
To identify the minimum horizontal stress 𝜎ℎ extended leak off test, ___ is introduced
(ELOT or XLOT)
Slope of the straight line region gives the compressibility of the drilling fluid.
Extended LEAK OFF TEST (XLOT)
what means FIT
FORMATION INTEGRITY TEST
The purpose of conducting a FIT is to _____
test the formation fracture pressure required for kick tolerance and safe drilling mud weight margin
The maximum pressure in the FIT test is _____
less than the fracture initiation pressure
___ is used to determine whether the rock in the open hole section of the well will withstand a specific predetermined pressure. This pressure represents the maximum pressure that the formation will be exposed to while drilling the next wellbore section.
FIT
The maximum allowable pressure on the formation just below the casing shoe is generally expressed as _____ so that it can be compared with the mud weight to be used in the subsequent hole section.
an equivalent mud gradient (EMG)
In LOT calculations, a safety factor of _____ is subtracted from the allowable mudweight.
0.5 ppg (0.026 psi/ft)
When the drilling fluid is circulating through the drillstring, the borehole pressure at the bottom of the annulus will be _____
greater than the hydrostatic pressure of the mud
what means ECD
equivalent circulating density
___ can then be calculated from the sum of the hydrostatic and frictional pressure divided by the true vertical depth of the well.
ECD
LOT Calculations – MAASP
MAASP = Maximum Allowable Pressure at the Shoe MINUS Hydrostatic Pressure of Mud at the Shoe
MAASP means
Maximum Allowable Annulus Surface Pressure
