MODULE 12-DIRECTIONAL DRILLING 2 Flashcards
What do all survey systems measure?
Inclination and azimuth at articular measured depths
What are the 3 reference systems used?
Depth references
Inclination references
Azimuth references
What are the 2 kinds of depths?
Measured or TVD
How is measured depth measured?
distance measured along the actual course of the borehole from the surface reference point.
How is TVD measured?
true vertical depth is the vertical distance from the depth reference level to a point on the borehole course.
In most drilling operatios, what is used as the working death reference?
Rotary table(RT) or Kelly Bushing Elevation (KBE)
Define Inclination reference
the angle that the well bore deviated from vertical
What is the azimuth reference?
The azimuth is the angle int he horizontal plane measure clockwise from a fixed reference direction (True North)
What is angle between magnetic north and true north called?
magnetic declination
What are 4 causes of magnetic inference?
- Drill string magnetization
- Nearby cased wells
- Nearby fish
- Magnetic deposition in the formation
What does a single shot survey instrument record?
inclination
direction
toolface
What is the most common surveying tools for DD?
MWD
What measurements can MWD take?
Gamma Ray Compass direction Tool Face Borehole pressure Temperature Vibration Torque Shock
MWD surveys every?
30-500ft or 10m to 150m
How often can the MWD survey?
after every drilling joint. 9.5m when doing precise steering in reservoir.
How far can the MWD go during an active change in angles
90ft
How far can the MWD go while drilling straight ahead
200-300ft
How does MWD tool work?
sends pressure pulses up the mud column inside the drillstring
How are the pulses picked up on a MWD tool?
picked up by a transducer installed on the standpipe
What are the binary code data rates for MWD tool?
1.5 to 40 bits/s
3 type of tool modulation mechanisms?
positive pulse
negative pulse
Continuous wave
Positive Pulse
Creates a restriction on the inside of the drill pipe and cause a positive pulse
Negative Pulse
Opens a discharge valve in the annulus and causes a negative pulse
Continuous wave
Gradually open and close valve.
Create Sine wave
EM tool is another form of?
MWD tool
How is the signal sent to receivers from the EM tool?
via EM waves up through formations to receivers
What is the best EM application?
Underbalance drilling because of signal attenuation
What are the EM limitations?
Depth (battery life)
Certain formations attenuate EM waves (salt)
What does EM eliminate?
the need to use fluid as a medium
