Lecture 6: DIRECTIONAL DRILLING Directional Drilling Fundamentals & Directional Trajectories
Arun S Chandel Assistant Professor
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1
Segments of Deviated Well
Segments of Deviated Well
Major Directional Well Profiles
Directional Drilling Terminologies KICK-OFF POINT The kick off point is defined as the point below the surface location where the well is deflected from the vertical. The osition of the kick off depends on several parameters including: geological considerations, geometry of well and proximity of other wells.
The maximum permissible build up /drop off rate is normally determined by one or more of the following: • The total depth of the well • Maximum torque and drag limitations • Mechanical limitations of the drill string or casing • Mechanical limitations of logging tools and production strings. The op t im u m b u ild u p an d d rop of f rat es in con ven t ion al d i r e c t i o n a l w e l l s a r e i n t h e r a n g e o f 1 . 5 0 t o 3 0 p e r 1 0 0 f t , a lt h o u g h m u ch h ig h e r b u il d u p r a t e s a r e u se d f o r h o r iz o n t a l a n d m u l t i l a t e r a l w e l l s .
INCLINATION ANGLE The inclination angle of a well at any point is the angle the wellbore forms between its axis and the vertical, see Figure 11.11. MEASURED DEPTH from one reference point to the survey point. Measured depth is also known as Along Hole Depth and is measured with the pipe tally or by a wireline. True vertical depth (TVD) is the vertical distance measured from a reference point to the survey point. TVD is usually referenced to
Northing: Horizontal distance between one survey point and the RKB, measured to the North. A distance to the South is generally eno e as e ng nega ve. Easting: Horizontal distance between one survey point and the RKB measured to the East. A distance to the West is enerall denoted as being negative.
Azimuth & Departure The azimuth of a wellbore at any point is defined as the direction of the wellbore on a horizontal plane measured clockwise form a north reference. Azimuths are usually expressed in angles from 0-360 , measure rom zero nor . Azimuths can also be expressed in a quadrant system from 0-90 measured from north in the northern quadrants and from south in the southern quadrants. The azimuth reading of 135 equates to S45 E in quadrant readings.
Azimuth and departure
Azimuth and departure N
B
A
84
W
E O
C
D n
D t
1852
γ
S
α
0
AZIMUTH = 272.6 . de re es
D e
Horizontal Departure: D
t
=
Azimuth of the well (α ) = tan
De
−1
2
+D
n
⎛ D ⎞ e
n
2
Azimuth and departure Given the following grid coordinates, determine the departure and azimuth of the target from the surface location. Grid Coordinates: Target 6,334,400.00 N (m) 200 600.00 E m Grid Coordinates: Surface 6,335,000.00 N (m) , .
Circular Functions
Circular Functions
Radius of curvature
Radius of curvature
Build-up Rate Formula
Determining End of Build
J-Profile (departure >R)
J-Profile (departure < R)
S-Profile (R1+R2 < total target displacement)
S-Profile (R1+R2 > total target displacement)
What’s Best…?
Manual Design: Build & Hold Trajectory (J‐Profile)
Manual Design: Build & Hold Trajectory (J‐Profile) To carry out the geometric planning for a Type I well, Figure 11.13, the following information is required: •
-
• Target Co-ordinates • TVD of target • TVD to KOP • Build-u
rate
Base Equations Using the detailed trigonometry shown in Figure 11.13, the maximum inclination angle αmax for type I trajectory can be calculated for two cases:
Base Equations
Base Equations
Problem: Build & Hold Trajectory (J‐Profile) Following data is given for a directional offshore we r e as -pro e:
Kick-off point (K) = 1000’ Build Rate BUR = 2.50 100’ Target data True vertical depth (V3) = 9500’ Northings (Dn) = +3507’ Eastings De = -1752
Find the following: 1.Horizontal Departure (D2) 2.Azimuth of the well (γ ) . 4.End of build at TVD (V2) 5.End of build at departure (D1) 6.Measured depth at end of build (OE) .
