4. Deflection Tools and Technique - Drilling...
Transcript of 4. Deflection Tools and Technique - Drilling...
4. Deflection Tools and Technique
4.1 Whipstocks
4.2 Jetting
4.3 Downhole motor with bent sub
4.4 Downhole motor with bent housing
4.5 Steerable Motor Assemblies
4.6 Rotary Steerable Systems
Oktay Mamedbekov. Directional Drilling. Deflection Tools.
4. Deflection Tools and Technique
Whipstocks – main deflection tool in 1930-1950
Jetting – technique was developed in mid-1950s
Downhole motors with bent sub – superseded whipstocks and jetting
Most commonly used today:
• Downhole motors with fixed bent housing
• Steerable motor assemblies with adjustable bent housing
• Rotary steerable systems
Oktay Mamedbekov. Directional Drilling. Deflection Tools.
4.1 Whipstocks Courtesy: Baker Hughes
1 – Standard Removable Whipstock
is used to kick off wells
2 – Circulating Whipstock
permits more efficient cleaning
of the bottom
3 – Casing Whipstock
is used where a “window” is to
be cut in casing for sidetracking
1 2 3
Oktay Mamedbekov. Directional Drilling. Deflection Tools.
4.1 Standard Removable Whipstock Courtesy: French Oil & Gas Industry Association
1 2 3
1 – Lowering and orientating
whipstock assembly
2 – Drilling the rat hole.
Pulling whipstock out of
the hole
3 – Running the hole opener
assembly
Oktay Mamedbekov. Directional Drilling. Deflection Tools.
4.1 Standard Removable Whipstock
Oktay Mamedbekov. Directional Drilling. Deflection Tools.
Advantages:
• Simple equipment
• Requires little maintenance
• No temperature limitations
Disadvantages:
• Large number of trips for kick-off (at least three)
• Produces high initial DLS (dogleg severity)
4.2 Jetting Courtesy: Short. Directional & Horizontal Drilling
Oktay Mamedbekov. Directional Drilling. Deflection Tools.
Jetting is a technique used to deviate wellbores in soft formations
4.2 Procedure for Jetting Courtesy: French Oil & Gas Industry Association
1 – Jetting
2 – Spudding
3 – Drilling
1 2 3
Oktay Mamedbekov. Directional Drilling. Deflection Tools.
4.2 Jetting
Requirements for jetting:
• A special jet bit or standard soft formation tri-cone bit, with one
very large nozzle and two smaller ones can be used
• The formations must be soft enough (penetration rates of
greater than 80 ft/hr using normal drilling parameters) to be
suitable for jetting
• Adequate rig hydraulic horsepower must be available (mud
velocity through the large jet should be at least 500 ft/sec)
Oktay Mamedbekov. Directional Drilling. Deflection Tools.
4.3 Downhole Motor with Bent Sub Courtesy: Baker Hughes
10-30
Oktay Mamedbekov. Directional Drilling. Deflection Tools.
Downhole motor with bent
sub may be used for:
• kicking off wells
• correction runs
• sidetracking
Bent sub is placed directly
above the motor
4.3 Bent Sub
10-30
Oktay Mamedbekov. Directional Drilling. Deflection Tools.
Bent sub’s lower thread (on the pin)
is inclined 1° - 3° from the axis of the
sub body
Dogleg severity (DLS) depends on:
• Bent sub angle
• OD of motor, bent sub, and drill
collars
• Length of motor
• Hole diameter
Usually DLS= 1°- 2°/10m (10° -
20°/30ft)
4.4 Downhole Motor with Bent Housing Courtesy: Baker Hughes
Bit Bearing Section
Bent Housing
Motor Section
Stabilizer Stabilizer
MWD
Oktay Mamedbekov. Directional Drilling. Deflection Tools.
4.4 Turbine with Bent Housing Courtesy: Neyrfor Turbodrill
Drive Shaft
Turbine Section Body
Turbine Stages
Replaceable Stabilizer
Bent Housing
Thrust Bearing
Lower Stabilizer
Flexible Drive Shaft
Lower Bearing
Bit
Oktay Mamedbekov. Directional Drilling. Deflection Tools.
4.4 Bent Housing vs Bent Sub
Bent housing is more effective than the bent sub because of a shorter bit to bend distance, which:
• Reduces the bit offset
• Creates a higher build rate for a given bend angle
• Reduces the moment arm
• Reduces the bending stress at the bend
• Allows assembly easier to orient
Oktay Mamedbekov. Directional Drilling. Deflection Tools.
4.5 Steerable Motor Assemblies
DTU ABH
Steerable Motor Assemblies are used in two modes:
- Oriented (non-rotational) mode – for drilling a curved path
- Rotary mode – for drilling a straight path
Benefits:
• Elimination of trips for directional assembly changes, saving rig
time
• More complex well paths can be drilled
• Wells are drilled more closely to the plan at all times
Oktay Mamedbekov. Directional Drilling. Deflection Tools.
4.5 Steerable Motor Assemblies Courtesy: Baker Hughes
DTU ABH
DTU – Double Tilted
U-joint Housing
ABH – Adjustable
Bent Housing
Oktay Mamedbekov. Directional Drilling. Deflection Tools.
4.5 Adjustable Bent Housing (ABH)
Oktay Mamedbekov. Directional Drilling. Deflection Tools.
4.5 Downhole Motor with ABH
Benefits:
• Bent angle easily can be changed by drilling crew on a rig floor
• Shorter bit to bent distance (between bearing and motor
sections)
• Wider variety of DLS from 0 (tangent section) to 4 degrees/30 ft
• Possibility to use in two modes: oriented and rotary
• MWD system allows continual control on borehole trajectory
and high accuracy of bent housing orientation
Oktay Mamedbekov. Directional Drilling. Deflection Tools.
4.5 Downhole Motor with ABH
Rotation of the drill string while drilling with downhole motor
and adjustable bent housing (ABH):
• Negates the effect of bit tilt and allows to drill the straight hole
• Drills slightly oversize hole
• Decreases the risk of stuck pipe
• Improves hole cleaning
• Decreases friction between drill string and borehole
• Increases ROP due to higher power at bit
Oktay Mamedbekov. Directional Drilling. Deflection Tools.
4.5 Maximum Recommended Bend Angle for Rotary
Mode (Speeds up to 100 RPM) Courtesy: Tomahawk Downhole
Oktay Mamedbekov. Directional Drilling. Deflection Tools.
6- ¾” Down Hole Motor Hole Size, inch Maximum Bend, degrees
Slick 7-7/8 1.25
8-1/2 1.50
8-3/4 1.50
9-7/8 1.75
Partially Stabilized Motor has a 1/8” under gauge near-bit stabilizer
7-7/8 1.25
8-1/2 1.50
8-3/4 1.75
9-7/8 1.75
Fully Stabilized Motor has a 1/8” under gauge near-bit stabilizer and a 1/8” under gauge top stabilizer above the motor
7-7/8 1.25
8-1/2 1.25
8-3/4 1.25
9-7/8 1.25
4.5 Bit Offset Courtesy: Short. Directional & Horizontal Drilling
DTU Bent Sub Bent Sub & Bent Housing
Oktay Mamedbekov. Directional Drilling. Deflection Tools.
4.5 Theoretical Build Rates
“Three-Point-Curvature” Calculations
Oktay Mamedbekov. Directional Drilling. Deflection Tools.
L2
θ
L1 Bit
Bent
Housing
Motor Top
Stabilizer
i – build rate, deg/100ft
θ – bent angle, deg
L1 – distance from bit to bent housing, ft
L2 – distance from bent housing to motor
top stabilizer, ft
4.5 Build Rates (deg/100ft) for 6-3/4” Mud Motor Courtesy: Tomahawk Downhole
Oktay Mamedbekov. Directional Drilling. Deflection Tools.
Angle Hole Size(in) – Slick Sleeve Hole Size(in) – Stabilized
(deg) 7-7/8 8-1/2 8-3/4 9-7/8 7-7/8 8-1/2 8-3/4 9-7/8
0.50 0.82 0.93 2.92 3.39 3.58 4.42
0.75 2.80 1.05 0.36 4.47 4.94 5.13 5.97
1.00 4.78 3.03 2.34 6.02 6.49 6.68 7.52
1.25 6.76 5.02 4.32 1.18 7.57 8.04 8.22 9.07
1.50 8.74 7.00 6.30 3.16 9.12 9.58 9.77 10.61
1.75 10.72 8.98 8.28 5.14 10.66 11.13 11.32 12.16
2.00 12.70 10.96 10.26 7.12 12.21 12.68 12.87 13.71
2.25 14.69 12.94 12.24 9.10 13.76 14.23 14.42 15.26
2.50 16.67 14.92 14.22 11.08 15.31 15.78 15.97 16.81
2.75 18.65 16.90 16.20 13.06 16.86 17.33 17.51 18.36
3.00 20.63 18.88 18.18 15.04 18.41 18.88 19.06 19.91
4.6 Rotary Steerable Systems
Auto Trak (Baker Hughes)
Power Drive (Schlumberger)
Geo-Pilot (Halliburton)
Oktay Mamedbekov. Directional Drilling. Deflection Tools.
4.6 AutoTrak Courtesy: Baker Hughes
Oktay Mamedbekov. Directional Drilling. Deflection Tools.
4.6 AutoTrak Courtesy: Baker Hughes
Oktay Mamedbekov. Directional Drilling. Deflection Tools.
4.6 Power Drive Courtesy: Schlumberger
Control Unit Steering Unit
Oktay Mamedbekov. Directional Drilling. Deflection Tools.
4.6 Power Drive Steering Unit
Courtesy: Schlumberger
Oktay Mamedbekov. Directional Drilling. Deflection Tools.
4.6 Rotary Steerable Systems
• Deliver consistent steering and high ROP
• Improve hole quality by reducing tortuosity
• Reduce torque and drag due to continuous string rotation
• Better hole cleaning and less clean up time
• Recommended for use in offshore and extended reach
applications
Oktay Mamedbekov. Directional Drilling. Deflection Tools.