Directional Drilling And Surveying
What is Directional Drilling? Directional Drilling is the process of directing a well bore along some trajectory to a predetermined target. Basically it refers to drilling in a non-vertical direction. Even “vertical” hole sometimes require directional drilling techniques. Examples: Slanted holes, high angle holes (far from vertical), Extended Reach Holes, and Horizontal holes.
Non-Vertical Wellbore
θ, α or I Inclination Angle
n o i t a n i l Inc e Y n a l P
Z Axis (True Vertical Depth) North Direction φ, ε or A Angle Direction Plane X
Lease Boundary Surface Location for Well No. 2
Surface Location for Well No. 1
Bottom Hole Location for Well 2 Houses
Oil-Water Contact
Figure 8.2 - Plan view of a typical oil and gas structure under a lake showing how directional wells could be used to develop it. Best locations? Drill from lake?
Top View
NOTE: All the wells are directional
5 - 50 wells per platform
Figure 8.3 - Typical offshore development platform with directional wells.
Drilling Rig Inside Building
Figure 8.4 - Developing a field under a city using directionally drilled wells.
Why not drill from top of mountain ?
Maximum lateral displacement
Fig. 8.5 - Drilling of directional wells where the reservoir is beneath a major surface obstruction.
Cement Plug
Fish Lost in Hole and Unable to Recover Sidetracked Hole Around Fish Figure 8.6 Sidetracking around a fish.
Figure 8.7 Using an old well to explore for new oil by sidetracking out of the casing and drilling directionally.
Oil Producing Well Ready to Abandon Sidetracked Out of Casing Possible New Oil Old Oil Reservoir
Horizontal Departure to Target
Type II Build-hold and Drop (“S Type”)
Type I Type III
Build and Hold Type
Build-hold Drop and/or Hold (Modified “S” Type)
Continuous Build
Figure 8.8 - Major types of wellbore trajectories.
Figure 8.10 Geometry of the build section.
Build Section θ
Build Radius:
18,000 r1 = π * BUR
Build Section: Length of arc, L = r1θ1 Vertical depth = C’D’ = r1 sin θ1 Horiz. Depart. = DD’ = r1 (1-cos θ1 ) r1
L = θ
1
100
=
1
↑
rad
18,000 r1 = π * BUR
θ
π * 180
1 ↑
deg
BUR = build rate in deg/100 ft
Start of Buildup End of Build
Type II
Drop Off Target
Build-hold-and drop for the case where: r1 < x 3 and r1 + r2 < x 4
Kickoff Type II
End of Build Maximum Inclination Angle
Build-hold-and drop for the case where:
r1 < x3 and r1 + r2 > x4
Drop Off
Target
Projected Trajectory
Projected Trajectory with Left Turn to Hit Targets
Target 1 Target 2 Target 3
Fig. 8-14. Directional well used to intersect multiple targets
N18E
S23E A = 157o
Fig. 8-15. Directional quadrants and compass measurements N55W S20W A=?
A = 305o
Lead Angle
Projected Well Path
Surface Location for Well No. 2 Lake
Figure 8-16: Plan View
Target at a TVD 9,659
Well profile
Directional Drilling Operation
Deviation due to Formation Dip
Deviation due to Hardness of Formation
Deviation due to Miniature Whipstock Theory
Directional Tools • (i) Whipstock • (ii) Jet Bits • (iii) Downhole motor and bent sub
Whipstocks
Standard retreivable
Circulating
Permanent Casing
Setting a Whipstock • Small bit used to start • Apply weight to: – set chisel point & – shear pin
• Drill 12’-20’ • Remove whipstock • Enlarge hole
Jetting Bit • Fast and economical • For soft formation • One large - two small nozzles • Orient large nozzle • Spud periodically • No rotation at first
Small Jets
Jetting • Wash out pocket • Return to normal drilling • Survey • Repeat for more angle if needed
Mud Motors Drillpipe Non-magnetic Drill Collar Bent Sub Mud Motor Rotating Sub
Increasing Inclination • Limber assembly • Near bit stabilizer • Weight on bit forces DC to bend to low side of hole. • Bit face kicks up
Hold Inclination • Packed hole assembly • Stiff assembly • Control bit weight and RPM
Decrease Inclination • Pendulum effect • Gravity pulls bit downward • No near bit stabilizer
Packed Hole Assemblies
Drill pipe
String String NB Stabilizer Stabilizer Stab Monel Steel DC Steel DC DC
String Stabilizer HW DP
Vertical Calculation
Horizontal Calculation
3D View
Dog Leg Angle
Deflecting Wellbore Trajectory 0
270
90
180
Bottom Hole Location Direction
: N 53
Distance
:
TVD
:
2,550
o
E ft
10,000 E = 2,550 sin 53 o = 2,037 ft N = 2,550 cos 53 o = 1,535 ft
Closure = 2,550
=
E 2 + N2
⎛E ⎞ Closure Direction = tan ⎜ ⎟ = 53 o ⎝N⎠ -1
Horizontal N View Vertical View We may plan a 2-D well, but we always get a 3D well (not all in one plane)
MD, α1, ε1 ∆MD β = dogleg angle
α2 , ε 2
Fig. 8-22. A curve representing a wellbore between survey stations A1 & A2
Bottom Hole Location Direction : N 53o E Distance : 2,550 ft TVD :
10,000 E = 2,550 sin 53 o = 2,037 ft N = 2,550 cos 53 o = 1,535 ft
Closure = 2,550
= E 2 + N2
⎛E⎞ Closure Direction = tan ⎜ ⎟ = 53o ⎝N⎠ -1
Survey Calculation Methods 1. Tangential Method = Backward Station Method = Terminal Angle Method
Assumption: Hole will maintain constant inclination and azimuth angles, IB and AB , between survey points.
A
Known : Location of A Distance AB Angles IA , IB
IA IB
Angles A A , A B Calculation : VAB = AB cosIB HAB = AB sinIB B IB
Poor accuracy!!
Average Angle Method = Angle Averaging Method Assumption: Borehole is parallel to the simple average drift and bearing angles between any two stations. Known: Location of A, Distance AB, Angles I A , IB , A A , A B
A
Average Angle Method (i) Simple enough for field use
IA
(ii) Much more accurate than “Tangential” Method
IB IAVG
Iavg B IAVG
A avg
⎛ I A + IB ⎞ =⎜ ⎟ ⎝ 2 ⎠ ⎛ A A + AB ⎞ =⎜ ⎟ 2 ⎠ ⎝
A
Average Angle Method Vertical Plane:
IA IB
Iavg
IAVG B IAVG
⎛ I A + IB ⎞ =⎜ ⎟ ⎝ 2 ⎠
V AB = AB cos Iavg H AB = AB sin Iavg
Average Angle Method
N
Horizontal Plane: AB
B AAVG
∆N
AA
∆E
A
H AB = AB sin Iavg
∆ E = AB sin Iavg sin A avg ∆ N = AB sin Iavg cos A avg ∆ Z = AB cos Iavg E
Change in position towards the east: ⎛ IA + IB ⎞ ⎛ A A + AB ⎞ ∆ x = ∆ E = L sin ⎜ ⎟ sin ⎜ ⎟..(1) 2 ⎝ 2 ⎠ ⎝ ⎠
Change in position towards the north: ⎛ I A + IB ⎞ ⎛ A A + AB ⎞ ∆ y = ∆ N = L sin ⎜ ⎟ cos ⎜ ⎟..( 2 ) 2 ⎝ 2 ⎠ ⎝ ⎠
Change in depth: ⎛ I A + IB ⎞ ∆ Z = L cos ⎜ ⎟ ⎝ 2 ⎠
..( 3 )
Where L is the measured distance between the two stations A & B (∆MDAB).
Example The coordinates of a point in a wellbore are: x = 1,000 ft (easting) y = 2,000 ft (northing) z = 3,000 ft (depth) At this point (station) a wellbore survey shows that the inclination is 15 degrees from vertical, and the direction is 45 degrees east of north. The measured distance between this station and the next is 300 ft….
Example The coordinates of point 1 are: x1 = 1,000 ft (easting) o y1 = 2,000 ft (northing) I1 = 15 o z1 = 3,000 ft (depth) A1 = 45 L12 = 300 ft o
At point 2, I2 = 25 Find
o
and A2 = 65
x2 , y2 and z2
Solution Iavg A avg
⎛ I1 + I2 ⎞ ⎛ 15 + 25 ⎞ =⎜ ⎟=⎜ ⎟ = 20 2 ⎝ 2 ⎠ ⎝ ⎠ ⎛ A 1 + A 2 ⎞ ⎛ 45 + 65 ⎞ =⎜ ⎟ = 55 ⎟=⎜ 2 2 ⎝ ⎠ ⎝ ⎠
H12 = L12 sin Iavg = 300 sin 20 = 103 ft ∆E = H12 sin Aavg = 103 sin 55 = 84 ft ∆N = H12 cos Aavg = 103 cos 55 = 59 ft ∆Z = L12 cos Iavg = 300 cos 20 = 282 ft
Solution - cont’d ∆E = 84 ft ∆N = 59 ft ∆Z = 282 ft x2 = x1 + ∆E = 1,000 + 84 ft = 1,084 ft y2 = y1 + ∆N = 2,000 + 59 ft = 2,059 ft z2 = z1 + ∆Z = 3,000 + 282 ft = 3,282 ft
Dog Leg
Problem 3 Determine the dogleg severity following a jetting run where the inclination was changed from 4.3o to 7.1o and the direction from N89E to S80E over a drilled interval of 85 feet. 1. Solve by calculation. 2. Solve using Ragland diagram
α = 4 .3 ε = 89
o
L = 85 ft
o
∆α = 7.1 - 4.3 = 2.8.
α N = 7.1
o
ε N = 100
o
∆ε = 100 - 89 = 11
Solution to Problem 3- Part 1 1. From Equation 8.55 ⎞⎤ ⎟⎥ ⎠⎦
1/ 2
⎡ 2 2 .8 2 11 2 ⎛ 4 .3 + 7 .1 ⎞ ⎤ sin ⎜ β = 2 sin ⎢ sin + sin ⎟⎥ 2 2 2 ⎝ ⎠⎦ ⎣
1/ 2
⎡ 2 ∆α 2 ∆ε 2 ⎛ α + αN β = 2 sin ⎢ sin + sin sin ⎜ 2 2 ⎝ 2 ⎣ −1
−1
β = 3.01
o
Solution to Problem 3- Part 1 1. From Equation 8.43 the dogleg severity,
δ =
β (i) L
δ = 3 .5
= o
3 . 01 85
∗ 100
/ 100 feet
Directional Drilling Measurements • The trajectory of a wellbore is determined by the measurement of: hinclination
θ, α, I
hdirection
φ, ε, A
hmeasured depth
∆MD, ∆L, L
Directional Drilling Measurements - cont’d • A tool-face measurement is required to orient: ha whipstock hthe large nozzle on a jetting bit ha bent sub or bent housing
Directional Drilling Measurements - cont’d • Tools available hsingle-shot magnetic or gyroscopic hmulti-shot magnetic or gyroscopic hmagnetometers, accelerometers, MWD tools
Magnetic Single-Shot Instrument • Records – inclination – direction – tool face position on sensitized paper or photographic film
• Inclination may be determined by – a float on a liquid – a pendulum
Magnetic Single-Shot Instrument • Unit may be triggered by: – clock timer. – inertial timer (after stop).
• Unit may be dropped (pumped down) and later retrieved by wireline or the drillpipe.
Magnetic Single-Shot Instrument • Single-shot instruments are used: – to monitor progress of directional-control well. – to monitor progress of deviation-control well. – to help orient tool face for trajectory change.
Magnetic Single-Shot Instrument - cont’d • Procedure: – load film into instrument – activate timer (activate stopwatch) – make up the tool – drop the tool – retrieve tool (wireline or drillpipe)
Light
Housing Center Post Float Fluid Reference Mark
Main Frame Photographic Disc A. 0-20o Angle-Compass Unit
B. 0-70o Angle-Compass Unit
Fig. 8.41: Schematic diagrams of magnetic single-shot angle-compass unit (courtesy Kuster Co.).
1. Pendulum
Fig. 8.43: Pendulum suspended inclinometer and compass unit for a 0 to oo 17 singeshot unit.
2. Circular Glass 3. Compass 4. Pressure equalization 5. Cover glass
Indicated inclination 5o. Direction of inclination N 45 degrees 0’ or azimuth 45 degrees.
A/C Units
Plumb-Bob Units
Incl. Only Units
Fig. 8.42: Single-shot film disks (courtesy of Kuster Co.). • Inclination • Direction • Tool Face Angle
Fig. 8.12: Pendulum assembly: a) plumbbob angle unit b) drift arc inclinometer Pendulum Glass ring Piston
(a)
(b)
Fig. 8.13: Schematic drawing of magnetic single and multi-shot instruments.
o
N35 W o I = 5.5
Hole direction with reference to Magnetic North
Compass Inclination Scale
Fig. 8.44: Cardan suspended compass and inclinometer for a single-shot o
o
5 to 90 unit.
Wire Line Socket Overshot
Rope Socket Swivel Stabilizer Stabilizer Fingers
Protective Case Orienting Anchor & Plug Mule Shoe Mandrel
Fig. 8.45: Typical magnetic single-shot tool with landing sub.
Bottom Hole Orienting Sub Bottom Landing Assembly Takes time. Rig time is costly. Temperature limitation. May have to pump down.
Ready to be Dropped
Free Falling to Bottom
Tool seated
Retrieve single shot
Fig. 8.46: Typical single-shot operation.
Timer On 3 min.
Compass Unit *Single Shot Instruments are run on slickline if there is a mule shoe sub in the hole
Single Shot Ready to be Dropped
Single Shot Free Falling in Mud to Bottom
Non Magnetic Drill Collar Orienting Sub Sleeve
Fig. 8.46: Typical single-shot operation.
Fig. 8.46: Typical single-shot operation. Tool seated in orienting sleeve or at stop taking picture
3 min.
10 min.
Overshot Used to Fish Single Shot
Wireline unit to retrieve single shot
Top View Direction of Tool Face Via Bent Sub
Fishing Neck Non Magnetic Collar Single Shot Mule Shoe Orienting Sub Orienting Sleeve Lined up with Bent Sub Bent Sub
Mule Shoe Key Position
New Centerline
Mud Motor
Existing Centerline
Fig. 8.47: Arrangement of the mule shoe for orienting a mud motor.
Magnetic Multishot Instruments • Are capable of taking numerous survey records in one run. • May be dropped down the drillpipe or run on wireline in open hole. • The unit contains a watch that is spring wound and uses the power of the spring to operate a timer cam.
Non-Magnetic Drill Collar(s)
Compass Position Multi-shot Instrument
Landing Plate
Fig. 8.48: Typical arrangement for landing a multi-shot instrument.
Bottom Landing Rope Socket Stabilizer with Rubber Pins Battery Case Battery Connector Connector Shock Absorber Watch Assembly
Protective Instrument Barrel Angle Unit Barrel Lower Ball Plug Aluminum Spacer Bar Bottom Shock Absorber Assembly
Fig. 8.49: Drop multi-shot survey instrument
Watch Section
Motor
Light Switch Lever
Geneva Gear
Knife Geneva Drive Winding Motor Wheel Assembly Switch Stem Lever Watch Switch Terminal Film Sprocket Switch
Time Cycle Cam
Takeup Film Supply Film Spool Spool
Fig. 8.50: Views of the watch and camera unit of a typical multi-shot tool.
Magnetic Multishot - cont’d • The multishot tool is usually dropped down the drillpipe and landed in the nonmagnetic drill collar. • During the trip out, a survey is taken every 90 ft, i.e. every stand.
Magnetic Multishot - cont’d • More closely spaced stations could be obtained by stopping the pipe more often, and waiting for a picture. • A stopwatch at the surface is synchronized with the instrument watch.
Fig. 8.51: Use of the surface watch while running a magnetic multi-shot operation.
Synchronize with instrument watch by starting at the instant camera lights go on.
Time Intervals: A. 10 seconds Lights are on, exposing film B. 15 seconds - Delay before moving. This is an allowance for instrument watch lag during survey.
Time Intervals - cont’d C. 20 seconds - Instrument is idle allowing movement of drill string without affecting picture. Most moves require sufficient time for taking one or more shots while moving D. 15 seconds - Minimum time for plumb bob and compass to settle for good picture, plus allowance for instrument gain during survey.
Fig. 8.52b: Projection of one survey frame for determining inclination and direction.
Steering Tools • Used with mud motors and bent sub • Can either pull every stand or use a side entry sub for continuous drilling
Standard Measuring Cable
Monel DC Probe Mule Shoe Bent Sub Mud Motor
MWD Tools
MWD Tools
Gyroscopic Tools • Non-magnetic drill collars used to prevent magnetic interference from drillstring • Gyros used if magnetic interference is from non drillstring source