Directionald Drilling 17pg.ppt

Directional Drilling

Directional Drilling  When is it used?  Type I Wells (build and hold)  Type II Wells (build, hold and drop)  Type III Wells (build)  Directional Well Planning & Design  Survey Calculation Methods

References: READ. “Applied Drilling Engineering” Ch. 8, pp. 351-363 REF. API Bulletin D20, “Directional Drilling Survey Calculation Methods and Terminology”

What is Directional Drilling? Directional Drilling is the process of directing a wellbore 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), and Horizontal holes.

Non-Vertical Wellbore

q, a or I Inclination Angle Z Axis (True Vertical Depth) North Direction f, e 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

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 displ.?

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

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

Build Radius:

18,000 r1   * BUR

Build Section: Length ofarc,L1  r1θ 1 Vert icaldepth  C'D' r1sinθ 1 Horiz.dev. DD' r1(1 cosθ 1) L1 100 r1   θ1 θ * π 1 180 



rad deg

18,000 r1   * BUR

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

Build-hold-and drop for the case where:

r1  x3 and r1  r2  x 4

End of Build Maximum Inclination Angle 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 = 157

o

Fig. 8-15. Directional quadrants and compass measurements N55W S20W

A = 305

o

Lead Angle

Projected Well Path

Surface Location for Well No. 2

Lake

Target at a TVD 9,659

Figure 8-16: Plan View

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, a1, e1

DMD b = dogleg angle

a 2, e2

Fig. 8-22. A curve representing a wellbore between survey stations A1 and A2

Directional Drilling 1. Drill the vertical (upper) section of the hole. 2. Select the proper tools for kicking off to a non-vertical direction 3. Build angle gradually

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 Stabilizer

HW DP

String String NB Stabilizer Stabilizer Stab Monel Steel DC Steel DC DC

Vertical Calculation

Horizontal Calculation

3D View

Dog Leg Angle

Deflecting Wellbore Trajectory 0

270

90

180

Bottom Hole Location 

Direction : N 53 E Distance : 2,550 ft TVD :

10,000 E  2,550 sin 53   2,037 ft N  2,550 cos 53   1,535 ft

Closure  2,550



E 2  N2

E Closure Direction  tan -1   53 o N