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.

North

Direction Angle

Direction Plane X

Inclination AngleZ Axis (True Vertical

Depth)Inclina

tion

Plane Y

, or I

, or A

Non-Vertical Wellbore

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?

Lease Boundary

Surface Location for Well No. 1

Bottom Hole Location for Well 2

Surface Location for Well No. 2

Houses

Oil-Water Contact

Figure 8.3 - Typical offshore development platform with directional wells.

NOTE: All the wells are directional

Top View

5 - 50 wells per platform

Figure 8.4 - Developing a field under a city using directionally drilled wells.

Drilling Rig Inside Building

Fig. 8.5 - Drilling of directional wells where the reservoir is beneath a major surface obstruction.

Why not drill from

top of mountain

?

Maximum lateraldisplacement

Figure 8.6 -Sidetracking

around a fish.

Sidetracked Hole Around Fish

Fish Lost in Hole and Unable to Recover

Cement Plug

Figure 8.7 -Using an old

well to explore for new oil by sidetracking

out of the casing and

drilling directionally.

Possible New Oil

Sidetracked Out of Casing

Oil Producing Well Ready to Abandon

Old Oil Reservoir

Figure 8.8 - Major types of wellbore trajectories.

Build and Hold Type

Continuous Build

Build-hold Drop and/or Hold (Modified S Type)

Build-hold and Drop (S Type)

Horizontal Departure to Target

Type I

Type III

Type II

Build Section

Build Radius:

BUR*,

=00018r1

Figure 8.10 -Geometry of the

build section.

Build Section:

==

deg rad

180*

100Lr 1

1

11

BUR*,

=00018r1 BUR = build rate in deg/100 ft

Length of arc, L = r11Vertical depth = CD = r1 sin 1Horiz. Depart. = DD = r1 (1-cos 1 )

Build-hold-and drop for the case where:42131 xrr and xr

Build-hold-and drop for the case where:

Kickoff

End of Build

Maximum Inclination Angle

Drop Off

Target

42131 xrr and xr >+