Petroleum Engineering 406

Lesson 21

Wellbore Trajectory Control

Lesson 18 - Wellbore Trajectory Control

Bent Motor and Bent Sub

Examples

Directional Drilling Measurements

Single Shot and Multishot

Magnetic and Gyro

Steering Tools

MWD tools

Homework

READ: “Applied Drilling Engineering”,

Ch. 8 (to page 390)

Fig. 8.39: Bent sub unconstrained and constrained in a wellbore.

Nonmagnetic

Drill Collar

HoleOrienting Sub

Bent Sub

Mud Motor

Bent Sub Angle

Bit

is not necessarily equal to the bent sub angle, but it may be close in (a) above

Problem 1

Determine the effective bent sub response for a 1 1/2o bent sub in a motor run where at 6,357’, = 1o and is S85E and at 6,382, = 1o and is S20E; the tool face is 160o right of high side.

95 160N65

ft25L

1601 1N

Solution to Problem 1

Calculate from Eq. 8.53:

Dogleg severity:

coscossinsincoscos NN1

1cos1cos1sin1sin65coscos 1

07.1999824.0cos 1

ft10028.425

10007.1

L

i o

Solution to Problem 1 - cont’d

If the mud motor length is 25 ft from the bit face to the bent sub, the maximum angle change that could be reached if there are no restrictions is:

The lower rate of build implies that the formation resisted the maximum rate of build by a factor of:

ft1000.625

1005.1 o

72.00.6

3.4

An efficiency factor?

= Bent Sub Angle?

Since the value of for any given run may differ from the bent sub angle, it should not surprise us if

predicted = measured

Let us look at some examples.

77th

62ac 30ac

14th 16ac

33th

Fig. 8.40: Example of three jetting stops while trying to kick off and set the wellbore lead.

Jetted 7’ 1745-52’

Surv 1722’: S32W 2.25o

Orient S90E

Final 1799’:

S30E 2.75o

= -122o

Nozzle Orientation

77th 62ac

Jetted 12’ 1850-62’

Surv 1814’ S20E 3.0o

Orient N80E

Final 1877’ S36E 3.25o

= -80o

14th 16ac

Jetted 6’ 1925-31’

Surv 1877’ S36E 3.25o

Orient N70E

Final 1940’ S66E 4.75o

= -74o

30ac 33th

Directional Drilling Measurements

The trajectory of a wellbore is determined

by the measurement of:

inclination I

direction A

measured depth MD, L, L

Directional Drilling Measurements - cont’d

A tool-face measurement is required to

orient:

a whipstock

the large nozzle on a jetting bit

a bent sub or bent housing

Directional Drilling Measurements - cont’d

Tools available

single-shot magnetic or gyroscopic multi-shot magnetic or gyroscopic magnetometers, 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)

Fig. 8.41: Schematic diagrams of magnetic single-shot angle-compass unit (courtesy Kuster Co.).

LightHousingCenter PostFloat

FluidReference Mark

Main Frame

Photographic Disc

A. 0-20o

Angle-Compass UnitB. 0-70o

Angle-Compass Unit

Fig. 8.43: Pendulum suspended

inclinometer and

compass unit for a 0 to

17oo singe-shot unit.

1. Pendulum

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.

Fig. 8.42: Single-shot film disks

(courtesy of Kuster Co.).

A/C Units Plumb-Bob Units Incl. Only Units

• Inclination • Direction• Tool Face Angle

Fig. 8.12:

Pendulum assembly:

a) plumb-bob angle unit

b) drift arc inclinometer

Pendulum

Glass ring

Piston

(a) (b)

Fig. 8.13: Schematic drawing of magnetic single and multi-shot

instruments.

Hole direction with reference to Magnetic North

N35oW I = 5.5o

Fig. 8.44: Cardan suspended

compass and inclinometer for a

single-shot

5o to 90o unit.

CompassInclination Scale

Fig. 8.45: Typical

magnetic single-shot

tool with landing sub.

Rope Socket

SwivelStabilizerStabilizer Fingers

Wire Line Socket

Overshot

Bottom Landing Assembly

Protective Case

Mule Shoe Mandrel

Bottom Hole Orienting Sub

Orienting Anchor & Plug

Takes time. Rig time is costly. Temperature limitation. May have to pump down.

Fig. 8.46: Typical single-shot operation.

Free Falling to Bottom

Tool seated

Ready to be Dropped

Retrieve single shot

Fig. 8.46: Typical

single-shot operation.

Compass Unit3 min.

Single Shot Free Falling in Mud to Bottom

Non Magnetic Drill Collar

Orienting Sub Sleeve

*Single Shot Instruments are run on slickline if there is a mule shoe sub in the hole

Single Shot Ready to be Dropped

Timer On

Fig. 8.46: Typical single-shot operation.

3 min.

Overshot Used to Fish Single Shot

Tool seated in orienting sleeve or at stop taking picture

Wireline unit to retrieve single shot

10 min.

Fig. 8.47: Arrangement of the

mule shoe for orienting a mud

motor.

Fishing Neck

Non Magnetic CollarSingle Shot

Mud Motor

Top View

Existing CenterlineNew Centerline

Bent SubMule Shoe Key Position

Mule Shoe Orienting Sub

Orienting Sleeve Lined up with Bent Sub

Direction of Tool Face Via Bent Sub

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.

Fig. 8.48: Typical

arrangement for landing a

multi-shot instrument.

Non-Magnetic Drill Collar(s)

Compass Position

Multi-shot Instrument

Landing Plate

Fig. 8.49: Drop

multi-shot survey

instrument

Angle Unit

Rope Socket

Bottom Landing

Battery CaseBattery Connector

Bottom Shock Absorber Assembly

Stabilizer with Rubber Pins

Connector Shock Absorber

Barrel Lower Ball Plug

Aluminum Spacer Bar

Protective Instrument Barrel

Watch Assembly

Fig. 8.50: Views of the watch and camera unit of a typical multi-shot tool.

Watch Section Motor

Light Switch Lever

Geneva Gear

Winding Stem

Time Cycle Cam

Watch Switch

Supply Film Spool

Takeup Film Spool

Film Sprocket

Motor Lever Switch

Geneva Drive Wheel Assembly

Knife Switch Terminal

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.

Synchronize with instrument watch by starting at the instant camera lights go on.

Fig. 8.51: Use of the

surface watch while running a magnetic multi-shot operation.

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:

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.

Time Intervals - cont’d

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

Mud Motor

Bent SubMule Shoe

Monel DC

Probe

Standard Measuring Cable

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