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OUIJA BOARD

Is a tool which can be used to determine the performance of themud motor referred to as the Ragland diagram or in its slide-rule form,the Ouija Board.

It is based on a simple vector diagram

- The vector has:

- a magnitude equal to the hole inclination

- a direction equal to hole direction

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VECTOR DIAGRAM (RAGLAND)showing dog leg required to change hole direction

Initial Inclination

New incl

ination

Direction change

Dog

Leg

f = Tool Face Orientation Relative to High Side

Observations:1. For a given dog leg, the change in direction which can be achieved decreases with increasing inclination2. When there is no change in direction between survey stations, the change in inclination becomes the dog leg

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OUIJA BOARD S SCALES

A. Previous Drift Angle (0-250 and 0-500)B. Dog Leg (Semicircles)

C. Direction Change - is the outside scale

D. New Drift Angle - is the rotating scale

E. Tool Rotation (0-1800 from High Side)

Dog Leg x 100Course LengthDog Leg Severity (

0/100ft) =

It is necessary to know 3 of these values,than use the Ouija Board to find the other 2!

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OUIJA BOARD S SCALES

APrevious Drift Angle

B Dog Leg

C Direction ChangeD New Drift Angle E Tool Rotation (0-1800)

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HOW TO USE THE OUIJA BOARD

1. Set Previous Drift Angle to the known value

2. Locate your other two known values on the Ouija Board

3. Read off the two unknown values from the Ouija Board

Notes:1.Ouija Board can not be used to measure the Reactive Torque2.Ouija Board can be used only at inclination > 50, when a good high side has been established in the hole

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TYPICAL USES OF THE OUIJA BOARD

A. Estimating Dog Leg and Dog Leg Severity (DLS)

1. Set value of inclination at first survey station on "Previous DriftAngle" scale.2. Set rotating scale to appropriate division on "Resultant DirectionChange on outside scale.3. Locate the value of the second inclination on the "New Drift Angleruler.4. Read off the dog leg where the second inclination intersects thedog leg semicircle.5. Normalize the dog leg to 100' course length to find DLS

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TYPICAL USES OF THE OUIJA BOARD

B. Find the Tool Face setting to give a desiredturn while building (or dropping) angle

C. Achieve a desired build (or drop) in anglewhile turning the hole

D. Calculate the expected new direction andinclination given a certain tool face and dog legseverity

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DEFLECTION TOOL CALCULATIONS

Dog Leg = ( cos )a b ab c2 2 2+ -where

b = drift angle of survey point 1

a = drift angle of survey point 2

c = change in direction

Tool Face Setting

1. If b > a, i.e., inclination dropping over the course length

TF = 180 - tan-1a c

b a csin

cos- 2. If b < a, i.e., inclination increasing over the course length

TF = tan-1a c

a c b

-sin

cos

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DEFLECTION TOOL CALCULATIONS

Expected Change of Hole Direction

c = tan -1Dogleg toolface setting

b Dog Leg toolface setting

+ sin ( )

( cos )

New drift angle

Dog Leg tool face settingExpected change of direction

sin ( )sin ( )a =

Maximum change of direction possible

cmax = sin -1(Dog Leg)

(Present Drift Angle) a