Concept Design of Look Ahead & Look Around LWD Tool

Shanjun Li & Weishan HanBeyond Bits Technology

4/25/2018

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Contents

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Introduction of ME Antenna

Concept Design of Look Around Tool

Concept Design of Look Ahead & Look Around Tool

Conclusions

X

Y

Z

Magnetic Dipole Antenna Electric Dipole Antenna

ME Antenna

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SHjVm lEVe

Half circle

SHjVm

lEVe +

Magnetic Dipole: Magnetic antenna

Electrical Dipole: Electrical Antenna

=

ME Antenna(Cont.)

anglerotationis BBT

ME Antenna

T R Z

X

Y

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ME Antenna(Cont.)

5ft

DTB=10ft

r = 4in

R = 1ohm.m

R = 1E-7 ohm.m

Frequency: 100KHz

Z

Signal Strength Difference: 74.2X

0.00104v

ME antenna as receiver: 0.5Vmmzz +VmezyCos(Pha)

1.4E-5v

Tilt coil as Receiver: Vmmzz+VmmzxCos(pha)

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ME Antenna(Cont.)

T R

Formation Model:

Z

ME Antenna(Cont.)

X

Y

SHjVmmzx

Spacing(in)

|Sig

nal

|(v)

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lEVmezy

Spacing(in)

|Sig

nal

|(v)

Signals is EM wave reflected by formation boundary, and measured by receiver.

Spacing Effects on Measurement

Frequency=100k(Hz)

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ME Antenna(Cont.)

Spacing Effects on MeasurementS

ign

al S

tren

gth

(v)

Tool Spacing(inch)

Vmezy Vmmzx

Rs=1(ohm.m)

Rd=100(ohm.m)

DTB

T R

Spacing:ME: 4 ft Tilt Coil: 4, 25, 50,75, 100ft

Depth

Formation Model:

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ME Antenna(Cont.)

DTB Effects on Measurement

Frequency: 100K(Hz)

Z

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V mmzx & Vmezy

ME Antenna(Cont.)

Tilt Coil, with 100ft spacing and more than 1000 turns, can receive similar strength signals one ME antenna, with 4ft spacing , does.

Contents

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Introduction of ME Antenna

Concept Design of Look Around Tool

Concept Design of Look Ahead & Look Around Tool

Conclusions

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T1 T2R1 R2

1. Conventional LWD resistivity measurement;

2. Geosteering measurement(like PeriScope, AziTrak and ADR);

3. Very deep measurement (like Geosphere, VisiTrak )

And with small tool dimension

Look Around Tool Structure

Two magnetic antenna transmitter and two ME antenna receiver

Rs=1(ohm.m)

Rd=100(ohm.m)

1010

DTB

T R

50 in

1000

990

1040

1030

1020

Depth

Model:

Look Around Tool Structure(Cont.)

ME Antenna receiver

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mezymmzz

mezymmzz

dn

up

VV

VV

V

VRatio

Frequency=100k(Hz)

Frequency：100KHz

Model

Phase To DTB

Look Around Tool Structure(Cont.)

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dn

up

V

VRatio

Frequency: 100KHz

Amplitude To DTB

Model

Look Around Tool Structure(Cont.)

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Frequency=4k(Hz)Boundary detection ability up to 60*5=300ft.

If the threshold is 0.02,

the boundary detection

range will reach 60 ft.

dn

up

V

VRatio

Depth(ft)S

ign

al (

v)

Amplitude To DTB

Depth(ft)

Sig

nal

(v)

Contents

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Introduction of ME Antenna

Concept Design of Look Around Tool

Concept Design of Look Ahead & Look Around Tool

Conclusions

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Look Ahead &Look Around Tool Structure

T1 T2R1 R2T3

1. Conventional LWD resistivity measurement;

2. Geosteering measurement(same as PeriScope, AziTrak and ADR);

3. Very deep measurement (same as Geosphere, VisiTrak )

4. Look ahead measurement

X

Y

Z

Look Ahead &Look Around Tool Structure(Cont.)

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R2

R1

X

Y

Z

Tmy

Rmz2

Rmz1

Rex2

Rex1

Tmy~Rmz1 & Tmy~Rmz2will measure Vmmyz (Vyz or Vxz))which will be used for look around. Vmmyz has no sensitivity to boundary ahead of bit.

Tmy~Rex1 & Tmy~Rex2will measure Vmeyx .

Symmetrical Design

Tmy has very large contribution to Vmeyx1 and Vmeyx2. Vmeyx1+ Vmeyx2 make the contributions on R1 and R2 cancel each other.

Vmeyx1+ Vmeyx2 is sensitivity to boundary ahead of it, only, and no signal in homogeneous medium.

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X

Y

Boundary

T

R

Spacing=4(ft)

Look Ahead Model

R1=1(ohm-m)

R2=100(ohm-m)

R1=1(ohm-m)

R2=100(ohm-m)

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Signal Strength Comparison

If Vxx can see boundary ahead 20ft, Vmexy can see boundary more than 65 ft away.

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Conclusions

1. ME antenna was defined as a combination of magnetic antenna and electric antenna.

2. ME antenna can receive much stronger signals reflected by formation boundary than coils as receiver does;

3. Experiment shows ME antenna works;4. Use ME antenna as receiver or transmitter, tool can

see ahead and around formation boundary far from it, and tool dimension can be small.

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