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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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