(015)Encoding&DecodingV2

TRANSMISSION SEQUENCE
Flow begins
Probe is powered up
30 second warm up period
Running pulses start
Probe controls the solenoid to actuate poppet
Poppet restricts flow area creating a positive pressure
Pulse is transmitted at about 4000 ft/sec
Pulses are measured by the transducer and encoded by the surface computer via the barrier box

MUD CIRCULATING SYSTEM

MUD CIRCULATING SYSTEM

DATA
ENCODING / DECODING
Encoding:
Manchester (more reliable)
Decoding:
Algorithm M12 (NEW)
Algorithm Double Level Threshold (DLT)

© 2000, Halliburton Energy Services, Inc.
09/16/2023
Manchester Encoding
Encoding is how the data is written
It Defines 0’s & 1’s with positive pulse pressure surges.

© 2000, Halliburton Energy Services, Inc.
09/16/2023
BIT
Smallest Piece of Information
Either data bits or parity bits
Bit is either 0 (Low to High) or 1 (High to Low)
Like letters of alphabet (,b,c,…)

WORD
Word is a piece of information ( Inclination, Azimuth, toolface, etc )
Made of 5 Bits (shortest) up to 13 Bits (longest)
Word contains data bits and one even parity bit.
Parity bit will be added Downhole before transmitting the word to be valid for detection.
Parity Bit will be 0 if the number of 1’s in data bits is devisable by 2, otherwise it will be 1.
Word is valid for encoding only if passed parity check.
Even parity: Sum of 1’s in a word is an even number

BLOCK
A group of words in a specific sequence
(i.e. Survey, Toolface list)
Always Begins with a Flag/Tag Sequence
Synchronizing Surface Computer with probe

© 2000, Halliburton Energy Services, Inc.
09/16/2023
Wait period
30 second
10 for 0.5 Hz
16 for .8 Hz
20 seconds

© 2000, Halliburton Energy Services, Inc.
09/16/2023
Flag
Synchronizes surface computer with down hole probe.
Made up of 0 1 1 1 1 1 1 0 (double high, 5short pulses and double low).
Surface computer halts pervious detection, identify new block start.
Defines the start of decoding (0’s & 1’s) as all the running pulses are zeros (10 for 0.5 Hz & 16 for 0.8 Hz).
Begins decoding new tag.
high
high
0
low
1
1
1
1
1
1
0

© 2000, Halliburton Energy Services, Inc.
09/16/2023
Tag
Used for block Identification.
Contains 5 bits, the first is used to identify toolface type : 0 for Magnetic & 1 for Gravity.
Toolface
Contains 7 bits ( six data bits +
one parity bit).
Toolface transmission time is 14 sec. At 0.5 Hz.
Toolface transmission time is 8.7 sec. At 0.8 Hz.

FREQUENCY

© 2000, Halliburton Energy Services, Inc.
09/16/2023
Transmission Frequency
1Pulse 1 Bit
0.5 (Hz) = =
2Seconds 2Seconds
8Pulse 1Pluse(Bit)
0.8 (Hz) = =
10Seconds 1.25 Seconds

MANCHESTER ENCODING
Low to High Pressure Change (Voltage) Represents a “0”

MANCHESTER ENCODING
High to Low Pressure Change (Voltage) Represents a “1”

MANCHESTER EXAMPLE

© 2000, Halliburton Energy Services, Inc.
09/16/2023
Decoding Schemes
Detection Algorithms are :
- Algorithm Double Level Threshold (DLT)
- Algorithm M12 (Mean 12- new)
- Manchester Max (Modified M12)

© 2000, Halliburton Energy Services, Inc.
09/16/2023
Decoding Schemes
Algorithm Double Level Threshold (DLT)
Not a filter but a decision making tool.
Looks at length of pulse to determine long and short pulses.
Pressure signal is sampled 64 times per bit,
Short Pulse < 48 > Long Pulse
Long pulse means change :-
-Long High means change from 0 to 1
-Long Low means change from 1 to 0
So pulses before or after can be sorted.

© 2000, Halliburton Energy Services, Inc.
09/16/2023

© 2000, Halliburton Energy Services, Inc.
09/16/2023
Decoding Schemes
Algorithm M12 (new)
Evaluates the pulse by looking at the slope change during the second half.
A positive slope is a “0”
A negative slope is “1”
it is helpful when receiving too many reflections.

Transmitted Surveys
FULL SURVEY
Probe transmits
Gx
Gy
Gz
Bx
By
Bz
Dmt
Surface computer calculates
Inclination
Raw Azimuth
Absolute Azimuth
Gtotal
Btotal
Dip
Aza-r
Transmission time is about 2.5 times longer than Short Survey

SHORT SURVEY
Probe transmits
Inclination
Raw Azimuth
Gtotal
Dmt
Short Collar Solution CANNOT be used
Probe must be properly spaced in NMDC
No magnetic interference present
Note: Short survey is best used when experiencing detection problems

DRILL STRING INTERFERENCE

SHORT COLLAR SOLUTION
Corrects azimuth for magnetic drill string interference
Bz is corrupted
Mathematically iterates a Bz using theoretical DIP and Btotal
Calculated downhole or surface computer
DEPII/PCD/DM

SHORT COLLAR LIMITATIONS
Cannot correct for cross-axis magnetic interference
Need accurate DIP and Btotal for location
Must have accurately calibrated probes
Must have stable sensor readings

© 2000, Halliburton Energy Services, Inc.
09/16/2023
Probe Operations
Directional Only Modes
Steering Modes :- 1, 2, 4, 5, 6, 8
- Used with steerable BHA
- Will transmit surveys and toolfaces continuously
Survey Only Modes :- 3, 7
- Used with rotary BHA
- Will only transmit three surveys then cease pulsing

© 2000, Halliburton Energy Services, Inc.
09/16/2023
Pumps Up Steering Survey
Available with Modes 1, 2, 4 or with PU Tag(CDS)
Survey sampled and stored during transmission of second TF

© 2000, Halliburton Energy Services, Inc.
09/16/2023
Pumps Up Rotary Survey
Available with Modes 3 & 7 or with PU Tag(CDS)
Survey sampled and stored during transmission of Tag.

© 2000, Halliburton Energy Services, Inc.
09/16/2023
Pumps Down Survey
Available with Modes 5-8 or with PD Tag(CDS)
Drill string is held still for 60 sec. before turning pumps off
Survey is sampled and stored 20-25 sec before pumps off to avoid reactive torque.

© 2000, Halliburton Energy Services, Inc.
09/16/2023
Pumps Off Survey
Survey taken with battery in Modes 5-8 with PD Tag
Survey sampled and stored 30 sec. after pumps off
Drill string is held still 45 sec. after pumps off

© 2000, Halliburton Energy Services, Inc.
09/16/2023
Custom Data String CDS Mode(PCD,DEPII)

© 2000, Halliburton Energy Services, Inc.
09/16/2023
CDS Mode

MUD CIRCULATING SYSTEM