WITSML Log Enhancement for Wireline Data

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WITSML Log Enhancement for Wireline Data

• Jim Theriot, POSC
• 16 Nov 2004
• Jim.Theriot_at_POSC.org
• 1 713 267 5109

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Log Data FormatsHistory

• LIS, DLIS
• comprehensive support for wireline data (/-)
• binary formats
• LAS
• text format
• simplified log model
• WellLogML v1.0
• text format (XML)
• simplified log model

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History (contd)

• POSC began work on WellLogML v2.0
• Requirement fully support wireline data
• WITSML developing Log object
• POSC committed to log format compatibility
• WellLogML v2.0 put on hold
• WITSML v1.2 released
• text format (XML)
• simplified log model

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History (contd)

• POSC WITSML SIG is formed
• POSC takes on role in maintenance of WITSML
  objects
• POSC envisions extended scope of WITSML
  objects, architecture across EP
• POSC proposes enhancements for wireline data

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New Features

• Multipass log model
• Fast channels efficiently supported
• Array data efficiently represented
• Dimensionality of array data characterized

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Terminology What is a log, anyway?

• pass set of curves, continuously recorded
  created by logging instrument and acquisition
  process
• log set of passes, packaged as deliverable of a
  logging job created by system at wellsite
• composite log merged result of multiple logging
  jobs created by technician in office pass and
  log context are minimized

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Log (loggers view)
Wellbore (context)
Job (event)
log
service type
Pass (event)
curve type
curve
data
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Log (simplified view)
wellbore
log pass
service type
curve type
curve
data
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Composite Logsupress artifacts job, pass
wellbore
log
service type
curve type
curve
data
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Single Pass Log schema
logs
log
logHeader
indexType, startIndex, endIndex, direction, indexC
urve
logData
logCurveInfo
data
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Multipass Log schema
logs
id, pass, indexType, startIndex, endIndex, directi
on, indexCurve
log
logHeader
block
channel
logData
logCurveInfo
blockId
level
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Fast/Slow ChannelsWhat is a fast channel?

• A fast channel is a channel which is recorded
  at a sample rate higher than the nominal sample
  rate of the concurrently recorded samples
  (usually an integer multiple of the nominal
  sample rate)
• Problems with simple representation
• Excessive nulls
• Cumulative indexing errors

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Array channels(representational)

• Simple channel
• atomic value at each depth
• e. g. X(6600.0 ft) 2.15 gm/cc
• Array channel
• array value at each depth
• e. g. Y(6600.0 ft) 1.3,1.6,1.4,2.1,4.3mD

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Array channels(logical)

• Simple channel S fcns(depth)
• Array channel A fcna(depth,)
• 1D A1 fcna1(depth,pty_a)
• 2D A2 fcna2(depth,pty_a, pty_b)
• 3D A3 fcna3(depth,pty_a, pty_b, pty_c)

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Array examples

• formation acoustic slowness fcn(depth)
• formation acoustic response fcn(depth,
  time)
• formation acoustic response, directional
  fcn(depth, time, azimuth)

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Array Dimensionality

• What is the positional semantics of the array?
• X2.1, 2.4, 2.7, 2.3, 2.6, 2.5 gt ???
• Ordered (by rank) list of dimensions
• Name, description, count, values,
• nameazimuth count6 values0,60,120,180,240,30
  0(deg)
• gtX120(deg)2.7

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Array Definition Schema
logCurveInfo
typeLogData
arrayDef
encodingDef
count, name, propertyType, uom
axisDef
axisValues
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Curve Data Schema
blockId
level
data
channelIndex
DoubleArray
Base64Array
channelIndex
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Base64 encoding

• Similar to hexadecimal
• Internet standard for encoding of binary data
  IETF RFCs 1421 2045
• encode 6 bits as A-Z,a-z,0-9,,/
• efficient representation expansion factor of
  1.33 compared to binary

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Conclusions

• Discussed by WITSML group in Paris
• Recommendation
• Retain current WITSML Log object
• Create new object with enhanced features
• If/when new object is taken up, decide whether to
  keep both objects or drop the current object

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Conclusions

• What about WellLogML?
• deprecate?
• freeze at v1.0?
• develop to distinct requirements?
• wait for WITSML Log enhancements takeup?
• Inviting suggestions and recommendations
  (especially from WellLogML early adopters!)

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Questions?

• Jim Theriot, POSC
• 16 Nov 2004
• Jim.Theriot_at_POSC.org
• 1 713 267 5109