Quest for quality data
Philippe P. Theys
Technip
AcknowledgementsV
ForewordVII
PrefaceXXI
Chapitre 1
Introduction
Part 1
Why measurements differ from reality
Chapitre 2
Setting the problem with simple examples
2.1 Measurements and reality
5
2.2 Measuring the length of a stick
5
2.3 Measuring the weight of a person with a bathroom scale
6
2.3.1 A minimalist mechanics course on how a bathroom scale works8
2.3.2 Sensitivity of the measurements to parameters9
2.3.3 The pleasing bathroom scale10
2.4 Combining measurements and how a calculator can be deceiving
11
2.5 Comparison with oil industry measurements
11
2.5.1 Unfounded feeling of accuracy and precision on derived properties12
2.5.2 Difference between rock properties and logging measurements13
2.6 Summary
13
References
14
Chapitre 3
All well measurements are indirect
3.1 A brief description of the logging process
15
3.2 Spontaneous potential
15
3.3 Resistivity
16
3.3.1 Early tools16
3.3.2 Recent tools18
3.3.3 Tri-axial resistivities20
3.3.4 Exploiting the difference of response between resistivity tools20
3.4 Gamma ray
21
3.5 Density
22
3.5.1 Electron density22
3.5.2 Density23
3.6 Compressional sonic
23
3.7 Other sonic information
24
3.8 Neutron logging
24
3.9 Recent technology
26
3.10 Summary
26
References
27
Chapitre 4
Logging measurements do not focus on zones of interest
4.1 Volumes investigated by logging tools
29
4.1.1 Open-hole conditions29
4.1.2 Cased-hole conditions30
4.1.3 Volumes of investigation of logging tools : some numbers32
4.1.4 Turning high-resolution as an advantage33
4.2 Environmental effects
35
4.2.1 Borehole effects35
4.2.2 Mud cake36
4.2.3 Invasion36
4.2.4 Shoulder beds and formation dip37
4.3 Modeling the environment
38
4.3.1 Borehole modeling38
4.3.2 Mud cake modeling : spine and ribs39
4.3.3 Invasion modeling39
4.4 Limitations of environmental modeling
40
4.5 Summary
41
References
41
Chapitre 5
Measurements are imprecise and inaccurate
5.1 Elements of reality
43
5.2 Some definitions
43
5.2.1 Academic definitions43
5.2.2 Practical considerations on errors44
5.2.3 Addition of errors45
5.3 What affects precision
46
5.3.1 Logging speed and sampling rate46
5.3.2 Filtering47
5.3.3 Technology47
5.4 What affects accuracy
48
5.4.1 Tool response48
5.4.2 Tool calibration48
5.4.3 Environmental corrections and environmental models48
5.4.4 Environmental effects49
5.5 Repeated measurements
49
5.5.1 Historical importance of repeated data acquisition50
5.5.2 Repeated measurements as an epiphany50
5.5.3 Repeat sections50
5.5.4 Potential issues with repeat sections50
5.5.5 Simultaneous measurements51
5.6 Reproducibility
52
5.6.1 Historical perspective52
5.6.2 Reproducibility tests53
5.6.3 Recent reproducibility studies55
5.7 What may go wrong with a measurement
55
5.8 Summary
55
References
56
Chapitre 6
How measurements can suffer from human bias
6.1 Introduction
57
6.2 Biased data
58
6.2.1 Examples58
6.2.2 Where can data bias be introduced ?58
6.3 Are data acquisition companies service companies ?
59
6.3.1 Attributes of a service activity59
6.3.2 Zero defect and zero pain60
6.3.3 Bringing bad news, an important and difficult duty of the logging company61
6.3.4 Historical shift from product quality to service quality62
6.4 Overemphasis on service quality has detrimental effects on oil companies
62
6.4.1 Bias on reporting problems62
6.4.2 Selecting the most pleasant information63
6.4.3 Oil companies may destroy the ability to get correct data63
6.4.4 Satisfying several oil companies may be ultimately impossible63
6.4.5 Satisfying some requests from an oil company may be illegal64
6.5 Long term use of data
64
6.5.1 An example of a century-old trouble-maker64
6.6 Summary
65
References
65
Chapitre 7
Complexity
7.1 Historical summary
68
7.1.1 From Colonel Drake to 198068
7.1.2 From the 1980s68
7.2 Borehole trajectory and shape
69
7.2.1 Horizontal wells69
7.2.2 3-D trajectories69
7.2.3 Multilateral wells70
7.2.4 Large holes70
7.2.5 Invasion patterns71
7.2.6 Movement of logging tools and drilling assemblies71
7.3 Mud composition
72
7.3.1 Formate Cesium72
7.3.2 Petrofree Mud72
7.3.3 Other muds72
7.4 Complexity induced by combined measurements
73
7.5 Complexity induced by the hole shape in the logging-while-drilling mode
74
7.6 Incidence of complexity on data acquisition
74
7.7 Summary
74
References
75
Chapitre 8
Complication
8.1 Increased complication
77
8.2 Complication in delivery
78
8.2.1 Simple beginnings78
8.2.2 Transition to digital data78
8.2.3 21st century deliverables79
8.3 Multiplicity of formats
79
8.3.1 Setting the problem79
8.3.2 RP 66/DLIS80
8.3.3 LAS80
8.3.4 Other formats80
8.3.5 Graphical formats81
8.3.6 Other digital platforms81
8.4 Content of the digital records
81
8.4.1 Classification of data objects82
8.4.2 First example : the gamma ray log83
8.4.3 Second example : a modern combination of measurements83
8.4.4 Composite logs84
8.4.5 Variability in the volume of delivery85
8.5 Additional issues related to data content
86
8.5.1 Further division : Real-time and memory mode86
8.5.2 Several versions of a job may exist86
8.5.3 Changes of formation parameters with time86
8.5.4 The seven dimensions of a data object88
8.6 Sophistication in measuring tools
88
8.7 Summary
89
References
89
Chapitre 9
Wysinwytii
9.1 Early permeability curve
91
9.2 Log headers
91
9.3 Depth
93
9.4 Volume integration
93
9.5 Calibrations
95
9.5.1 Caliper calibration case study96
9.6 Remarks
98
9.7 Tool sketch
99
9.8 Validated and complete information
100
9.8.1 Annotations101
9.9 Summary
102
References
102
Chapitre 10
Misconceptions
10.1 The supremacy of real time and of short term
103
10.2 Normalization
103
10.2.1 Example of normalization104
10.3 Data cleansing
104
10.4 Interpretation as data quality control
105
10.4.1 Example 1 of erroneous data that can be interpreted105
10.4.2 Example 2 of erroneous data that can be interpreted105
10.5 The recovery factor
106
10.6 Summary
106
References
106
Part 2
Quest for quality data
Chapitre 11
The different uses of logging data
11.1 Data and decisions
109
11.1.1 Medical example : control of cholesterol content in blood110
11.1.2 Example of decisions taken with a bathroom weighting scale110
11.1.3 Example of decision process with geoscience data111
11.1.4 Increased challenge in log interpretation112
11.2 Role of logging data
113
11.2.1 Depth correlations113
11.2.2 Quantitative reserve evaluation at an early field stage116
11.2.3 Enhanced recovery116
11.2.4 Field study116
11.2.5 Unitization and redetermination117
11.2.6 Example of multiple use of data117
11.3 Value of data
118
11.3.1 Invisible data loss120
11.4 Summary
120
References
121
Chapitre 12
Brochure specifications
12.1 Importance of specifications
123
12.2 Specifications proposed by the data vendors
124
12.2.1 Strong emphasis on operating specifications124
12.2.2 Suspiciously similar specifications from different vendors125
12.2.3 Hyperbole125
12.2.4 Minimum specifications126
12.3 Underlying definitions of the specifications
126
12.3.1 Precision126
12.3.2 Vertical resolution127
12.3.3 Depth of investigation127
12.3.4 Conditions of applications of the specifications127
12.3.5 Testing the specifications in the real world127
12.4 Getting accuracy specifications
127
12.4.1 Quantifying systematic errors127
12.4.2 The challenge of improved technology128
12.5 Obtaining precision specifications
129
12.6 Developing reproducibility specifications
129
12.7 Examples of complete specifications
129
12.7.1 Accuracy and precision of density measurements129
12.7.2 Vertical resolution of a resistivity tool130
12.7.3 Depth of investigation of a resistivity tool130
12.8 Additional measurement information
131
12.8.1 Planning tables131
12.9 A first look at uncertainties
132
12.10 Planning of a logging job with specifications
133
12.11 Summary
135
References
135
Chapitre 13
Quest for uncertainties : from brochure specifications to real uncertainties
13.1 Starting from vendors specifications
137
13.2 Real uncertainties
138
13.2.1 Uncertainties reported by data vendors138
13.2.2 Uncertainties observed when multiple passes are available139
13.3 Defining homogeneous beds
141
13.4 Estimating random errors for uncertainty analysis
142
13.4.1 From vendor specification to actual well conditions142
13.4.2 Using a different logging speed (rate of penetration) or a different sampling rate from the one used in the vendor's specification142
13.4.3 Using a different signal processing method143
13.4.4 Using a different (...)143
13.4.5 Using a different value than the reference given by the vendor143
13.4.6 Example of computation of the precision for the density144
13.4.7 Taking into account the thickness of the zones of interest145
13.5 Handling systematic errors
146
13.5.1 Quantifying propagated errors147
13.5.2 Integrating tool drift in the uncertainty149
13.6 One step further : Anticipating other sources of uncertainty
150
13.6.1 Density measurement150
13.6.2 Density uncertainty due to the hole diameter151
13.6.3 Uncertainty originating from (...)151
13.6.4 Uncertainty due to the hole rugosity151
13.6.5 Combining uncertainties151
13.6.6 Uncertainty due to a depth-matching error152
13.7 Visualization of uncertainties
152
13.8 Summary
153
References
153
Chapitre 14
Deliverables
14.1 Importance of data completeness
155
14.1.1 Who defines the deliverables ?155
14.1.2 The need for graphical displays156
14.1.3 Standardization156
14.1.4 Format and content156
14.2 Content of the graphical files
159
14.2.1 Depth-related information160
14.2.2 Tool sketch160
14.2.3 Remarks161
14.2.4 Job chronology162
14.2.5 Parameter summary and parameter change163
14.2.6 Raw and QC curves163
14.2.7 LQC stamp165
14.3 Digital files
165
14.3.1 The basic digital file165
14.3.2 Raw data on digital files165
14.3.3 Time based data165
14.3.4 Data in digital files167
14.4 The importance of contextual information
168
14.5 Summary
169
References
169
Chapitre 15
Depth
15.1 Importance of depth
171
15.1.1 Examples of challenges proposed by depth measurements171
15.2 The different depths
172
15.2.1 Wireline mark-derived depth172
15.2.2 Wireline calibrated-wheel depth173
15.2.3 Driller's and LWD depth174
15.2.4 Expected differences between the measured depths175
15.3 Importance of getting it right at surface
175
15.3.1 Datums176
15.3.2 Clear definition of the North reference177
15.3.3 Elevation model177
15.4 The depth information box
178
15.4.1 General178
15.4.2 Example: Schlumberger179
15.4.3 Depth policy documentation and traceability179
15.5 Reconciliation of depths
180
15.6 Wireline creep
181
15.6.1 Definition of wireline creep181
15.6.2 Causes of creep181
15.6.3 Modeling creep181
15.6.4 Confirmation of creep182
15.6.5 Practical examples182
15.6.6 Effects in cased-hole182
15.7 Summary
183
References
184
Chapitre 16
Hidden treasures
16.1 Chart books
185
16.1.1 Old charts185
16.2 Job planners
186
16.3 Quality Control curves
188
16.4 Details on calibrations
191
16.4.1 Calibration guides191
16.4.2 Detailed information on calibration193
16.4.3 Successive calibrations194
16.5 Information on wear
194
16.6 Summary
195
References
197
Chapitre 17
Contribution of the field engineer to the quality of data
17.1 Historical context
199
17.1.1 Early field engineers199
17.1.2 The field engineer in the future201
17.1.3 An intermediate step - Remote support and control202
17.2 The human factor
202
17.2.1 Motivation and performance203
17.3 The multiple functions of the field engineer
204
17.3.1 A diplomat204
17.3.2 A safety manager204
17.3.3 An experimentalist, a troubleshooter and an entrepreneur205
17.3.4 A physicist205
17.3.5 A reporter205
17.3.6 The guardian of data205
17.3.7 A decision maker205
17.4 Human error management
206
17.5 Blunder management
206
17.5.1 The field engineer and the computer206
17.5.2 Tasks managed by computer technology206
17.5.3 Duties of the engineer207
17.6 Integrity or handling voluntary human errors
208
17.6.1 The field engineer oath208
17.6.2 Reinforcement in logging companies208
17.7 Emphasis on data
209
17.7.1 A log is not only the main pass209
17.8 Summary
210
References
210
Chapitre 18
Drilling data
18.1 Drilling data, also
211
18.2 Historical context
211
18.2.1 Surface measurements211
18.2.2 Enter MWD212
18.2.3 Drilling isn't getting easier213
18.3 The specific nature of drilling data
213
18.3.1 What is measured and observed213
18.3.2 The time domain213
18.3.3 Lack of standards214
18.3.4 Quality control and quality assurance215
18.4 Data processing
218
18.4.1 Example of incorrect processing219
18.4.2 Sampling, processing and statistics220
18.4.3 Graphical data presentation221
18.5 Cost of inferior quality
221
18.5.1 Example of an incorrect decision as a result of poor fluid data and inadequate data flow222
18.5.2 Non-productive time (NPT) and Invisible lost time (ILT)223
18.6 Improving communication
223
18.7 Drilling data in the future
224
18.8 Summary
224
References
225
Chapitre 19
Coring data
19.1 Measurements on cores
227
19.1.1 Multiple measurements on core plugs227
19.1.2 Additional issues on core plugs228
19.2 Combining data from different sources
228
19.3 Summary
229
References
229
Chapitre 20
Conclusions and recommendations
20.1 Difference between real and measured values
232
20.1.1 No misnomer232
20.1.2 Start with a higher profile for measurement specifications232
20.1.3 The path to errors and uncertainties232
20.2 Standardization
233
20.2.1 Similar structure of deliverables233
20.2.2 No danger of commoditization233
20.3 The logger's oath
233
20.4 Improved databases
234
20.5 Documentation
234
20.6 The required evolution of interpretation software
235
20.7 Beginning of the journey
235
References
235
Appendix
Appendix 1 : Quantifying the level of proficiency in data quality
237
Appendix 2 : Deliverables
239
Appendix 3 : Lexicon
240
Appendix 4 : Metrological definitions
241
Appendix 5 : Log Quality Control checklist
243
Appendix 6 : Advanced computation of uncertainties for the density log
245
Appendix 7 : Quest for mnemonics
248