Integrated Petrophysics Course Details

INTRODUCTION 15
Course Overview 15
Objective of Formation Evaluation 16
Difficult Conditions for Formation Evaluation 17
Data Sources 17
Non-Numerical Information 17
Limitations of Data Sources - General 18
Scales of Measurement and Heterogeneity 18
Increased Heterogeneity Requires Increased Sampling 18
Micropractical

Fine Scale Data Requires Log Correlation 18
Inequalities Between Laboratory and Reservoir 19
Non-Unique Transforms between Measured Parameter and Reservoir Parameter 19
Lack of Rigid Calibration Grid 20
Deterministic vs. Probabilistic Petrophysics 21

BASIC LOG ANALYSIS 21
Operations Petrophysics: Chronological Tasks and Responsibilities 22
Environmentally Correct Logs 24
Compute Vsh 24
Compute Ø 24
Micropractical

Compute Sw 25
Compute k 26
Compute Netpay 27

DATA PREPARATION 29
Log Data Preparation 29
Missing Data 29
Log to Log Depth Matching 29
Environmental Corrections 30
Log Normalisation 30
Core Data Preparation 31
Core to Log Depth Matching 32
Vetting Special Core Data 32
Preliminary Zonation 32

LITHOLOGY and CLAY CONTENT: Vcl , Vsh 34
Objective 34
Distinction Between Clay and Shale 34
Uses of Vclay , Vshale 34
Importance 35
Common Problems 35
Non-Radioactive Fines and Radioactive Non-fines 35
Gas and other Non-Shale Influences Vshale Logs 35
Is Vclay / Vshale Relevant to Reservoir Beds? 36
Lack of Core Calibration and a Certain Vshale = Zero Reference 36
Scales of Heterogeneity in Core Calibration 36
Lithology, Vcl, Vsh Input Data 36
Bulk Volume Irreducible from Magnetic Resonance Logs, mbvi, bvf 36
Movie

Vshale, Vclay & Capillarity from Laser Particle Analysis Grain Size Distribution 37
Clay Volume from Core Plugs or Trims, Vclcore 37
Clay Volume from Thin Sections, Vcltx 37
Thin Section Limitations 37
Core Photographs and Descriptions 38
X-Ray Diffraction and Scanning Electron Microscope 38
Mudlogs and Lithlogs 38

Practical Session
Log Integration 38
Method 38
Shale Volume from Gamma Ray: Vshgr 39
Non-linear Vsh 39
Shale Volume from Density-neutron: Vshdn 40
Shale Volume from Density-sonic: Vshds 41
Shale Volume from Resistivity: Vshres 41
Vshgr, Vshdn, Vshds or Vshres ? 41

Thomas-Steiber clay distribution

POROSITY: Ø 42
Objective 42
Importance 42
Common Problems 43
Badhole Conditions 43
Minimising Badhole Conditions 43
Effective Porosity 43
Shale 43
Gas 44
Unknown Grain Density 44
Lack of Density Tool 44
Morning Daily Recap, Questions, Debate

Non Shale Corrected Density-neutron Total Porosity 44
Porosity Input Data 44
Conventional Coring Criteria 44
Core Porosity and Grain Density, Øcore, rhog 45
Recommended Routine Core Analysis procedure

Core Porosity Method 46
Core Overburden Porosities 47
Log Integration 48
Total and Effective Porosity: Øt, Øe 48
Carbonates: Intergranular and Vuggy Porosity, Øv 50
Fracture Porosity, Øf 50
Density Total Porosity, Ød 51
Mean Grain Density Determination 51
Grain Density in Complex Lithologies 51
Correct rhog, neutron & sonic matrix in shales 51
Fluid Density, rhof 51
Magnetic Resonance Total Porosity, Ømrt 52
Magnetic Resonance Effective Porosity, Ømre 52
Shale Corrected Neutron Total Porosity, Øn 52
Neutron Porosity Method 53
Shale Corrected Density-Neutron Total Porosity, Ødn 54
Gas Zones 54
Shale Corrected Sonic Total Porosity, Øs 54
Sonic Porosity Method 55
Limitations of Multiple Linear Regression Porosity, Ømlr 56
Probabilistic Porosities 56
Badhole Conditions 56
Shale Volume Derived Porosity, Øvsh 57
Water Saturated Resistivity Porosity, Øro 57
Two Stage Minimum Porosity: Øs, Øvsh 57
Effective Porosity Equations, Øe 58

What is Effective Porosity?

Mainstream Petrophysics Effective Porosity

Traditional log analysis Effective Porosity
Magnetic Resonance Porosities, Øe, Øt

Vary rhog with shale
Recap - Summary of Typical Porosity Evaluation 59

FORMATION WATER RESISTIVITY: Rw 60
Rw Input Data 60
Recovered Formation Water 60
Well Tests 61
Reservoir Temperature, Tres 61
Wireline Formation Tester Water Samples 61
Archie Apparent Water Resistivity, Rwa 62
Certain water zones, Sw100 62
Micropractical

Archie Apparent Flushed Zone Water Resistivity, Rmfa 63
Resistivity Ratio Apparent Water Resistivity, Rwrr 63
SP Logs 65
Origin of SP 65
Determining Rwsp 65
Rwsp Recipe 65
Rw Catalogues 66
Wireline Formation Tester Water Gradients 66
Integration of Rw Values 66

Practical Session

WATER SATURATED RESISTIVITY: Ro 66
Summary of Common Problems 67
Special Core Analysis 'm' Not Equal To In-situ 'm' 67
Invalid Ø, a, or m or Rw and Sw100 zones 67
Øsca ¹ Ørca ¹ Ølog 67
Ro Equation Inputs 67
Total Porosity, Øt 67
Formation Water Resistivity, Rw 68
Cementation Exponent 'm' 68
'm' Objective 68
Pickett Plot 68
'm' Importance 69
'm' Input Data 69
Electrical Special Core Analysis Laboratory 'a' and 'm' 69
Problems with Laboratory 'm' values 69
Log Analysis Water Zone 'm' 70
Carbonates: Øv and Water Zone 'm' 71
Problems with Log Analysis 'm' values 71
'm' Log Integration 72

RESISTIVITY SATURATION: Swrt 72
Summary of Common Problems 72
Absence of Conventional Core Calibration 73
Core Analysis 'n' Not Equal To In-situ 'n' 73
Freshwater Shaly Sands 73
Formation Heterogeneity Un-Resolved by Rt 73
Sw Equation Inputs 73
Formation True Resistivity, Rt 74
Which Logging Tool? 74
Rt Problems 75
Inadequate or Inappropriate Rock Volume Resolution 75
Deep Invasion 75
Shoulder Beds 76
Horizontal and Vertically Resistivity in Laminated Beds (3DEX) 76
Groningen and Delaware Effects 76
Cased Hole Resistivity Tool (CHFR) xx 77
Saturation Exponent, 'n' 77
'n' Objective 77
'n' Importance 77
Laboratory 'n' Problems 78
Wettability - Containing the Problem 78
Laboratory 'n' Input Data 79
Electrical Special Core Analysis Laboratory 'n' 79
Guidelines for Improved Laboratory 'n' 80

SHALY SAND Swrt 80
Waxman Smits Equation Inputs 81
Cation Exchange Capacity (CEC) and Qv 81
Qv from Magnetic Resonance Logs, Qvmr 82
Qv from Archie apparent water zone 'm' 83
Equivalent Conductivity of Exchange Cations, B 83
Waxman & Smits Cementation Exponent, mws (m*) 84
Waxman & Smits Saturation Exponent, nws (n*) 84
ImageLog Facies as Classes of Clay Distribution and B 84
Shaly Sand Swrt Log Integration 85
Is a Shaly Sand Equation Required ? 85
Log Data 85
Laboratory Electrical Data 86
Selecting a Suitably Structured Resistivity Swrt Equation 86
Core Sw Equation Inputs Do Not Guarantee Sw Output 88

CORE SATURATIONS 88
Oil Base Mud Core Sw and 'n' Calibration (Swobm) 88
Low Invasion Water Base Mud Core Sw and 'n' Calibration 89
Conventional Core Porosity and Permeability Sw and 'n' Calibration 90
Minimum Fluids Exchange 91
Conventional Core Fluid Saturations as Sw Constraints 91
1 Limitations of Conventional Core Fluid Saturations 92
Restored State Core 92
Well Tests as Sw Constraints 92
Reservoir Saturation Tool, RST 93

MAGNETIC RESONANCE SATURATION, Swmr 93
Magnetic Resonance Tool's Swi 93

CONTACTS, FLUID ZONES AND CAPILLARY PRESSURE 94
Objective 94
Hydrocarbon Types 94
Reservoir Capillary Pressure: Pc 95
Importance 95
Summary of Common Problems 95
Badhole Unknown Formation Pressure Gradients 95
Logs respond to Bulk Volumes Not Mobility 95
Marginal Reservoir 96
Lack of Density-neutron 96
Fluid Zone Input Data 96
Wireline Formation Pressure Gradients and Samples 96
WFT Problems 97
Supercharging 97
WFT Operation and Operational Recommendations 97
WFT Further Details 98
GeoTap MWD Formation Tester 99
Recovered Fluids: Tests, Wireline, Kicks 99
Kicks 99
Early Formation Pressure System, EFPS 99
While Drilling Formation Pressure Tester 100
rhob-npsc, dt-nphi, and rhob-dt will Detect Gas! 100
Calculated Sw 100
Bulk Volume Water, BVW 100
Bulk Density - Rt Trend 100
Rt/Rxo vs SP 100
Residual Hydrocarbons seen by Rmfa 101
Shale Corrected Density-neutron Separation 101
Non shale corrected Neutron-Sonic Separation for Gas Carbonates 101
Magnetic Resonance Log Hydrocarbon Typing 101
Core UV Visible Spectroscopy 101
Reservoir Master Equation's prediction of Height 102
Chromatograph, Lithlog / Mudlog: Cut, Fluorescence, Stain 102
Quantitative Fluorescence Tool 102
IPL and Neutron Tools 102
Sonic Tool vp/vs 103
Maps and Cross Sections 103
Log Integration 103
Gas Zone 103
Oil Zone 103
Transition Zones 104
Residual Oil Zones 104
Coals and False Bulk Volume Hydrocarbon 104
Water Zone, Sw100 zones 105

PERMEABILITY: k 105
Objective 105
Importance 105
Relevance of Permeability to Special Log Processing 106
Common Problems 106
Dynamic Property Inferred from Static Properties 106
Inadequate Data for Analytic or Predictive Pore Typing 107
Core Ø - k Regression Applied with Log Effective Ø 107
Unidentified but Influential High Permeability Streaks 107
Invalid Low End Core kair 107
Shale and Extreme Low End Prediction 108
Unrecognised Sw > Swi Zones 108
Lack of k overburden data 108
k Input Data 108
Core Permeability 108
Conventional Air Permeabilities, kair 109
Klinkenburg Correction 109
Equivalent Overburden kbrine 109
Altered Core Permeabilities 110
Core Effective Permeability 110
Magnetic Resonance, kmr 111
Bulk volume hydrocarbon, bvh 111
Normalised Resistivity Ratio, RRn 112
Sidewall Core Laser Particle Analysis 112
WFT Permeability, kwft 112
Well Tests Permeability, kh 113
Well Test Problems 113
Permeability Averaging 114
Zonation 114
Pore Type Zonation: [Ø-Sw-k-Pc] 114
Core Capillary Pressure Data 115
Core Ø - k plots 116
Log Pore Typing Parameters 116
Is Facies Based Zonation Useful? 116
Borehole Image-log Facies Zonation 117
Other Log Permeability Predictors 117
Sonic Responses 118
Specific Surface Area 118
Log Integration 118
Summary of Conventional Log Permeability Evaluation 119
Effective Porosity, kpor 119
Saturation, ksw 119
Reservoir Master Equation Enables k from Sw as well as Swi 120
Clay / Shale Volume, kvsh 120
Multiple k Inputs: Accuracy versus Stability 120
Estimated Production Rates 121

CAPILLARY PRESSURE SATURATION, Swpc 121
Capillary Pressure Derived Sw and 'n' Calibration 121
What Is Capillary Pressure? 121
Capillary Pressure Data Acquisition 122
Identifying Bad Capillary Pressure Data 122
Capillary Pressure Data Interpretation 123
The Reservoir Master Equation, [Sw-Ø-k-Height] 123
The J Function Method 124
The Regression Method 124
Individual Plug Curve Fit Methods, Skelt etc 124
Log Integration of Swpc 125
Problems with Capillary Pressure Derived Sw and 'n' 125

RECONCILLIATION OF Swrt via n 126
'n' Log Integration 126
Implied Sw Constraint from Electrical versus Capillary Pressure 'n' values ? 127
Field Example of Data Integration Constraining 'n' 127
Earth Tide Downhole Pressure Variations and Netgas Porosity xx 127
Sw Logical Constraints 127
Resistivity Ratio, Swrr 128
Log(Rt/Rxo) v SP Movable Hydrocarbon Indicator 128

BASE CASE SATURATION - THE Sw DECISION TREE 128

SATURATION DERIVATIVES 128
Movable Oil Saturation, Som 128
Residual Oil Saturation, Sor 129
Log / Core Minimum Rt for Maximum Water Cut - Netpay 129

NETPAY and NETROCK: N:G 130
Objective 130
Importance 131
Common Problems 131
Relevant Hard Data Usually Not Available 131
Different Understanding of Meaning and Function 131
Violating the integrity of the petrophysical results table 132
Impact of Marginal Bed's Thickness and Location 132
Use Core-log Data not stand-alone Core data 132
Reservoir Geometry May Isolate Rock Volumes 132
N:G Input Data 133
N:G Non-Log-Inputs 133
Water Encroachment 133
Depletion 133
Permeability at Zero Movable Oil from Relative Permeability Data 133
Core Fluorescence 134
Capillary Threshold Height and Closure 135
Borehole Image Logs 135
Conventional Core Porosity Permeability Data 135
Well Tests and Production Data 135
WFTs 136
Hydrocarbon Pore Volume from Material Balance 136
N:G Log Inputs 137
Magnetic Resonance Logs 137
Invasion Profiles 137
0.5 Micron Mean Pore Throat Radius 138
Mudcake Build-up - Microlog 138
Mudcake Build-up - Caliper 139
Borehole Image-logs in heterolithic beds 139
Evaluated Saturation, Porosity and Clay / Shale Volume 139
Micro Spherically Focused and Microlateral Logs 140
Log Integration 140
Criteria: Why Permeability? 141
Determine Netpay first then Netrock 142
Determine the Cut-off from Direct Reservoir Observations If Possible 142
Netpay and Fluid Zones 142

UNCERTAINTY 143
Importance 143
Recalculation Sensitivity Studies 143
Cost-Benfit Uncertainty Reduction 143

SEISMIC - PETROPHYSICAL INTEGRATION 143
Depth-Time Conversion 143
Synthetic Seismograms 143
Fluid Substitution 143
Seismic Attributes 143

REPORTING RESULTS 143
Objective 143
Importance 143
Common Problems 143
Input Data 144
Data Extraction 144
Field Petrophysical Reference - The Results Table 144

WHY INTEGRATE ? 145
Problems Resulting from Isolated Analyses 145
Formats for Integration 146
Field Database 146
Electronically Mobile Data 146
Core Data Sheets 146
Comprehensive Log Evaluations / Displays 147
Field Petrophysical Reference - The Answer Table 147
Enemies of Integration 148
Principles of Integration 148
Criteria for Data Hierarchy 148
Directness of Measurement to Reservoir Parameter 148
Accuracy of Measurement 149
Spatial Definition of Measurement 149
Reservoir Data Hierarchy 149
Non-Log-Data 150
Over-determined Systems 150

FORMATION EVALUATION RECOMMENDATIONS 151
Data Acquisition 151
Mud 151
Core 151
Core Description 151
Core Analysis 152
Logs 152
Saturation 153
Evaluation 153

CASE HISTORY: LOW POROSITY RESISTIVITY 154
Review of Core - Log - Well Test and Petrographic Data Integration 154
Problem 154
Data 155
Method 155
Key Findings 156
Conclusion: To be Announced 157

EQUATIONS 158
Lithology 158
M and N lithology parameters 158
Shale Volume from Gamma Ray 158
Shale Volume from SP 158
Shale Volume from Density-neutron 159
Porosity 159
Conversion of Laboratory to Reservoir Core Overburden Porosity 159
Density Porosity 159
Density-neutron Porosity 159
Density-neutron Gas Zone Porosity 159
Sonic Porosity 160
Porosity from Ro (water zones) assuming Rw and 'm' 160
Effective Porosity 160
Formation Water Resistivity, Rw 161
Porosity, m Apparent Water Resistivity, Rwa 161
Resistivity Ratio Apparent Water Resistivity, Rwrr and equivalent NaCl (chart Gen-9) 161
Saturation 161
Formation Factor 161
Cementation Exponent 161
Waxman Smits prediction of water saturated resistivity, Ro 161
Resistivity Index 161
Saturation Exponent 162
Archie Saturation 162
Logarithmic Form of Archie Equation (where a = 1) 162
Archie Cementation Exponent from Water Zones 162
Sxo from Rmfa 162
Dual Water Model Saturation 162
Waxman & Smits Model Saturation 163
Equivalent Conductivity of Exchange Cations 163
Effective Concentration of Exchange Cations per Unit Volume of Pore Fluid 163
Actual BQv Required to Satisfy W-S Equation in water zones (Swt = 1.00) 164
Qv from Archie apparent water zone 'm' 164
Waxman Smits mws from Archie m 164
Popoun & Leveaux 'Indonesia' Shaly Sand Saturation 164
J Function Correlation of Pore Types 165
Conversion to Height above Free Water Level 165
Mercury capillary pressure clay bound water correction 165
Saturation Exponent from log independent Sw (Swx) 165
Layer Sw for Mapping Wedge Zones 166
Rt for Economic Production (max. water cut) 166
Permeability 166
Darcy Permeability 166
Well Test Permeability Thickness 166
Empirical Klinkenberg Correction 166
Kbrine from Kair and CEC (Qv) 167
Example klog for Above Transition Zone 167
klog for Above Transition Zone - Log Data Only 167
Normalised resistivity ratio, RRn 167
Fractional Flow Equation 167

FIGURE CAPTIONS 167
REFERENCES 171
Petrophysicaly Related Websites 175
ABBREVIATIONS 176
ESSENTIAL SCHLUMBERGER CHARTS 180