Log Interpretation Principles Applications [PDF]

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Contents

Laterolog 8 ................................... Dual Laterolog-R,, System ...................... Delaware Effect ............................ Groningen Effect ........................... Scales ........................................ Spherically Focused Log ........................ Influence of Wellbore Variables and Log Corrections Borehole Effect ............................ Adjacent Bed Effect ........................ Pseudogeometrical Factors ................... Invasion Correction ......................... Induction Logginoc.. ............................... Principle ..................................... Geometrical Factor ............................. Focusing ..................................... ............ Deconvolution .................... ................................... Skin Effect Equipment .................................... Log Presentation and Scales ..................... Environmental Corrections Prior to Phasor Induction. Borehole Correction ........................ Surrounding Bed Correction .................. Invasion Correction ......................... High-Resistivity Formations .................. Effect of Dipping Beds ...................... Annulus .................................. Salt Muds ................................. Phasor Induction SFL Tool ...................... Phasor Tool Description and Features ............. Environmental Corrections ...................... Shoulder Effect and Vertical Resolution ........ Skin Effect ................................ Borehole and Cave Effect. ................... Large Boreholes ............................ Invasion Corrections ..............................................

7-8 7-8 7-9 7-9 7-10 7-10 7-l 1 7-I 1 7-l 1 7-l 1 7-12 7-12 7-12 7-13 7-13 7-13 7-14 7-14 7-1s 7-15 7-16 7-16 7-16 7-16 7-16 7-17 7-18 7-18 7-18 7-19 7-20 7-2 I 7-21 7-22 7-23

Contents

Interpretation in the Presence of Transition Zones .................. Oil-Based Mud ............................................... Phasor Case Studies .................................................. Induction Versus Laterolog Measurements. ............................... Microresistivity Devices .................................................. Microlog ........................................................... Principle.. ...................................................... Interpretation .................................................... Microlaterolog ....................................................... Principle.. ...................................................... Response ........................................................ Proximity Log ....................................................... Principle.. ...................................................... Response ........................................................ Vertical Resolution ............................................... MicroSFL .......................................................... Environmental Corrections ............................................ Resistivity Interpretation .............................................. Determination of 9, ................................................. Resistivity Invasion Corrections ........................................ Compensated Dual Resistivity .......................................... References .............................................................

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7-25 7-25 7-26 7-32 7-33 7-34 7-34 7-34 7-34 7-34 7-34 7-35 7-35 7-35 7-35 7-35 7-36 7-36 7-36 7-36 7-37 7-39

Determination of Saturation . . , . . , . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . S- 1 Introduction .......................... Clean Formations. ..................... Resistivity - Vs. - Porosity Crossplots . Microresistivity-Vs.-Porosity Crossplots R,,u Comparison ................... Logarithmic Overlays .................. Log F-Log R,, Overlay ........... R, Overlay and F Overlay ........... Resistivity Ratio Methods ............... Flushed Zone Method .............. Invaded Zone Method .............. Porosity Balance ................... Other Ratio Charts .................

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. 8-1 8-1 8-l 8-3 . 8-4 8-5 8-5 . . 8-5 8-6 . 8-7 . 8-7 . 8-7 8-9

Contents

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Invasion-Corrected Ratio Methods ...... Rx, /R, Overlay ...................... R,,iR, Quicklook .................... F-MOP Movable Oil Plot ................. Porosity and Gas Saturation in Empty Holes Shaly Formations ........................ Laminated Sand-Shale Simplified Model Dispersed Shale Simplified Model ...... Total Shale Relationship .............. Saraband* and Coriband* Models .......... Saraband Mode1 ..................... Coriband Mode1 ..................... Dual Water Models ...................... VOLAN* Mode1 ..................... Cyberlook* Program ................. GLOBAL* Method ...................... References .............................

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Electromagnetic Propagation Logs Introduction ..................... EPT Log ........................ ADEPT: The Adaptable EPT Tool Interpretation Methods ............ CRIM Method. ............... CTA Mode1 .................. tpt, Method. .................. Endfire Array. ................... Broadside Array .................. Deep Propagation Tool (DPT) ...... Environmental Effects ......... Interpretation Methods ............ tpo Modified Method .......... Dual Water tpo Modified Method The pn Versus Rj, Plot ........ Dual Saturation Method ........

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8-9 8-9 8-10 8-12 8-12 8-13 8-14 8-15 8-15 8-16 8-16 . 8-18 8-20 8-22 8-24 8-26 8-30 . . . . . . . . . 9-l

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9-l . 9-2 9-3 9-4 9-5 9-5 9-6 9-7 9-8 9-8 9-10 9-11 . 9-11 9-12 9-12 9-13

Contents

Tool Specifications and Limitations ......................................... References .............................................................

10

Permeability and Productivity .......................... Permeability ............................................... Irreducible Saturations ................................... The Transition Zone - Capillary Pressure Effects ............. Permeability From Resistivity Gradients .................... Permeability Estimates From 4 and S,(,, ..................... Permeability and the Nuclear Magnetism Log. ............... Principle.. ......................................... Applications/Interpretation ............................ Effective and Relative Permeabilities ....................... Water-Cut Prediction .................................... Permeability From Geochemically Derived Mineral Abundances Permeability From the Formation Tester Tools. .............. Drawdown Analysis ................................. Pressure Buildup Analysis ............................ Productivity ............................................... The Producibility Log ................................... References ................................................

11

Wellbore Seismic .......................... Well Seismic Equipment ......................... Digital Check-Shot Survey ....................... Time-to-Depth Conversion and Velocity Profile Geogram Processing ............................ Vertical Seismic Profile ......................... VSP Processing. ............................ Offset Vertical Seismic Profile ................ Walkaway Surveys .......................... DSA Tool for VSP Acquisition ................... Primary Uses of the VSP Summary ............... Proximity Survey Interpretation ................... References ....................................

9- 15 9-16 . . . . . . . 10-l .10-l . lO-2 . lO-2 . lO-2 10-3 . lO-5 10-5 10-6 10-7 10-7 10-7 . lO-8 . lO-9 IO-10 .lO-12 .lO-13 .lO-14

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. 11-l 11-3 11-3 11-4 11-5 11-8 1 l-8 11-8 11-13 1l-14 11-14 11-14

Contents

12

Geologic Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12- 1 Introduction ........................... Correlation ............................ Stratigraphic Information From the Dipmeter HDT Dipmeter Tool. ................ Dual Dipmeter Tool ................. Wellsite Processing. ................. Dipmeter Advisor* Program .......... Formation MicroScanner* Service ..... Electrofacies Identification ............... Faciolog Computation ............... Geocolumn Display ................. Reservoir Description Services. ........... Missing Data. ...................... Estimation of Permeability. ........... Lumping .......................... Gridding and Mapping ............... References ............................

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Mechanical Properties of Rocks . . . . _

12-1 12-l 12-6 12-8 12-9 12-13 12-13 12-14 12-14 12-15 12-16 12-19 12-19 12-20 12-21 12-22 12-23

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Natural Fractures .................................................... Fracture Detection ............................................... Sonic Measurements .......................................... Caliper Measurements. ........................................ Density Measurements ........................................ Resistivity Measurements ...................................... Photoelectric Absorption Measurements .......................... Dipmeter Measurements ....................................... Borehole Televiewer Tool ..................................... Formation MicroScanner* Tool ................................. Other Measurements .......................................... Conclusion ...................................................... Elastic Constants .................................................... Inherent Strength Computations and Their Relationship to Formation Collapse Stresses Around a Producing Cavity. ................................ Solution to the “Collapse” Problem ................................

13-l 13-l 13-l 13-3 13-4 13-5 13-5 13-5 13-6 13-6 13-6 13-7 13-7 13-8 13-8 13-9

Contents

Griffith Failure Criterion ................... Mohr-Coulomb Failure Criterion ............ Stress Analysis in Relation to Hydraulic Fracturing Calibration with Mini-Frac Data ............. Fracture Pressure Computations ............. Hydraulic Fracture Geometry Analysis ........... Fracture Height, .......................... The FracHite* Program .................... Fracture Propagation Azimuth. .............. References ..................................

.13-9 .13-10 13-l 1 .13-12 .13-13 .13-13 .13-14 .13-15 .13-15 .13-19

Note: A companion book “Cased Hole Log Interpretation Principles/Applications-1989,” provides similar information for cased hole services. Throughout this document references are made to charts, nomograms, and tables necessary for quantitative interpretation of data from our various logging tools. Refer to the Schlumberger Log Znqvretution Chart--1989 book for the most up-to-date version of these charts.