Supercharge, Invasion, and Mudcake Growth in Downhole Applications E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Serie: Advances in Petroleum Engineering
• Sprache: Englisch

Seitenzahl: 631

Veröffentlichungsjahr: 2021

Beschreibung

Mysterious "supercharge effects," encountered in formation testing pressure transient analysis, and reservoir invasion, mudcake growth, dynamic filtration, stuck-pipe remediation, and so on, are often discussed in contrasting petrophysical versus drilling contexts.  However, these effects are physically coupled and intricately related. The authors focus on a comprehensive formulation, provide solutions for different specialized limits, and develop applications that illustrate how the central ideas can be used in seemingly unrelated disciplines. This approach contributes to a firm understanding of logging and drilling principles. Fortran source code, furnished where applicable, is listed together with recently developed software applications and conveniently summarized throughout the book. In addition, common (incorrect) methods used in the industry are re-analyzed and replaced with more accurate models, which are then used to address challenging field objectives.

Sophisticated mathematics is explained in "down to earth" terms, but empirical validations, in this case through Catscan experiments, are used to "keep predictions honest." Similarly, early-time, low mobility, permeability prediction models used in formation testing, several invented by one of the authors, are extended to handle supercharge effects in overbalanced drilling and near-well pressure deficits encountered in underbalanced drilling. These methods are also motivated by reality. For instance, overpressures of 2,000 psi and underpressures near 500 psi are routinely reported in field work, thus imparting a special significance to the methods reported in the book.

This new volume discusses old problems and modern challenges, formulates and develops advanced models applicable to both drilling and petrophysical objectives. The presentation focuses on central unifying physical models which are carefully formulated and mathematically solved. The wealth of applications examples and supporting software discussed provides readers with a unified focus behind daily work activities, emphasizing common features and themes rather than unrelated methods and work flows. This comprehensive book is "must" reading for every petroleum engineer.

Leseprobe

Table of Contents

Cover

Title Page

Copyright

Preface

Acknowledgements

1 Pressure Transient Analysis and Sampling in Formation Testing

1.1 Conventional Formation Testing Concepts

1.2 Prototypes, Tools and Systems

2 Spherical Source Models for Forward and Inverse Formulations

2.1 Basic Approaches, Interpretation Issues and Modeling Hierarchies

2.2 Basic Single-Phase Flow Forward and Inverse Algorithms

2.3 Advanced Forward and Inverse Algorithms

2.4 References

3 Practical Applications Examples

3.1 Non-constant Flow Rate Effects

3.2 Supercharging – Effects of Nonuniform Initial Pressure

3.3 Dual Probe Anisotropy Inverse Analysis

3.4 Multiprobe “DOI,” Inverse and Barrier Analysis

3.5 Rapid Batch Analysis for History Matching

3.6 Supercharge, Contamination Depth and Mudcake Growth in “Large Boreholes” – Lineal Flow

3.7 Supercharge, Contamination Depth and Mudcake Growth in Slimholes or “Clogged Wells” – Radial Flow

3.8 References

4 Supercharge, Pressure Change, Fluid Invasion and Mudcake Growth

4.1 Governing equations and moving interface modeling

4.2 Static and dynamic filtration

4.3 Coupled Dynamical Problems: Mudcake and Formation Interaction

4.4 Inverse Models in Time Lapse Logging

4.5 Porosity, Permeability, Oil Viscosity and Pore Pressure

4.6 Examples of Time Lapse Analysis

4.7 References

5 Numerical Supercharge, Pressure, Displacement and Multiphase Flow Models

5.1 Finite Difference Solutions

5.2 Forward and Inverse Multiphase Flow Modeling

5.3 Closing Remarks

5.4 References

Cumulative References

Index

About the Authors

Also of Interest

End User License Agreement

List of Illustrations

Chapter 1

Figure 1.1. Drawdown-buildup pressure response with dynamic pumping action and f...

Figure 1.2. Downhole, surface and logging truck operations.

Figure 1.3. Recent formation testing book publications.

Figure 1.4. Conventional formation tester tool strings.

Figure 1.5. Formation testers, additional developments.

Figure 1.6. Conventional dual and triple probe testers.

Figure 1.7. Dual probe tester with dual packer.

Figure 1.8. Early COSL single and dual probe prototype formation testers (detail...

Figure 1.9. COSL pad designs with varied sizes and shapes, for different applica...

Figure 1.10. Tool string configurations.

Figure 1.11. Tool architectures.

Figure 1.12. Surface control interface.

Figure 1.13. Pressure measurement chart (left) and real-time fluid monitoring ch...

Figure 1.14. Tool string configurations.

Figure 1.15. Tool architecture.

Figure 1.16. Tool and surface system.

Figure 1.17. Pressure drawdown curve (left) and fluid contact curve (right).

Figure 1.18. IPSRD stuck tool release mechanism.

Figure 1.19. Rigsite facilities.

Figure 1.20. New triple probe formation tester. Pads with “small round nozzle an...

Figure 1.21. New COSL triple probe tester, perspective view.

Figure 1.22. Simulator menu for Probes 3, 7 and 11 (top), sink Probe 7 pressure ...

Chapter 2

Figure 2.1. Early COSL single and dual probe formation testers (where “dual” ref...

Figure 2.2. Single probe formation tester (courtesy, COSL).

Figure 2.3. Dual probe formation tester (courtesy, COSL).

Figure 2.4. Piston pad pressed against the sandface.

Figure 2.5a. Idealized spherical flow for isotropic formations, ellipsoidal flow...

Figure 2.5b. Axisymmetric “ring” source.

Figure 2.6. Ellipsoidal anisotropic flow, skin layer, three-dimensional finite e...

Figure 2.7. “Near-Wellbore, Finite-Element Simulator (NEWS™)” from Halliburton E...

Figure 2.8. Dual probe, pretest, simulation-pressure contours, 100 md isotropic ...

Figure 2.9. Pressure contours for the first drawdown with two probes and the sec...

Figure 2.10a. Forward simulation assumptions.

Figure 2.10b. Pumpout schedule, volume flow rate.

Figure 2.10c. Source probe pressure.

Figure 2.10d. Observation probe pressure.

Figure 2.11a. Source (bottom) and observation probe (top) pressure responses.

Figure 2.11b. Inverse steady-state solver.

Figure 2.12a. Constant rate pumping example.

Figure 2.12b. Source probe response (all runs).

Figure 2.12c. Observation probe response versus dip angle.

Figure 2.13a. k

h

= 10 md, k

v

= 1 md (that is, k

h

> k

v

).

Figure 2.13b. k

h

= k

v

= 4.642 md (that is, isotropic).

Figure 2.13c. k

h

= 1 md, k

v

= 100.0 md (that is, k

h

< k

v

).

Figure 2.14a. Three-dimensional computational mesh.

Figure 2.14b. Borehole orientation.

Figure 2.14c. Azimuthal pressure response in layered media.

Figure 2.15a. Layered anisotropic media with dipping tool.

Figure 2.15b. Pressure transient response, amplitude and phase contrasts clear (...

Figure 2.15c. Multiple receiver phase delay formation tester (see, Section 2.3.5...

Figure 2.15d. Transmitter-receiver, receiver-receiver operational modes (see, Se...

Figure 2.16a. Nomenclature for pressure transient analysis.

Figure 2.16b. Exact FT-00 forward simulation results from single pre-test (note ...

Figure 2.16c. Predicted pore pressure and mobility (lower right).

Figure 2.16d. Exact FT-00 forward simulation pressures for two sequential pre-te...

Figure 2.16e. Predictions (first pre-test).

Figure 2.16f. Predictions (second pre-test).

Figure 2.17a. FT-06 liquid-gas simulator inputs.

Figure 2.17b. FT-06 pump rate and pressure solutions.

Figure 2.18. Repeat formation tester (RFT™).

Figure 2.19a. Test procedure from Schlumberger U.S. Patent 5,279,153 (flat press...

Figure 2.19b. New method for multiple drawdowns (refer to lower transient curves...

Figure 2.20a. Schlumberger mobility parameters assumed.

Figure 2.20b. Pressure response inferred from steady Schlumberger.

Figure 2.21a. Flowline volume, 200 cc.

Figure 2.21b. Flowline volume, 500 cc.

Figure 2.21c. Flowline volume, 1,000 cc.

Figure 2.21d. Flowline volume, 2,000 cc.

Figure 2.22a. Time-dependent flowline volume.

Figure 2.22b. Volume flow rate, flowline volume, source probe pressure plots.

Figure 2.23. Simple “two-receiver” observation probe.

Figure 2.24. Transmitter “marker” defines instant of departure.

Figure 2.25a. Estimating time delays for given parameters.

Figure 2.25b. Predicting permeability from time delay.

Figure 2.26. Amplitude (left) and phase delay (right) versus r and ω.

Figure 2.27a. Constant frequency pump excitation.

Figure 2.27b. Input data and exploded view.

Figure 2.27c. Source and observation probe pressure.

Figure 2.28a. Square wave assumptions and pressure responses.

Figure 2.28b. Pressure responses, exploded view.

Figure 2.29a. Layered anisotropic medium with dipping tool.

Figure 2.29b. Discretized grid for finite difference solution.

Figure 2.30. Windows-based program interface.

Figure 2.31. Rotatable plot of √(P

r 2

+ P

i 2

) versus x and y for given layer (“...

Figure 2.32. Phase delay plot (-100 to +100 psi for source pressure).

Figure 2.33. Output text summaries.

Figure 2.34a. Very high 1,000 md run.

Figure 2.34b. High 100 md run.

Figure 2.34c. Moderate 10 md run.

Figure 2.34d. Low 1 md run.

Figure 2.35a. Isotropic run, high permeability middle layer.

Figure 2.35b. Isotropic run, low permeability middle layer.

Figure 2.35c. Anisotropic run, high permeability middle layer.

Figure 2.35d. Anisotropic run, low permeability middle layer.

Figure 2.36a. Vertical tool (0° dip) in layered anisotropic medium.

Figure 2.36b. Horizontal tool (90° dip) in layered anisotropic medium.

Figure 2.36c. Deviated tool (45° dip) in layered anisotropic medium.

Figure 2.37a. Isotropic three-layer system.

Figure 2.37b. Dual probe system entirely in top layer.

Figure 2.37c. Source in middle layer, observation probe outside.

Figure 2.37d. Dual probe system entirely in middle layer.

Figure 2.38a. Three layer example.

Figure 2.38b. Observation probe responses at 10 Hz (left) and 0.5 Hz (right).

Figure 2.39a. FT-00 (Main Interactive) exact forward liquid simulator.

Figure 2.39b. FT-00 (Batch Mode) exact forward liquid simulator.

Figure 2.39c. FT-00 (DOI) exact forward liquid simulator.

Figure 2.40. FT-01, exact inverse liquid simulator.

Figure 2.41. FT-02, exact, steady forward and inverse gas simulators.

Figure 2.42a. FT-06, numerical liquid and gas forward simulator.

Figure 2.42b. FT-06, general flow rate functions, forward simulator.

Figure 2.42c. FT-07, a FT-06 extension supporting general time-varying flowline ...

Figure 2.43. FT-PTA-DDBU, early time, low mobility, flowline volume non-negligib...

Figure 2.44. Classic inverse model.

Figure 2.45. Both software modules apply to drawdown-buildup applications using ...

Figure 2.46. Input screen for “Model SC-DD-INVERSE-2.”

Figure 2.47. Input screen for “Model SC-DD-FORWARD-3B.”

Figure 2.48a. Input screen for “Model SC-DD-FORWARD-2-CREATE-TABLES-3B.”

Figure 2.48b. Pressure trends for selected overbalance pressures.

Figure 2.49a. Input screen for “Model SC-DDBU-INVERSE-2.”

Figure 2.49b. Input screen for “Model SC-DDBU-FORWARD-4NOPOR.”

Figure 2.50. Input screen for integrated forward simulator for both “drawdown on...

Figure 2.51. Main interface, “multiple drawdown and buildup” inverse models (MDD...

Figure 2.52. Exact steady-state inverse solver (see “center button,” main menu).

Figure 2.53. Inverse method, Model 2 (same as FT-PTA-DDBU).

Figure 2.54. Eleven transient inverse situations supported.

Figure 2.55. Original Schlumberger double-drawdown application.

Figure 2.56. Main system level simulation menus and options.

Figure 2.57. Run-time simulation menus for specific run.

Figure 2.58. Initial cylindrical invasion and mudcake buildup.

Figure 2.59. Pumpout (red) and simultaneous invasion (blue).

Figure 2.60. Early results (left) and later dynamics (right) times.

Figure 2.61. Integrated software platform, a beginning.

Figure 2.62. Underbalanced drilling with reservoir outflow.

Figure 2.63. Overbalanced drilling with wellbore inflow.

Figure 2.64. Overbalanced and underbalanced drilling applications with sealed bo...

Figure 2.65a. Pressure transient response with overbalance.

Figure 2.65b. Pressure transient response with overbalance.

Figure 2.65c. Pressure transient response with overbalance.

Figure 2.65d. Pressure trends for selected overbalance pressures.

Figure 2.65e. Pressure trends for selected overbalance pressures.

Figure 2.65f. Pressure transient response with overbalance.

Figure 2.65g. Pressure transient response with overbalance.

Figure 2.66a. Pressure transient response with overbalance.

Figure 2.66b. Pressure transient response with overbalance. Inverse calculation ...

Figure 2.66c. Pressure transient response with overbalance.

Figure 2.66d. Pressure transient response with overbalance.

Figure 2.66e. Pressure transient response with overbalance.

Figure 2.67. Eleven general drawdown-buildup inverse models.

Figure 2.68a. Model 1 rate function (black dots denote data points).

Figure 2.68b. Model 2 rate function (black dots denote data points).

Figure 2.68c. Model 3 rate function.

Figure 2.68d. Model 4 rate function.

Figure 2.68e. Model 5 rate function.

Figure 2.68f. Model 6 rate function.

Figure 2.68g. Model 7 rate function.

Figure 2.68h. Model 8 rate function.

Figure 2.68i. Model 9 rate function.

Figure 2.68j. Model 10 rate function.

Figure 2.69a. Model 11 rate function (three “black circles” show pressure data s...

Figure 2.69b. FT-00 exact inputs.

Figure 2.69c. Source probe pressure and pumpout schedule (all rates > 0). Flow r...

Figure 2.69d. Inverse model screen.

Figure 2.69e. FT-00 exact inputs.

Figure 2.69f. Source probe pressure and pumpout schedule (mixed signs).

Figure 2.69g. Inverse model screen.

Figure 2.69h. FT-00 exact inputs.

Figure 2.69i. Source probe pressure and pumpout schedule (mixed signs).

Figure 2.69j. Inverse model screen.

Figure 2.69k. FT-00 exact inputs.

Figure 2.69l. Source probe pressure and pumpout schedule (mixed signs).

Figure 2.69m. Inverse model screen.

Figure 2.70a. Catscan, linear test vessel with core sample (flow, top to bottom)...

Figure 2.70b. Radial flow Catscan test vessel.

Figure 2.70c. Catscan, invasion in radial core sample (inner invaded white zone ...

Figure 2.70d. Linear flow Catscans, thin dark mudcake at center of core and inva...

Figure 2.70e. Linear flow Catscans, standard optical contrast.

Figure 2.70f. Linear flow Catscans, high contrast visualization.

Figure 2.71. Single-probe supercharging and pumping model.

Figure 2.72. Pressure and contamination profiles in r-z plane.

Figure 2.73a. Pressure-concentration profiles, 0.33 sec.

Figure 2.73b. Pressure-concentration profiles, 1.00 min.

Figure 2.73c. Pressure-concentration profiles, 3.33 min.

Figure 2.73d. Pressure-concentration profiles, 3.67 min.

Figure 2.73e. Pressure-concentration profiles, 5.67 min.

Figure 2.73f. Formation fluid concentration at source probe.

Figure 2.73g. Source probe pressure transient history.

Figure 2.73h. Observation probe pressure transient history.

Figure 2.74a. Initial pumping, highly invaded upper zone.

Figure 2.74b. Supercharging seen in left pressure plot.

Figure 2.74c. Continued supercharging and invasion.

Figure 2.75a. Initial cylindrical invasion before pumping.

Figure 2.75b. Dual probe pumping initiated.

Figure 2.75c. Supercharging evident at large times.

Figure 2.76a. Initial pumping of cylindrical invaded region.

Figure 2.76b. Continued straddle packer pumping.

Figure 2.76c. Strong lateral pumping.

Figure 2.76d. Lower formation strongly affected.

Figure 2.77. Source and observation probe pressures.

Figure 2.78. Source probe formation fluid concentration.

Figure 2.79a. Field log, multirate flow and pressure.

Figure 2.79b. Source and observation probe simulation.

Chapter 3

Figure 3.1. Total pumpout of 5 cc, for all three piston scenarios.

Figure 3.2a. Constant rate pumping (idealization).

Figure 3.2b. FT-00 forward simulator input menu.

Figure 3.2c. Pumpout schedule.

Figure 3.2d. Source probe pressure.

Figure 3.2e. Observation probe pressure.

Figure 3.2f. Model 1, for drawdown “pressure-time” data.

Figure 3.2g. Inverse pressure buildup problem (Model 2).

Figure 3.2h. Inverse worksheet.

Figure 3.3a. Slow ramp up/down rate pumping.

Figure 3.3b. FT-00 forward simulator input menu.

Figure 3.3c. Pumpout schedule.

Figure 3.3d. Source probe pressure.

Figure 3.3e. Observation probe pressure.

Figure 3.3f. Model 6 inverse problem.

Figure 3.4a. Impulsive start/stop rate pumping.

Figure 3.4b. FT-00 forward simulator assumptions.

Figure 3.4c. Pumpout schedule.

Figure 3.4d. Source prove pressure.

Figure 3.4e. Observation probe pressure.

Figure 3.4f. Model 6, inverse solver.

Figure 3.5a. “Fast Forward” forward supercharge simulator.

Figure 3.5b. Drawdown-buildup with strong supercharge.

Figure 3.5c. Drawdown – only curve with supercharge.

Figure 3.5d. Drawdown-only inverse supercharge model.

Figure 3.5e. Drawdown-buildup inverse supercharge model.

Figure 3.6a. Creating FT-00 pressure transient data for an anisotropic simulatio...

Figure 3.6b. Source and observation probe pressures versus time at different mag...

Figure 3.6c. FT-01 input screen.

Figure 3.6d. Drawdown inverse method.

Figure 3.6e. Exact direct gas solver for dual probe steady flows.

Figure 3.7. Conventional dual and triple probe testers.

Figure 3.8. Multiple “receiver” formation tester (having multiple spaced observa...

Figure 3.9. Transmitter-receiver, receiver-receiver operations modes (see Chapte...

Figure 3.10. Main FT-00 menu, see bottom right “Run” button.

Figure 3.11. Depth of investigation, DOI” analysis setup.

Figure 3.12a. Flow rate schedule.

Figure 3.12b. Source probe response.

Figure 3.12c. Pressure response at 10 cm (3.9 in).

Figure 3.12d. Pressure response at 20 cm (7.9 in).

Figure 3.12e. Pressure response at 20 cm (7.9 in), continued.

Figure 3.12f. Pressure response at 50 cm.

Figure 3.12g. Pressure response at 90 cm (35 in).

Figure 3.13. FT-00 host simulator.

Figure 3.14. Batch mode information message.

Figure 3.15. Loop parameter setup.

Figure 3.16. FT-00 running in automated batch mode (note, ? and ??).

Figure 3.17. Option to view pressure plots.

Figure 3.18a. Simulation No. 1, input parameters.

Figure 3.18b. Simulation No. 1, Source probe response.

Figure 3.18c. Simulation No. 1, Observation probe response.

Figure 3.19a. Simulation No. 2, with kh = 1 md again, kv increased.

Figure 3.19b. Simulation No. 2, Source probe response.

Figure 3.19c. Simulation No. 2, Observation probe response.

Figure 3.20a. Simulation No. 25, last kh = 500 md, kv = 100 md.

Figure 3.20b. Simulation No. 25, Source probe response.

Figure 3.20c. Simulation No. 25, Observation probe response.

Figure 3.21. Mudcake thickness and hole radius considerations.

Figure 3.22. Exact lineal invasion solution (Chin et al., 1986).

Figure 3.23a. Radial flow Catscan test vessel.

Figure 3.23b. Catscan invasion in radial core sample (inner invaded white zone d...

Chapter 4

Figure 4.1a. Supercharge problem in formation testing.

Figure 4.1b. Linear flow Catscans, thin dark mudcake at center of core and invas...

Figure 4.1c. Stuck tool removal mechanism.

Figure 4.2. Exact lineal invasion solution (Chin et al., 1986).

Figure 4.3. Any surface f(x,y,z,t) = 0 in a reservoir.

Figure 4.4. Lineal flow.

Figure 4.5. Cylindrical radial flow.

Figure 4.6. Spherical flow at the drillbit.

Figure 4.7. Simple laboratory mudcake buildup.

Figure 4.8. Simple linear flow of two dissimilar fluids.

Figure 4.9. Three-layer lineal flow.

Figure 4.10. Three-layer radial flow.

Figure 4.11. Lineal flow.

Figure 4.12. Radial flow test, 15 ppg mud, Δp = 150 psi.

Figure 4.13. Radial mudcake growth on filter paper.

Figure 4.14. Radial versus lineal mudcake theory.

Figure 4.15. Radial invasion without mudcake.

Figure 4.16. Numerical results, forward invasion simulation.

Figure 4.17. Numerical results, inverse invasion simulation.

Figure 4.18. Numerical results, forward invasion simulation.

Figure 4.19. Numerical results, inverse invasion simulation.

Chapter 5

Figure 5.1. Finite difference discretizations.

Figure 5.2. Tridiagonal equation solver.

Figure 5.3a. Fortran source code (Example 5-1).

Figure 5.3b. Numerical results (Example 5-1).

Figure 5.3c. Numerical results (Example 5-1).

Figure 5.4a. Fortran source code (Example 5-2).

Figure 5.4b. Numerical results (Example 5-2).

Figure 5.4c. Numerical results (Example 5-2).

Figure 5.5a. Numerical results (Example 5-3).

Figure 5.5b. Numerical results (Example 5-3).

Figure 5.6a. Fortran source code (Example 5-4).

Figure 5.6b. Numerical results (Example 5-4).

Figure 5.7. Gas displacement by liquid.

Figure 5.8a. Fortran source code (Example 5-6).

Figure 5.8b. Numerical results (Example 5-6).

Figure 5.8c. Numerical results (Example 5-6).

Figure 5.9a. Three-layer lineal flow problem.

Figure 5.9b. Fortran source code (Example 5-7).

Figure 5.9c. Numerical results (Example 5-7).

Figure 5.10. Pressure in lineal core.

Figure 5.11. Diffusive front motion.

Figure 5.12a. A diffusing lineal flow.

Figure 5.12b. An “un-diffusing” lineal flow.

Figure 5.13a. A diffusing radial flow.

Figure 5.13b. An “undiffusing” radial flow.

Figure 5.14. Nonlinear saturation solver.

Figure 5.15a. Zero mud filtrate influx.

Figure 5.15b. Very slow constant injection rate.

Figure 5.15c. Q = 1, constant rate, high inertia flow.

Figure 5.15d. Q = 2, constant rate, high inertia flow.

Figure 5.15e. Q = 3, constant rate, high inertia flow.

Figure 5.16. Mudcake-dominated invasion.

Figure 5.17a. High filtration rate mudcake model (α = 1).

Figure 5.17b. Very high filtration rate mudcake model (α = 5).

Figure 5.17c. Very slow filtration rate model (α = 0.001).

Figure 5.18. “Un-shocking” a steep gradient.

Figure 5.19a. Forward shock formation.

Figure 5.19b. Backward shock migration.

Figure 5.20. Implicit pressure – implicit saturation solver.

Figure 5.21a. Early time saturation and pressure.

Figure 5.21b. Intermediate time saturation and pressure.

Figure 5.21c. Late time saturation and pressure.

Figure 5.22. Two-layer mudcake-rock, immiscible flow model.

Figure 5.23a. Early time solution.

Figure 5.23b. Intermediate time solution.

Figure 5.23c. Late time solution.

Figure 5.24a. Early time solution.

Figure 5.24b. Intermediate time solution.

Figure 5.24c. Late time solution.

Figure 5.25a. COSL formation testing software platform.

Figure 5.25b. COSL formation testing software platform.

Figure 5.25c. COSL formation testing software platform.

Figure 5.25d. COSL formation testing software platform.

Figure 5.25e. COSL formation testing software platform.

Guide

Cover

Table of Contents

Title Page

Copyright

Preface

Acknowledgements

Begin Reading

Cumulative References

Index

About the Authors

Also of Interest

End User License Agreement

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Scrivener Publishing100 Cummings Center, Suite 541JBeverly, MA 01915-6106

Handbook of Petroleum Engineering Series

Series Editor: Wilson C. Chin

Scope: Covering every aspect of petroleum engineering, this new series sets the standard in best practices for the petroleum engineer. This is a must-have for any petroleum engineer in today’s changing industry.

About the Series Editor:

Wilson Chin earned his PhD from M.I.T. and his M.Sc. from Caltech. He has authored over twenty books with Wiley-Scrivener and other major scientific publishers, has more than four dozen domestic and international patents to his credit, and has published over one hundred journal articles, in the areas of reservoir engineering, formation testing, well logging, measurement while drilling, and drilling and cementing rheology.

Submission to the series:Phil Carmical, PublisherScrivener Publishing(512)[email protected]

Publishers at ScrivenerMartin Scrivener ([email protected])Phillip Carmical ([email protected])

Supercharge, Invasion and Mudcake Growth in Downhole Applications

by

Tao Lu

Xiaofei Qin

Yongren Feng

Yanmin Zhou

and

Wilson Chin

This edition first published 2021 by John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA and Scrivener Publishing LLC, 100 Cummings Center, Suite 541J, Beverly, MA 01915, USA

© 2021 Scrivener Publishing LLC

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Library of Congress Cataloging-in-Publication Data

ISBN 978-1-119-28332-4

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10 9 8 7 6 5 4 3 2 1

Preface

Formation testing, unlike conventional logging methods focused on resistivity, acoustic, nuclear or magnetic resonance approaches, provides direct results as opposed to indirect inferred properties. In sampling, actual in-situ fluids are collected for surface evaluation. And in pressure transient analysis, properties that pertain to production economics like mobility, compressibility, anisotropy and pore pressure are obtained directly from the underlying Darcy flow equations. By and large, the conventional subject matter deals with single, dual and multiprobe tools where pad nozzles are displaced axially relative to each other and along the same azimuth. This being so, idealized spherical “source” or “sink” methods are used in formulating forward and inverse problems.

Even so, few models have proven useful. An early steady model for spherical flow no longer applies to the lower mobility formations encountered in practice. Later transient models contain complicated Bessel functions and integrals whose effective use in the field is questionable. And then, a rapid, early-time prediction method for “effective permeability” and pore pressure, addressing the low mobility and “not so low” flowline volume limit – while significant in the 1990s and, in fact, invented by the last author, does not address all-important supercharging effects uncovered in recent field-based publications.

Fortunately, progress in source methods has been made, but at such an unusual pace that any presentations at industry meetings would have been rapidly dated. In support of our work, John Wiley & Sons has published our research in three volumes during 2014 – 2019, introducing the latest ideas and techniques to the industry, complete with derivations, equations and software. The present work, our latest formation testing addition to Wiley-Scrivener’s Petroleum Engineering Handbook Series, serves several purposes. While “handbooks” normally refer to summaries of decades-old technologies, this edition is timely because numerous new advances have been made in related and interdependent areas. These include pressure transient analysis, forward and inverse modeling, supercharge, mudcake growth and fluid invasion formulations, and contamination and cleaning multiphase methods – and all during the past two decades by the present authors. While China Oilfield Services Limited (COSL) does manufacture its own conventional single and dual probe tools, it is the availability of our complete suite of software models that allows its tools to be used in many more innovative ways.

For example, methods are available to predict permeability and pore pressure rapidly from early time data in low mobility formations with strong flowline volume. But what if significant supercharging exists? Most inverse methods require constant flow rate drawdowns. What if this is not possible? And unacceptably, few authors have ever rigorously studied mudcake growth and fluid invasion, which produce the thick cakes responsible for stuck formation testers – the same phenomena associated with supercharge. Nor do they address the thin cakes that wreak havoc on nozzle pad sealing – leakages that would doom any formation testing job. Numerous related questions are treated in this comprehensive volume. And so this handbook, which addresses all of these problems from source model perspectives, provides unified discussions in forward and inverse formation testing analysis, supercharge in pressure evolution and permeability prediction, plus related topics in fluid invasion, mudcake growth and displacement front prediction. It is our hope that this work stimulates continuing research and enhances the innovative use of conventional tools in the field.

During the past several years, other high risk research and development projects were undertaken at COSL. In the early 1990s, an innovative “multiprobe” formation tester was introduced by a major service company that has greatly benefited the industry. This tool, consisting of an active “sink probe” and a passive “horizontal” observation probe displaced at 180° azimuthally from the sink, would provide measurements for horizontal and vertical permeability. However, in low mobility applications, measured pressure drops at the latter probe were often orders-of-magnitude less than those obtained at the pumping probe. This limitation attracted the interests of COSL engineers, who raised several unusual design challenges. “What if three azimuthally displaced probes, each separated by 120° from the others, were used?” And further, “What if each probe in the triple multiprobe tool were capable of operating independently from the others?”

What would be the logging advantages? What additional parameters of formation evaluation interest could we predict? Is it possible to detect heterogeneities? Dip angle? Can we pump at high rates without releasing dissolved gas? In order to design such a multiprobe tool, a fully three-dimensional transient model would be required to guide mechanical design as well as to support interpretation procedures at the rigsite. Can a rapid, stable, accurate and easy-to-use computational method be devised? Is it possible to develop a robust procedure that supports field work in horizontal and vertical mobility definition? How would we apply “big data” statistical approaches using advanced algorithms? Can inverse procedures be solved accurately and rapidly at the rigsite and in field offices?

These questions are addressed in a companion 2021 volume in John Wiley’s Advances in Petroleum Engineering series, entitled Multiprobe Pressure Analysis and Interpretation, by Tao Lu, Minggao Zhou, Yongren Feng, Yuqing Yang and Wilson Chin. This complementary volume contains math models entirely different from the present, but which are also applicable to conventional 180° dual probe tools. Both of our 2021 books, drawing on research and engineering developed over more than a decade, are essential to modern formation testing, and we hope that both will find permanent places on petroleum engineers’ bookshelves. In this time of great uncertainty, one truth prevails: now, more than ever, innovation is needed to explore and produce natural resources more efficiently. And innovation in engineering means nothing less than a thorough understanding of physics and mathematics and putting both to important practical use.

The Authors,Beijing and Houston

Acknowledgements

The authors wish to thank the management of China Oilfield Services Limited (COSL) for permission to publish this manuscript. Our research efforts hope to advance formation testing, algorithm design and well logging technology and bring greater efficiencies to exploration and production. We are also indebted to Xiaoying Zhuang for her interpretation and translation skills, and usual hard work and perseverance, which have been instrumental in communicating a wide range of engineering and technical ideas to English-speaking audiences over the past decade. And last but not least, we again thank Phil Carmical, Acquisitions Editor and Publisher, for his confidence and faith in our research activities. In times of economic uncertainty such as ours, it is imperative that “the show must go on” and oil and gas industry professionals continue to “push the envelope” despite the headwinds. This monograph describes our persistent and continuing efforts in this endeavor and we are pleased to present our ideas to our petroleum engineering colleagues.

1Pressure Transient Analysis and Sampling in Formation Testing

The formation tester is a well logging instrument with extendable pad nozzles which, when pressed against the borehole sandface, extracts in situ formation fluids for delivery to the surface for chemical examination. This process characterizes its fluid “sampling” function. By-products of this operation are pressure transient histories, which can be interrogated using Darcy math models for fluid and formation properties such as permeability, mobility, anisotropy, compressibility and pore pressure. This is referred to as “pressure transient analysis,” or simply, “PTA.” Both can be conducted as wireline or Measurement While Drilling, or “MWD,” applications, where these operations now represent invaluable elements of the standard well logging suite.

Pressure transient analysis challenges. While collecting and transporting fluids is relatively straightforward, e.g., storing samples in secure vessels that maintain downhole conditions, the PTA process poses a greater design challenge. A well designed tool often begins with a good understanding of the environment, plus physics coupled with sound experience in mathematical modeling. Some ideas are obvious. For example, a single “source” or “sink” probe, serving both pumping and pressure observation functions, will at most provide the “spherical permeability” kh2/3kv/1/3, where kh and kv are horizontal and vertical permeabilities. Thus, “single probe” tools, while mechanically simple, will offer fewer logging advantages than “dual probe” or “multiprobe tools” which provide much greater formation evaluation information.

Figure 1.1. Drawdown-buildup pressure response with dynamic pumping action and flowline.

But how are probe arrays configured and placed for optimal effect? Figures 1.1 and 1.2 illustrate the operation of a single probe tool that withdraws fluid and then stops, creating the expected “drawdown and buildup” shown. If a second probe is desired, should it be placed an axial distance apart but along the same azimuth? Or azimuthally apart, at 180° away along the borehole circumference? What about a “drawdown only” pumpout? Or perhaps, have the pump oscillate sinusoidally in place, thus mimicking the AC transmissions of an electromagnetic logging tool? How many probes are best? What are their flow areas? Do answers to these questions depend on fluid and formation properties?

Figure 1.2. Downhole, surface and logging truck operations.

Background development. The present book addresses these questions for “source” or “sink models” of the pumping nozzle, these terms referring to ideal representations of the flow where borehole and pad geometry are described using mathematically small closed surfaces. The recent books due to Chin et al. (2014) or Formation Testing: Pressure Transient and Contamination Analysis, Chin et al. (2015) or Formation Testing: Low Mobility Pressure Transient Analysis, and Chin (2019) or Formation Testing: Supercharge, Pressure Testing and Contamination Models, published by John Wiley & Sons, contain complete math derivations and detailed validations. However, the rapid pace of recent development suggests a separate volume in Wiley’s Handbook of Petroleum Engineering Series, focused on the main ideas behind the recent works. These ideas are essential as they are also used in the design of newer COSL formation testing tools as well as in interpretation software now available to the petroleum industry. What engineers lack, at present, are job planning and PTA tools both useful at the rigsite and at engineers’ desktops. It is our purpose to support this pressing need.

Figure 1.3. Recent formation testing book publications.

1.1 Conventional Formation Testing Concepts.

Formation testing design concepts are rich and varied. A pumping probe, operating as a “sink” or (equivalently) a “source,” or both, also tracks pressure transient responses. Other pressure probes my reside along the tool body, displaced axially, azimuthally or both, which may actively pump or act as passive observers. While the primary formation tester function is fluid sampling, where in-situ reservoir fluids are collected and transported to the surface for analysis, pressure measurements represent critical by-products important to formation evaluation. Examples of testers offered by different manufacturers for wireline and MWD applications are given in Figures 1.4 – 1.7.

Figure 1.4. Conventional formation tester tool strings.

Figure 1.5. Formation testers, additional developments.

Figure 1.6. Conventional dual and triple probe testers.

Figure 1.7. Dual probe tester with dual packer.

1.2 Prototypes, Tools and Systems.

In a “handbook” such as this, it is important to provide examples of prototypes, commercial tools and systems. The wide ranges in design parameters can be surprising to newcomers in formation testing. For example, the “vertical and sink probes” in Figure 1.6, which are displaced axially but lie along the same azimuth, can range from six or seven inches to as much as 2.3 ft (27.6 in) and 10.3 ft (123.6 in), where the latter two distances are obtained from the manufacturer’s figure in SPE Paper No. 36176. We might, for example, ask, “Just what does the distant observation probe “see” under different mobility backgrounds?” “Will the tool do the job for my formation?” This book attempts to answer the most obvious questions, but it also aims at providing the tools and software for readers to address those pressing questions that invariably arise in any new logging scenario. To provide a flavor of how hardware literature and specifications might appear, we have included discussion of COSL material related to its standard product lines. Note that COSL’s new “triple probe, 120° tool” (as opposed to a conventional 180° tool) is treated separately in our companion 2021 book.

Close-ups of early single and dual probe prototype formation testers are shown in Figure 1.8. These photographs were obtained during field tests. The black pads shown perform an important sealing function, which prevents leakage of fluid through its contact surface with the sandface. However, they are not as “simple” as they appear. For instance, at any given pump rate, the pressure drop, which depends on nozzle diameter, may be excessive and allow the undesired release of dissolved gas – orifice sizes must be chosen judiciously, as suggested by the wide variety of choices shown in Figure 1.9. The shape of the hole or slot is also important; circular or oval shapes may be acceptable for consolidated matrix rock, but slotted models may be required for naturally fractured media or unconsolidated formations. Of course, in supporting PTA interpretation objectives, the size and shape of a formation tester’s pads must be incorporated into the host math model. More often than not, the model must be simple and mathematically tractable in order to obtain useful answers in a reasonable amount of time. This may require the use of idealized source or sink models, or numerical models with limited numbers of grids in the case of finite difference or finite modeling – consequently, questions related to calibration or geometric factors arise, along with test procedures, etc.

Figure 1.8. Early COSL single and dual probe prototype formation testers (details in 2014 and 2015 books).

Figure 1.9. COSL pad designs with varied sizes and shapes, for different applications, e.g., firm matrix rock, unconsolidated formations, fractured media, and so on..

Pressures obtained in PTA logging are used for multiple applications. For example, depending on the tool, permeability, anisotropy, compressibility and pore pressure are all possible (the term “mobility,” defined as the ratio of permeability to viscosity, is often interchangeably used, assuming that the viscosity is known). The pore pressure itself is used to identify fluids by their vertical hydrostatic gradients; this is possible because changes in pressure are affected by changes in fluid density. Sudden changes in pressure, for instance, may indicate the presence of barriers. However, the raw measured pressure, unless corrected for the “cushioning” effects associated with flowline volume, will not reflect pore pressures accurately. The correction depends, in turn, on the line volume as well as the compressibility and the mobility of the formation fluid. All said, the physics and math can be challenging, but solutions and analytical highlights are presented in the next chapter for a wide variety of tools and applications. Chapter 2 provides a broad state-of-the-art review for source and sink models.

1.2.1 Enhanced Formation Dynamic Tester (EFDT ®).

The “Enhanced Formation Dynamic Tester” is an advanced wireline formation testing system that delivers: (1) Multiple, large-volume high-purity formation fluid samples with downhole fluid characterization, (2) Reliable formation pressure testing, and (3) Real-time downhole fluid analyze, and more. Typical tool string configurations and architectures are shown in Figures 1.10 and 1.11. For detailed specifications, the reader is referred to the latest updated manufacturer’s literature.

Figure 1.10. Tool string configurations.

COSL’s EFDT is designed to obtain formation pressures and formation fluid samples at discrete depths within a reservoir. Analyzing pressure buildup profile and the properties of fluid samples helps provide a more complete description of reservoir fluids and behavior. The EFDT service provides key petrophysical information to determine the reservoir volume, producibility of a formation, type and composition of the movable fluids, and to predict reservoir behavior during production.

THE EFDT is a modular formation testing system. It can be customized for the specialized applications. The modularity of EFDT ensures its ability to test and sample fluids in a wide range of geological environments and borehole conditions. For its basic configuration, the string includes a fully controllable Dual Probe Module for fluid in-taking, a Flow Pump Module for variable-volume drawdown and pump out of contaminated fluids, a Fluid Sensor Module for dynamic properties of fluids, a PVT Carrier Module for monophase sampling, and a Large Sample Carrier Module for large-volume normal sampling. It can also be configured with a Straddle Packer Module, an Optical Analysis Module, a Focused Probe Module and a Multi-PVT Tank Module to meet the requirements of complex reservoir formation tests, such as low permeability rock or natural fractures.

The EFDT enables up to five properties of fluid and formation to be monitored during testing: fluid conductivity or capacitivity, fluid density, fluid dynamic pressure, fluid optical analysis and formation permeability and anisotropy. The EFDT provides up to four MonoPhase Sampling Tanks (MPST) for one run, which recovers high-quality pressure-compensated reservoir fluid samples during borehole formation testing operations. The new Multi-PVT Module can take up to 24-48 PVT samples in one run (6 X 350 ml per module). The EFDT uses standard EDIB telemetry protocol, is combinable with other EDIB logging tools, and requires the company’s ELIS surface acquisition system. Surface control interfaces and user output displays are given in Figures 1.12 and 1.13. Applications, benefits and features are summarized below.

Applications

Formation pressure measurements and fluid contact identification

Repeatable formation fluid sampling

Measurement of formation permeability and anisotropy

Vertical interference testing

ln-situ downhole fluid analysis

Benefits

Fast, high-accuracy pressure measurement using Quartz Pressure Gauges (QPG) with temperature compensation

Conductivity/capacitivity, density, fluid dynamic pressure, NIR optical analysis and formation permeability anisotropy for real-time reservoir evaluation

Savings of 50% sampling time using focus probe

Multiple samples in one run, providing high quality PVT samples

Features

Modularity, offering expanded testing versatility

Accurate pressure measurement using QPG

Real time downhole fluid assessment

PVT quality formation fluid samples

Figure 1.11. Tool architectures.

Figure 1.12. Surface control interface.

Figure 1.13. Pressure measurement chart (left) and real-time fluid monitoring chart (right).

1.2.2 Basic Reservoir Characteristic Tester (BASIC-RCT™).

COSL’s “Basic Reservoir Characteristic Tester” or “BASIC-RCT” is a third generation product of the formation tester family, characterized by its pump through function. BASIC RCT is a compact, convenient, safe and efficient tool. It can replace in part Drill Stem Testing (DST) operations in order to save rig time. BASIC RCT provides economical and reliable solutions to formation evaluation for oilfield exploration and engineering, representing a good means to reduce cost while solving difficult technical problems. BASIC RCT can be run on any service company logging unit, requiring only winch, cable head and depth measurement. All services, telemetry, gamma ray recording, test recording (digital, numerical listing, screen and printer graphics) are provided in real time. Tool configurations are shown in Figure 1.14. For latest specifications, the reader should refer to the manufacturer’s updates.

Functions

Measuring formation pressure accurately

Taking multi-samples of formation fluids

Taking large samples

Pumping through contaminated formation fluids

Monitoring formation fluid properties in real time.

Flowing formation fluids at controlled rates

Pumping through in reverse

Making quick well site sampler transfer

Providing real time and reliable data for analyzing permeability and formation damage

Structure

The BASIC RCT is a combination of surface system and downhole tools. The surface system includes the Acquisition and Data Process software, PC and DC control panel, and AC power supply. The downhole tools include the upper electronics section, mechanical/hydraulic section, sensor section, lower electronics section with a standard configuration, and also include the 2 × 520 cc large sampler with optional configuration (see Figures 1.15 and 1.16).

Figure 1.14. Tool string configurations.

Figure 1.15. Tool architecture.

Figure 1.16. Tool and surface system.

Figure 1.17. Pressure drawdown curve (left) and fluid contact curve (right).

1.2.3 Enhancing and enabling technologies.

While we principally focus on pressure transient analysis in this volume, a number of enabling technologies contribute to the operational success of formation testers in general, and in particular the robustness of the tools mentioned in Sections 1.2.1 and 1.2.2. A critical problem is that associated with “stuck tools,” which results in expensive fishing jobs, lost tools and increased rig costs.

Stuck tool alleviation. Issues related to stuck pipe are as old as drilling itself. In “Development on Incongruous Pushing and Stuck Releasing Device of EFDT,” by Qin, X., Feng, Y., Song, W., Chu, X. and Wang, L. and appearing in Journal of China Offshore Oilfield Technology, Vol. 4, No. 1, April 2016, pp. 70-74, the authors analyze the causes of differential pressure sticking during openhole wireline logging. Their modular IPSRD releasing device, designed for EFDT formation tester applications, could be seamlessly assembled to the tool. “Stuck Release Arms” (SRA) are driven by hydraulic forces that free the dual probe tool from adhesive forces. In Chapters 4 and 5, we show how mudcake thicknesses can be accurately modeled and predicted – small values to reduce chances for tool loss are needed, while larger thicknesses are required to seal tester pads to the sandface – at the same time, providing excellent descriptions for supercharge pressure effects.

The authors importantly point out that while measuring pressure and sampling, even at a single point in the well, duration times may last several hours or even tens of hours. In particular, for higher mud densities, the possibility of differential sticking – and the likelihood of expensive fishing jobs – is high. In extreme cases, loss of the tool downhole and well abandonment are possible. Figure 1.18 explains the conceptual ideas behind IPSRD. The left diagram illustrates the differential sticking process, with the following nomenclature: 1-Wellbore fluid, 2-Backup, 3-EFDT, 4-Mudcake, 5-Probe, 6-Protector and 7-Formation. The right side outlines the tool architecture. Upper Stuck and Lower Stuck release modules USRM and LSRM are found at the top and bottom, with the Dual Probe Module (DPM) residing between the two. The “stuck release arms” (SRA) for each releasing module are designed in opposite directions for pushing separately. The paper describes several field applications and savings in logging costs.

Figure 1.18. IPSRD stuck tool release mechanism.

Field facilities. Finally, we offer some snapshots of COSL logging trucks and rigsite facilities from which formation testing jobs are run. The photographs are self-explanatory.

Figure 1.19. Rigsite facilities.

1.3 Recent Formation Testing Developments.

Conventional formation tester tools with single and dual probes are shown in Figures 1.8 and 1.9, noting that different testers may be outfitted with different pad designs depending on the application. For instance, small round nozzles may be used with firm matrix rock; in low permeability formations, larger nozzles may be preferable in order to prevent excessive pressure drawdowns that result in the undesired release of dissolved gas or increased mechanical demands. Larger slot nozzles are ideal when formations are lower in permeability or naturally fractured and higher pump rates are desired.

The right-side diagram in Figure 1.6 shows an active pumping “sink probe” mounted on the mandrel, with a passive “horizontal” observation probe located 180° circumferentially away around the borehole. A “vertical probe” is also shown displaced axially from the sink probe and lying along the same azimuth. This conventional 1990s designed “triple probe” tool has seen wide application since its introduction. However, in low mobility formations, questions related to weak pressure signal detection and large diffusion arise.

These have motivated the design of a new and different type of “triple probe” tester, where three independently operated, closer probes are located about the borehole at 120° separations, all residing in the same axial plane and supporting pumping and pressure measurement. Axially displaced “vertical probes” also augment the new triple probe design. The new COSL tool offers advantages over conventional instruments and these are described in a companion 2021 book Formation Testing – Multiprobe Design and Pressure Analysis by Lu, Zhou, Feng, Yang and Chin (John Wiley & Sons). Because of the three-dimensional nature of the physics, the complementary volume develops new analysis and interpretation methods that account for borehole size and shape, and without invoking symmetry assumptions, since the probes may differ during any logging run and pump with different flow rate schedules. Figures 1.20 – 1.22 show example graphics from the book.

Figure 1.20. New triple probe formation tester. Pads with “small round nozzle and slot probe” (top) and “all long slot nozzles” (bottom).

Figure 1.21. New COSL triple probe tester, perspective view.

Figure 1.22. Simulator menu for Probes 3, 7 and 11 (top), sink Probe 7 pressure drop versus kh and kv at fixed rate (bottom).

1.4 References.

• Chin, W.C., Formation Testing: Supercharge, Pressure Testing and Contamination Models, John Wiley & Sons, Hoboken, New Jersey, 2019.

• Chin, W.C., Zhou, Y., Feng, Y. and Yu, Q., Formation Testing: Low Mobility Pressure Transient Analysis, John Wiley & Sons, Hoboken, New Jersey, 2015.

• Chin, W.C., Zhou, Y., Feng, Y., Yu, Q. and Zhao, L., Formation Testing: Pressure Transient and Contamination Analysis, John Wiley & Sons, Hoboken, New Jersey, 2014.

• Lu, T., Qin, X., Feng, Y., Zhou, Y. and Chin, W.C., Supercharge, Invasion and Mudcake Growth in Downhole Applications, John Wiley & Sons, Hoboken, New Jersey, 2021.

• Lu, T., Zhou, M., Feng, Y., Yang, Y. and Chin, W.C., Multiprobe Pressure Analysis and Interpretation, John Wiley & Sons, Hoboken, New Jersey, 2021.

• Qin, X., Feng, Y., Wu, L., Tan, Z., Zhou, Y. and Chin, W.C., “Permeability and Pore Pressure Prediction in Highly Supercharged FTWD Environments,” submitted for publication, 2020.

• Qin, X., Feng, Y., Song, W., Chu, X. and Wang, L., “Development on Incongruous Pushing and Stuck Releasing Device of EFDT,” Journal of China Offshore Oilfield Technology, Vol. 4, No. 1, April 2016, pp. 70-74.

• Zhou, M., Feng, Y., Xue, Y., Zhou, Y., Chen, Y. and Chin, W.C., “Multiprobe Formation Testing – New Triple Arm Logging Instrument,” submitted for publication, 2020.

2Spherical Source Models for Forward and Inverse Formulations

The 1990s sparked important innovations in formation tester design, e.g., single, dual and triple probe tools, straddle packer applications, optical fluid analysis, and so on. Very well received were the “early time, low mobility, non-negligible flowline volume” inverse methods used to predict mobility and pore pressure in formations where earlier steady state methods were no longer optimal – for example, Halliburton’s GeoTap™ method was successful in commercializing such models. One of its inventors, W.C. Chin, later went on to win two Small Business Innovation Research (SBIR) awards from the United States Department of Energy in 2004 to extend the early work and to embark on other promising avenues of pressure transient and sampling research.

This work continued beyond the life of the DOE contracts, resulting in many new methods and algorithms that would see book publication in the 2000s. In particular, these were Chin et al. (2014) or Formation Testing: Pressure Transient and Contamination Analysis, Chin et al. (2015) or Formation Testing: Low Mobility Pressure Transient Analysis, and Chin (2019) or Formation Testing: Supercharge, Pressure Testing and Contamination, all with John Wiley & Sons. These research monographs introduced new methods and provided mathematical and algorithmic details, practical validations, approaches motivated by electromagnetic logging, and so on, which the present authors hope would stimulate further advances. Nonetheless, the very rapid pace with which the new models were introduced meant that the entire portfolio of ideal “source models” could not be understood in perspective, even by those actively engaged in research and engineering. A practical state-of-the-art summary emphasizing key ideas, and less so the formal math, was long overdue and is presented in this “introductory” chapter. Our methods are applicable to all formation tester manufacturers’ tools.

However, this need was not driven by dissemination objectives alone. During the same time frame, China Oilfield Services Limited (COSL) would embark on several programs to develop leading edge formation testing tools, a technology dominated by leading oil service companies Schlumberger, Halliburton and BakerHughes. This effort was all-the-more ambitious because COSL, a newcomer to formation testing, would need to establish its competence in conventional tools before its long term objective could be achieved. What was this objective? The industry’s leading tester, at its most basic level, consisted of a source (or sink) probe nozzle which, when pressed against the sandface, would extract formation fluid samples for surface evaluation. By products of this extraction are pressure transients measured at the source nozzle – and also at a passive observation probe displaced 180° circumferentially about the borehole. But physical intuition and field observation would confirm extremely small pressures from the faraway probe, or weak signal to noise ratios, especially at low mobilities, that would lead to inaccurate predictions in demanding reservoir applications.

COSL engineering staff asked, “What if 180° probe spacings were reduced?” What if three probes, each spaced 120° apart, were used? And what if each probe were capable of operating independently, playing active as well as passive roles, during the logging process? This clearly opens up new possibilities in formation tester interpretation. An accurate, robust and rapid full three-dimensional simulator accounting for borehole curvature and pad geometry was needed which would also support mechanical design and field operations. It would address practical questions. For instance, what pump rate and nozzle combinations would allow fluid withdrawal without releasing dissolved gas? How are pump characteristics specified? How can triple probe redundancies support determination of local heterogeneities? Dip angle? Before such a simulator could be developed, the limitations in existing state-of-art methods must be understood. Such a simulator has been developed and is reported in 2021 companion book. The present chapter summarizes our knowledge of existing models, in particular, the advanced spherical and ring “source models” derived in the three prior books, which will continue to be useful in ongoing developments related to the new triple probe formation tester. Our compilation of general algorithms, in a single volume, provides a comprehensive discussion of key formation testing interpretation methods applicable to all manufacturers’ tools.

2.1 Basic Approaches, Interpretation Issues and Modeling Hierarchies.

In this opening section, we review the main ideas and models developed in the books Formation Testing: Pressure Transient and Contamination Analysis, Formation Testing: Low Mobility Pressure Transient Analysis and Formation Testing: Supercharge, Pressure Testing and Contamination Models published by John Wiley & Sons in 2014, 2015 and 2019. Our discussions provide greater insight than existed at the time and our ideas are now presented from the perspective of developers who have designed a much broader three-dimensional model. This does not mean that the earlier works, based on idealized spherical and ring sources, are dated. In fact, the work is just as relevant to future testers, which will host circumferentially positioned sensors and also passive and active pressure displaced axially along the tool axis.

Early steady flow model. What are formation testers? Simply said, they are borehole logging instruments with pad nozzles which, when pressed against the sandface, extract or “sample” formation fluids for detailed examination at the surface. By-products of the sampling process are flowline pressure transient histories (at one or more probes) associated with pumping actions, which can be interrogated for valuable information related to formation properties like mobility, permeability, anisotropy, compressibility and pore pressure. The earliest methods, now several decades old, are based on formulas like “ks = CQμ/(2πrp