Formation Testing E-Book

Wilson Chin

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

Seitenzahl: 296

Veröffentlichungsjahr: 2015

Beschreibung

Traditional well logging methods, such as resistivity, acoustic, nuclear and NMR, provide indirect information related to fluid and formation properties. The "formation tester," offered in wireline and MWD/LWD operations, is different. It collects actual downhole fluid samples for surface analysis, and through pressure transient analysis, provides direct measurements for pore pressure, mobility, permeability and anisotropy. These are vital to real-time drilling safety, geosteering, hydraulic fracturing and economic analysis. Methods for formation testing analysis, while commercially important and accounting for a substantial part of service company profits, however, are shrouded in secrecy. Unfortunately, many are poorly constructed, and because details are not available, industry researchers are not able to improve upon them. This new book explains conventional models and develops new powerful algorithms for "double-drawdown" and "advanced phase delay" early-time analysis - importantly, it is now possible to predict both horizontal and vertical permeabilities, plus pore pressure, within seconds of well logging in very low mobility reservoirs. Other subjects including inertial Forchheimer effects in contamination modeling and time-dependent flowline volumes are also developed. All of the methods are explained in complete detail. Equations are offered for users to incorporate in their own models, but convenient, easy-to-use software is available for those needing immediate answers. The leading author is a well known petrophysicist, with hands-on experience at Schlumberger, Halliburton, BP Exploration and other companies. His work is used commercially at major oil service companies, and important extensions to his formation testing models have been supported by prestigious grants from the United States Department of Energy. His new collaboration with China National Offshore Oil Corporation marks an important turning point, where advanced simulation models and hardware are evolving side-by-side to define a new generation of formation testing logging instruments. The present book provides more than formulations and solutions: it offers a close look at formation tester development "behind the scenes," as the China National Offshore Oil Corporation opens up its research, engineering and manufacturing facilities through a collection of interesting photographs to show how formation testing tools are developed from start to finish.

Leseprobe

Contents

Cover

Half Title page

Title page

Copyright page

Preface

Acknowledgements

Chapter 1: Basic Ideas, Interpretation Issues and Modeling Hierarchies

1.1 Background and Approaches

1.2 Modeling Hierarchies

1.3 Experimental Methods and Tool Calibration

1.4 References

Chapter 2: Single-Phase Flow Forward and Inverse Algorithms

2.1 Overview

2.2 Basic Model Summaries

Chapter 3: Advanced Drawdown and Buildup Interpretation in Low Mobility Environments

3.1 Basic Steady Flow Model

3.2 Transient Spherical Flow Models

3.3 Multiple-Drawdown Pressure Analysis (Patent Pending)

3.4 Forward Analysis with Illustrative Calibration

3.5 Mobility and Pore Pressure Using First Drawdown Data

3.6 Mobility and Pore Pressure from Last Buildup Data

3.7 Tool Calibration in Low Mobility Applications

3.8 Closing Remarks

3.9 References

Chapter 4: Phase Delay and Amplitude Attenuation for Mobility Prediction in Anisotropic Media with Dip*

4.1 Basic Mathematical Results

4.2 Numerical Examples and Typical Results

4.3 Layered Model Formulation

4.4 Phase Delay Software Interface

4.5 Detailed Phase Delay Results in Layered Anisotropic Media

4.6 Typical Experimental Results

4.7 Closing Remarks – Extensions and Additional Applications

4.8 References

Chapter 5: Four Permeability Prediction Methods

5.1 Steady-State Drawdown Example

5.2 Early-Time, Low-Mobility Drawdown-Buildup

5.3 Early-Time, Low-Mobility Drawdown Approach

5.4 Phase Delay, Non-Ideal Rectangular Flow Excitation

Chapter 6: Multiphase Flow with Inertial Effects

6.1 Physical Problem Description

6.2 Immiscible Flow Formulation

6.3 Miscible Flow Formulation

6.4 Inertial Effects with Forchheimer Corrections

6.5 References

Chapter 7: Multiphase Flow – Miscible Mixing Clean-Up Examples

7.1 Overview Capabilities

7.2 Source Code and User Interface Improvements

7.3 Detailed Applications

Chapter 8: Time-Varying Flowline Volume

8.1 Transient Anisotropic Formulation for Ellipsoidal Source

8.2 FT-06 Software Interface and Example Calculations

8.3 Time-Varying Flowline Volume Model

Chapter 9: Closing Remarks

References

Index

About the Authors

Formation Testing

Scrivener Publishing 100 Cummings Center, Suite 541J Beverly, MA 01915-6106

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

Copyright © 2016 by Scrivener Publishing LLC. All rights reserved.

Co-published by John Wiley & Sons, Inc. Hoboken, New Jersey, and Scrivener Publishing LLC, Salem, Massachusetts. Published simultaneously in Canada.

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Library of Congress Cataloging-in-Publication Data:

ISBN 978-1-118-92594-2

Preface

Just two years ago, the authors published Formation Testing Pressure Transient and Contamination Analysis with Scrivener Publishing, focusing on advanced forward models and inverse solutions pertinent to modern interpretation and job planning. Many of the new models were exact analytical solutions. For example, the flagship module FT-00 solved a general formulation allowing for anisotropic media, skin effects and flowline storage pressure distortions; inverse models complementing this solution were able to provide horizontal and vertical permeabilities at any dip angle for both linear liquid and nonlinear gas flows. We could have stopped with these very satisfying results, but the “bug” that haunts researchers is a terrible beast which never sleeps.

Our results required steady-state pressure drop data at both source and observation probes, a limitation that restricted their applicability to medium-to-high mobility applications. For modern low-mobility reservoirs, this could mean hour-long wait times or more, implying low efficiencies, high costs and increasing risks of lost tools. So the authors asked, “Are there physical processes that take advantage of low mobilities – providing spherical permeability predictions within seconds?” Later, this took an even more ambitious focus. “Is it possible to predict both horizontal and vertical permeability, also within seconds, using only standard dual-probe tools?”

It is well known that fast transient drawdown-buildup methods employing single probes could, at best, provide only the “spherical permeability” kh2/3kv1/3. Because the two perms can vary by a factor of ten in anisotropic media, spherical predictions are limited in usefulness – a serious issue since both are crucial to hydraulic fracturing, borehole stability, and so on. A second equation was required to uniquely provide two numbers – ideally, one that could be rapidly evaluated from early time data. We successfully followed one important clue. In resistivity logging, where time delays and amplitude decays between transmitter and receiver coils are used to determine formation resistivity, the quantity “sin2 δ /Rh + cos2 δ /Rv” always appeared, where δ is the dip angle. In fact, the more conductive (diffusive) the medium, the better the well log. Finding an estimate for “sin2 δ /kh + cos2 δ/kv” would surely help predict the relative values of horizontal and vertical permeability for a known kh2/3kv1/3. This observation motivated us to develop formation testing analogies to electromagnetic logging – our key results are reported in Chapters 3 and 4.

The authors are pleased to present these important new results, and the present book, which completely explains the ideas, methods, equations and algorithms, also provides detailed calculations and applications examples. At the present time, we are developing sophisticated test fixtures to validate our methods and calibrate new tools. This is surely an exciting time for formation tester development and for petroleum exploration well logging.

It is important to emphasize that the approaches developed here did not materialize overnight – they required a long-term commitment to understanding the fundamental physics, developing analogies between seemingly different disciplines like fluid dynamics and electromagnetics, and an obsession with solving important problems that ultimately benefit everyone in society. The authors recognize that creative work requires continuing motivation and investment in people – so our endeavors will continue, whether or not oil prices drop further – we won’t be the ones turning out the lights anytime soon.

Wilson C. Chin, Ph.D., M.I.T. Houston, Texas Email: [email protected] Phone: [phone]

Acknowledgements

The lead author gratefully acknowledges the insights, experiences and friendships he acquired during his early exposure to formation testing at Halliburton Energy Services in the 1990s; and in particular, the contributions of his colleague and friend Mark Proett, now with Saudi Aramco, who shaped his initial thinking and approach to pressure transient and contamination analysis.

In 2004, the United States Department of Energy, through its Small Business Innovation Research (SBIR) program, awarded approximately two hundred grants in support of high-risk efforts in all areas of energy, e.g., nuclear fusion, plasma physics, batteries, green energy, and so on. Four were allocated to fossil fuels – and, of these, two would support the lead author’s projects, entitled “Formation Tester Permeability Prediction in Tight Gas Sands” and “Formation Tester Immiscible Flow Response in Horizontally Layered Media.” The insights acquired in these researches no doubt fueled further innovations. For these past opportunities, the lead author is very appreciative.

All of the authors are indebted to China National Of shore Oil Corporation (CNOOC) and its subsidiary China Oilfield Services Limited (COSL) for its support and encouragement throughout our work in formation testing. Without the open access that we were granted to its tools, plans, staff and insights, we would not have been able to focus on the problems that really mattered. The authors appreciate the company’s permission to publish significant portions of an internal report documenting our new low mobility inverse methods.

Phillip Carmical, Acquisitions Editor and Publisher, has been extremely supportive of this book project and others in progress. His philosophy, to explain scientific principles the way they must be told, with equations and algorithms, is refreshing in an environment of en shrouded in secrecy and commercialism. The authors are optimistic that their story-telling will advance the technology and explain why “black boxes” aren’t so mysterious after all. Finally, the authors thank Xiaoying “Jenny” Zhuang for her hard work and commitment to ably working both sides of the language barrier (the lead author neither speaks nor reads Chinese, while the CNOOC/COSL team is newly conversant in English). Without Jenny’s interpretation skills and willingness to learn the technology, progress would have slowed and this formation testing monograph – the second in two years – may not have seen publication.

Chapter 1

Basic Ideas, Interpretation Issues and Modeling Hierarchies

In this opening chapter, we informally introduce some of the subjects covered in the present manuscript, a sequel to the book Formation Testing Pressure Transient and Contamination Analysis published by the present authors with John Wiley & Sons as recently as 2014. While that work contained many new materials not previously available, the present provides even more interpretation methods, algorithms and extensions resulting from the rapid pace of research advances achieved over the intervening two years. The content offered in this publication is intended to not only stimulate innovation in pressure transient analysis, but encourage early and confident acceptance of new approaches certain to make exploration more efficient and cost-effective.

1.1 Background and Approaches

Figure 1.1. CNOOC/COSL single and dual-probe formation testers.

The above formula, which again required steady conditions, was excellent for high mobility formations where pressure equilibrium could be achieved in minutes or seconds. However, it does not apply in the presence of larger flow line volumes when mobilities are low. Pressures normally indicative of the downhole flow environment are initially forced to compress or expand the fluid cushion residing in the line so that formation characteristics are obscured or hidden – an analogy can be made to gauging the power of a boxer’s punch with the boxer wearing heavily padded gloves. When flowline volume effects are large, bearing in mind that “large” is relative and depends on unknown fluid compressibility and mobility, measured pressures are distorted and cannot be used to calculate properties like mobility, permeability or viscosity – the Darcy component of pressure cannot be identified (the foregoing problem is akin to “wellbore storage” issues in well testing). In response to this, petroleum engineers simply waited for flowline effects to dissipate or subside, which in low mobility applications may require many hours. Not only did this increase logging time and expense, but the risk of stuck tools rose substantially. Flowline storage problems had been accepted as inevitable until a series of interesting breakthroughs achieved in the 1990s.

In graduate school, students are taught that boundary value problems governing physical phenomena consist of partial differential equations constrained by boundary and initial conditions. Solve the relevant formulation and the problem is fully understood. But the real problem is practical: many important formulations cannot be solved in closed analytical form, so that any physical insights and convenient formulas that would have been useful remain hidden in numerical data. And computational solutions are only partly reliable: “artificial viscosities” arising from truncation and round-off errors contribute to uncertainties in permeability. Mark Proett, the author’s colleague and friend at Halliburton (now with Saudi Aramco), developed a “boundary condition only” analytical approach valid at early times when storage and flow effects were equally strong (a similar approach developed for isotropic media at Baker-Hughes evolved to become the company’s “formation rate analysis”).

Proett’s approach is discussed in United States Patent No. 5,602,334, “Wireline Formation Testing for Low Permeability Formations Utilizing Pressure Transients,” awarded to M.A. Proett and M.C. Waid in February 1997. From its Abstract, “An improved formation testing method for measuring initial sandface pressure and formation permeability in tight zone formations exhibiting formation permeabilities on the order of 1.0-0.001 millidarcies based on pressure transients which occur shortly after the tester enters its pressure buildup cycle and substantially before reaching final buildup pressure. The method makes an estimate of formation permeability based on fluid decompression transients which occur in the formation tester flowlines which occur shortly after the tester begins its buildup cycle. The method further estimates initial sandface pressure based on the change in pressure over time shortly after beginning the buildup phase. The method of the present invention thereby permits accurate estimates of formation permeability and initial sandface pressure to be made relatively early in the buildup cycle, thus substantially reducing the time required to make the pressure and permeability measurements.”

Proett’s heuristic model, surprisingly, was extremely successful in predicting spherical mobility and (steady) pore pressure in low mobility environments from highly transient data. In retrospect, this is not altogether surprising. Many problems in mathematical physics can be studied, at least for initial times, without solving the complete formulation. As a case in point, consider classical mass-spring-damper systems: if a small mass is struck quickly, its initial motion is completely determined by auxiliary conditions, but only subsequently does the differential equation matter. Similarly, in formation testing, the differential equation would need to be solved if additional information is required.

Motivated by this need, the lead author solved the complete anisotropic formulation in the mid-1990s, with both flowline storage and skin effects in closed analytical form, and demonstrated how Proett’s constant rate solution provided the leading term of an asymptotic, low mobility expansion whose application could be further extended. This “exact solution” forms the basis for Halliburton’s drawdown-buildup GeoTap™ model used in real-time mobility and pore pressure prediction in “formation testing while drilling” (FTWD) or Measurement While Drilling (MWD) tools. Typical predictions require less than one minute of test time, thus enabling higher density and more economical well logging.

We emphasize that the method, which assumes a single-probe tool, provides pore pressure and spherical permeability predictions using early time data – it does not, however, give horizontal and vertical mobility or permeability individually – these can differ substantially in different directions, and as we will show, their determination requires dual-probe formation testing tools. The success of the physics-based approach motivated a second question. While the new drawdown-buildup interpretation method focused on flowline storage and flow as the dominant physical interaction, rather than avoiding storage but having to endure long wait times, is it possible to take advantage of pressure diffusion in such a way that test times can be significantly reduced?

Many of the formation testing ideas introduced in this book were motivated by electromagnetic logging. Yes, resistivity prediction in high conductivity diffusive formations. In electromagnetic well logging, a transmitter broadcasts constant frequency AC waves, whose amplitude decay and phase (that is, time) delay are recorded at neighboring coil receivers. These measurements are interpreted using Maxwell’s equations as the host math model and anisotropic resistivities can be estimated – in fact, the greater the diffusion, the higher the signal-to-noise ratio and the better the predictions.

The lead author introduced his “phase delay” approach to formation tester mobility prediction by developing an analogy to electromagnetic logging as follows (e.g., refer to United States Patent No. 5,672,819, “Formation Evaluation Using Phase Shift Periodic Pressure Pulse Testing,” awarded to W.C. Chin and M.A. Proett in September 1997). The tester pump was taken as the “transmitter” while a second observation probe assumed the role of the “receiver.” When the pump piston oscillates sinusoidally, it creates an AC wave whose pressure amplitude and time delay can be measured at the observation probe. These measurements are interpreted using Darcy’s equations to give mobility estimates, thus completing the analogy to electromagnetic logging.

Experiments performed at Halliburton were successful. Interestingly, time delays, in contrast to those observed in resistivity logging, are large and could be ascertained visually from strip charts, thus reducing demands on computational and electronic resources. And mechanical requirements were not demanding – pump frequencies on the order of 1 Hz were sufficient. But many questions remained unanswered at the time. Once a pressure signal leaves the pumping probe, its fate is completely determined by the formation – the “receiver,” so to say, “sees what it sees.” But what happens if what it sees is poor in quality? And what if the pump piston cannot execute pure sinusoidal waves as required by theory, but only limited numbers of wave cycles that are, say, rectangular in shape? It turns out, however, that the form of the created wave can be controlled by varying flowline volume, thus providing a means for customization and quality control (e.g., see Chapter 9, Example 7), and that deviations from pure sinusoids are a secondary concern (refer to Chapter 5).

At the time the work was first performed, there was little incentive to commercialize the phase delay approach at Halliburton. The invention applied only to isotropic media – the required theoretical extensions to anisotropic formations, in which the effects of dip angle would figure prominently, were not available. To determine isotropic permeability, the single-probe early-time drawdown method was more cost-effective, simpler and additionally provided pore pressure. The phase delay approach, while elegant and interesting, required dual-probe tools and could not give pore pressure estimates. Now, some two decades later, the needed generalization to anisotropic media with dip has been completed, together with more powerful extensions to low-mobility, early-time, drawdown-buildup methods. The combination of the two, as we will demonstrate in this book, allow both horizontal and vertical permeabilities – not “spherical permeabilities” alone – to be predicted from early time data in very low mobility formations. These methods are discussed for the first time in print and patent applications have been appropriately filed. Before presenting details, it is necessary to emphasize the limitations of idealized mathematical models and the physical implications of their consequences.

1.2 Modeling Hierarchies

Few innovations to pressure transient interpretation appeared until the 1990s with Halliburton sponsored research. These initial efforts, summarized in “Advanced Permeability and Anisotropy Measurements While Testing and Sampling in Real-Time Using a Dual Probe Formation Tester,” SPE Paper 64650, presented at the Seventh International Oil & Gas Conference and Exhibition in Beijing by Proett, Chin and Mandal in November 2000, introduced several avenues of research which saw subsequent development. The first was the low-mobility, early-time drawdown buildup method discussed earlier; the second, a completely analytical solution to the full boundary value problem developed by the lead author; and the third, the phase delay method, also due to the lead author, although restricted then to isotropic media. Difficulties with the analytical solution, which manifested themselves only years later, would motivate further work supported by the United States Department of Energy.

In the two decades since the “exact solution” appeared, some two dozen papers bearing this citation have been authored. And given the wide dissemination of these publications, appearing in journals and conferences associated with the Society of Petrophysicists and Well Log Analysts (SPWLA), the Society of Petroleum Engineers (SPE) and other organizations, it is important to clarify now what is meant by “exact” and the significance (or lack of) in that designation. To understand this further, we need to understand the difference between real-world tools and their mathematical idealizations.

Now, Figures 1.2 and 1.3 for single and dual-probe testers provide exploded views showing what single and dual probe formation testers really look like. When lowered into the hole and pressed against the sandface, the Darcy flow schematics given in Figure 1.4 applies. In these diagrams, the areas to the right of the red dashed line are taken as the flow domains; the left sides containing the pad and borehole are ignored. Since the resulting domains possess right-left symmetry, the flow due to a “source” (or a “sink”) is considered for modeling purposes.

Figure 1.2. Single-probe formation tester (enlarged view).

Figure 1.3. Dual-probe formation tester (enlarged view).

Figure 1.4. Piston pad pressed against the sandface.

Different source models exist which are not “created equal” by any means. Originally, decades ago, “point sources” were assumed at which fluid literally vanished and pressures became infinite; flowline storage and skin effects could not be modeled. The work of Proett, Chin and Mandal (2000) introduced spherical and ellipsoidal sources with nonzero dimensions as shown in Figure 1.5. Although the hardware associated with a flowline does not appear in this figure, flowline volume is accounted for by a term in the boundary condition formulation, as are skin effects, e.g., see Chin et al (2014). An “exact” closed form analytical solution for Darcy pressure, expressed in terms of complex complementary error functions, was given in the original publications.

Figure 1.5. Idealized spherical flow for isotropic formations, ellipsoidal flow for transversely isotropic (anisotropic) media.

Just how are calibration constants determined? Quite simply, one needs to have truly “exact solutions” in a physical sense. These can be obtained computationally using three-dimensional simulations or experimentally in test fixtures developed for formation testing applications. Examples of numerical solutions from the lead author’s prior work are shown in Figures 1.6 – 1.9. Effects include mudcake modeling, cylindrical borehole radius effects, pad geometry influence, and so on. Despite the apparent geometric generality, such models are not exact in a true sense. All numerical models, whether they are finite difference or finite element in nature, approximate derivatives using Taylor series and neglect higher-order terms. This omission, together with computer round-off errors, results in “artificial viscosity” which effectively changes the assumed input permeabilities. In other words, forward simulation results will typically not correspond to the permeabilities entered into the input box; inverse permeability predictions, for this reason, will not be correct if they are obtained by repeatedly running a forward simulator.

Figure 1.6. Near-Wellbore, Finite-Element Simulator (NEWS™) from Halliburton Energy Services.*

Figure 1.7. Dual-probe, pretest, simulation-pressure contours, 100-md isotropic formation (to the left are 1-psi color bands, and to the right are 10-psi color bands).*

Figure 1.8. Pressure contours for the first drawdown with two probes and the second drawdown with one source probe, 100 md horizontal permeability, 0.1 kv/kh, and 10 psi color contour bands.*

Figure 1.9. Ellipsoidal anisotropic flow, skin layer, three-dimensional finite element, boundary conforming mesh.**

*From “New Wireline Formation Testing Tool with Advanced Sampling Technology,” by M.A. Proett, G.N. Gilbert, W.C. Chin and M.L. Monroe, SPE Paper 56711 presented at the 1999 SPE Annual Technical Conference and Exhibition held in Houston, Texas, October 3-6, 1999.

** From “Advanced Dual Probe Formation Tester with Transient, Harmonic, and Pulsed Time-Delay Testing Methods Determines Permeability, Skin, and Anisotropy,” by M.A. Proett, W.C. Chin and B. Mandal, SPE Paper 64650 presented at the SPE International Oil and Gas Conference and Exhibition in China held in Beijing, China, November 7-10, 2000.

Fully three-dimensional simulators such as those cited in Figures 1.6 – 1.9 are not ideal for other reasons. First, they are difficult to set up; and second, they require significant computation times, often hours. As such, they are typically not used for inverse methods or engineering trend analysis. An intermediate compromise between these methods and the spherical or ellipsoidal source methods in Figure 1.5 is the axisymmetric “ring source” sketched in Figure 1.10. While the red vertical line of symmetry in Figures 1.4 and 1.5 disallows flow across it, thus making the modeling of fluid invasion, mudcake growth and borehole mud pressure impossible, the annular ring at the top of Figure 1.10, when hosted by cylindrical coordinates as suggested at the lower sketch, does allow the specification of additional physical effects.

Figure 1.10. Axisymmetric ring source.

Such models allow us to address the effects of “supercharging.” In many modern low-mobility applications, mudcakes do not form rapidly because filtration is inhibited by formation resistance. Consequently, the effects of high mud pressure are “felt” by the formation, and predicted pore pressures based on idealized inverse models such as those assuming Figure 1.5 are not correct. Thus, their properties must be well understood, and the development of multiphase flow models with time-varying invasion, as discussed later in this book, helps in this endeavor. But ring source models, still, are approximate; while they do allow borehole effects, pad geometries are however neglected and “calibration constants” are still required.

1.3 Experimental Methods and Tool Calibration

Figure 1.11a. Laboratory calibration facility

(reprinted with permission from the Society of Petrophysicists and Well Log Analysts (SPWLA)).

Figure 1.11b. Laboratory calibration facility

(reprinted with permission from the Society of Petrophysicists and Well Log Analysts (SPWLA)).

Figure 1.12. Experimental fixture for formation tester operation under downhole conditions with mud and fluid invasion

(reprinted with permission from the Society of Petrophysicists and Well Log Analysts).

Figure 1.13a. Formation testing lab experimental fixture.

Figure 1.13b. Core holder (includes housing, core, probe section, rubber pad, snorkel and filter).

Figure 1.13c. Outer housing, core end view.

Figure 1.13d. Core samples (note curvature).

From “Results of Laboratory Experiments to Simulate the Downhole Environment of Formation Testing While Drilling,” by H. Lee, M. Proett, P. Weintraub, J. Fogal and C. Torres-Verdín, SPWLA 45th Annual Logging Symposium, The Netherlands, June 2004, with graphics and photographs from a complementary SPWLA 2004 poster. Reprinted with permission from the Society of Petrophysicists and Well Log Analysts.

Figure 1.13e. Cylinder with oil with viscosity of formation fluid.

Figure 1.13f. Pump injects oil at constant pressure to simulate reservoir.

Figure 1.13g. Piston for drawdown-buildup controlled by accumulators activated by solenoid valves.

Figure 1.13h. Mudcake formed on core surface by circulating water-based mud (thickness is monitored and controlled).

From “Results of Laboratory Experiments to Simulate the Downhole Environment of Formation Testing While Drilling,” by H. Lee, M. Proett, P. Weintraub, J. Fogal and C. Torres-Verdín, SPWLA 45th Annual Logging Symposium, The Netherlands, June 2004, with graphics and photographs from a complementary SPWLA 2004 poster. Reprinted with permission from the Society of Petrophysicists and Well Log Analysts.

Figure 1.13i. Mud chambers.

Figure 1.13j. Solenoid valves control drawdown-buildup piston.

Figure 1.13k. System pump (accumulators are attached to solenoids and powered by system pump).

Figure 1.13l. Hydrostatic pump (hydrostatic and formation pressures maintained by accurate, point-operating relief valve attached to formation and hydrostatic pumps).

From “Results of Laboratory Experiments to Simulate the Downhole Environment of Formation Testing While Drilling,” by H. Lee, M. Proett, P. Weintraub, J. Fogal and C. Torres-Verdín, SPWLA 45th Annual Logging Symposium, The Netherlands, June 2004, with graphics and photographs from a complementary SPWLA 2004 poster. Reprinted with permission from the Society of Petrophysicists and Well Log Analysts.

Figure 1.13m. Pressure transducer (two used, one on formation side and other on flowline side).

Figure 1.13n. Control module.

Figure 1.13o. Computer with graphical user interface.

Figure 1.13p. Mother board (experiment controlled by computer connected to mother board).

From “Results of Laboratory Experiments to Simulate the Downhole Environment of Formation Testing While Drilling,” by H. Lee, M. Proett, P. Weintraub, J. Fogal and C. Torres-Verdín, SPWLA 45th Annual Logging Symposium, The Netherlands, June 2004, with graphics and photographs from a complementary SPWLA 2004 poster. Reprinted with permission from the Society of Petrophysicists and Well Log Analysts.

Of course, in many low-mobility applications, cake formation is slowed by reduced filtration and the dynamics of mudcake growth are important – this is particularly so in studying “supercharging” where the pressure near the sandface is a combination of borehole and reservoir values. In this case, how much of the pressure measured by the formation tester “belongs” to reservoir effects is crucial and must be studied by multiphase simulators such as those presented in Chapters 6, 7 and 8. These, too, must be calibrated, with laboratory based experimental results. These had been reported in “Formation Evaluation Using Repeated MWD Logging Measurements,” by Chin, Suresh, Holbrook, Affleck and Robertson, presented at the SPWLA 27th Annual Logging Symposium, Houston, TX, June 9–13, 1986, and subsequent math models were derived in the lead author’s book Formation Invasion, with Applications to Measurement-While-Drilling, Time Lapse Analysis and Formation Damage (Gulf Publishing, 1995). These works drew upon experimental results from linear and radial flow test vessels placed within Catscan imaging machines. Under constant pressure drop conditions, both invasion front and mudcake thickness were monitored versus time, and analytical models were constructed using “moving boundary” methods which allowed dynamic boundary motion. Examples of the work are shown below.

Figure 1.14a. Catscan, linear test vessel with core sample.

Figure 1.14b. Radial flow test vessel.

Figure 1.14c. Catscan, invasion in radial core sample.

Figure 1.14d. Linear flow Catscans, thin dark mudcake at center of core and invasion front at density contrast (flow, left to right).

Figure 1.14e. Linear flow Catscans, standard optical contrast.

Figure 1.14f. Linear flow Catscans, enhanced contrast.

1.4 References

Chin, W.C., Formation Invasion, with Applications to Measurement-While-Drilling, Time Lapse Analysis and Formation Damage, Gulf Publishing, Houston, 1995.

Chin, W.C. and Proett, M.A., “Formation Evaluation Using Phase Shift Periodic Pressure Pulse Testing,” United States Patent No. 5,672,819, awarded September 30, 1997.

Chin, W.C., Suresh, A., Holbrook, P., Affleck, L., and Robertson, H., “Formation Evaluation Using Repeated MWD Logging Measurements,” SPWLA 27th Annual Logging Symposium