Table Of ContentMultilateral Wells
Other SPE Books (Coming Soon)
Formation, Removal, and Inhibition of Scale in the Oilfield Environment
Analysis of Production Decline Curves
Hydraulic Fracturing
Book Editor
William R. Landrum, ConocoPhillips Company
Books Committee (2008)
Lee Dillenbeck (Chair), Chevron Energy Technology Company
Rosalind A. Archer, University of Auckland
James N. Collins, ConocoPhillips Company
Tarek Ghazi, Aramco Services Company
Eirik Kaarstad, University of Stavanger
Robert F. Mitchell, Halliburton
Graham Openshaw, PanGeo Subsea
Jorge E. Pinedo, Santos Limited
Ronald L. Sparks, The Hanover Company
Multilateral Wells
A.D. Hill
Texas A&M University
Ding Zhu
Texas A&M University
Michael J. Economides
University of Houston
Society of Petroleum Engineers
© Copyright 2008 Society of Petroleum Engineers
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Preface
There are few technologies in modern oil- and gas-production practices that exemplify the complexities faced
by, and the resulting innovations of, this industry more than multilateral wells. From the 3D seismic needed to
plan such wells, to the unique drilling and completion practices used to create them, to the coupled reservoir/
wellbore flow models required to predict their performance, these complex well structures are expanding the
boundaries of petroleum engineering technology. The extensive contact with widely distributed reservoir bod-
ies connected by a well network requires a coupling of reservoir and wellbore flow aspects much more so than
for conventional wells. There is a rapidly growing literature documenting all aspects of multilateral well tech-
nology, but it is dispersed throughout the many subdisciplines of petroleum engineering.
This book is intended to illuminate the most important aspects of multilateral wells in a concise way. We hope
that it will be a valuable resource for engineers and geoscientists desiring an introduction to complex well archi-
tectures. We have tried to be comprehensive enough to give readers practical tools they can apply in the design and
analysis of multilateral wells, while also pointing to the appropriate literature for more advanced studies.
We would be remiss if we did not acknowledge the efforts of the many scientists and engineers whose work
on multilateral-well technology is documented here. We also thank our many students who helped us comb the
literature, worked through example calculations, and in some cases, developed some of the methods described
in this book.
Dedication
To Woody and Andy
Contents
Preface
1 . Introduction—Purp o ses and Applications of Multilateral Wells . . . . . . . . . . . . . . . . . 1
1.1 The Utility of Multilateral Wells .......................................... 1
1.2 History of Multilateral Wells ............................................ 2
1.3 Synergistic Technologies .............................................. 6
1.4 Organization of This Book ............................................. 6
2 . Application of Complex Well Architecture to Common Geological Settings . . . . . . . 7
2.1 Introduction ........................................................ 7
2.2 Geometry of the Well Drainage Volume ................................... 7
2.3 Using Seismic Techniques for Reservoir Description and Complex Well Planning ... 13
3 . Drilling Multilaterals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.1 Initiating a Lateral From the Main Wellbore—Sidetracking .................... 17
3.2 Drilling the Lateral ................................................... 23
3.3 Well Control for Multilateral Wells ....................................... 28
3.4 Multilateral Drilling Case Histories ....................................... 28
4 . Multilateral Well Completions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
4.1 Introduction ........................................................ 35
4.2 Considerations in Designing a Multilateral Completion ....................... 35
4.3 Junction Classifications ............................................... 36
4.4 Lateral Completions .................................................. 47
5 . Multilateral Well Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
5.1 Introduction ........................................................ 65
5.2 Horizontal Well Reservoir Inflow Performance .............................. 65
5.3 Wellbore Flow Behavior ............................................... 82
5.4 Multilateral Well Deliverability ........................................... 91
5.5 Wellbore Crossflow in Multilateral Wells .................................. 100
Appendix 5A ....................................................... 103
Appendix 5B—Derivation of Dimensionless Transform of Diffusivity Equation ..... 103
Appendix 5C—Point/Plane Source Method ................................ 105
6 . Multilateral Well Performance Case Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
6.1 Introduction ........................................................ 111
6.2 Low-Cost Reserves Access With Multilaterals .............................. 111
6.3 Heavy-Oil Development With Multilaterals ................................. 115
6.4 Multilaterals for Improved Sweep Efficiency ............................... 115
6.5 Low-Cost Reserves Access With Multilaterals .............................. 119
7 . Enhanced Multilateral Well Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
7.1 Introduction ........................................................ 123
7.2 Multilateral-Well Performance Diagnosis .................................. 123
7.3 Well Stimulation in Multilateral Wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
8 . Intelligent and Smart Well Completions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
8.1 Introduction ........................................................ 143
8.2 Intelligent-Completion Equipment ....................................... 143
8.3 Intelligent Completion Models .......................................... 146
8.4 Examples of Field Applications of Intelligent Completions ..................... 153
9 . Multilateral Well Economics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
9.1 Introduction ........................................................ 157
9.2 Costs of Different Classifications of Multilateral Wells ........................ 157
9.3 Basic Economic Considerations ........................................ 158
9.4 Multilateral Wells Driven by Capital Expenditure Reductions ................... 162
9.5 Multilateral Value Driven by Reserves Additions ............................ 163
9.6 Real Options Valuation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
Nomenclature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
Author Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
Subject Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
Chapter 1
Introduction—Purposes and
Applications of Multilateral Wells
1.1 The Utility of Multilateral Wells
Oil and gas wells are no longer just for accessing hydrocarbon formations, a task that they have accomplished
for more than a century and which they still do in a far improved and targeted way. Over the past 20 years,
with the rapid evolution of, fi rst, horizontal wells and, eventually, multilateral wells, reservoir-to-well expo-
sure has increased dramatically to orders of magnitude larger than ever before. Multilateral wells accomplish
both of these tasks, the accessing and the exposure, effectively.
There are some obvious examples that fall under the category of accessing. Multilateral wells can be drilled
to drain discontinuous geological fl ow units, especially those which could not by themselves rationalize
dedicated individual wells. Such structures include lenticular sands or braided channels, where the reservoirs
are distributed areally, and layered reservoirs having vertically discontinuous bodies.
Exposure is also clear. Reservoirs with low mobility—that is, having low permeability or containing high-
viscosity fl uids—can readily benefi t from large well-to-reservoir exposure. Such reservoirs include tight oil
and gas formations or heavy-crude reservoirs.
Needless to say, all applications are subject to rigorous economics, and as usual, while production econom-
ics are almost universal, the costs of well construction are eminently local and vary widely. Thus, well
architecture that may be attractive in one petroleum province of the world may not be attractive elsewhere.
We address all these issues in detail in Chapters 2 and 9.
There are, of course, other even more sophisticated and subtle uses of multilateral wells. Consider the
following list of simple examples, which is by no means complete, on the uses of multilateral wells to
augment reservoir exploitation strategies above and beyond single horizontal wells:
· Horizontal wells are relatively more attractive compared to vertical wells in thin reservoirs, irrespective
of vertical-to-horizontal permeability anisotropy. They become less attractive as the reservoirs become
thicker and with poorer vertical communication. However, stacked multilaterals, drilled on top of each
other and spaced in a thick reservoir, may create impromptu vertical no-fl ow boundaries, producing
very large production rates and rendering the thick formation eminently attractive.
· It is also well known that production rates from horizontal wells, while logically they should be greater
from longer wells, even in the best cases, do not come close to monotonically increasing with length.
Reasons include the fact that fl ow disproportionately comes from the edges of the well; the adverse
effects of pressure drop in the well itself, which is a function of the length; and the greater likelihood
of lateral heterogeneities. Thus, for example, two opposing laterals, each of a certain moderate length,
would produce in many cases at least 50% larger production rate than a single horizontal well as long
as or longer than the sum of the lengths of the two opposing laterals.
· Horizontal well orientation is quite important in areally anisotropic reservoirs. Drilling a well in natu-
rally fractured formations is generally not a problem. But permeability anisotropy always occurs, and
