i

The BitFifth Edition

ROTARY DRILLING SERIESUnit I, Lesson 2

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By Mark Jordan

Published by

PETROLEUM EXTENSION SERVICEThe University of Texas at AustinDivision of Continuing & Innovative EducationAustin, Texas

Originally produced by

INTERNATIONAL ASSOCIATION OF DRILLING CONTRACTORSHouston, Texas

2013

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DisclaimerAlthough all reasonable care has been taken in preparing this publication, the authors, the Petroleum Extension Service (PETEX™) of The University of Texas at Austin, and any other individuals and their affiliated groups involved in preparing this content, assume no responsibility for the consequences of its use. Each recipient should ensure he or she is properly trained and informed about the unique policies and practices regarding application of the information contained herein. Any recommendations, descriptions, and methods in this book are presented solely for educational purposes.

Editors: Christopher Parker and Dewey Badeaux

Graphic Designer: Debbie Caples

Illustrator: E.K. Weaver

©2013 by The University of Texas at AustinAll rights reservedFirst Edition published 1966. Fourth Edition published 1995Fifth Edition published 2013Printed in the United States of America

This book or parts thereof may not be reproduced in any form without permission of Petroleum Extension Service, The University of Texas at Austin.

Brand names, company names, trademarks, or other identifying symbols appearing in illustrations and/or text are used for educational purposes only and do not constitute an endorsement by the author or the publisher.

Catalog no. 2.10250ISBN 0-88698-243-X 978-0-88698-243-0

No state tax funds were used to publish this book. The University of Texas at Austin is an equal opportunity employer.

Library of Congress Cataloging-in-Publication Data

Jordan, Mark L., 1954— The bit / by Mark L. Jordan. — 5th ed. p. cm. — (Rotary drilling series ; unit I, lesson 2) Rev. ed. of: The bit / by Kate Van Dyke. 4th ed. 1995. "In cooperation with International Association of Drilling Contractors." Includes index. ISBN 978-0-88698-243-0 (alk. paper)1. Bits (Drilling and boring) 2. Oil well drilling--Equipment and sup-plies. I. Van Dyke, Kate, 1951- Bit. II. University of Texas at Austin. Petroleum Extension Service. III. International Association of Drilling Contractors. IV. Title.TN871.3.V269 2011 622'.3381—dc23

2011034087

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Contents▼▼▼

Figures vii

Foreword ix

Preface xi

Acknowledgments xiii

About the Author xv

Units of Measurement xvi

Introduction 1To summarize 3

Bit Selection 5Factors to Consider 5

Formation and Lithology 6Rate of Penetration 7Durability and Longevity 7Gauge 7Cost 8

To summarize 8

Roller Cone Bits 9History 11Types of Roller Cone Bits 13

Steel-Tooth Bits 13Tungsten Carbide Insert Bits 14Powder-Forged Bits 15

Manufacture and Design 16Cones 17

Cone Alignment 18Interfit 20Journal Angle 20

Cutting Structures 21Steel Teeth 21Tungsten Carbide Inserts 22Powder-Forged Cutting Structures 23

Bit Gauge 24Drilling Fluid and Hydraulics 26

Reactive and Nonreactive Materials 27Air and Gas Drilling Fluids 27

Cleaning 28Watercourses 28Jet Nozzles 28Hydraulic Horsepower 30

Bearings 31Cone Retention Systems 32Roller Bearing Bits 32Journal Bearing Bits 34

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Bearing Lubrication 36Wear 38

Cone Wear 39Cutting Structure Wear 42Bearing Wear 48Other Types of Wear 49

To summarize 51

Diamond Bits 53Properties of Diamonds 54

Extreme Hardness 54High Strength and Elasticity 54Good Thermal Conductivity 55Low-Friction Force 55Thermal Instability 55Low-Impact Shock 56

Natural and Diamond Impregnated Bits 56Manufacture and Design 57

Profiles 58Cutting Structure 60Hydraulics 62

PDC Bits 64Manufacture and Design 64Profiles 65PDC Cutters 66Hydraulics 71

Features of New Bit Designs 72Other PDC Bit Components 74Wear 76

Bit Whirl and Lateral Vibration 77PDC Cutter Wear 80

To summarize 81

Special-Purpose Bits 83Roller Cone Bits 83Fixed-Cutter Bits 85To summarize 88

Formations and Bit Performance 89Formation Properties 90Formation Analysis 91

Analyze Seismic Data 91Examine a Core 91Review Data 91Test the Formation 91

How Bits Drill 92To summarize 93

WOB, Rotary Speed, and ROP 95

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Roller Cone Bits 96Diamond Bits 97To summarize 98

Bit Classification 99Roller Cone Bits 100Diamond Bits 102To summarize 105

Dull Bit Grading 107To summarize 111

Expenses to Consider 113To summarize 114

Field Operating Procedures 115Drilling with a Roller Cone Bit 115Drilling with a Diamond Bit 116To summarize 118

Conclusion 119

Appendices 121

Glossary 133

Review Questions 151

Index 157

Answer Key 165

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1

BIT SELECTION

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Introduction

In this chapter:

• An overview on how bits are used

• Cutting structures and diamond cutters

• Drilling fluid circulation

• Range of bit sizes

Figure 1. A bit is designed to cut through layers of rock.

DRILLSTRING

DERRICK

BIT

The bit is a rotating device located at the bottom of a drill string. It is used to cut and dislodge layers of underground rock (fig. 1).

As the bit rotates, cutting structures in the form of steel teeth, inserts, diamonds, or diamond compacts (called cutters) chip away at the rock (fig. 2). As the rock is cut, drilling fluid, in the form of air, gas, water, oil-based mud, or a variety of substances, is circulated through the bit to displace the broken material (fig. 3). The small, fragmented pieces of rock, referred to as cuttings, travel through the annular space in the borehole back to the earth’s surface.

Bits are available in various sizes. Most bits are 26 inches (660 millimetres) or less in diameter, although sizes range from 3 inches (76 millimetres) to 42 inches (1,067 millimetres). As detailed in sub-sequent sections of this book, a number of factors influence the size and type of bit that is selected. A thorough evaluation of these factors can help ensure the success of a drilling operation.

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THE BIT

Steel Teeth Inserts

Diamonds Cutters

Figure 2. Examples of cutting structures and diamond cutters

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BIT SELECTIONINTRODUCTION

Figure 3. Circulating drilling fluid lifts cuttings.

Wells can be drilled using:• Barite, clay, water, and

other chemicals• Air• Gas • Water• Oil-based mud

To summarize—

How bits function

• The bit is a rotating device that is used to cut and dislodge layers of underground rock.

• As the bit rotates, cutting structures chip away at the rock.

• As the rock is displaced, drilling fluid is circulated through the bit to displace the broken material (cuttings). Cuttings travel through the annular space back to the earth’s surface.

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4

THE BIT

5

BIT SELECTION

Factors to ConsiderWhether a company is drilling a wildcat well (the first well constructed in a particular area) or drilling in a known oil field, it is important that a rig operator or contractor choose a bit that is most appropri-ate for the job. Prior to selecting a bit, the operator should consider the following:

• Formation and lithology

• Rate of penetration (ROP)

• Durability and longevity

• Gauge

• Cost

The above factors play a critical role in the selection process. Therefore, it is important for operators to become familiar with the key terms and concepts identified throughout this chapter. Moreover, all those responsible for handling a bit can benefit prior to the com-mencement of a drilling operation by reviewing the criteria addressed within this section.

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Bit Selection

In this chapter:

• How formations and lithology impact bit selection

• Rate of penetration, durability, and longevity

• The importance of drilling a full-gauge hole

• The costs and benefits of high-quality bits

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THE BIT

Figure 4. Many layers of rock occur in the earth.

Formation and Lithology

Bits are designed to drill through underground rock (formation). The term formation refers to a series of beds or deposits of a particular age and depositional environment. A formation is located in a limited geo-graphic area and appears as a particular series of layers of rock under the earth’s surface (fig. 4). Lithology refers to the individual character of a rock, including its mineral composition, grain size, angularity, and texture. Rocks with the same and/or different lithology can be present and repeated throughout a single formation. In other words, a formation is composed of a mix of lithologies.

Formations, therefore, vary in terms of their strength and com-position. Layers of rock can be hard, soft, brittle, abrasive, sticky, or include a variety of materials. A formation can include medium-soft rocks with thin streaks of hard, abrasive rocks running through it. Moreover, it is common for operators to encounter different forma-tion layers before they reach a reservoir (an underground layer that contains hydrocarbons).

It would be impractical for rig operators to change a bit each time a new formation is encountered. Given this irregularity, operators should select a bit that can effectively penetrate a particular forma-tion and a variety of lithologies. Formations and bit performance is discussed in more detail on page 89.