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After completing a part-time PhD in petroleum engineering, he received a professorship position at the technical mining university of Freiberg (TU Bergakademie Freiberg), where he holds the chair for drilling engineering and mining machinery. Since 2007 he is the director of the Institute for Drilling Engineering and Fluid Mining. Matthias Reich became widely known in the drilling world with his publication, „The fascinating world of drilling technology.“

Dr. Catalin Teodoriu Sub-Department Head of Drilling Technology, Completion and Workover, Institute of Petroleum Engineering, Technical University of Clausthal, Germany “How wonderful! Finally there is a book that explains deep drilling technology to the layman in an entertaining and informative way. Prof. Matthias Reich is especially skilled at rendering these complex topics understandable. This book will help allay the fear that some people have about drilling rigs, because it places great emphasis on safety, and also on the environment.” Jürgen Lorenz, Deep drilling technologist

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The ideal introduction to the fascinating world of deep drilling technology!

In 1990 he opted for a career in petroleum engineering. As an employee of Baker Hughes (a leading global service company having their headquarters in Texas) he worked for 16 years as a design engineer, application engineer, technical-services manager and finally marketing manager, where he was responsible for managing the development, testing, optimization and marketing of advanced drilling systems.

“Prof. Reich with his book succeeds to make the diversity of the “oil and gas industry” accessible to a broad audience. The content convinces the reader through easy to understand explanations of concepts and simple presentations of complex aspects. The title of the book is justified: The book reads like a technology thriller and the reader is hooked till the end. The text is accompanied by cartoons drawn by the author and provides the reader with an entertaining way to gain an intuitive understanding of the subject. This book is perfect for those who want to enter the world of deep drilling technology!“


Matthias Reich was born in 1959 in the Harz Mountains in Lower Saxony, Germany. After graduating from secondary school he studied chemical engineering at the Technical University of Clausthal. He then spent several years working as a development engineer near Lake Constance.

Matthias Reich


The ideal introduction to the fascinating world of deep drilling technology!


HUNUDENRGTRIONUNGD and A high-tech search for oil, gas Reich geothermal energy. By Matthias

The ideal introduction to the fascinating world of deep drilling technology! Whether we like it or not, the society of today is dependent on oil and gas! The days when these coveted raw materials sputtered from the Earth are long gone. Today’s search for oil and gas is a first-class adventure. Modern boreholes can be as long as 35 000 feet, as hot as an oven and with pressures similar to those found under the wheels of a Jumbo Jet. A high-tech drill must function reliably under these conditions! This book explains in plain language how a modern deep well is drilled.


ISBN -Nr. 978-3-00 -032008-8 Copyright ©2012 by add-book s and Matthias Reich Translation copyright © 2012 by Quirina Roode-Gutzmer Verlag add-book s Germany www.add-book First English edition. All right s reser ved. Design add-wise Designoffice

Text Design Caput und Compacta Printing Benatzky-Münstermann Translation Quirina Roode-Gutzmer ns Photos/Black-and-white Illustratio Reich (unless otherwise stated) Matthias in this The contents and work s contained laws of book are subject to the copyright this book Germany. This book or parts of in datamay not be reproduced, stored without bases or transmitted in any form sher. the written permission of the publi Printed in Germany

HUNTING UNDERGROUND oil,faszinierende fordie rch ech g in h-tle stie higidea Einsea A Der erg en al rm the k. y. hni geo d rtec an ga Weslt der Tiefboh



CONTENTS 1 2 3 4 5


5.1 The derrick 26 Mast or rig? 26

The draw works 28 The rotary drive for the drill string 29 The blowout preventer 31

5.2 The mud circulating system 34

Drilling mud, the universal genie 34 Machinery and equipment in the mud circulating system 37



6.1 6.2 6.3 6.4 6.5 6.6 6.7




Installation of the conductor pipe 42 Preparation of the well site 43 Preparation of the surface casing 43 Placement of the intermediate casing strings 45 Production casing 46 Borehole construction 46 How does the cement get behind the casing? 48 Drill bit 52

Roller Cone or rock bit 53 Diamond bit 54 Which drill bit is the best? 54

7.2 Drill pipes 55 7.3 Drill collars 56 7.4 Heavy weight drill pipes 57 7.5 Neutral point 57 7.6 Stabilizers 58 7.7 Downhole motor 58 7.8 Shock sub 60 7.9 Drilling jar 61 7.10 Crossover sub 61

8 9


9.1 Vertical drilling 66 9.2 Directional drilling 67 9.3 Horizontal drilling 68

10 11


11.1 Directional drilling equipment 76

Directional downhole motor 77 Rotary steerable systems 78 The Baker Hughes’ AutoTrak™ system 81 Schlumberger’s PowerDrive™ system 82 Halliburton’s GeoPilot™ system 83

11.2 Vertical drilling system 83



12.1 Directional control 88

How do we know where we are? 88 How do measurement data get to the surface? 91 Mud-pulse telemetry 91 Can it be done faster? 92

12.2 What do we know about the rock that has been drilled? 96

12.3 Is the drill bit running smoothly on bottom? 106



13.1 Drilling with coiled tubing 114

Are there pores? 97 How big are the pores? 98 What is found in the pores? 101 Can the discovered oil or gas be produced? 102 How abundant is the reservoir? 104

What is coiled tubing? 114 Underbalanced drilling 115 Coiled-tubing drilling rig 117 Coiled-tubing bottom-hole assembly 118

13.2 Drilling geothermal wells 120 13.3 Drilling at sea 123

Working life on an offshore rig 124 Particular aspects of offshore drilling 125 Jack-up rig 127 Drilling platforms 127 Semi-submersible rigs 128 Drilling ships 129






窶各llo! Perhaps you turned on a reading lamp before you opened this book. This is absolutely normal and would not usually be worth mentioning, but in this case it is, because this book is about oil and gas, or more generally about our energy supply. More specifically, this book is about how the gas and oil that we consume is brought from the depths of the Earth to the surface. Every one of us consumes energy. Nobody wants to go to sleep merely because it is dark outside. We no longer want to live without computers and internet access, and certainly not without television, radio or even our favorite music from an MP3-player. And by no means do we want to do without the luxury of modern transport such as trains, planes and automobiles. A life without microwaves, heaters, refrigerators, or our cherished cell phones has become unimaginable!

1 INTRODUCTION But where does this energy come from? About 80 % of our energy demands are met by fossil fuels, that is, by coal, natural gas and crude oil, which respectively contribute approximately one fifth, one quarter and one third of the fossil fuel supply. The remaining fifth is covered by nuclear power and renewable energy, for example, wind energy, solar power and geothermal energy. Many people claim that one should use more energy from alternative sources in order to reduce detrimental climate change and to protect our atmosphere. This is certainly true in principal. Despite all our efforts, however, we barely manage to supply one fifth of the enormous energy demand in this way. To supply more simply is not yet possible! And because nobody wants to relinquish four fifths of the current energy requirements, one must assume that humankind will recover, in the foreseeable future, by far the biggest proportion of their energy from fossil fuels. It is worth pointing out that newer and better methods of producing energy from renewable resources are being developed. Could all the new geothermal power plants, biogas plants, tidal power plant, and solar parks that are being erected alleviate the problem? Alternative energy sources are indeed on the advance. At the same time, the world energy demand is rising rapidly. All serious forecasts indicate that the requirement for oil and gas in the coming decades will rise even further. It is also becoming increasingly difficult to find new and attractive deposits of oil and gas. All the large, easily accessible and particularly abundant sources have probably already been discovered and thoroughly exploited. We therefore need to become satisfied with ever-smaller deposits and to be willing to exploit them with more intensive technical effort. For example, the average drilling length that is necessary to obtain a barrel of oil becomes increasingly longer. Deep drilling is becoming more important in securing our future energy supply. Currently 80 million barrels of oil are consumed daily. This occurs on each of the 365 days in a year! But how much are 80 million barrels? Here our imagination unfortunately lets us down. A barrel has a volume of approximately 42 gallons (159 liters). Converting barrels into cubic feet yields a volume of ~420 million cubic feet (12 million cubic meters) per day. That corresponds to an enormous cube with side lengths of 755 feet, filled to the brim with oil. This cube would be as high as the Bank of America Tower in Midtown Manhattan, New York (Figure 1). To produce such vast amounts of oil, deep holes need to be drilled into the Earth’s crust in order to connect the reservoir with the surface. These holes mostly have a diameter of 6 to 12 ¼ inches (1 inch = 25.4 mm or approximately the width of a thumb) and run a length of many miles. Many of these extremely long holes are bored along curves and meander through the reservoir in order to optimize recovery. One can imagine the extreme dimensions of today’s oil and gas wells by the following example. Imagine yourself in an airplane sitting on a sought after window seat. At an altitude of 3 to 4 miles (5 to 6 kilometers) you are able to discern the houses on the ground. If a hose of 8 ½ inches (20 cm) in diameter was hung out of the airplane window all the way to the ground and the end lies another 1.5 miles horizontally along one of the

many fields, the hose would correspond more or less in dimension and form to the drilling path for oil. Of course, nobody, who is prospecting for oil and gas, can drill a deep hole anywhere simply on a hunch and expect to make a discovery. At the outset, geologists and geophysicists make measurements with the most modern instruments to prospect for places where deposits could have formed millions of years ago. The only way to confirm such a deposit, however, is to drill an exploration well (Figure 2) and to take samples. One therefore needs to drill a deep, mostly vertical, hole into the potential deposit and thoroughly examine the rocks that are found underneath. If the rock is found to be porous and these pores happen to be interconnected, this would allow any fluids it contains to move freely underground. If these fluids are found to be gas or oil, the exploration is deemed successful and revenue can be earned. Not too much should be anticipated initially, however. Despite the most modern technology, only one in seven exploration wells yields exploitable oil. Fig. 1: The side of our The other six exploration wells can be considered as failures, either oil-consumption cube due to the fluid being ground water (in most cases high in salt content) would measure the or hydrocarbons that are not mobile enough to be of any commercial height of the Bank interest. of America Tower, in Prospecting for oil is a very expensive and risky enterprise. But Midtown Manhattan, let us just assume for the moment that our exploration well was suc- New York cessful. In this case, we usually drill several production wells. Modern wells are placed very precisely through the reservoir so that recovery can be maximized. Application of sophisticated measuring devices in the drill string allows the driller to see what the actual well path looks like. The drill bit at the bottom of the drill string is combined with a steering head so that the drill path can be controlled, thus enabling the driller to lead the well into any desired direction. Other devices in the drill string survey the rock, the surroundings of the drill bit and the dynamic behavior of the drill string during the drilling process; the readings are then transmitted to the surface. We therefore always know WHERE we are drilling, WHAT we are drilling (what sort of rock is found at the bit and does it contain oil or gas?), and HOW we are drilling (are the current drilling parameters set correctly?). A chapter in this book is dedicated to explaining how these measuring devices work and how the data is transferred all the way from the drill bit to the surface. Modern drilling and measuring equipment are required to function reliably under extreme working conditions, where a pressure of several hundred bar (several thousand psi) prevails. The temperatures are so high that ordinary commercial electronic components can no longer function. All drilling components are subjected to constant vibration and shock, enough to render any human unconscious. It is therefore essential that the drilling and measuring equipment for deep drilling function reliably under these conditions. Should a tiny component in the drill string fail deep down in the borehole,





rilling a deep well is very expensive. As a rule of thumb about 650 to 850 USD is required for every foot drilled (1 500 to 2 000 â‚Ź per meter). Offshore wells are usually even more expensive. Typically a well with a depth of 15 000 ft (5 000 meters) will easily cost about 10 million USD. It goes without saying that the rental cost for the massive derrick, the preparation of the large well site at surface and the drilling crew contribute significantly to the overall cost. What is not well known, however, is that approximately a third of the entire investment disappears downhole in the form of steel pipes and cement and is, under normal circumstances, not seen again.

6 HOW IS A DEEP WELL DRILLED? Installation of the conductor pipe 42 Preparation of the well site 43 Preparation of the surface casing 43 Placement of the intermediate casing strings 45 Production casing 46 Borehole construction 46 How does the cement get behind the casing? 48


ou have in all likelihood tried to dig a hole on the beach; you would have probably noticed that as soon as the water table is reached the hole becomes unstable. The more you strive to deepen the hole beyond the water table, the more the sand caves in from the sides. Digging a deep hole through uncompressed layers, hosting ground water, is not always a simple matter. Exactly the same applies for a deep well. Therefore, before the derrick is even delivered and erected, a specialized underground civil engineering company will arrive at the designated well site and will install a so-called conductor pipe into the ground (Figure 18). The conductor pipe is a steel pipe with a diameter of up to two feet (half a meter). The conductor pipe must be driven deep enough into the ground so that the surrounding loose soil layers cannot cave in when the soil is removed from the inside of the pipe. This is the beginning. What is now stuck in our Fig. 18: Conductor lawn is a pipe perhaps 15 to 60 feet long and hollow on the inside. It pipe with drill cellar is through this hole that we want to begin the actual drilling operation.


ow the well site needs to be prepared. Because we want to drill for oil, we need to ensure from the outset that no environmental damage during the drilling phase occurs. The entire well site is therefore sealed with concrete and asphalt. Small banks are built around the outside of the well site to prevent liquids (even rain water) to run off the site. This liquid is then collected into special tanks, so that it can later be disposed of according to specifications. The large and heavy derrick must be installed onto a stable concrete foundation. Around the conductor pipe, a drill cellar–a sealed pit several feet deep–is constructed (Figure 18). When the well site is prepared, the trucks can deliver the derrick, all the additional components, the office trailers and the drill string. The derrick is erected on the concrete foundation above the drill cellar.


he drilling can finally begin. The drillers install a big drill bit below the drill collars, start the mud pumps, and initiate the string into rotation, which drives the drill string down through the conductor pipe towards the bottom of the borehole. The hole is quickly filled with drilling mud. The conductor pipe in the drill cellar allows a controlled circulation of the drilling fluid. The mudflow captures the dissolved drill cuttings at the bit and transports them to the vibrating screens at surface, where a geologist takes samples. The geologist analyses the samples in the laboratory and in this way is informed of the kind of rock and its properties that is found at the bottom of the borehole. When the drill bit has pierced the loose rock layers and has penetrated the solid underlying rock, the first stage of drilling has been completed and the surface casing can be prepared. The surface casing is a sturdy steel pipe, which is run into the borehole (Figure 20).

Fig. 19: Well site, viewed from the work floor. Pipe rack (below left), office trailer (in the background)

Fig. 20: Elements of the surface casing prior to assembly (photo by R. Ritschel)

6 HOW IS A DEEP WELL DRILLED? The outer diameter of the pipe is by design slightly smaller than the inside diameter of the hole, resulting in a gap having a width of one or two inches (25–50 mm). This gap is now carefully filled with cement. The cement adheres to the rock formation as well as to the steel pipe. When the cement hardens, the steel pipe is firmly anchored to the surrounding rock. A carefully set casing is crucial for the drilling project. In the search for oil and gas, the possibility of drilling into a gas deposit under unexpectedly high pressure should always be considered. If this is the case, it is possible that a gas bubble can squeeze into the borehole. Anything undesirable that develops in the borehole is referred to as a kick. The gas kick rises in the viscous drilling fluid towards the surface. On the way up, the pressure in the borehole gradually decreases. This results in the gas bubble expanding and as it becomes larger and larger it pushes more and more of the drilling mud out of the borehole. The drilling team should timeously recognize such a dangerous situation by observing that more drilling mud is leaving the borehole than what is being pumped into it. If this is not immediately acted upon, the situation can escalate. In extreme cases, the gas will shoot up suddenly with all the drilling mud in the form of a giant high-pressure fountain roaring out of the borehole. This is called an eruption—a blowout, which is the worst possible accident that can happen during drilling. The smallest spark can ignite the escaping gas causing a jet of flame, where just a moment ago a derrick stood. An essential task of the surface casing is to prevent such situations. After the surface casing has been cemented into the ground, the blowout preventer (the safety valve) is mounted securely onto the upper end of the casing, which is protruding Fig. 21: Installafrom the drilling cellar (Figure 21). Should there be indications of a kick, tion of a blowout the blowout preventer can tightly seal the borehole within seconds. For preventer below the the time being the borehole will be closed and the pressurized gas will working platform not be able to escape, thereby preventing any damage. The driller will (Photo: P. Finenko) have gained some time to get the situation under control using tried and tested methods. The closure of the hole is only possible when the surface casing is firmly anchored in the rock! If it were not sufficiently bound to the rock, the surface casing together with the blowout preventer would shoot out like a cork from a shaken champagne bottle. The anchorage of the surface casing to the rock formation is an essential life insurance for the drilling crew and is therefore a vital investment.


he surface casing is firmly in the ground and the blowout preventer is screwed onto it. We can now prepare a new bottom-hole assembly, select a drill bit that fits through the blowout preventer and surface casing, and drive it to the bottom of the borehole. From here we begin to drill the next borehole section. On the way to the reservoir, several different rock formations are usually penetrated. Most rock formations are fairly easy to drill through, while some, such as salt formations, are considered problematic. At first sight salt appears to be solid like rock. The salt grains on your breakfast egg are hard after all. But deep down in the borehole very different conditions prevail than on our breakfast table. Under the high temperature and pressure conditions in the borehole, salt starts to flow and gradually squeezes into the hole. In cases where we ignore this by simply continuing to drill, it could happen that when we want to trip out the drill string, that the drill bit may no longer fit through the hole. In the worst-case scenario, the salt may even jam the drill string in the hole. We could of course try to solve this problem by pumping water into the borehole to dissolve the salt, but this might create uncontrolled cavities, which would then cause other problems. Salt is not the only formation that is difficult to drill through. Layers of shale or clay can swell, become sticky or muddy or get dissolved in the drilling fluid. Other stable formations, however, could contain cracks through which we could lose considerable amounts of expensive drilling mud or through which unwanted groundwater could seep into the borehole. The only way to control such problems is to install another pipe, called a casing string, and cement it into place. In this way the problematic areas are isolated from the borehole. These casing strings are referred to as intermediate casings. In order to continue drilling we will now have to use an even smaller drill bit and prepare a new bottom-hole assembly. During the course of drilling further complicated formations may of course be encountered. If this is the case, it will be necessary to install further intermediate casing strings. Eventually, however, we reach our reservoir. The prior investment in the borehole was merely a means to an end. It is only now becoming interesting for the oil company. To ensure that the procured connection between the reservoir and the Earth’s surface remains stable, an additional intermediate casing is installed and cemented.





A measure of the compass direction, which is usually specified in degrees, where 0 ° indicates north, 90 ° east, 180 ° south and so on.


An eruption caused by fluid (gas, oil or water) entering the borehole from the surrounding rock and escaping uncontrollably from the well.

Blowout preventer

The blowout preventer (BOP) is a safety valve that is mounted by flanges on top of the surface casing and it is used to safely close the borehole at any time.

Borehole construction

The sum of all the casings that have been installed in a borehole. It also includes all certificates for all the casings as well as the casing-setting depths and cement-head heights.

Bottom-hole assembly

The bottom-hole assembly (BHA) is the “intelligent” part of the drill string, which is used to control the direction of the drill path, and which contains position-determination sensors and devices for measurement of rock properties. It also contains the potentially available drilling-motor, a jar, shock absorbers, stabilizers and other special equipment. Of course, the drill bit is also part of the bottom-hole assembly.

Build rate

A measure of the curvature of the borehole with respect to the vertical plane specified in the unit °/100 ft. It indicates how strongly the borehole increases in inclination per 100 ft of drilled distance.


Short for casing string, a casing, in contrast to a liner, always extends from the casing shoe at setting depth up to the surface. It is used to isolate critical rock layers, such as floating minerals, swelling clay or vug-containing rock formations.


A device on the rig to separate very fine undesirable solids from the drilling mud.

Company man

The company man on a drilling rig represents the interests of the investors, which is generally the oil company.


The completion of the borehole involves the installation of production tubing and valves to facilitate controlled and sustainable production of the raw material.

Hunting Underground  

The ideal introduction to the fascinating world of deep drilling technology!

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