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- Herausgeber: John Wiley & Sons
- Kategorie: Fachliteratur
- Sprache: Englisch
Oil and Gas Well Cementing for Engineers Practical approach covering the chemistry, processes, and modeling in the field of cementing engineering Oil and Gas Well Cementing for Engineers is a comprehensive and reader-friendly book that delves into the chemistry, processes, and modeling involved in cementing engineering in the oil and gas industry. The book brings together traditional cementing technologies and the latest advancements, providing a practical approach for both students and field specialists. It then proceeds to cover the entire cementing process, including the initial phase of Portland cement production and practical calculations needed during complex cementing operations. In a rapidly evolving industry, where the number of well workover and bottom-hole zone stimulation operations is on the rise, understanding cementing systems and cementing technology is crucial for field operation efficiency. This book fills the knowledge gap often left by educational institutions that fail to provide well cementing as a separate course, opting to cover only fragments of the process within related subjects. Oil and Gas Well Cementing for Engineers serves as an essential primer for students, offering a comprehensive overview of cementing operations. For field specialists, the book provides practical insights and calculations required on-site, making it a valuable resource for enhancing operational proficiency. The logical sequence in which the material is presented simplifies the reader's perception, making it easier to grasp the wide range of information covered in the book. Whether you are a student or an industry professional, this practical guide offers a wealth of knowledge on cementing technology, empowering you to excel in oil and gas well construction and production processes.
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Table of Contents
Cover
Table of Contents
Title Page
Copyright Page
Foreword
Introduction
1 Theoretical and Practical Aspects of Well Cementing
1.1 Oil Well, Its Elements, and Construction
1.2 Objectives of Well Cementing
1.3 Primary Cementing
1.4 History of Oil Well Cementing Technology Development
2 Composition and Classification of Portland Cement
2.1 Chemical Composition
2.2 Portland Cement Manufacturing
2.3 API (American Petroleum Institute) Classification of Portland Cement
2.4 GOST (Russian: ГОСТ) Classification of Portland Cement
3 Cement Additives
3.1 Introduction
3.2 Accelerators
3.3 Retarders
3.4 Extenders
3.5 Weighting Agents
3.6 Dispersants
3.7 Fluid Loss Agents
3.8 Lost Circulation Prevention Agents
3.9 Special Cement Additives
4 Special Cement Systems
4.1 Thixotropic Cement
4.2 Expansive Cement
4.3 Freeze‐Protected Cement
4.4 Salt‐Cement Systems
4.5 Latex‐Cement Systems
4.6 Corrosion‐Resistant Cement
4.7 BFS Systems
4.8 Engineered Particle‐Size Distribution Cements
4.9 Low‐Density Cements
4.10 Flexible Cement
4.11 Microfine Cements
4.12 Acid‐Soluble Cements
4.13 Chemically Bonded Phosphate Ceramics
4.14 Special Cement Systems
5 Cementing Equipment
5.1 Surface Equipment
5.2 Casing Types
5.3 Technical Characteristics of Casing
5.4 Casing Hardware
5.5 Remedial Cementing Equipment
6 Primary Cementing
6.1 Planning
6.2 Slurry Selection
6.3 Theoretical Basis of Mud Displacement
6.4 Methods of Well Cementing
6.5 Multistage Cementing
6.6 Liner Cementing
6.7 Critical Factors in Cementing Operations
7 Remedial Cementing
7.1 Plug Cementing
7.2 Squeeze Cementing
8 Cement Job Evaluation
8.1 Hydraulic Testing
8.2 Temperature Log
8.3 Radioactive Logging
8.4 Acoustic Logging
8.5 Types of Logging Tools
9 Laboratory Testing and Evaluation of Well Cements
9.1 Preparation of Cement Slurry
9.2 Test Methods of Cement Slurries
9.3 Test Methods of Cement Stone
9.4 Laboratory Evaluation of Spacers and Washers
9.5 Chemical Analysis of Mix Water
10 Typical Calculations for Well Cementing
10.1 Slurry Preparation Calculations
10.2 Primary Cementing Calculation
10.3 Remedial Cementing Calculations
Annex. Conversion Tables
Recommended Literature
Index
End User License Agreement
List of Tables
Chapter 2
Table 2.1 Chemical composition of Portland cement.
Table 2.2 Main cement classes according to API classification.
Table 2.3 Clinker composition for the main cement classes according to API ...
Chapter 3
Table 3.1 Effect of calcium chloride on thickening time and compressive str...
Table 3.2 Extenders.
Table 3.3 Influence of bentonite on cement slurry properties.
Table 3.4 Chemical composition requirements for fly ash according to ASTM c...
Table 3.5 Physical properties of cement slurry weighting agents.
Table 3.6 Hematite slurries with H‐grade cement.
Chapter 5
Table 5.1 Casing steel grades according to API 5CT/ISO 11960.
Table 5.2 Casing steel grades for sour environments as recommended by the N...
Table 5.3 Chemical composition of steel grades according to API classificat...
Table 5.4 Empirical formulas for determining the casing collapse pressure....
Chapter 6
Table 6.1 Influence of the type of caliper used and the shape of the wellbo...
Chapter 7
Table 7.1 Goals and objectives of remedial cementing.
Chapter 8
Table 8.1 Radioactive tracers.
Table 8.2 Acoustic properties of different cementing formulations.
Table 8.3 Acoustic properties of some homogeneous liquids.
Table 8.4 Acoustic properties of different types of drilling mud.
Chapter 9
Table 9.1 Example of the results of rheological measurements on a rotary vi...
Chapter 10
Table 10.1 Main grades of cements according to the API classification.
Table 10.2 Absolute volume and specific gravity of some cementing materials...
Table 10.3 Absolute volume of NaCl‐a aqueous solution at 80 °F (26.7 °C).
List of Illustrations
Introduction
Figure 1 Simplified scheme of the well construction technological cycle.
Chapter 1
Figure 1.1 Well construction elements.
Figure 1.2 Drill bit types.
Figure 1.3 Kelly.
Figure 1.4 Schematic representation of the drilling operation.
Figure 1.5 Schematic representation of drilling along the whole face area (а...
Figure 1.6 Types of boreholes according to borehole curvature.
Figure 1.7 Pore pressure gradient graph.
Figure 1.8 Different types of schematic representation of casing. (a) Schema...
Figure 1.9 Single‐stage cementing with two plugs.
Figure 1.10 Two‐stage cementing.
Figure 1.11 Basket cementing.
Figure 1.12 Liner cementing.
Figure 1.13 Reverse cementing.
Figure 1.14 Cementing plugs.
Chapter 2
Figure 2.1 Schematic representation of the Portland cement hydration process...
Figure 2.2 Hydration process of Portland cement.
Figure 2.3 The “dry” method of Portland cement production.
Figure 2.4 “Wet” method of Portland cement production.
Chapter 3
Figure 3.1 Influence of sodium chloride on thickening time and compressive s...
Figure 3.2 Effect of lignosulphate retarder on the setting time of class G c...
Figure 3.3 Three different processes for the sedimentation of cement slurry....
Chapter 4
Figure 4.1 Arrangement of cement particles in mathematical models.
Chapter 5
Figure 5.1 Schematic representation of storage, transportation, and preparat...
Figure 5.2 Storage silo.
Figure 5.3 Pneumatic loading (dry material).
Figure 5.4 Screw‐type unloader.
Figure 5.5 Pneumatic mixing tank.
Figure 5.6 Cement trucks of various designs.
Figure 5.7 Displacement tank system.
Figure 5.8 Liquid additive metering system.
Figure 5.9 Surge tank.
Figure 5.10 Conventional jet mixer.
Figure 5.11 Recirculating jet mixer.
Figure 5.12 Mixing and pumping equipment on rig site (typical setup).
Figure 5.13 Universal cementing unit (Halliburton Corporation).
Figure 5.14 Possible casing diameter depending on the bit diameter used duri...
Figure 5.15 Types of liners.
Figure 5.16 Interpretation of steel grades according to API standards.
Figure 5.17 Connection with coupling.
Figure 5.18 Connection without coupling.
Figure 5.19 Types of non‐coupling connection.
Figure 5.20 Casing equipment.
Figure 5.21 Guide shoe АО “ПО СТРОНГ”.
Figure 5.22 Reamer shoe.
Figure 5.23 Self‐orienting shoe.
Figure 5.24 Lipstick shoe.
Figure 5.25 Flapper‐type check valve.
Figure 5.26 Ball‐type check valve.
Figure 5.27 Poppet‐type check valve.
Figure 5.28 Bow‐spring centralizers (a) slip‐on centralizer; (b) hinged cent...
Figure 5.29 Rigid centralizers.
Figure 5.30 Roller centralizers АО “ПО СТРОНГ”.
Figure 5.31 Turbulator. www.zavodnpo.ru
Figure 5.32 Scratchers.
Figure 5.33 Upper (black) and Lower (red) cementing plugs. MED, Inc.
Figure 5.34 Cementing head (a) double plug cementing head; (b) single plug c...
Figure 5.35 Screening device.
Figure 5.36 Cementing basket.
Chapter 6
Figure 6.1 Caliper tool types: (a) one‐arm caliper; (b) two‐arm caliper; (c)...
Figure 6.2 Schematic representation of the displacement profile of fluid #1 ...
Figure 6.3 Schematic representation of the displacement efficiency curve.
Figure 6.4 Schematic representation of flow area distribution in case of poo...
Figure 6.5 U‐tube effect.
Figure 6.6 Through drill‐pipe stab‐in cementing.
Figure 6.7 Cementing through small diameter tubing.
Figure 6.8 Stage cementing plugs ООО”АЛЬКОР”.
Figure 6.9 Well cementing process with the use of a stage cementing collar....
Figure 6.10 Continuous multistage cementing.
Figure 6.11 Three‐stage cementing.
Figure 6.12 Types of liners.
Figure 6.13 The tool for installing the liner and the hanger assembly.
Figure 6.14 Cementing head for liner cementing.
Figure 6.15 Schematic representation of the liner cementing process.
Figure 6.16 Schematic representation of the liner cementing method using two...
Figure 6.17 Nomogram for estimating the mixing temperature using cement slur...
Figure 6.18 Graph of the hydrostatic pressure range.
Chapter 7
Figure 7.1 Balance method of cement plug placement.
Figure 7.2 Cement plug installation using a dump‐bailer.
Figure 7.3 Installation of a cement plug using the two‐plug method.
Figure 7.4 Schematic representation of the formation of a filtration crust a...
Figure 7.5 Schematic representation of the formed nodes in the wellbore depe...
Figure 7.6 Dynamics of wellhead pressure changes during continuous injection...
Figure 7.7 Wellhead pressure changes during sequential injection of cementin...
Figure 7.8 Schematic representation of squeeze cementing without a packer.
Figure 7.9 Schematic representation of the negative pressure test (inflow te...
Figure 7.10 Dynamics of hydrostatic pressure change during a negative pressu...
Chapter 8
Figure 8.1 Leak‐off test.
Figure 8.2 Dynamics of hydrostatic pressure change during negative pressure ...
Figure 8.3 Typical temperature log curve.
Figure 8.4 Influence of temperature on the hydration kinetics of G‐class cem...
Figure 8.5 Typical radioactive log diagram.
Figure 8.6 Types of sound waves.
Figure 8.7 Lamb wave.
Figure 8.8 Schematic representation of the CBL‐VDL tool.
Figure 8.9 Operating principle of the acoustic logging tool.
Chapter 9
Figure 9.1 Cement slurry mixers (Fann Instrument Company).
Figure 9.2 Pressurized mud balance for determining the density of cement slu...
Figure 9.3 High pressure and high temperature consistometer (Fann Instrument...
Figure 9.4 Atmospheric consistometer (Fann Instrument Company).
Figure 9.5 An example of the result of measuring the consistency of a cement...
Figure 9.6 Filter presses for cement slurry fluid loss tests (Fann Instrumen...
Figure 9.7 Free water.
Figure 9.8 Flow velocity profile for Newtonian fluid in laminar flow in a pi...
Figure 9.9 Flow velocity profile for Newtonian fluid in plug fluid flow.
Figure 9.10 Turbulent flow.
Figure 9.11 Fluid flow between two parallel plates.
Figure 9.12 Dependence between shear rate and shear stress for Newtonian flu...
Figure 9.13 Dependence between shear rate and shear stress for Power‐law flu...
Figure 9.14 Dependence between shear rate and shear stress for the Bingham f...
Figure 9.15 The relationship between shear rate and shear stress for a fluid...
Figure 9.16 Rotary viscometer (Fann Instrument Company).
Figure 9.17 MACS II multipurpose cement slurry analysis system (Fann Instrum...
Figure 9.18 Cone of AzNII (Azerbaijan Scientific Research Petroleum Institut...
Figure 9.19 Cubic molds for cement stone strength tests (Fann Instrument Com...
Figure 9.20 Ultrasonic cement analyzer (Fann Instrument Company).
Figure 9.21 Example of a result of measuring the compressive strength of cem...
Figure 9.22 Instrument for measuring the linear coefficient of thermal expan...
Chapter 10
Figure 10.1 Schematic representation of the well design and cementing interv...
Figure 10.2 Schematic representation of the wellbore for calculating the val...
Figure 10.3 Schematic representation of the wellbore for calculations made d...
Figure 10.4 Schematic representation of the wellbore for calculations made d...
Figure 10.5 Schematic representation of the wellbore for calculations during...
Figure 10.6 Schematic representation of the wellbore for calculations during...
Guide
Cover Page
Title Page
Copyright Page
Foreword
Introduction
Table of Contents
Begin Reading
Annex. Conversion Tables
Recommended Literature
Index
WILEY END USER LICENSE AGREEMENT
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Oil and Gas Well Cementing for Engineers
Baghir A. Suleimanov
Oil and Gas Scientific Research Project InstituteState Oil Company of Azerbaijan Republic (SOCAR)Baku, Azerbaijan
Elchin F. Veliyev
Oil and Gas Scientific Research Project InstituteState Oil Company of Azerbaijan Republic (SOCAR)Baku, Azerbaijan
Azizagha A. Aliyev
Oil and Gas Scientific Research Project InstituteState Oil Company of Azerbaijan Republic (SOCAR)Baku, Azerbaijan
This edition first published 2023© 2023 John Wiley & Sons Ltd
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The right of Baghir A. Suleimanov, Elchin F. Veliyev, and Azizagha A. Aliyev to be identified as the authors of this work has been asserted in accordance with law.
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Library of Congress Cataloging‐in‐Publication Data
Names: Suleimanov, Baghir, author. | Veliyev, Elchin F., author. | Aliyev, Azizagha, author.Title: Oil and gas well cementing for engineers / Baghir A. Suleimanov, Elchin F. Veliyev, Azizagha A. Aliyev.Description: Hoboken, NJ : Wiley, 2023. | Includes index.Identifiers: LCCN 2023017127 (print) | LCCN 2023017128 (ebook) | ISBN 9781394164851 (hardback) | ISBN 9781394164868 (adobe pdf) | ISBN 9781394164875 (epub)Subjects: LCSH: Oil well cementing.Classification: LCC TN871.2 .S83 2023 (print) | LCC TN871.2 (ebook) | DDC 624.1/833–dc23/eng/20230427LC record available at https://lccn.loc.gov/2023017127LC ebook record available at https://lccn.loc.gov/2023017128
Cover Design: WileyCover Image: © Edelweiss/Adobe Stock Photos
Foreword
Well cementing is largely integrated into the well construction process, being one of the two most common operations involved. It would be wrong to consider this process without taking into account the processes preceding and following this operation because the use of the cementing materials is not limited to drilling wells, but it is also widely used in the operation and production processes, being an inseparable part of them. Nowadays the number of fields at later stages of development is increasing year by year, and it is not difficult to assume that the number of operations related to well workover and bottomhole zone stimulation is rising almost proportionally. Considering the fact that a significant share of technologies used for this very purpose is based on the application of various plugging materials, knowledge of theoretical and practical aspects of plugging systems application is one of the key factors increasing the field operation efficiency. Unfortunately, today the majority of educational institutions of higher education do not provide well cementing as a separate course. They cover only some aspects of the process in the context of various related subjects. Such an approach eventually leads to significant gaps in the integrity of the ideas of young professionals, and graduate and undergraduate students about cementing operations. In this book, the authors tried to cover all major aspects of oil and gas well cementing technology – from the initial phase of Portland cement production to the practical calculations carried out during complex cementing operations. However, the way the material is presented in the book is based on the logical sequence of cementing operations, which significantly simplifies the reader's perception, despite the wide range of presented information.
The first chapter of the book introduces the reader to the basic concepts used by experts in the plugging process, such as the concept of well design, goals, objectives, and basic methods of well cementing. Chapters 2–4 are devoted to production, properties, types, and classification of plugging materials. The use of cementitious materials in human life has its roots in antiquity: clay and lime have long been used by humankind as a binding material in masonry, and ancient Egyptians used unrefined lime in the construction of the pyramids. However, with the increase in the industrial production of cement, the range of cementitious materials increased significantly and there was a need for their standardization and classification. These chapters introduce the reader to the modern production process of cementitious materials, chemical composition, and additives used to regulate their properties. The two most common classifications of Portland cement according to API and QOST standards are also given.
The fifth chapter of the book is devoted to surface and downhole equipment used in cementing operations. It contains schematic drawings of almost all types of modern cementing equipment, describing their operating principles and mechanisms. The material allows the reader to understand the main tasks they perform and to become familiar with the technical limitations of their application, without being immersed in complex engineering descriptions of the devices and mechanisms.
Chapters 6–7 provide a detailed description of primary and secondary well cementing. By reading these chapters, the reader will get a sufficiently accurate idea of the types of modern cementing operations, tasks they perform, and factors the engineer is guided by when selecting a cement slurry formulation or type of cementing operations on a well.
Chapter 8 discusses the most commonly used methods for evaluating the quality of casing cementing. The theoretical and practical basics of logging are described in detail, and the advantages and disadvantages of the main methods are listed.
The ninth chapter is devoted to perhaps one of the least covered areas of well cementing, namely laboratory testing methods for cementitious materials. The chapter describes experiments to determine cement slurry properties, outlines extensive theoretical and practical material for a better understanding of the goals and objectives of the experiments conducted, and the role of the parameters to be determined in the casing string cementing process.
The tenth chapter is the final chapter of the book and is of practical application. It explains in detail, with examples, all the basic typical calculations involved in planning or carrying out cementing operations.
The book is intended for researchers, petroleum engineers, postgraduates, students, and specialists in relevant fields.
The authors are grateful to Prof. E.M. Suleimanov for valuable discussion on theoretical aspects of cementing efficiency evaluation, as well as to Prof. N.M. Gadzhiev for valuable discussions on practical aspects of oil and gas well cementing.
Introduction
Well cementing is largely integrated into the well construction process, being one of the two most frequent operations involved. The process should be considered solely in terms of the processes that precede and follow it. Such an approach provides the most complete picture of the purpose and objectives of well cementing while making the learning material much easier to grasp.
In well construction, the drilling phase can be simplified into the following major cycles (Figure 1):
Drilling
Casing and cementing the well
Drilling into the reservoir and testing for oil and gas flow
Figure 1 Simplified scheme of the well construction technological cycle.
The first two cycles alternate (i.e. drilling and casing), and once the pay zone has been reached, the process is completed by penetrating the reservoir and testing for oil and gas flow [1].
The number of such repeated cycles is individual for each well and depends on specific geological conditions.
1Theoretical and Practical Aspects of Well Cementing
1.1 Oil Well, Its Elements, and Construction
What is oil and gas drilling? According to the classic definition: “Well drilling is the process of making a directional cylindrical rock hole in the earth, the diameter of which is tiny in comparison to its length, without human access to the bottom hole.” (A hole drilled into the earth for the purpose of exploring for or extracting oil, gas, or other hydrocarbon substances.) A well is a cylindrical rock excavation that has a diameter many times smaller than its length (Figure 1.1).
The point where the drilling starts at the surface is called the wellhead, at the opposite end of the excavation is the bottom hole, and the entire borehole volume between these two points is called the borehole. An imaginary line drawn through the centers of the cross sections of the borehole is called the borehole axis.
Drilling begins with running the drill string. The drill string is an assembly of pipes connected by interlocks and designed to supply hydraulic and mechanical energy to the bit and create an axial load on it, as well as to control the path of the borehole being drilled. The drill bit is the main element of the drilling tool for the mechanical destruction of rock on the bottom hole in the process of penetrating (drilling) the borehole (Figure 1.2).
In the traditional drilling method, the drill bit is connected to the bottom end of the bottom hole assembly (BHA), i.e. the first weighted drill pipe (Heavy Weight Drill Pipe – HWDP), while the top end of the BHA is connected to the lead drill pipe (Kelly). The kelly, a square or hexagonal pipe, which is located at the top of the drill string, serves as the connection between the drill string and the drill rig to ensure the effective interaction between them (Figure 1.3). The drill string then begins to rotate and the drilling process begins. It should be noted that when a Top Drive is used, the top end of the BHA is connected to the power swivel.
Figure 1.1 Well construction elements.
Figure 1.2 Drill bit types.
Once the drill string is deepened by the length of the kelly, the rotation is stopped, the drill string is raised, a new pipe is added, and the drill string is run back into the borehole and drilling is continued. This operation is repeated until the required depth is reached or the drill bit is replaced (Figure 1.4).
There are two main types of drilling based on the area where the rock destruction tool (bit) affects the bottom hole:
Drilling along the whole face area.
Continuous bottom hole drilling, in this type of drilling, the whole rock in the borehole is destroyed by the bit (
Figure 1.5
a).
Drilling along the peripheral part of the face (annular face).
Core drilling, this type of drilling preserves the inner part of the rock (
Figure 1.5
b).
Depending on the curvature of the borehole, wells are subdivided (Figure 1.6) into the following types:
Vertical (
Figure 1.6
[1])
Slant (
Figure 1.6
[2])
Inclined (
Figure 1.6
[3])
Horizontal (
Figure 1.6
[4])
S‐type (
Figure 1.6
[5])
Figure 1.3 Kelly.
Figure 1.4 Schematic representation of the drilling operation.
Figure 1.5 Schematic representation of drilling along the whole face area (а) and drilling along the peripheral part of the face – annular face (b).
Figure 1.6 Types of boreholes according to borehole curvature.
The following types of wells are distinguished according to their purpose:
Production wells.
Those drilled directly for production by the well (i.e. oil, gas, and condensate).
Injection wells.
Drilled to maintain reservoir pressure and enhance oil recovery by injecting different displacing agents into the reservoir (e.g. water, gas, and polymer solutions).
Exploration wells.
Wildcat and appraisal wells are collectively referred to as exploration wells:
Wildcat well.
Drilling an exploration well to determine the existence of petroleum in a probable hydrocarbon deposit.
Appraisal well.
Drilled, as a rule, after the wildcat well to assess the hydrocarbon reserves, collect geophysical information, and outline the reservoir.
Special wells.
Observation, parametric, and stratigraphic – drilled to study the dynamics of reservoir properties, pressure, and degree of depletion in certain reservoir sections, as well as to ensure the in situ burning. The goals and objectives of this group of wells vary considerably from field to field and are determined by the course of the development process and the individual peculiarities of a reservoir.
Structural exploration wells.
These wells include all the wells drilled in the exploration area before the commercial flow of oil or gas is achieved. These wells are generally of small diameter and depth to reduce the cost of the drilling process.
1.2 Objectives of Well Cementing
The geological conditions, which change with depth, impose certain limitations on the drilling process, and it is not possible to reach a productive formation in a single drilling trip.
A drilling trip is a set of basic and auxiliary activities to deepen a well with a single rock‐drilling tool (bit), starting from the preparation of the drilling tool to be run into the well and finishing work after it has been lifted.
The well trajectory, divided into sections composed of formations with similar geological characteristics and therefore compatible in terms of drilling conditions, is called drilling intervals.
Each drilling interval has different requirements for both the drilling process and the technology, i.e. the intervals have different drilling conditions. In other words, it is not possible to drill the underlying interval without complications in the overlying interval drilled, unless the latter is secured with casing and cementing. Let us consider, in a simplified way, the process of drilling intervals selection by the example of conventional well “A” (Figure 1.7). Initially, based on geological conditions pore pressure gradient (PPG) graph is constructed, which illustrates the change along the depth of the well: hydraulic fracturing pressure, formation pressure, and hydrostatic pressure of the drilling fluid column. The PPG graph, taking into account geological complications, makes it possible to identify drilling intervals in the well trajectory and identify the need for intermediate casing strings, their number, and depth of penetration. In this example, the PPG chart clearly identifies three zones that are incompatible in terms of drilling conditions.
Figure 1.7 Pore pressure gradient graph.
Thus, drilling “Zone 2” with the same mud as “Zone 1” will inevitably result in fluid influx because, for “Zone 2,” the hydrostatic pressure of the drilling fluid column will already be below the reservoir pressure. Drilling “Zone 3” with the same density as “Zone 2,” on the other hand, will result in hydraulic fracturing. In order to meet the compatibility conditions, these zones must be bridged with casing, increasing the number of intermediate casing strings in the well design to two.
It should be noted that even if the well would consist of a single drilling interval (which of course is not realistic), an uncased wellbore (i.e. without casing) would be a very unstable structure with a constant risk of rock debris or even collapse into it.
As mentioned earlier, the borehole is secured by running special pipes, known as casing strings, into the borehole. The space between the casing and the wellbore wall is filled with a plugging material. The most widely used plugging material is mortar on the basis of Portland cement, hence the name of this process: well cementing. The main functions of cementing include:
Isolation of layers, i.e. prevention of fluid transfer from one layer to another. For example, isolating freshwater formations from mixing with highly saline formation water.
A cement sheath around the casing contributes to preventing gas and water seepage into the well.
Protection against corrosive effects of formation fluids on the casing.
Protection of casing against drilling stresses.
Sealing of absorption zones.
Cementing is also applied when abandoning depleted wells or isolating depleted layers.
The alternation of drilling and cementing processes results in a stable underground structure called a well construction. Thus, a well construction is a set of data reflecting the following information:
Casing lengths and diameters
Wellbore diameters corresponding to the casing used to secure the interval
Cementing intervals
Completion method and payzone interval
Casing is usually classified according to its purpose, so there are four main types of casing (Figure 1.8).
Let us take a closer look at each casing type.
Conductor casing – This type of casing is designed to reinforce the wellhead against collapse and destruction as a result of the drilling process and to allow circulation of drilling mud. A conductor is usually comprised of a single casing, less frequently a single pipe, and the pipes used as a conductor are not pressurized. The running depth of a conductor could be as much as 100 m (extended direction), but in practice, it rarely exceeds 10 m; the diameter of the casing ranges from 245 to 1250 mm. The conductor is secured either by concreting or simply by driving the casing into the ground (piling method).
The surface casing is the subsequent casing string running to a depth of 100–600 m, with an average casing diameter of 177–508 mm. The main purpose of running the surface casing is to prevent contamination of the freshwater horizons in the upper horizon of the rock section, as well as to install wellhead equipment (i.e. casing head and blowout control equipment). Unlike the conductor, surface casing and the cement ring behind it are compressed.
It should be noted that the conductor and surface casings are fixed parts of all well designs.
Intermediate casing – The main purpose of running intermediate casing is to separate different drilling intervals. As there may be several drilling intervals, depending on geological conditions, the number of intermediate casing strings run is often more than two and varies from well to well.
The following types of intermediate casing are distinguished:
Continuous intermediate casing.
The entire annular space from the bottom hole to the wellhead is cemented.
Liner.
Used for casing the non‐cased section of the wellbore. In this case, the casing itself is installed by overlapping a part of the previous casing string and does not extend to the surface. Running liner is often economically advantageous as it allows for a significant simplification of well construction and reduction of metal and insulation material consumption.
Tie‐back liner
is a special type of casing that is not connected to other casing strings included in the well design and serves to isolate the selected interval.
Figure 1.8 Different types of schematic representation of casing. (a) Schematics of well construction in relation to payzone; (b) different types of well construction drawings.
The production casing is the final casing string run to isolate the reservoir and bring the well product to the surface. In practice, it is not uncommon for the last intermediate casing to perform the role of production casing, and the production casing itself is used not only to produce oil or gas but also to inject fluids into the reservoir.
Well design development is based on the following main geological and technical‐economic factors:
geological features of rock occurrence, their physical and mechanical characteristics, the presence of fluid‐bearing horizons, reservoir temperatures and pressures, and the fracturing pressure of the rocks being penetrated;
the purpose and aim of drilling the well;
the intended method of completing the well;
the method of drilling the well;
the level of organization, technique, drilling technology, and geological knowledge of the drilling area;
level of qualification of drilling team and organization of logistics; and
methods and techniques of well completion, operation, and workover.
1.3 Primary Cementing
There is no universal technology of cementing because this process depends on many factors, such as geological conditions, well design and its current condition, cementing team logistical support, etc. Therefore, the selection of cementing technology is performed individually for each particular well, but nevertheless, there are the following general requirements, which should be met by the chosen technology of cementing:
Provision of safe anchoring of the whole borehole section.
Preventing drilling mud contamination with cement slurry.
Complete displacement of drilling mud from the cemented interval.
Obtaining a quality cement ring in the annulus.
In practice, the following well cementing techniques are the most commonly used:
Single‐stage cementing with two plugs
Two‐stage cementing
Basket cementing
Liner cementing
Reverse cementing
Cement plug installation
Let us take a short description of each technology separately. (Note: Each technology will be described in more detail in Chapter 6.)
1.3.1 Single‐Stage Cementing with Two Plugs
Well cementing operation in single stage using two cementing plugs was first carried out in Baku (Azerbaijan) in 1905 by engineer Bogushevsky. Simplified this technology looks as follows (Figure 1.9):
After lowering the casing, a cementing head is installed to connect it tightly to the injection lines of the cementing units. The wellbore at this stage is filled with drilling fluid. Before pumping the cement slurry, the bottom plug is released from the cementing head, which serves as a kind of barrier between the drilling fluid in the borehole and the cementing slurry. It should be noted that in addition to cementing plug serving as a mechanical barrier between fluids in the wellbore, not infrequently in order to create a natural barrier, spacer fluids are also used.
After pumping a calculated amount of cement slurry into the well, the upper plug is released, which, in turn, is forced down the wellbore by drilling fluid. Thus, the cement slurry column in the wellbore is actually limited on both sides by cementing plugs.
Figure 1.9 Single‐stage cementing with two plugs.
Unlike the upper plug, which is a solid plug, the lower plug has a rubber diaphragm, and upon reaching the stopper ring with increasing wellhead pressure, the diaphragm ruptures and the cement slurry rushes into the annulus.
When the top plug reaches the stopper ring (
Note
: The top plug actually sits on the bottom plug), because of the solid design the diaphragm is not destroyed and the pressure at the cementing head increases sharply, which serves as a signal to stop pumping the flushing fluid. The well is sealed and left for the time required for setting of cementing slurry.
As a rule, some amount of cement slurry remains under the plug in the casing, forming a so‐called shoe track of 10–25 m height. If further drilling is required, the upper cement plug and shoe track are drilled out.
1.3.2 Two‐Stage (Two‐Cycle) Cementing
This technology divides the cemented section of the wellbore into two intervals (upper and lower), and each interval is cemented separately (Figure 1.10).
Two‐stage cementing has the following advantages over single‐stage cementing technology:
Significantly lower hydrostatic pressure of the cement slurry column on the formation, thus avoiding a number of complications when cementing deep wells.
It allows avoiding a considerable increase in injection pressure due to a decrease in cement slurry lifting height in the annulus.
Figure 1.10 Two‐stage cementing.
The cement slurry used for the upper interval is much less susceptible to high temperatures, which simplifies the cement slurry formulation for this interval while reducing the consumption of the used reagents.
Two‐stage cementing technology can be simplified into the following stages:
A cementing sleeve is installed at the interface between the upper and lower cementing intervals. The process of preparing the well for work is absolutely identical to the previous method. The volume of cementing slurry necessary for setting the lower interval is pumped into the borehole. At that, as well as in the first method, drilling and cementing slurry are separated with cementing plugs. Both plugs freely pass through the cementing (filling) sleeve. The cement slurry is displaced into annular space by the casing volume, which corresponds to the casing volume in the lower cementing interval.
Note. In practice, it is often the case that the bottom plug is not used, and the entire process is carried out using only three plugs, two for the upper and one for the lower cementing interval.
After pumping the calculated volume of the displacement fluid, the bottom plug of the upper cementing interval is released. It does not pass through the cementing sleeve freely, but sits on a special sleeve, sliding it down. As a result, the sleeve opens the holes in the annulus of the upper cementing interval, accompanied by a sharp drop in injection pressure at the wellhead.
Then there are two scenarios for the development of the process:
The bottom plug of the upper cementing interval is squeezed with cement slurry. This method is called the two‐stage method of continuous cementing.
The bottom plug of the upper cementing interval is squeezed with drilling mud, and the cement slurry is pumped after a certain time (usually necessary for the formation of a strong cement ring in the lower cementing interval). This method is referred to as the two‐stage cementing method with a breakout.
After pumping a calculated volume of cement slurry to secure the upper interval, the upper plug (the last one) is released and pressed with drilling fluid until it reaches the cement collar. During the setting of the plug in the cement collar, the sleeve shifts, blocking access holes to the annulus and causing a sharp increase in pressure, which signals the completion of the process. The well is then left to rest for the time necessary to form a strong cement ring.
1.3.3 Basket Cementing
The current method of cementing is widely used in case of low formation pressure in productive formation or for preventing cementing fluid contamination of perforated interval of wellbore (i.e. screen interval). The technology consists of installing a cement collar at the level of the lower cementing interval and a basket made of high‐strength metal and features overlapping fins on the outside, hence the name of the current method of cementing (Figure 1.11). This design prevents the cement slurry from moving down the wellbore, directing the flow in one direction only: up. A valve is installed inside the casing itself, which performs an identical function, that is, it does not allow cement slurry to penetrate to the bottom of the casing.
Figure 1.11 Basket cementing.
1.3.4 Liner Cementing
In this method of cementing, the casing is run in sections using drill pipes, with casing sections connected to drill pipes with a left‐hand transfer tube (i.e. a left‐hand threaded transfer tube) (Figure 1.12). Another feature of this technology is the use of a two‐part separating plug:
The female plug
is of the same diameter as the inner diameter of the casing section to be cemented. The borehole plug is mounted at the junction of the casing and drillpipe.
Male plug –
with a diameter smaller than the inner diameter of the drill pipe.
The male plug, installed in the cementing head, is released after the calculated volume of cementing solution is pumped and pressed with drilling fluid until it reaches the female plug. The male plug gets stuck in the female plug, causing an increase in pressure, as a result of which the pins holding the female plug are cut off and both plugs move down the wellbore to the stopper ring as a single unit. As the plugs reach the stopper, the pressure rises sharply, signaling the end of the operation and the presence of the pumped cement slurry in the annulus. Then the drill pipe is unscrewed from the left sub and flushed from the cement slurry residue and removed from the borehole.
Figure 1.12 Liner cementing.
