Handbook of Natural Gas Transmission and Processing

Saeid Mokhatab, William A. Poe

• Publisher: Gulf Professional Publishing
• Year: 2012
• Print ISBN: 9780123869142
• eBook ISBN: 9780123869753
• Edition: 2
• Topic: Technik & Maschinenbau
• Subtopic: Maschinen- und Anlagebau

A unique, well-documented, and forward-thinking work, the second edition of Handbook of Natural Gas Transmission and Processing continues to present a thoroughly updated, authoritative, and comprehensive description of all major aspects of natural gas transmission and processing. It provides an ideal platform for engineers, technologists, and operations personnel working in the natural gas industry to get a better understanding of any special requirements for optimal design and operations of natural gas transmission pipelines and processing plants.- First book of its kind that covers all aspects of natural gas transmission and processing- Provides pivotal updates on the latest technologies, which have not been addressed in-depth in any existing books- Offers practical advice for design and operation based on sound engineering principles and established techniques- Examines ways to select the best processing route for optimal design of gas-processing plants- Contains new discussions on process modeling, control, and optimization in gas processing industry

Chapter 1

Natural Gas Fundamentals

1.1 Introduction

Natural gas is the most energy-efficient fossil fuel; it offers important energy-saving benefits when it is used instead of oil or coal. Although the primary use of natural gas is as a fuel, it is also a source of hydrocarbons for petrochemical feedstocks and a major source of elemental sulfur, an important industrial chemical. Its popularity as an energy source is expected to grow substantially in the future because natural gas can help achieve two important energy goals for the twenty-first century: providing the sustainable energy supplies and services needed for social and economic development and reducing adverse impacts on global climate and the environment in general. Natural gas consumption and trade have been growing steadily over the past two decades, and natural gas has strengthened its position in the world energy mix. Although natural gas demand declined in 2009, as a result of the economic slowdown, it is expected to resume growth in both emerging and traditional markets in the coming decades. Such increase in the near future will be driven because of additional demand in current uses, primarily power generation. There is yet little overlap between the use of natural gas and oil in all large markets. However, there are certain moves in the horizon, including the electrifying of transportation, that will push natural gas use to even higher levels.

This chapter gives the reader an introduction to natural gas by describing the origin and composition of natural gas, gas sources, phase behavior and properties, and transportation methods.

1.2 Natural Gas History

The discovery of natural gas dates from ancient times in the Middle East. It was considered by ancients to be a supernatural manifestation. Noticed only when ignited, it appeared as a mysterious fire bursting from fissures in the ground. Natural gas seeps were discovered in Iran between 6000 and 2000 B.C. The practical use of natural gas dates back to the Chinese of 2,500 years ago, who used bamboo pipes to collect it from natural seeps and convey it to gas-fired evaporators, where it was used to boil ocean water for the salt. Apparently, natural gas was unknown in Europe until its discovery in England in 1659. However, since manufactured gas (coal gas) was already commercially available, natural gas remained unpopular. In 1815, natural gas was discovered in the United States during the digging of a salt brine well in Charleston, West Virginia. In 1821, an American gunsmith named William Aaron Hart drilled the first natural gas well in the United States. It was covered with a large barrel, and the gas was directed through wooden pipes that were replaced a few years later with lead pipe. One of the earliest attempts to harness it for economic use occurred in 1824 in Fredonia, New York, and led to the formation of the first natural gas company in the United States, the Fredonia Gas Light Company, in 1858.

The nineteenth century is considered as the starting point of the gas industry. In the early 1900s, huge amounts of natural gas were found in Texas and Oklahoma, and in the 1920s modern seamless steel pipe was introduced. The strength of this new pipe, which could be welded into long sections, allowed gas to be carried under higher pressures and, thus, in greater quantities. As the technology to create seamless steel pipe and related equipment advanced, the size and length of pipelines increased, as did the volumes of gas that could be transported easily and safely over many miles. The first natural gas pipeline longer than 200 miles was built in 1925, from Louisiana to Texas.

Steady growth in the use of gas marked the early and mid-twentieth century. However, it was the shortages of crude oil in the late 1960s and early 1970s that forced major industrial nations to seek energy alternatives. Since those events, gas has become a central fossil fuel energy source. Today, natural gas has become extremely important as a concentrated, clean fuel for home heating and cooking and electrical power generation, and is sought after almost as much as oil.

1.3 Natural Gas Origin and Sources

There are different theories as to the origins of fossil fuels. The most widely accepted theory of the origin of natural gas assumes that natural gas hydrocarbons come from organic matter (the remains of land and aquatic plants, animals and micro-organisms) that was trapped within sediments as they were deposited and transformed over long periods of time into their present form. Two main mechanisms, namely, biogenic and thermogenic, are responsible for the degradation of fossil organic material in sediments (Rojey et al., 1997). Biogenic gas is formed at shallow depths and low temperatures due to the action of bacteria on the organic debris accumulating in the sediments. In contrast, thermogenic gas is formed at deeper depths by degradation of organic matter, called kerogen, accumulated in fine-grained sediments, especially clays and shales. This degradation occurs through the combined effects of temperature and pressure. Thermogenic gas is believed to be produced through two mechanisms, namely, direct thermal cracking of sedimentary organic matter and secondary thermal cracking of oil that is formed in the first stage. The former is called primary thermogenic gas, which co-exists with oil, while the latter is called secondary thermogenic gas, which co-exists with insoluble solid matter, called pyrobitumen. Both mechanisms involve thermal cracking with some degree of sustained pressure, mainly through the weight of the sedimentary formation. Little information is available on the time required to generate thermogenic gas other than the general assumption that it is a long time.

Natural gas comes from both “conventional” (easier to produce) and “unconventional” (more difficult to produce) geological formations. Conventional gas is typically “free gas” trapped in multiple, relatively small, porous zones in various naturally occurring rock formations such as carbonates, sandstones, and siltstones. Conventional natural gas generally occurs in deep reservoirs, either associated with crude oil (associated gas¹) or in reservoirs that contain little or no crude oil (nonassociated gas²). Natural gas from coal (also known as coal-bed methane, CBM), tight gas sands, gas shales, geopressurized aquifers, and gas hydrates³ are often referred to as unconventional gas resources. The common characteristic of the different types of unconventional gas resources is that they contain large quantities of natural gas, but it is usually more difficult to produce this gas as compared to conventional reservoir rocks. New technologies are continually being developed to allow more accurate estimations of the amount of gas in these unconventional reservoirs and to stimulate these rocks to produce the gas.

1.4 Natural Gas Composition and Classification

Natural gas is a complex mixture of hydrocarbon and nonhydrocarbon constituents and exists as a gas under atmospheric conditions. Virtually hundreds of different compounds may be present in natural gas in varying amounts. Even two wells producing from the same reservoir may produce gases of different composition as the reservoir is depleted.

While natural gas is formed primarily of methane (CH₄), it can also include significant quantities of ethane (C₂H₆), propane (C₃H₈), butane (C₄H₁₀), and pentane (C₅H₁₂), as well as traces of hexane (C₆H₁₄) and heavier hydrocarbons. Many natural gases often contain nitrogen (N₂), carbon dioxide (CO₂), hydrogen sulfide (H₂S), and other sulfur components such as mercaptans (R-SH),⁴ carbonyl sulfide (COS), and carbon disulfide (CS₂). Trace quantities of argon, hydrogen, and helium may also be present. Trace quantities of metallic substances are known to exist in natural gases including arsenic, selenium, mercury, and uranium.

According to the proportion of hydrocarbons heavier than methane, different types of natural gas (dry, wet, and condensate) can be considered. Natural gas is considered “dry” when it is almost pure methane, having had most of the other commonly associated hydrocarbons removed. When other hydrocarbons are present, the natural gas is “wet,” where it forms a liquid phase during production at surface conditions. “Condensate” gases have a high content of hydrocarbon liquids and form a liquid phase in the reservoir during production, during the depletion process.

Natural gases commonly are classified according to their liquids content as either lean or rich and according to the sulfur content as either sweet or sour.

The lean and rich terms refer to the amount of potentially recoverable liquids. The ...

Table of contents

• Cover image
• Title page
• Table of Contents
• Endorsements for the Second
• Copyright
• Dedication
• Foreword
• Preface to the Second Edition
• Authors Biographical Sketches
• Chapter 1. Natural Gas Fundamentals
• Chapter 2. Natural Gas Energy Pricing
• Chapter 3. Raw Gas Transmission
• Chapter 4. Basic Concepts of Natural Gas Processing
• Chapter 5. Phase Separation
• Chapter 6. Condensate Stabilization
• Chapter 7. Natural Gas Sweetening
• Chapter 8. Sulfur Recovery and Handling
• Chapter 9. Natural Gas Dehydration
• Chapter 10. Natural Gas Liquids Recovery
• Chapter 11. Natural Gas Compression
• Chapter 12. Sales Gas Transmission
• Chapter 13. Selecting the Best Gas Processing Route
• Chapter 14. Process Control Fundamentals
• Chapter 15. Process Modeling in the Natural Gas Processing Industry
• Chapter 16. Gas Processing Plant Controls and Automation
• Chapter 17. Dynamic Simulation of Gas Processing Plants
• Chapter 18. Real-Time Optimization of Gas Processing Plants
• Chapter 19. Environmental Aspects of the Natural Gas Supply Chain
• Chapter 20. Maximizing Profitability of Gas Plant Assets
• Chapter 21. Gas Plant Project Management
• APPENDIX 1. Three-Phase Flash Calculation for Hydrocarbon Systems Containing Water
• APPENDIX 2. Conversion Factors
• APPENDIX 3. Physical Properties of Fluids
• APPENDIX 4. Glossary
• Index