Natural gas processing technology and engineering design

Many environmentalists view natural gas as a natural bridge fuel between the dominant fossil fuels of today and the renewable fuels of tomorrow.. For a given amount of heat energy, burni

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Natural Gas Processing

Technology and Engineering Design

Alireza Bahadori, Ph.D.

School of Environment, Science and Engineering, Southern Cross University, Lismore, NSW, Australia

AMSTERDAM • BOSTON • HEIDELBERG • LONDON NEW YORK • OXFORD • PARIS • SAN DIEGO SAN FRANCISCO • SINGAPORE • SYDNEY • TOKYO Gulf Professional Publishing is an imprint of Elsevier

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ISBN: 978-0-08-099971-5

Dedicated to the loving memory of my parents, grandparents and to all who

contributed so much to my work over the years

About the Author

Alireza Bahadori, Ph.D is a research staff member in the School of Environment, Science & Engineering at Southern Cross University, Lismore, New South Wales, Australia He received his Ph.D from Curtin University, Western Australia For the better part of 20 years, Dr Bahadori has held various process engineering positions and involved in many large-scale projects at the National Iranian Oil Company, Petroleum Development Oman, and Clough AMEC Pty Ltd

He is the author of over 250 articles and 12 books Dr Bahadori is the recipient of the highly competitive and prestigious Australian Government’s Endeavour International Postgraduate Research award as part of his research in the oil and gas area He also received the Top-Up award from the State Government of Western Australia through Western Australia Energy Research Alliance in 2009

Dr Bahadori serves on many editorial boards for a number of journals He was honored by Elsevier as

an outstanding author for the Journal of Natural Gas Science and Engineering in 2009

xvii

The demand for primary energy is ever growing As the world struggles to find new sources of energy it

is clear that the fossil fuels will continue to play a dominant role in the foreseeable future

Many environmentalists view natural gas as a natural bridge fuel between the dominant fossil fuels

of today and the renewable fuels of tomorrow Within the hydrocarbon family the fastest growing hydrocarbon is natural gas Most estimates put the average rate of growth of 1.5–2.0%

For a given amount of heat energy, burning natural gas produces about half as much carbon dioxide, the main cause of global warming, as burning coal One of the primary consumption of natural gas is as a source for electrical generation, and it is increasingly becoming popular because it burns cleaner than oil and coal and produces less greenhouse gases This ability of natural gas raises the possibility that it could emerge as a critical transition fuel that could help to battle global warming The discovery of unconventional gas and, in particular, “Shale Gas” is perceived by many to be

a game changer

Unconventional gas refers to natural gas resources trapped in coals, shales, and tight sands These resources differ markedly from conventional gas reservoirs, in that they are diffuse, continuous accumulations of natural gas, covering very large geographical areas There are huge untapped unconventional reserves in many countries

Developing unconventional gas resources requires a different approach from exploring for and developing conventional gas reservoirs Exploration is focused on identifying productive fairways and developments that typically involve a relatively high number of wells, spread over a large development region New technologies such as horizontal drilling, fracture stimulation, and dewatering have enabled the industry to develop these resources on a commercial scale Some developments will use unconventional gas as a feedstock for liquefied natural gas (LNG) This new technology and commercial approach is reshaping gas markets throughout the world

In nature, natural gas is much more in abundance than oil Most oil economists put the natural gas reserves at least 50% higher than oil reserves at the current consumption rates

At one point in the past, natural gas used to be a regionally based fuel, frequently flared off in oil fields because it was of little use, but now with the creation of pipelines and LNG, it is now fast becoming a major international commodity

In the case of natural gas, the drilling of gas wells has some carbon footprint, as does the shipping

of the gas by pipeline or in the form of LNG A gas pipeline, for example, requires compressors, typically fueled by gas, to push the gas through the line The production of gas from shale, in addition

to requiring a relatively large number of wells, requires energy for the fracturing of the underground shale using high-pressure water

But, unlike gasoline and diesel fuel, the production of natural gas does not require an energy-consuming refinery Natural gas offers significant environmental, energy security, and economic benefits It produces lower tailpipe emissions and greenhouse gases than diesel or gasoline (mainly because methane is less carbon-rich than petroleum) Also unlike gasoline, natural gas is nontoxic, noncorrosive, and noncarcinogenic and presents no threat to soil, surface water, or groundwater The comparison of a fuel such as natural gas with renewable energy sources also requires full life cycle analysis For example, the production of corn ethanol requires energy for the operation of

xix

agricultural machinery; fertilizers, perhaps produced from natural gas; and the energy required for the extraction of alcohol from fermented corn Solar cells require energy for their manufacture And so on Then there are less tangible considerations, such as the relative impact on surface land of, say,

a wind farm compared with a gas field

So, figuring out the relative environmental impacts of different fuels can become a complex and sometimes uncertain exercise involving many different factors And as well as encompassing full life cycle environmental impacts, those factors need to include cost comparisons between different ways of minimizing undesirable emissionsdit could turn out, for example, to be more cost effective to remove pollutants from the exhaust from a cheaply produced fuel than to use an expensive fuel that does not require so much pollutant handling

But there does seem to be a widely held view that natural gas, with its relatively benign exhaust products and ready availability, will play an important role in mankind’s future energy mix, at least in the midterm

As an abundant energy resource, an affordable energy choice, a safe and reliable fuel and the cleanest burning hydrocarbon, natural gas is a foundational element in the future energy supply mix Many countries advocate for a diverse energy supply mix and the use of the right fuel in the right place

at the right time and natural gas has a very important role to play in this equation

Determining the correct size of equipment and facilities in natural gas processing is key to achieving perfect engineering design and saving on initial and operating costs Size of natural gas processing facilities is particularly critical for optimal energy efficiency When equipment is oversized, initial costs are higher, efficiency is reduced, energy costs increase, and operational costs must be compromised

In view of the above it is an essential need to write a new book related to natural gas processing These design guidelines in this book are general and not for specific design cases They were designed for engineers to do preliminary designs and process specification sheets Of course, the final design must always be guaranteed for the service selected by the manufacturing vendor, but these guidelines will greatly reduce the amount of up-front engineering hours that are required to develop the final design The guidelines in this book are a training tool for young engineers or a resource for engineers with experience

The materials used in this book are compiled from various sources including high-quality reports, articles, catalogs, and other contributions in recent years, standards and recommendations published

by several institutions

Last but not least, I would like to extend my special thanks to Elsevier editorial team especially Mrs Katie Hammon and Ms Kattie Washington for their advice and editorial assistance during production

of this book

Alireza Bahadori

January 8, 2014

Overview of Natural Gas Resources

1

Natural gas is a vital component of the world’s supply of energy It is one of the cleanest, safest, and most useful of all energy sources

As the world moves toward a lower carbon economy, gas is becoming a fuel of choice, particularly for power generation, in many regions Gas is an attractive choice for emerging economies aiming to meet rapid growth in demand in fast-growing cities as urbanization increases

The International Energy Agency (IEA) (2012) forecast that gas consumption is set to increase significantly, reflecting its greater use in power generation Gas-fired electrical generation is typi-cally characterized by lower capital expenditures, shorter construction times, greater flexibility in meeting peak demand, lower carbon emissions, and higher thermal efficiencies relative to other substitute fossil fuels

Gas-fired generation can also serve to complement renewable energy sources and help to overcome intermittency problems associated with renewable energy sources, such as solar and wind Although substantial growth in gas demand is projected to come from electrical generation, it will depend on the price of gas relative to substitute fuels, as well as domestic policy settings regarding nuclear energy and carbon pricing, and other carbon-limiting regulations or measures Factors such as commitments

to energy security, climate change, and local pollution issues will have substantial bearing on the setting and adaptation of policy

Globally, natural gas has a proved reserves life index of 64 years The IEA (2012) estimates that there are nearly 404 trillion cubic meters (tcm) (14,285 trillion cubic feet (tcf)) of remaining recov-erable resources (including all resource categories) of conventional gas worldwide, a value that is equivalent to almost 130 years of production at 2011 rates Russia, Iran, and Qatar together hold around half of the world’s proved gas reserves

The share of unconventional gas in total global gas production is projected to rise from 13% in

2009 to 22% in 2035 However, these projections are subject to a great deal of uncertainty, particularly

in regions where unconventional gas production is yet to occur or is in its infancy Environmental concerns and policy constraints also have the potential to limit unconventional gas output, particularly

in Europe The future of unconventional gas production and the extent to which it is developed over the coming decades is heavily dependent on government and industry response to environmental chal-lenges, public acceptance, regulatory and fiscal regimes, and widespread access to expertise, tech-nology, and water Given that unconventional resources are more widely dispersed than conventional resources, patterns of future gas production and trade may change This change is because all major consuming regions have estimated recoverable gas resources that are much larger than those estimated only 5 years ago

Shale gas projects have recently contributed significantly to increased production in the United States There is an expectation that rapid exploitation of shale gas developments is also likely to occur

in other regions of the world China is the only country with estimated shale gas resources greater than

CHAPTER

Natural Gas Processing http://dx.doi.org/10.1016/B978-0-08-099971-5.00001-5

© 2014 Elsevier Inc All rights reserved. 1

the United States The IEA has stated that Chinese shale reserves are the world’s largest, estimated to

be around 36.10 tcm (1275 tcf), although exploitation activities remain in their infancy due to chal-lenges not present in the United States

Natural gas develops naturally over millions of years from the carbon and hydrogen molecules of ancient organic matter trapped within geological formations Natural gas consists primarily of methane, but also ethane, propane, butane, pentanes, and heavier hydrocarbons

Natural gas is a fossil fuel Like oil and coal, this means that it is, essentially, the remains of plants and animals and microorganisms that lived millions and millions of years ago

There are many different theories as to the origins of fossil fuels The most widely accepted theory says that fossil fuels are formed when organic matter (such as the remains of a plant or animal) is compressed under the earth, at very high pressure for a very long time This type of methane is referred

to as thermogenic methane Similar to the formation of oil, thermogenic methane is formed from organic particles that are covered in mud and other sediment Over time, more and more sediment and mud and other debris are piled on top of the organic matter

This sediment and debris put a great deal of pressure on the organic matter, compressing it This compression, combined with high temperatures found deep underneath the earth (deeper and deeper under the earth’s crust, the temperature gets higher and higher), breaks down the carbon bonds in the organic matter

At low temperatures (shallower deposits), more oil is produced relative to natural gas At higher temperatures, however, more natural gas is created, as opposed to oil That is why natural gas is usually associated with oil in deposits that are 1609–3219 m (1–2 mi) below the earth’s crust Deeper deposits, very far underground, usually contain primarily natural gas, and in many cases, pure methane Natural gas can also be formed through the transformation of organic matter by tiny microor-ganisms This type of methane is referred to as biogenic methane Methanogens, tiny methane-producing microorganisms, chemically break down organic matter to produce methane These microorganisms are commonly found in areas near the surface of the earth that are void of oxygen These microorganisms also live in the intestines of most animals, including humans

Formation of methane in this manner usually takes place close to the surface of the earth, and the methane produced is usually lost into the atmosphere In certain circumstances, however, this methane can be trapped underground, recoverable as natural gas An example of biogenic methane is landfill gas Waste-containing landfills produce a relatively large amount of natural gas from the decompo-sition of the waste materials that they contain New technologies are allowing this gas to be harvested and used to add to the supply of natural gas

A third way in which methane (and natural gas) may be formed is through abiogenic processes Extremely deep under the earth’s crust, there exist hydrogen-rich gases and carbon molecules As these gases gradually rise toward the surface of the earth, they may interact with minerals that also exist underground, in the absence of oxygen

This interaction may result in a reaction, forming elements and compounds that are found in the atmosphere (including nitrogen, oxygen, carbon dioxide, argon, and water) If these gases are under

2 CHAPTER 1 Overview of Natural Gas Resources