Natural Gas Processing

Technology and Engineering Design

Alireza Bahadori

• Publisher: Gulf Professional Publishing
• Year: 2014
• ISBN:
  9780124202047
• Topic: Tecnología e ingeniería
• Subtopic: Combustibles fósiles

Natural gas is considered the dominant worldwide bridge between fossil fuels of today and future resources of tomorrow. Thanks to the recent shale boom in North America, natural gas is in a surplus and quickly becoming a major international commodity. Stay current with conventional and now unconventional gas standards and procedures with Natural Gas Processing: Technology and Engineering Design. Covering the entire natural gas process, Bahadori's must-have handbook provides everything you need to know about natural gas, including:

• Fundamental background on natural gas properties and single/multiphase flow factors
• How to pinpoint equipment selection criteria, such as US and international standards, codes, and critical design considerations
• A step-by-step simplification of the major gas processing procedures, like sweetening, dehydration, and sulfur recovery
• Detailed explanation on plant engineering and design steps for natural gas projects, helping managers and contractors understand how to schedule, plan, and manage a safe and efficient processing plant

• Covers both conventional and unconventional gas resources such as coal bed methane and shale gas
• Bridges natural gas processing with basic and advanced engineering design of natural gas projects including real world case studies
• Digs deeper with practical equipment sizing calculations for flare systems, safety relief valves, and control valves

Chapter 1

Overview of Natural Gas Resources

Abstract

This chapter provides an overview of both conventional and unconventional natural gas resources. Unconventional gas resources, including tight gas, coal bed methane (coal seam gas), gas hydrates, and shale gas, are discussed. Hydraulic fracturing (HF), a process undertaken on a well after it has been drilled to depth, is presented. Hydraulic fracturing involves pumping fluids (mostly water) under controlled pressure into the well bore to fracture the rock formations that hold gas accumulation, thereby allowing the gas to migrate out of the rock and be extracted through the well.

Keywords

Coal bed methane; Coal seam gas; Conventional gas resource; Gas hydrates; Hydraulic fracturing; Natural gas; Shale gas resources; Tight gas resources; Unconventional gas resources

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 typically 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 recoverable 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 challenges, public acceptance, regulatory and fiscal regimes, and widespread access to expertise, technology, 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 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 challenges not present in the United States.

1.1. The formation of natural gas

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 microorganisms. 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 decomposition 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 very high pressure as they move toward the surface of the earth, they are likely to form methane deposits,...