Natural Gas Liquids: Lesser Known Side Of The Shale Revolution

 | Oct 17, 2016 12:36AM ET

Many people think of fossil fuels as coal, crude oil and natural gas, with the nastiness of their toxic emissions lying in that order. Among the less colorful comments during the second Presidential debate was Hillary Clinton’s reference to natural gas as a “bridge” fuel, sitting between today’s reliance on hydrocarbons and a future of renewables (solar, wind and so on). Methane (or, to use its Chemical symbols, CH4 since it combines four hydrogen atoms with one Carbon atom), is colloquially known as natural gas, and is the simplest and cleanest burning fuel. It is helping the U.S. limit its carbon footprint since as the Shale Revolution has made it plentiful domestically, it’s replacing far dirtier coal as the fuel of choice for power plants.

Natural Gas Liquids (NGLs) are a set of hydrocarbons that lie between Methane (also called “Dry” Gas”) and the lightest blends of crude oil (such as Naphtha). Methane is often extracted mixed with NGLs and crude oil. It’s used for residential gas stoves and heating, electricity generation and, when chilled to -260F turns to Liquid Natural Gas (LNG) in which form it can be transported by ship. The mix of NGLs and oil found in a well with methane affects the value of the play since after being separated from the dry gas the NGLs can be put to other purposes. “Wet” gas wells that contain more NGLs often generate more attractive returns as NGLs fetch higher prices.

The energy infrastructure business provides the ability to gather and process the mix of hydrocarbons into Gas, NGLs and Crude Oil. Dry gas then is piped to customers, crude oil heads to storage & refiners, and NGLs are sent to fractionation plants. By exploiting their different boiling points the NGLs are then separated into into their components: Ethane (C2H6), Propane (C3H8), Butane(C4H10), Iso-Butane (C4H10 with tertiary carbon), and natural gasoline (C5+). Although NGLs are gases, their production is usually expressed in barrels a day, like oil. The conversion is based on energy equivalence, so a barrel of an NGL has the same energy output measured in BTUs (British Thermal Units) as a barrel of oil. Nothing gets moved in barrels anymore, but the industry has retained it as a common measure of volume.

Although often ignored, NGLs are significant. The U.S currently produces 3.6MMBD (Millions of Barrels a Day) of NGLs. Compare this with U.S shale oil production of 4.5MMBD and it’s a big business in its own right.

Ethane is most readily found with methane, although it’s also a by-product of refining crude oil. Some portion of ethane can be left in the gas stream for residential and commercial use if its price doesn’t justify separating it out. However, by far its most important use is as a feedstock for petrochemical plants to produce polyethylene, the most commonly created organic compound in the world. It winds up as plastics in various forms with thousands of ultimate uses across consumer products as packaging, containers, plastic bags carpeting and clothing (including swimwear). As the U.S. steps up its production of ethane, the low price caused by America’s shift towards energy independence is leading to a substantial cost advantage in polyethylene production. Currently the U.S produces 1.3MMBD of ethane.

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Credit for the first industrial synthesis of polyethylene generally goes to Imperial Chemical Industries (ICI) in the UK in 1933.

Propane exists as a gas at temperatures above -44F, but turns to a liquid under pressure when it occupies 1/270th of the space, allowing it to be stored in propane tanks and bottles (such as the one under your gas grill outside). It has many other uses as a fuel from heating homes (particularly mobile homes which often lack a permanent connection to the local gas supply) to drying crops. The U.S produces 1.15MMBD of Propane. Butane is the fuel in pocket lighters, the propellant in aerosols, and is blended with gasoline during the summer to reduce pollution (it’s the vapors that come out while you’re pumping). Iso-butane is primarily used to increase the octane in gasoline while making it cleaner burning. The U.S produces 300MMBD each of butane and i-butane.

The chart below shows forecast growth in NGLs (referred to as “Natural Gas Plant Liquids”) provided by the U.S. Energy Information Administration (EIA) in their 2016 Annual Energy Outlook.