Natural gas is one of the earth’s most valuable natural resources and a major source of the world’s energy supply. It is believed that gas was first discovered by the Chinese, who noticed gas escaping from just beneath the earth’s surface. Realizing the burning properties of this gas, the Chinese piped it though bamboo reeds over short distances and used it as a fuel source, and much later as an “eternal flame.”
Today, natural gas is among the cleanest of all fossil fuels. It is hard to visualize, as it is colorless, odorless and shapeless in its natural form. What makes it so valuable is that it is highly combustible and environmentally pretty friendly. In other words, when it is burned, it releases a lot of energy, but relatively few potentially harmful byproducts into the air.
The word “gas” conjures many connotations. Upon hearing or reading it, our minds might jump to the gas we pump into our vehicles to make them run – gasoline. Or, we might think of the gas used by heavy duty trucks and large machinery – diesel. While these commonly are referred to as “gas,” they are petroleum-based liquids with far greater and more complex carbon molecule chains. But when we’re talking about natural gas, we are referring to a different natural resource found below the earth’s surface that we use every day – to generate electricity, light our cities, heat our homes, power our factories and run our appliances. In liquid form, it is an essential raw material (also known as propane) used to fire up backyard barbeque grills, as an agent in fertilizers that produce an abundant harvest, as well as an ingredient in paints and plastics, numerous chemicals and even in medicines.
2017 Domestic natural gas consumption by sector (based on billion cubic feet )
Measuring the invisible
Although we can’t see, smell, taste or touch raw natural gas, we can measure it, and in several different ways. The energy content of natural gas (as well as other forms of energy) can be measured in British thermal units (Btus). A Btu is the amount of energy needed to heat one pound of water by one degree Fahrenheit. Natural gas is also measured in cubic feet. One cubic foot equals roughly 1,000 Btus. Another term used in measuring natural gas is billion cubic feet (Bcf); one Bcf equals around one trillion Btus. Here’s a look at the various terms and what they represent.
Natural gas conversion
|1 cf||1 cv||1,024 Btus|
|1 mcF||1,000 cf||1,024,000,000 Btus|
|1 Bcf||1 billion (1,000,000,000) cf||1.024 trillion Btus|
|1 TcF||1 trillion (1,000,000,000) cf||1,024 quadrillion Btus|
Producing natural gas
Natural gas can be produced both conventionally and unconventionally. Conventional exploration for oil and gas has been the focus of most exploration and production companies over the course of the last century. Conventionally produced gas has been drilled and gathered from depths of less than 1,000 feet to more than 35,000 feet. In recent years, advanced drilling exploration and extraction technologies have enabled greater access to deep reservoirs, although due to increased temperatures and pressures (to say nothing of the time involved) drilling at great depths is still a costly operation. However, most of the growth in supply today comes from shale, or a combination of other lower-quality reservoir rocks.
Shale is a fine-grained, sedimentary rock that is composed of clay and tiny particles of other minerals, such as quartz and calcite, and organic materials derived from plants and animals that died while the precursor sediments were being deposited. “Shale gas” is locked in small pores inside the shale, which must be hydraulically fractured to release the gas (or oil, as the case may be). Gas is also being produced from “tight gas sandstone” – low-quality, mostly non-porous and impermeable rock. Gas is also associated with coal beds, and “coal bed methane” has been targeted at several locations around the world, most notably in the U.S., China and Australia.