This paper presents fundamental information necessary to understand and appreciate the concept of total gas energy in a natural gas pipeline. That is, to be able to converse with peers within the natural gas industry and understand basic concepts and terminology.

Discussed is the historical transition from volumetric measurement to total gas energy including some of the basic terminology, physics, measurement, as well as the reasons for changes in methodologies. Included is industry acceptance of new concepts and regulations involving custody transfer as well as the instrumentation and systems involved in traditional and newer, more progressive forms of gas measurement.

Where Does Natural Gas Come From?

Millions of years ago, the remains of plants and animals decayed and built up in thick layers. This decayed matter from plants and animals is called organic material — it was once alive. Over time, the mud and soil changed to rock, covered the organic material, and trapped it beneath the rock. Pressure and heat changed some of this organic material into coal, some into oil (petroleum), and some into natural gas — tiny bubbles of odorless gas. The main ingredient in natural gas is methane, a gas (or compound) composed of one carbon atom and four hydrogen atoms.

Figure 1 shows an Ocean bed at 300 to 400 million years ago. Tiny sea plants and animals died and were buried on the ocean floor. Over time, they were covered by layers of sand and silt.