Page 40 - Synthetic Fuels Handbook

28 CHAPTER TWO

Manufactured natural gas of this type (as opposed to naturally occurring gas) was first
brought to the United States in 1816, when it was used to light the streets of Baltimore,
Maryland. This manufactured gas was much less efficient, and less environment friendly,
than modern natural gas that comes from underground.
In 1821 in Fredonia, United States, residents observed gas bubbles rising to the surface
from a creek. William Hart, considered as America’s father of natural gas, dug there the
first natural gas well in North America (Speight, 1993, Chap. 1 and references cited therein;
Speight, 2007b). The American natural gas industry got its beginnings in this area. In 1859,
Colonel Edwin Drake (a former railroad conductor who adopted the title “Colonel” to
impress the townspeople) dug the first well. Drake hit oil and natural gas at 69 ft below the
surface of the earth.
More recently, natural gas was discovered as a consequence of prospecting for crude
oil. Natural gas was often an unwelcome by-product, as natural gas reservoirs were tapped
in the drilling process and workers were forced to stop drilling to let the gas vent freely
into the air. Now, and particularly after the crude oil shortages of the 1970s, natural gas has
become an important source of energy in the world.
Throughout the nineteenth century, natural gas was used almost exclusively as source of
light and its use remained localized because of lack of transport structures, making difficult
to transport large quantities of natural gas through long distances. There was an important
change in 1890 with the invention of leak proof pipeline coupling but transportation of
natural gas to long distance customers did not become practical until the 1920s as a result
of technological advances in pipelines. Moreover, it was only after World War II that the
use of natural gas grew rapidly because of the development of pipeline networks and stor-
age systems.

2.2 FORMATION AND OCCURRENCE

Natural gas is found occurring with petroleum (associated gas) or alone (nonassociated
gas) in reservoirs and in coalbeds (coalbed methane) (Mokhatab et al., 2006 and references
cited therein; Speight, 2007a and references cited therein).
Natural gas often occurs in conjunction with crude oil, although natural gas reservoirs
that contain condensate (higher molecular weight hydrocarbons up to about C ) but no
10
crude oil are equally well known.
Like crude oil, natural gas has been generated over geologic time by the decay of ani-
mal remains and plant remains (organic debris) that has occurred over millions of years.
Over time, the mud and soil that covered the organic debris changed to rock and trapped
the debris beneath the newly formed rock sediments. Pressure and, to some extent, heat
(the geothermal gradient) changed some of the organic material into coal, some into oil
(petroleum), and some into natural gas. Whether or not the debris formed coal, petroleum,
or gas depended upon the nature of the debris and the localized conditions under which the
changes occurred.
Although the geothermal gradient varies from place to place, it is generally on the order
of 25 to 30°C/km (15°F/1000 ft or 120°C/1000 ft, i.e., 0.015°C/ft of depth or 0.012°C/ft of
depth), that is, approximately 1°C for every 100 ft below the surface. Thus, with increasing
depth of the reservoir, there is a tendency for crude oil to become lighter insofar as it con-
tains increasing amounts of low molecular weight hydrocarbons and decreasing amounts
of the higher molecular weight constituents.
However, there is considerable discussion about the heat to which the organic precur-
sors have been subjected. Cracking temperatures (≥300°C, ≥572°F) are not by any means
certain as having played a role in natural gas formation. Maturation of the organic debris