Natural Gasoline (Mostly Pentanes C5, Hexanes C6, and C6+): Gasoline
Blendstock, Tar Sands Diluent, Heavy Petrochemical Feedstock, and Niche Solvent
Unlike the other NGLs natural gasoline is a liquid at
ambient temperatures, but an unstable one. Its vapor pressure is between that
of natural gas condensate (drip gas) and LP gas. Natural gasoline is a mixture
of C5s (pentanes) such as pentane, isopentane (both C5H12), C6s, and a smaller
percentage of heavier C6+s. Often natural gasoline is referred to as ‘pentanes
plus.’ Natural gasoline as a petrochemical feedstock is similar to light
naptha, also a mostly C5/C6 blend, except that natural gasoline comes from
natural gas processing and light naptha comes from oil refining. Natural gasoline
and light naptha make up a small percentage of ethylene feedstock. Due to
pricing the lighter hydrocarbons, particularly ethane, are preferred feedstock
and use of natural gasoline for this purpose may decline further. Pentane
mixtures (pentane, isopentane, and cyclopentane) are used as a blowing agent
for polystyrene foam and as a polystyrene solvent. Pentanes are good solvents
for certain materials. Due to their low boiling points pentanes are used in
refrigerant blends. They are used for this purpose in geothermal power
stations. They are also used in some pesticides. Hexane (C6H14) and its isomers
are widely used as solvents as well as gasoline additives. They are used to
extract cooking oils and for glues as well. Much of natural gasoline is used as
a blendstock in gasoline. It also used to denature ethanol and sometimes to
make E85. In denaturing ethanol (making it unfit for human consumption) natural
gasoline is required to be added to make up 2% of the ethanol by volume.
Plant Condensate vs. Lease Condensate
Another name for natural gasoline is “plant condensate” to
differentiate it from “lease condensate.” They are called condensates because
they are light liquids. Plant condensate is derived from gas processing plants
while lease condensate comes from wells. Lease condensate also separates out by
gravity in the geographical low points of pipelines, where it is called “drip
gas.” Lease condensate typically has more heavies, C6 through C8. These
definitions, or naming conventions are becoming more specific and official. The
EIA recently proposed (2013) definitions are as follows:
Lease Condensate: Light
liquid hydrocarbons recovered from lease separators or field facilities at
associated and non-associated natural gas wells. Mostly pentanes and heavier
hydrocarbons. Normally enters the crude oil stream after production.
Plant Condensate: Liquid
hydrocarbons recovered at inlet separators or scrubbers in natural gas
processing plants at atmospheric pressure and ambient temperatures. Mostly
pentanes and heavier hydrocarbons, equivalent to pentanes plus.
The EIA also proposed that natural gasoline be considered a specific
subset of pentanes plus that is mostly pentanes and hexanes and that is a
commodity product.
Tar Sands Diluent
In the U.S., over 40% of natural gasoline is shipped to
Canada via truck and/or pipeline to be used as a diluent – to dilute the thick bitumen
of the tar sands so that it becomes less viscous and more liquid. It also
increases the API gravity. Basically the
diluent allows the bitumen to flow better in the pipelines. Many U.S.
refineries are set up to refine heavy crude such as this composite.
Natural Gasoline Pricing and Supply/Demand Dynamics
Natural gasoline is the highest priced of the NGLs. An NGL
composite price is also utilized in the market. NGLs are transported as “y-grade,”
also called “raw mix,” to processing plants that separate out the alkanes (C2,
C3, C4, C5+) into “purity products.” The EIA predicts near-term low to modest
growth in natural gasoline production, flat to slight consumption growth, and low
to modest growth in exports. They also point out that 2015 was a big growth
year for natural gasoline production, consumption, and export growth so up to
modest growth going forward is still good news for producers. 40% of U.S.
natural gasoline is exported to Canada, for diluent. In 2014 the Cochin
Pipeline that previously brought propane from Canada to the U.S. Midwest, was
reversed to flow natural gasoline and other light petroleum liquids to Canada.
There are interconnects coming from the Marcellus/Utica rich gas and condensate
areas. This is one of quite a few pipeline reversals brought about by increased
Appalachian NGL and nat gas supply. A recent example of a new natural gasoline
pipeline is the 42 mile Cornerstone Pipeline by Marathon currently being built
from the Utica rich gas area in Harrison County, Ohio to a refinery in Canton,
Ohio. This pipeline will also ship propane, butane, and condensate mix, in
batches.
As mentioned earlier the use of natural gasoline for
petrochem feedstock is declining. As with the other NGLs the U.S is
oversupplied but as long as there is global demand and with new and recently
activated pipelines and export facilities the exports will flow. Rusty Braziel
thinks natural gasoline could lose some demand from its use for blending into
gasoline from competition from light crude, condensate, and from diluent
recovery from heavy Canadian crude at the refineries. Naptha around the world is
in a similar position, being displaced as a petrochem feedstock by cheaper U.S.
NGLs. Natural gasoline, as well as the other NGLs, requires special processing
and special pipelines so those costs are added to the market costs when
figuring margins. These are called F & T costs, which refer to
fractionation and transportation costs.
Hydrocarbon Gas Liquids have more than doubled over the last
7 years and one question is: How much room will there be for exports in the
coming years? Modest growth in demand is predicted in the short-term. Natural
gasoline is the least abundant of the NGLs and the highest priced. Yet its continued
demand is not certain. The price of natural gasoline trends well with the the WTI index NGL composite price.
References:
Natural Gasoline – entry at Wikipedia.com
It’s a Natural Fact – Let’s Get Crackin – Part V: Natural Gasoline – by
Rusty Braziel, in RBN Energy Blog, June 17, 2012
Short-Term Energy Outlook for Hydrocarbon Gases – by Energy Information
Administration (EIA), March 16, 2016
What Are Natural Gas Liquids and How Are They Used? – by EIA, April 20,
2012
Pentane – entry at Wikipedia.org
Hexane – entry at Wikipedia.org
The Domino Effect: How the Shale Revolution is Transforming Energy
Markets, Industries, and Economies - by E. Russell Braziel
EIA Proposed Definitions for Natural Gas Liquids – Energy Information
Administration, June 14, 2013
