Chemical Technology April 2016

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6 Chemical Technology • April 2016
Processing
light tight oil
by Tim Olsen, Emerson Process Management
Opportunity crudes have been around for many
years, but not until recently has the abundance
of these discounted crudes changed the behav-
iour of refiners to shift away from their usual feedstocks.
Tight oil, sometimes referred to as light tight oil or LTO,
is also an opportunity crude oil from shales or other low
permeability formations. Although most of the news about
tight oil production is in the United States, tight oil is not
unique to this region and is found throughout the world;
see Figure 1 with the map of basins with assessed shale
oil and shale gas formations, as of September 2015 (US
Energy Information Administration, EIA). Production from
tight oil formations requires the same hydraulic fracturing
and often uses the same horizontal well technology used
in the production of shale gas.
The main challenges with processing opportunity crudes
include: crude blending to match refiner’s configuration and
processing capabilities, crude switch disturbances, fouling
and accelerated fouling from incompatible crude blends,
corrosion, and energy balancing across the crude unit
pre-heat exchangers. In addition to the above mentioned
issues, light tight oils also have challenges typically related
to H2S (treated with amine-based H2S scavengers), paraffin
waxes, significant quantities of filterable solids, variability in
API gravity from the same source, and catalyst performance
related to cold flow properties.
Heat exchanger fouling is one of the biggest challenges
in refinery operations. Many refiners still use a spreadsheet
with monthly calculations typically based on incomplete
data to evaluate heat exchanger condition, with manual
checks on individual bundles just prior to a turnaround to
determine if cleaning is required. The traditional approach
to monitor heat exchanger fouling through spreadsheets
with manual entry of temperatures and pressures was usu-
ally sufficient before the increase in crude blending from
opportunity crudes such as tight oil. However, some crude
oil blends are not compatible, leading to unanticipated
accelerated fouling.
Because tight oils tend to be lighter, they need to be
blended with other crude oils to get the right balance for
best utilisation of existing downstream units. Having a more
consistent feed to the crude unit also allows for the oppor-
tunity to optimise operation. If light tight oil feeds are not
blended, the lighter oil can bottleneck the crude overhead
and downstream naphtha processing units, and limit pro-
duction for bottom of the barrel processing. Some refiners
are blending more than two crudes to get the right balance
of feed qualities which creates unknown issues with crude
incompatibilities. When crudes are incompatible, acceler-
ated fouling occurs in the crude unit pre-heat exchanger
train due to asphaltene precipitation. Accelerated fouling
can lead to additional energy costs with the crude unit fired
The refining industry has changed over
the past few years with an ample supply of
opportunity crude oils available.