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Oct-2007

Unconventional crude upgrading challenges

Case studies of upgrader technology selection such as blending of syncrude with bitumen and other intermediates

Scott Sayles, KBC Advanced Technologies
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Article Summary
Rude markets are being influenced by increasing prices, stagnate discovery rates, increased world demand, and competition from alternate sources such as biofuels, coal and unconventional crude. Future crude supplies from conventional sources are anticipated to be incrementally replaced in part by the production of unconventional crude from Western Canada and Venezuela, in addition to other sources. Upgrading unconventional crude presents processing challenges both for the upgrader and the oil refinery.  These challenges require careful consideration to ensure viable operation over the project’s lifecycle. Adding to the challenge is the fact that upgraders are being expanded almost before they are in operation due to high market demand. Uncertainties surrounding construction costs, the availability of skilled manpower and the political climate put added pressure on the challenges facing upgrade operations.

What is an upgrader?
The term upgrader is used to describe the unconventional crude processing plants designed to produce crude for conventional oil refinery consumption. Raw unconventional crude from the oil sands is high in viscosity and requires dilution to enable pipeline transportation. Even if it could be delivered, conventional refineries cannot process large volumes of raw crude. Upgrader operations utilise unique technologies to produce suitable synthetic crude for conventional refinery operations. The selection and bundling of upgrading technologies determines the product’s flexibility and the range of refineries that can be serviced by a given design.

Unconventional crude is located mainly in Canada’s Alberta Province and Venezuela’s Orinoco Belt region. The unconventional crude deposits in Canada are estimated to be 1.7 trillion barrels, of which only 10% is recoverable using current technology. Recovery methods are expected to improve, increasing the quantity that is recoverable.6

The Canadian oil sands investment profile is expected to increase, peaking in 2008 or 2009 and then slowly declining until 2012.10 The investment is in line with increasing production from the current 1.0 mmbpd level to 3.0 mmbpd in 2012. The Venezuelan Orinoco Belt region is producing about 600 mbpd and is located in the centre of the country.

The effect of the recent nationalisation of foreign assets on production has not been fully assessed. However, it is anticipated that production will be reduced from current levels due to a lack of skilled foreign labour to advise and assist in the operations. Although current production may not be affected, future planned investment to expand production has been stopped and projects are not progressing.

Unconventional crude and upgraded crudequality
The quality of the unconventional crude is dependent on the production location, production method, upgrader design and final blending. Unconventional crude production from Canada differs from that in Venezuela in the use of mining for some of the production, due to the shallow depth of the deposit. When possible in Canada, steam-enhanced methods for new production are used, just as in Venezuela.

The finished product from an upgrader is generally referred to as syncrude. Recent trends in Canada due to the blending of syncrude with bitumen and other intermediates have opened the possibility of custom-blending a crude for a given refinery configuration. The synergy between the upgrader and refinery operation is recognised, with Encana Energy/ConocoPhillips and Shell Canada announcing separate projects to capture the economic benefits.10

A summary of the qualities for some of the production methods is shown in Table 1 for unconventional Canadian crudes.11 Typical Venezuela Orinoco Basin syncrude is summarised in Table 2.12 Due to the quality difference of the unconventional crudes, making each one requires different treatment options. A summary of the major quality concerns and their significance is discussed in Table 3.

Unconventional crude upgrading technology
Given the quality of unconventional crude, primary upgrades are required to convert this material into something typical refineries can process. Most upgraders receive the crude with diluents, which must be removed. The upgrader uses a conventional crude fractionation system to remove the diluents. Using a diluent with these materials may cause some incompatibility, unless the diluent is aromatic. Incompatibility between crude and diluent may cause fouling and sedimentation. Aromatic diluents are depleting in volume and replacements are being sought through processing of the bitumen. The majority of the crude (or bitumen) is produced at 975°F+ and requires further upgrades that include carbon rejection, H2 addition and solvent separation.

Carbon rejection involves processes that increase product hydrogen content by removing carbon from the feed. Examples of these processes are coking and fluid catalytic cracking, of which only coking is appropriate for this service. Delayed and fluid coking were used in the first upgrading operations. The products are high in sulphur and olefins, requiring hydrotreating to produce low-sulphur syncrude.

Recent trends include using coker products as a diluent to produce a blend suitable for pumping in the pipeline, but they require special handling at the refinery. The co-ordination between upgrading technology and refining process is one of the key factors in a successful business.

Primary H2 addition is accomplished by ebullated-bed processes. The ability to add catalyst allows these units to continue to process high containment levels. The use of these units is a technological challenge and requires specialist knowledge to operate successfully. The products have a volume swell and are lower in sulphur and nitrogen. Further treating is needed to produce finished fuels, and a significant quantity of hydrogen is required per barrel of feed. 

A recent trend is to consider the use of solvent extraction or a solvent deasphalting unit (SDU) to produce a deasphalted oil (DAO) to further upgrade and a tar for either coking or gasification. Solvent deasphalting selectively removes the asphaltenes from the oil portion of the bitumen. The concept is that the metals and other contaminants will remain in the asphalt and the deasphalted oil will be clean.
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