Note the double bond in this compound linking the two carbon atoms.
Although all crude oils contain the compounds described above, rarely are
there two crude oils with the same characteristics. This is so because every crude
oil from whatever geographical source contains different quantities of the various
compounds that make up its composition. Crude oils produced in Nigeria, for
example, would be high in cyclic paraffin content and have a relatively low
specific gravity. Crude drilled in some of the fields in Venezuela on the other
hand would have a very high specific gravity and a low content of material
boiling below 350
C. Table 1 summarizes some of the crude oils from various
locations.
Worthy of note in the table is the difference in the character of the various crudes
that enables refiners to improve their operation by selecting the best crude or crudes
that meet their product marketing requirements. For example, where a refining
product slate demands a high quantity of “no-lead” gasoline and a modest outlet for
fuel oils, then a crude oil feed such as Hassi Messaoud would be a prime choice. Its
selection provides a high naphtha yield with a high naphthene content as catalytic
reforming feedstock. Fuel oil in this case also is less than 50 % of the barrel. The
Iranian light crude would also be a contender but for the undesirably high metal
content of the fuel oil (residuum).
In the case of a good middle of the road crude, Kuwait or the Arabian crude oils
offer a reasonably balanced product slate with good middle distillate quality and
yields.
For bitumen manufacture and lube oil manufacture, the South American crude
oils are formidable competitors. Both major crudes from this area, Bachequero, the
heavier crude, and Tia Juana, the lighter, are highly acidic (naphthenic acids) which
enhances bitumen and lube oil qualities. There is a problem with these crude oils
however as naphthenic acids are very corrosive in atmospheric distillation columns,
particularly in the middle distillate sections. Normal distillation units may require
relining of sections of the tower with 410 stainless steel and/or injection of caustic if
extended processing of these crude oils is envisaged.
Refiners often mix selected crude oils to optimize a product slate that has been
programmed for the refinery. This exercise requires careful examination of the
various crude assays (data compilation) and modeling the refinery operation to set
the crude oil mix and its operating parameters.
The Crude Oil Assay
The crude oil assay is a compilation of laboratory and pilot plant data that define the
properties of the specific crude oil. At a minimum, the assay should contain a
distillation curve for the crude and a specific gravity curve. Most assays however
contain data on pour point (flowing criteria), sulfur content, viscosity, and many
other properties. The assay is usually prepared by the company selling the crude oil;
it is used extensively by refiners in their plant operation, development of product
schedules, and examination of future processing ventures. Engineering companies
8
D.S.J. Jones
Although all crude oils contain the compounds described above, rarely are
there two crude oils with the same characteristics. This is so because every crude
oil from whatever geographical source contains different quantities of the various
compounds that make up its composition. Crude oils produced in Nigeria, for
example, would be high in cyclic paraffin content and have a relatively low
specific gravity. Crude drilled in some of the fields in Venezuela on the other
hand would have a very high specific gravity and a low content of material
boiling below 350
C. Table 1 summarizes some of the crude oils from various
locations.
Worthy of note in the table is the difference in the character of the various crudes
that enables refiners to improve their operation by selecting the best crude or crudes
that meet their product marketing requirements. For example, where a refining
product slate demands a high quantity of “no-lead” gasoline and a modest outlet for
fuel oils, then a crude oil feed such as Hassi Messaoud would be a prime choice. Its
selection provides a high naphtha yield with a high naphthene content as catalytic
reforming feedstock. Fuel oil in this case also is less than 50 % of the barrel. The
Iranian light crude would also be a contender but for the undesirably high metal
content of the fuel oil (residuum).
In the case of a good middle of the road crude, Kuwait or the Arabian crude oils
offer a reasonably balanced product slate with good middle distillate quality and
yields.
For bitumen manufacture and lube oil manufacture, the South American crude
oils are formidable competitors. Both major crudes from this area, Bachequero, the
heavier crude, and Tia Juana, the lighter, are highly acidic (naphthenic acids) which
enhances bitumen and lube oil qualities. There is a problem with these crude oils
however as naphthenic acids are very corrosive in atmospheric distillation columns,
particularly in the middle distillate sections. Normal distillation units may require
relining of sections of the tower with 410 stainless steel and/or injection of caustic if
extended processing of these crude oils is envisaged.
Refiners often mix selected crude oils to optimize a product slate that has been
programmed for the refinery. This exercise requires careful examination of the
various crude assays (data compilation) and modeling the refinery operation to set
the crude oil mix and its operating parameters.
The Crude Oil Assay
The crude oil assay is a compilation of laboratory and pilot plant data that define the
properties of the specific crude oil. At a minimum, the assay should contain a
distillation curve for the crude and a specific gravity curve. Most assays however
contain data on pour point (flowing criteria), sulfur content, viscosity, and many
other properties. The assay is usually prepared by the company selling the crude oil;
it is used extensively by refiners in their plant operation, development of product
schedules, and examination of future processing ventures. Engineering companies
8
D.S.J. Jones