146
The Chemistry and Technology of Petroleum
One other aspect of transportation is the shipment of bitumen separated from tar sand (or the
whole oil sand or even bitumen-enriched oil sand, produced by, say, a less efficient once-through
hot water separation) in trucks or trains. Currently, economic constraints related to the amount of
material that would have to be moved to enable even a nominal conversion or upgrading operation
to run continuously (hazards of weather and mechanical constraints notwithstanding) have caused
these types of operation to be downgraded in priority.
Finally, it is also possible for bitumen to be emulsified and shipped (by pipeline) as an emulsion.
This particular idea has received some attention, especially in regard to bitumen recovery by aqueous
flooding methods. The idea is to produce the bitumen from the formation as an oil-in-water emulsion
at the remote site followed by shipping of the emulsion to an oil recovery and upgrading site.
Natural gas is also transported by seagoing vessels. The gas is either transported under pressure at
ambient temperatures (e.g., propane and butanes) or at atmospheric pressure but with the cargo under
refrigeration (e.g., LPG). For safety reasons, petroleum tankers are constructed with several independent tanks so that rupture of one tank will not necessarily drain the whole ship, unless it is a severe
bow-to-stern (or stern-to-bow) rupture. Similarly, gas tankers also contain several separate tanks.
Natural gas presents different transportation requirements problems. Before World War II its use
was limited by the difficulty in transporting it over long distances. The gas found in oil fields was frequently burned off; and unassociated (dry) gas was usually abandoned. After the war new steel alloys
permitted the laying of large-diameter pipes for gas transport in the United States. The discovery of the
Groningen field in the Netherlands in the early 1960s and the exploitation of huge deposits in Siberia in
the 1970s and the 1980s led to a similar expansion of pipelines and natural gas use in Europe.
Because of its lower density natural gas is much more expensive to ship than crude oil. Most natural
gas moves by pipeline, but in the late 1960s tanker shipment of cryogenically LNG began, particularly
from the producing nations in the Pacific to Japan. Special alloys are required to prevent the tanks
from becoming brittle at the low temperatures (−161°C, −258°F) required to keep the gas liquid.
Thus, the means by which natural gas is transported depends upon several factors: (1) the physical characteristics of the gas to be transported, whether in the gaseous or the liquid phase, (2) the
distance over which the gas will be moved, (3) features such as the geological and geographic characteristics of the terrain, including land and sea operations, (4) the complexity of the distribution
systems, and (5) the environmental regulations that are relevant to the mode of transportation.
In the last case, such factors as the possibility of pipeline rupture as well as the effect of the
pipeline itself on the econosystems need to be addressed. In general, and aside from any economic
factors, it is possible to construct and put in place a system capable of transporting natural gas in the
gaseous or liquid phase that allows system flexibility.
There are many such pipeline systems throughout the world and the United States (Considine,
1977). However, natural gas pipeline companies must meet environmental and legal standards.
Economic standards are also a necessity: it would be extremely foolhardy (and economic suicide!)
if a company were to construct several pipelines when one such system would suffice. Construction
of a pipeline system involves not only environmental and legal considerations but also compliance
with the regulations of the local, state, and/or federal authorities.
In general, many of the pipeline systems available use pipe material up to 48 in. in diameter
(although lately larger diameter pipe has become more favorable) and sections of pipe may be up to
40 ft long. Protective coatings are usually applied to the pipe to prevent corrosion of the pipe from
outside influences.
The gas pressure in long-distance pipelines may vary up to 5000 psi, but pressures up to 1500 psi
are more usual. To complete the pipeline, it is necessary to install a variety of valves and regulators
that can be opened or closed to adjust the flow of gas. The system must also be capable of shut down of
any section in which an unexpected rupture may be caused by natural events (such as weather) or even
by unnatural events (such as sabotage). Most of the valves or regulators in the pipeline system can now
be operated by remote control, so that in the event of a rupture the system can be closed down. This is
especially valuable where it may take a repair crew considerable time to reach the site of the breakdown.
The Chemistry and Technology of Petroleum
One other aspect of transportation is the shipment of bitumen separated from tar sand (or the
whole oil sand or even bitumen-enriched oil sand, produced by, say, a less efficient once-through
hot water separation) in trucks or trains. Currently, economic constraints related to the amount of
material that would have to be moved to enable even a nominal conversion or upgrading operation
to run continuously (hazards of weather and mechanical constraints notwithstanding) have caused
these types of operation to be downgraded in priority.
Finally, it is also possible for bitumen to be emulsified and shipped (by pipeline) as an emulsion.
This particular idea has received some attention, especially in regard to bitumen recovery by aqueous
flooding methods. The idea is to produce the bitumen from the formation as an oil-in-water emulsion
at the remote site followed by shipping of the emulsion to an oil recovery and upgrading site.
Natural gas is also transported by seagoing vessels. The gas is either transported under pressure at
ambient temperatures (e.g., propane and butanes) or at atmospheric pressure but with the cargo under
refrigeration (e.g., LPG). For safety reasons, petroleum tankers are constructed with several independent tanks so that rupture of one tank will not necessarily drain the whole ship, unless it is a severe
bow-to-stern (or stern-to-bow) rupture. Similarly, gas tankers also contain several separate tanks.
Natural gas presents different transportation requirements problems. Before World War II its use
was limited by the difficulty in transporting it over long distances. The gas found in oil fields was frequently burned off; and unassociated (dry) gas was usually abandoned. After the war new steel alloys
permitted the laying of large-diameter pipes for gas transport in the United States. The discovery of the
Groningen field in the Netherlands in the early 1960s and the exploitation of huge deposits in Siberia in
the 1970s and the 1980s led to a similar expansion of pipelines and natural gas use in Europe.
Because of its lower density natural gas is much more expensive to ship than crude oil. Most natural
gas moves by pipeline, but in the late 1960s tanker shipment of cryogenically LNG began, particularly
from the producing nations in the Pacific to Japan. Special alloys are required to prevent the tanks
from becoming brittle at the low temperatures (−161°C, −258°F) required to keep the gas liquid.
Thus, the means by which natural gas is transported depends upon several factors: (1) the physical characteristics of the gas to be transported, whether in the gaseous or the liquid phase, (2) the
distance over which the gas will be moved, (3) features such as the geological and geographic characteristics of the terrain, including land and sea operations, (4) the complexity of the distribution
systems, and (5) the environmental regulations that are relevant to the mode of transportation.
In the last case, such factors as the possibility of pipeline rupture as well as the effect of the
pipeline itself on the econosystems need to be addressed. In general, and aside from any economic
factors, it is possible to construct and put in place a system capable of transporting natural gas in the
gaseous or liquid phase that allows system flexibility.
There are many such pipeline systems throughout the world and the United States (Considine,
1977). However, natural gas pipeline companies must meet environmental and legal standards.
Economic standards are also a necessity: it would be extremely foolhardy (and economic suicide!)
if a company were to construct several pipelines when one such system would suffice. Construction
of a pipeline system involves not only environmental and legal considerations but also compliance
with the regulations of the local, state, and/or federal authorities.
In general, many of the pipeline systems available use pipe material up to 48 in. in diameter
(although lately larger diameter pipe has become more favorable) and sections of pipe may be up to
40 ft long. Protective coatings are usually applied to the pipe to prevent corrosion of the pipe from
outside influences.
The gas pressure in long-distance pipelines may vary up to 5000 psi, but pressures up to 1500 psi
are more usual. To complete the pipeline, it is necessary to install a variety of valves and regulators
that can be opened or closed to adjust the flow of gas. The system must also be capable of shut down of
any section in which an unexpected rupture may be caused by natural events (such as weather) or even
by unnatural events (such as sabotage). Most of the valves or regulators in the pipeline system can now
be operated by remote control, so that in the event of a rupture the system can be closed down. This is
especially valuable where it may take a repair crew considerable time to reach the site of the breakdown.