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The Chemistry and Technology of Petroleum
effectively driven to producing wells. In addition to adding heat, these processes provide a driving
force (pressure) to move oil to producing wells.
Thermal recovery methods include cyclic steam injection, steam flooding, and in situ combustion. The steam processes are the most advanced of all EOR methods in terms of field experience and thus have the least uncertainty in estimating performance, provided that a good reservoir
description is available. Steam processes are most often applied in reservoirs containing viscous
oils and tars, usually in place of rather than following secondary or primary methods. Commercial
application of steam processes has been under way since the early 1960s. In situ combustion has
been field tested under a wide variety of reservoir conditions, but few projects have proven economical and advanced to commercial scale.
Steam drive injection (steam injection) has been commercially applied since the early 1960s. The
process occurs in two steps: (1) steam stimulation of production wells, that is, direct steam stimulation, and (2) steam drive by steam injection to increase production from other wells (indirect steam
stimulation).
When there is some natural reservoir energy, steam stimulation normally precedes steam drive.
In steam stimulation, heat is applied to the reservoir by the injection of high-quality steam into the
produce well. This cyclic process, also called huff and puff or steam soak, uses the same well for
both injection and production. The period of steam injection is followed by production of reduced
viscosity oil and condensed steam (water). One mechanism that aids production of the oil is the
flashing of hot water (originally condensed from steam injected under high pressure) back to steam
as pressure is lowered when a well is put back on production.
When natural reservoir drive energy is depleted and productivity declines, most cyclic steam
injection projects are converted to steam drives. In some projects, producing wells are periodically
steam stimulated to maintain high production rates. Normally, stream drive projects are developed
on relatively close well spacing to achieve thermal communication between adjacent injection and
production wells. To date, steam methods have been applied almost exclusively in relatively thick
reservoirs containing viscous crude oil.
Cyclic steam injection is the alternating injection of steam and production of oil with condensed
steam from the same well or wells. Thus, steam generated at surface is injected in a well and the
same well is subsequently put back on production.
A cyclic steam injection process includes three stages. In the first stage is injection, during which a measured amount of steam is introduced into the reservoir. In the second stage
(the soak period) requires that the well be shut in for a period of time (usually several days) to
allow uniform heat distribution to reduce the viscosity of the oil (alternatively, to raise the reservoir temperature above the pour point of the oil). Finally, during the third stage, the now-mobile
oil is produced through the same well. The cycle is repeated until the flow of oil diminishes to a
point of no returns.
Cyclic steam injection is used extensively in heavy-oil reservoirs, tar sand deposits, and in some
cases to improve injectivity prior to steam flooding or in situ combustion operations. Cyclic steam
injection is also called steam soak or the huff “n” puff method.
In practice steam is injected into the formation at greater than fracturing pressure (150–1600 psi
for Athabasca sands) followed by a soak period after which production is commenced (Burger,
1978). The technique has also been applied to the California tar sand deposits and in some heavy
oil reservoirs north of the Orinoco deposits (Ballard et al., 1976). The steam flooding technique has
been applied, with some degree of success, to the Utah tar sands (Watts et al., 1982) and has been
proposed for the San Miguel (Texas) tar sands (Hertzberg et al., 1983).
In situ combustion is normally applied to reservoirs containing low-gravity oil but has been
tested over perhaps the widest spectrum of conditions of any EOR process. In the process, heat is
generated within the reservoir by injecting air and burning part of the crude oil. This reduces the
oil viscosity and partially vaporizes the oil in place, and the oil is driven out of the reservoir by a
combination of steam, hot water, and gas drive. Forward combustion involves movement of the hot
The Chemistry and Technology of Petroleum
effectively driven to producing wells. In addition to adding heat, these processes provide a driving
force (pressure) to move oil to producing wells.
Thermal recovery methods include cyclic steam injection, steam flooding, and in situ combustion. The steam processes are the most advanced of all EOR methods in terms of field experience and thus have the least uncertainty in estimating performance, provided that a good reservoir
description is available. Steam processes are most often applied in reservoirs containing viscous
oils and tars, usually in place of rather than following secondary or primary methods. Commercial
application of steam processes has been under way since the early 1960s. In situ combustion has
been field tested under a wide variety of reservoir conditions, but few projects have proven economical and advanced to commercial scale.
Steam drive injection (steam injection) has been commercially applied since the early 1960s. The
process occurs in two steps: (1) steam stimulation of production wells, that is, direct steam stimulation, and (2) steam drive by steam injection to increase production from other wells (indirect steam
stimulation).
When there is some natural reservoir energy, steam stimulation normally precedes steam drive.
In steam stimulation, heat is applied to the reservoir by the injection of high-quality steam into the
produce well. This cyclic process, also called huff and puff or steam soak, uses the same well for
both injection and production. The period of steam injection is followed by production of reduced
viscosity oil and condensed steam (water). One mechanism that aids production of the oil is the
flashing of hot water (originally condensed from steam injected under high pressure) back to steam
as pressure is lowered when a well is put back on production.
When natural reservoir drive energy is depleted and productivity declines, most cyclic steam
injection projects are converted to steam drives. In some projects, producing wells are periodically
steam stimulated to maintain high production rates. Normally, stream drive projects are developed
on relatively close well spacing to achieve thermal communication between adjacent injection and
production wells. To date, steam methods have been applied almost exclusively in relatively thick
reservoirs containing viscous crude oil.
Cyclic steam injection is the alternating injection of steam and production of oil with condensed
steam from the same well or wells. Thus, steam generated at surface is injected in a well and the
same well is subsequently put back on production.
A cyclic steam injection process includes three stages. In the first stage is injection, during which a measured amount of steam is introduced into the reservoir. In the second stage
(the soak period) requires that the well be shut in for a period of time (usually several days) to
allow uniform heat distribution to reduce the viscosity of the oil (alternatively, to raise the reservoir temperature above the pour point of the oil). Finally, during the third stage, the now-mobile
oil is produced through the same well. The cycle is repeated until the flow of oil diminishes to a
point of no returns.
Cyclic steam injection is used extensively in heavy-oil reservoirs, tar sand deposits, and in some
cases to improve injectivity prior to steam flooding or in situ combustion operations. Cyclic steam
injection is also called steam soak or the huff “n” puff method.
In practice steam is injected into the formation at greater than fracturing pressure (150–1600 psi
for Athabasca sands) followed by a soak period after which production is commenced (Burger,
1978). The technique has also been applied to the California tar sand deposits and in some heavy
oil reservoirs north of the Orinoco deposits (Ballard et al., 1976). The steam flooding technique has
been applied, with some degree of success, to the Utah tar sands (Watts et al., 1982) and has been
proposed for the San Miguel (Texas) tar sands (Hertzberg et al., 1983).
In situ combustion is normally applied to reservoirs containing low-gravity oil but has been
tested over perhaps the widest spectrum of conditions of any EOR process. In the process, heat is
generated within the reservoir by injecting air and burning part of the crude oil. This reduces the
oil viscosity and partially vaporizes the oil in place, and the oil is driven out of the reservoir by a
combination of steam, hot water, and gas drive. Forward combustion involves movement of the hot