149
7
Recovery of Heavy Oil
and Tar Sand Bitumen
7.1 INTRODUCTION
Heavy oil and bitumen (the primary organic component of tar sand) are often defined (loosely and
incorrectly) in terms of API gravity. A more appropriate definition of bitumen, which sets it aside
from heavy oil and conventional petroleum, is based on the definition offered by the US government
as the extremely viscous hydrocarbon which is not recoverable in its natural state by conventional
oil well production methods including currently used enhanced recovery techniques (Chapter 1).
By inference, conventional petroleum and heavy oil (recoverable by conventional oil well production methods including currently used enhanced recovery techniques) are different to tar sand bitumen. Be that as it may, some stage of production, conventional petroleum (in the later stages of
recovery) and heavy oil (in the earlier stages of recovery) may require the application of enhanced
oil recovery (EOR) methods for recovery (Speight, 2009).
Initially, conventional crude oil is produced from the oil-bearing formations by drilling wells
into the formation and recovery of the oil by any one of several possible methods (Figure 7.1). The
oil is driven from the formation up through the wells (production wells) by energy stored in the
formation, such as the pressure of water, dissolved natural gas (primary recovery). If this natural
energy of the formation is expended, then energy must be injected into the formation in order to
stimulate production through addition of energy to the formation through added water and gas
(secondary recovery), followed by other more energy intensive methods of recovery (enhanced
recovery) (Figure 7.1) (Chapter 6) (Chakma et al., 1991; Islam et al., 1994). Furthermore, crude oil
recovery depends upon several factors that, in turn, are site specific and a variety of selection criteria are involved (Figure 7.2).
In reservoirs that contain heavy oil, it is often desirable to initiate EOR operations as early as
possible. In tar sand deposits that contain bitumen, it is often desirable to initiate EOR operations
as early as possible. This may mean considerably abbreviating conventional secondary recovery
operations or bypassing them altogether. Thermal floods using steam and controlled in situ combustion methods are also used. Thermal methods of recovery reduce the viscosity of the crude oil by
heat so that it flows more easily into the production well (Prats, 1986). Thus advanced techniques
are usually variations of secondary methods with a goal of improving the sweeping action of the
invading fluid.
The technologies applied to oil recovery involve different concepts, some of which can cause
changes to the oil during production. Technologies such as alkaline flooding, microemulsion
(micellar/emulsion) flooding, polymer-augmented water flooding, and carbon dioxide miscible/
immiscible flooding do not require or cause any change to the oil. The steaming technologies
may cause some steam distillation that can augment the process when the steam-distilled material
moves with the steam front and acts as a solvent for oil ahead of the steam front. Again, there is
no change to the oil although there may be favorable compositional changes to the oil insofar as
lighter fractions are recovered and heavier materials remain in the reservoir.
The technology where changes do occur involves combustion of the oil in situ. The concept of
any combustion technology requires that the oil be partially combusted and that thermal decomposition occur to other parts of the oil. This is sufficient to cause irreversible chemical and physical
changes to the oil to the extent that the product is markedly different to the oil in place indicating
7
Recovery of Heavy Oil
and Tar Sand Bitumen
7.1 INTRODUCTION
Heavy oil and bitumen (the primary organic component of tar sand) are often defined (loosely and
incorrectly) in terms of API gravity. A more appropriate definition of bitumen, which sets it aside
from heavy oil and conventional petroleum, is based on the definition offered by the US government
as the extremely viscous hydrocarbon which is not recoverable in its natural state by conventional
oil well production methods including currently used enhanced recovery techniques (Chapter 1).
By inference, conventional petroleum and heavy oil (recoverable by conventional oil well production methods including currently used enhanced recovery techniques) are different to tar sand bitumen. Be that as it may, some stage of production, conventional petroleum (in the later stages of
recovery) and heavy oil (in the earlier stages of recovery) may require the application of enhanced
oil recovery (EOR) methods for recovery (Speight, 2009).
Initially, conventional crude oil is produced from the oil-bearing formations by drilling wells
into the formation and recovery of the oil by any one of several possible methods (Figure 7.1). The
oil is driven from the formation up through the wells (production wells) by energy stored in the
formation, such as the pressure of water, dissolved natural gas (primary recovery). If this natural
energy of the formation is expended, then energy must be injected into the formation in order to
stimulate production through addition of energy to the formation through added water and gas
(secondary recovery), followed by other more energy intensive methods of recovery (enhanced
recovery) (Figure 7.1) (Chapter 6) (Chakma et al., 1991; Islam et al., 1994). Furthermore, crude oil
recovery depends upon several factors that, in turn, are site specific and a variety of selection criteria are involved (Figure 7.2).
In reservoirs that contain heavy oil, it is often desirable to initiate EOR operations as early as
possible. In tar sand deposits that contain bitumen, it is often desirable to initiate EOR operations
as early as possible. This may mean considerably abbreviating conventional secondary recovery
operations or bypassing them altogether. Thermal floods using steam and controlled in situ combustion methods are also used. Thermal methods of recovery reduce the viscosity of the crude oil by
heat so that it flows more easily into the production well (Prats, 1986). Thus advanced techniques
are usually variations of secondary methods with a goal of improving the sweeping action of the
invading fluid.
The technologies applied to oil recovery involve different concepts, some of which can cause
changes to the oil during production. Technologies such as alkaline flooding, microemulsion
(micellar/emulsion) flooding, polymer-augmented water flooding, and carbon dioxide miscible/
immiscible flooding do not require or cause any change to the oil. The steaming technologies
may cause some steam distillation that can augment the process when the steam-distilled material
moves with the steam front and acts as a solvent for oil ahead of the steam front. Again, there is
no change to the oil although there may be favorable compositional changes to the oil insofar as
lighter fractions are recovered and heavier materials remain in the reservoir.
The technology where changes do occur involves combustion of the oil in situ. The concept of
any combustion technology requires that the oil be partially combusted and that thermal decomposition occur to other parts of the oil. This is sufficient to cause irreversible chemical and physical
changes to the oil to the extent that the product is markedly different to the oil in place indicating