154
The Chemistry and Technology of Petroleum
7.2.1 tAr sAnd mInIng
The bitumen occurring in oil sand deposits poses a major recovery problem. The material is notoriously immobile at formation temperatures and must therefore require some stimulation (usually by
thermal means) in order to ensure recovery. Alternately, proposals have been noted that advocate
bitumen recovery by solvent flooding or by the use of emulsifiers. There is no doubt that with time
one or more of these functions may come to fruition, but for the present the two commercial operations rely on the mining technique.
The oil mining method of recovery has received considerable attention since it was chosen as
the technique of preference for the only two commercial bitumen recovery plants in operation in
North America. In situ processes have been tested many times in the United States, Canada, and
other parts of the world and are ready for commercialization. There are also conceptual schemes
that are a combination of both mining (above-ground recovery) and in situ (nonmining recovery)
methods.
Engineering a successful oil mining project must address a number of items because there must
be sufficient recoverable resources, the project must be conducted safely, and the project should be
engineered to maximize recovery within economic limits. The use of a reliable screening technique
is necessary to locate viable candidates. Once the candidate is defined, this should be followed by
an exhaustive literature search covering the local geology, drilling, production, completion, and
secondary and tertiary recovery operations.
The reservoir properties, which can affect the efficiency of heavy oil or bitumen production by
mining technology, can be grouped into three classes:
1. Primary properties, that is, those properties that have an influence on the fluid flow and
fluid storage properties and include rock and fluid properties, such as porosity, permeability, wettability, crude oil viscosity, and pour point
2. Secondary properties, that is, those properties that significantly influence the primary
properties, including pore size distribution, clay type, and content
3. Tertiary properties, that is, those other properties that mainly influence oil production
operation (fracture breakdown pressure, hardness, and thermal properties) and the mining
operations (e.g., temperature, subsidence potential, and fault distribution)
There are also important rock mechanical parameters of the formation in which a tunnel is
to be mined and from where all oil mining operations will be conducted. These properties are
mostly related to the mining aspects of the operations, and not all are of equal importance in their
influence on the mining technology. Their relative importance also depends on the individual
reservoir.
Many of the candidate reservoirs for application of improved oil mining are those with high
oil saturation resulting from the adverse effects of reservoir heterogeneity. Faulting, fracturing,
and barriers to fluid flow are features that cause production of shallow reservoirs by conventional
methods to be inefficient. Production of heterogeneous reservoirs by underground oil production
methods requires consideration of the manner in which fractures alter the flow of fluids.
In a highly fractured formation with low matrix permeability, the fluid conductivity of the fracture system may be many times that of the matrix rock. In a highly fractured reservoir with low
matrix permeability and reasonably high porosity, the fracture system provides the highest permeability to the flow of oil but the matrix rock contains the greater volume of the oil in place. The
rate of the flow of oil from the matrix rock into the fracture system, the extent and continuity of the
fracture system, and the degree to which the production wells effectively intersect the fracture system determine the production rate. Special consideration must be given to these factors in predicting
production rates in fractured reservoirs. Under favorable circumstances, higher production rates
The Chemistry and Technology of Petroleum
7.2.1 tAr sAnd mInIng
The bitumen occurring in oil sand deposits poses a major recovery problem. The material is notoriously immobile at formation temperatures and must therefore require some stimulation (usually by
thermal means) in order to ensure recovery. Alternately, proposals have been noted that advocate
bitumen recovery by solvent flooding or by the use of emulsifiers. There is no doubt that with time
one or more of these functions may come to fruition, but for the present the two commercial operations rely on the mining technique.
The oil mining method of recovery has received considerable attention since it was chosen as
the technique of preference for the only two commercial bitumen recovery plants in operation in
North America. In situ processes have been tested many times in the United States, Canada, and
other parts of the world and are ready for commercialization. There are also conceptual schemes
that are a combination of both mining (above-ground recovery) and in situ (nonmining recovery)
methods.
Engineering a successful oil mining project must address a number of items because there must
be sufficient recoverable resources, the project must be conducted safely, and the project should be
engineered to maximize recovery within economic limits. The use of a reliable screening technique
is necessary to locate viable candidates. Once the candidate is defined, this should be followed by
an exhaustive literature search covering the local geology, drilling, production, completion, and
secondary and tertiary recovery operations.
The reservoir properties, which can affect the efficiency of heavy oil or bitumen production by
mining technology, can be grouped into three classes:
1. Primary properties, that is, those properties that have an influence on the fluid flow and
fluid storage properties and include rock and fluid properties, such as porosity, permeability, wettability, crude oil viscosity, and pour point
2. Secondary properties, that is, those properties that significantly influence the primary
properties, including pore size distribution, clay type, and content
3. Tertiary properties, that is, those other properties that mainly influence oil production
operation (fracture breakdown pressure, hardness, and thermal properties) and the mining
operations (e.g., temperature, subsidence potential, and fault distribution)
There are also important rock mechanical parameters of the formation in which a tunnel is
to be mined and from where all oil mining operations will be conducted. These properties are
mostly related to the mining aspects of the operations, and not all are of equal importance in their
influence on the mining technology. Their relative importance also depends on the individual
reservoir.
Many of the candidate reservoirs for application of improved oil mining are those with high
oil saturation resulting from the adverse effects of reservoir heterogeneity. Faulting, fracturing,
and barriers to fluid flow are features that cause production of shallow reservoirs by conventional
methods to be inefficient. Production of heterogeneous reservoirs by underground oil production
methods requires consideration of the manner in which fractures alter the flow of fluids.
In a highly fractured formation with low matrix permeability, the fluid conductivity of the fracture system may be many times that of the matrix rock. In a highly fractured reservoir with low
matrix permeability and reasonably high porosity, the fracture system provides the highest permeability to the flow of oil but the matrix rock contains the greater volume of the oil in place. The
rate of the flow of oil from the matrix rock into the fracture system, the extent and continuity of the
fracture system, and the degree to which the production wells effectively intersect the fracture system determine the production rate. Special consideration must be given to these factors in predicting
production rates in fractured reservoirs. Under favorable circumstances, higher production rates