as.Field.Processing.doc>dome is circular in outline, and the anticline is long and narrow. Oil and / or gas moved or migrated upward through the porous strata where it was trapped by the sealing cap rock and the shape of the structure.
. Faulted Reservoirs: reservoirs are formed by shearing and offsetting of the strata (faulting), as shown in Figure 3.2.4. <file:///C:Documents%20and%20SettingsLoner-XPРабочий%20столНастеAbdel-Aal.et.al.Petroleum.and.Gas.Field.Processing.doc> The movement of the nonporous rock opposite the porous formation containing the oil / gas creates the sealing. The tilt of the petroleum-bearing rock and the faulting trap the oil / gas in the reservoir.
3.2.3. A reservoir formed by folding of rock layers
3.2.4. A cross section of a faulted reservoir.
. Salt-Dome Reservoirs: type of reservoir structure, which takes the shape of a dome, was formed due to the upwardof large, impermeable salt dome that deformed and lifted the overlying layers of rock. As shown inFigure 3.2.5, <file:///C:Documents%20and%20SettingsLoner-XPРабочий%20столНастеAbdel-Aal.et.al.Petroleum.and.Gas.Field.Processing.doc> petroleum is trapped between the cap rock and an underlying impermeable rock layer, or between two impermeable layers of rock and the salt dome.
. Unconformitiestype of reservoir structure, shown in Figure 3.2.6, was formed as a result of an unconformity where the impermeable cap rock was laid down across the cutoff surfaces of the lower beds.
3.2.5. Section in a salt-dome structure.
3.2.6. A reservoir formed by unconformity
. Lense-Type Reservoirs: this type of reservoir, the petroleum-bearing porous formation is sealed by the surrounding, nonporous formation. Irregular deposition of sediments and shale at the time the formation was laid down is the probable cause for this abrupt change in formation porosity. An example of this type of reservoirs is shown in Figure 3.2.7.
3.2.7 An example of a sandstone lense-type reservoir.
. Combination Reservoirs: this case, combinations of folding, faulting, abrupt changes in porosity, or other conditions that create the trap, from this common type of reservoir.
Reservoir Drive Mechanisms
the time oil was forming and accumulating in the reservoir, the pressure energy of the associated gas and water was also stored. When a well is drilled through the reservoir and the pressure in the well is made to be lower than the pressure in the oil formation, it is that energy of the gas, or the water, or both that would displace the oil from the formation into the well and lift it up to the surface. Therefore, another way of classifying petroleum reservoirs, which is of interest to reservoir and production engineers, is to characterize the reservoir according to the production (drive) mechanism responsible for displacing the oil from the formation into the wellbore and up to the surface.are three main drive mechanisms:. Solution-Gas-Drive Reservoirs: on the reservoir pressure and temperature, the oil in the reservoir would have varying amounts of gas dissolved within the oil (solution gas). gas would evolve out of the oil only if the pressure is lowered below a certain value, known as thebubble point pressure, which is a property of the oil. When a well is dr...
