7 Flashcards
_____ is quantified by comparing initial and final volumes in place. It takes into account volumetric and displacement efficiencies.
Recovery efficiency
The different aspects of recovery efficiency are defined and then combined to form _____
overall recovery efficiency
_____ accounts for the efficiency of recovering mobile hydrocarbon.
• defined as the ratio of mobile oil to original oil in place at reservoir conditions
Displacement efficiency
_____ can approach 100% if residual oil saturation can be driven to zero.
Displacement efficiency
One of the goals of enhanced oil recovery processes such as micellar-polymer flooding or miscible flooding is to _____
reduce residual oil saturation and increase displacement efficiency.
volumetric factors are needed to determine overall recovery efficiency – this is based on _____
areal efficiency and sweep efficiency
_____ must account for both volumetric and displacement
effects. It is therefore defined as the product of volumetric sweep efficiency and displacement efficiency
Overall recovery efficiency
variety of patterns
• line drive (direct & staggered)
• three & two-spot pattern
• four-spot pattern
• five-spot pattern
• irregular five-spot pattern layout
• seven-spot pattern
• nine-spot pattern
• peripheral flood pattern
The location of injection wells depends on factors such as:
• Reservoir structure
• Injected fluid type
• Displacement mechanism
_____ is an estimate of the area being drained by a production well.
Well spacing
A reduction in well spacing requires an _____, which is the number of production wells in a specified area.
increase in the density of production wells
Well density can be increased by drilling additional wells in the space between wells in a process called _____. It is an effective means of altering flow patterns and improving recovery efficiency, but can be more expensive than a fluid displacement process.
infill drilling
Optimum performance may be achieved with the patterns defined by controlling the rates of injectors and producers. These calculations can be performed analytically if we assume:
• The displacing and displaced fluids are incompressible
• The mobility ratio is one
• The reservoir has uniform properties
______ is the mobility of the displacing fluid behind the front divided by the mobility of the displaced fluid ahead of the front.
Mobility ratio
Mobility ratios less than or equal to one are considered _____, while mobility ratios greater than one are considered ______.
favorable ; unfavorable
_____ often occur when gas is displacing oil or water is displacing high viscosity oil.
Unfavorable mobility ratios
An example of a flood with a favorable mobility ratio is the _____
displacement of a low-viscosity oil by water
varying model parameters to determine the effect on model result
Sensitivity Testing
BOAST
Black Oil Applied Simulation Tool
MRST
The MATLAB Reservoir Simulation Toolbox
OPM
The Open Porous Media
finds the pressure distribution for a given time step first then calculates the saturation distribution for the same time step isothermal.
(BOAST) Black Oil Applied Simulation Tool
The toolbox consists of two main parts: a core offering basic functionality and single and two-phase solvers, and a set of add-on modules offering more advanced models, viewers and solvers.
(MRST) The MATLAB Reservoir Simulation Toolbox
______ provides a set of open-source tools centered around the simulation of flow and transport of fluids in porous media.
(OPM) The Open Porous Media
Using finer grids in running the model
sensitivity testing
A combination of experience and common sense.
HEURISTIC GRIDDING RULES
When strong directional permeability trends _____ exist, the grid system should be parallel to these trends since most models allows flow only across the cell interfaces.
ANISOTROPY
_____ (from well to well) best approximates field conditions (requiring the least amount of relative permeability adjustment to match history).
FLOW VIA DIAGONALS
_____ (either areal or cross-sectional) to minimize the number of cells not in the simulated region; these cells have no porosity.
Rotate your grid
In orienting the grid system, if faults are _____ to the axes, it is much simpler to define them.
parallel
If individual data is important, a ______
minimum of three cells should exist between wells
Wells should be located as close as possible to the _____; results will not vary significantly as long as the well is in the central-half of the pore volume of the cell.
center of the cell
A common sense rule, but one often overlooked, is to _____ when laying out the original grid.
plan ahead for future wells
_____ should not vary in pore volume by more than a factor of two for ease of timestep solution.
surrounding cells
_____ models are usually easier to define than areal considerations.
CROSS-SECTIONAL GRIDS
heuristic gridding rules for cross-sectional grids
• Geologically varying strata
• Existing well completions
• Future well completions
• GOC and WOC
_____ presents a special problem in that the size of the aquifer is usually huge when compared to the reservoir.
Modeling an aquifer
_____ may be modeled using boundary modifications
Aquifer
Using an exceptionally long cell length would invalidate _____
transmissibility
______ incorrect fluid movement due to the gridblock effect.
numerical dispersion
we must be concerned with _____ due to the fact that unless a very fine grid is employed, several cells will contain only part of the reservoir.
partial cells
must be calculated to fit the grid
cell property determination
is accomplished by modifying transmissibilities, pore volumes, and rates
partial field modeling
allows the use of a fine grid within a coarse grid, as for example, defining well cells in a field-wide model
Local Grid Refinement (LGR)
allows the use of non-orthogonal shapes in describing reservoirs
Corner Point Gridding
pakopya
a. yes
b. no
yes lang ang sagot
