5 Flashcards
is a technique used in models TO SPEED UP IN DETERMING FLUID PROPERTIES which are required for every cell iteration.
Equal-spacing of PVT Data
Solution to the problems of Equal-spacing of PVT Data
• add dummy but realistic pressure entries (6050 and 6100)
• retain the shape of the curve
• add those values above the bubble point to reduce the spacing
• extrapolate and add additional entries
• equally-space your PVT data
• add values below the bubble point to
reduce the spacing
• terminate the table at 2100 psi (in some
models)
• extrapolate and add additional entries
• equally-space your PVT data
is a necessity to avoid large amounts of pressure iterations and/ or timestep reductions.
Smoothness
Multiple Sets of PVT Tables fluid properties:
• compositional
• multiple reservoirs
is used to model varying fluid properties as in either compositional effects or multiple reservoirs within a field.
Multiple Sets of PVT Tables
different fluid properties but only in one reservoir, should be used instead of beta simulator
compositional
different fluid properties but signifies different reservoirs found
multiple reservoirs
Equipment used in determining if compositional or multiple reservoirs
• oil (or gas) tracking feature
• tracer tracking
Basic concepts of Multiphase Flow
• interfacial tension
• wettability
• contact angle
_____ refers to the tension between liquids at a liquid/liquid interface
• energy per unit of surface area, or force per unit length.
• The value depends on the composition of the two fluids at the interface between phases.
Interfacial tension (IFT)
The _____ of component i can be estimated using the molecular weight Mi of component i and the empirical regression equation
parachor
_____ is the ability of a fluid phase to preferentially wet a solid surface in the presence of a second immiscible phase. The wetting, or wettability, condition in a rock/fluid system depends on IFT.
Wettability
Wettability is measured by _____. It is always measured through the more dense phase.
contact angle
Capillary pressure theory
Equilibrium between fluid phases in a capillary tube is satisfied by the relationship force up = force down. These forces are expressed in terms of the radius r of the capillary tube, the contact angle, and the interfacial tension.
Expressing Pc in terms of force down
Equivalent Height
_____ is the pressure difference across the curved interface formed by two immiscible fluids in a small capillary tube.
Capillary pressure
• The _____ provides an estimate of the height of the transition zone between immiscible phases.
• Equivalent height is inversely proportional to the difference in densities between two immiscible phases
equivalent height
In gas-oil systems, gas usually behaves as the nonwetting phase and oil is the wetting phase
Gas-Oil Capillary Pressure
A measure of the ability of a fluid to move through interconnected pore space is the concept of mobility. It is defined here for single phase and multiphase flow.
Mobility
Fluid prevent the flow of oil
Relative Permeability
______ is defined as the ratio of effective phase permeability to phase viscosity
Fluid phase mobility
_____ is defined as the mobility of the displacing fluid, behind the front, divided by the mobility of the displaced fluid, ahead of the front
Mobility Ratio
The ______ of water is the ratio of water production rate to total production rate.
fractional flow
A _____ is obtained by replacing flow rates with Darcy’s Law in the definition of fractional flow.
• it can also be simplified using phase mobility
simplified fractional flow equation
Gravity can be included in the fractional flow equation as follows. First, let us consider the two-phase flow of oil and water in a tilted linear system.
Fractional Flow Equation with Gravity
This data is commonly used in petroleum
industry
PVT Data
happens when we inject gas and water
Repressurization
Basic PVT Data requirements:
• solution-gas ratio
• formation volume factors
• viscosity
• density
• compressibility
• effective porosity
• permeability
Other PVT Data Requirements:
• Repressurization
• Equal-spacing of PVT Data
• Smoothness
• Multiple sets of PVT Table
Factors that affect repressurization:
- amount of the pressure
- amount of free gas available to be dissolved
Properties affected by repressurization:
- oil formation volume factor
- solution gas
- oil viscosity
How to define bubble point pressure in repressurization for undersaturated reservoir?
it is the pressure at which the first bubble of gas comes out of solution
How to define bubble point pressure in repressurization for undersaturated reservoir?
it is the pressure at the gas oil contact
when produced, the bubble point shall be defined as the pressure which all free gas
could be dissolved or also called as the _____
“saturation pressure”
Oil is the nonwetting phase in a water-wet reservoir
Oil-Water Capillary Pressure
basic concepts of miltiphase flow
• interfacial tension
• wettability
• contact angle
• On all interfaces between solids and fluids, and between immiscible fluids, there is a surface free energy resulting from electrical forces.
• refers to the tension between liquids at a
liquid/liquid interface
Interfacial tension (IFT)
_____ is the ability of a fluid phase to preferentially wet a solid surface in the presence of a second immiscible phase. The wetting, or wettability, condition in a rock/fluid system depends on IFT.
Wettability
Wettability is measured by _____. It is always measured through the more dense phase.
contact angle.
_____ is the pressure difference across the curved interface formed by two immiscible fluids in a small capillary tube.
Capillary pressure
Capillary Pressure Theory
Equilibrium between fluid phases in a capillary tube is satisfied by the relationship force up = force down. These forces are expressed in terms of the radius r of the capillary tube, the contact angle θ, and the interfacial tension
Expressing capillary pressure in terms of force up per unit area
Capillary Pressure and Pore Radius
Expressing Pc in terms of force down
Equivalent Height
The _____ provides an estimate of the height of the transition zone between immiscible phases.
equivalent height
_____ is inversely proportional to the difference in densities between two immiscible phases.
Equivalent height
Oil is the nonwetting phase in a water-wet reservoir.
Oil-Water Capillary Pressure
In gas-oil systems, gas usually behaves as the nonwetting phase and oil is the wetting phase
Gas-Oil Capillary Pressure
A measure of the ability of a fluid to move through interconnected pore space is the concept of mobility. It is defined here for single phase and multiphase flow.
Mobility
______ is defined as the ratio of effective phase permeability to phase viscosity.
Fluid phase mobility
_____ is defined as the mobility of the displacing fluid, behind the front divided by the mobility of the displaced fluid, ahead of the front
Mobility Ratio
The _____ of water is the ratio of water production rate to total production rate
fractional flow
A simplified fractional flow equation is obtained by replacing flow rates with Darcy’s Law
Simplified Fractional Flow Equation
Gravity can be included in the fractional flow equation. First, let us consider the two-phase flow of oil and water in a tilted linear system.
Fractional Flow Equation with
Gravity
This data is commonly used in petroleum
industry
PVT Data
happens when we inject gas and water
Repressurization
Factors that affect repressurization:
- amount of the pressure
- amount of free gas available to be dissolved
Properties affected by repressurization:
- oil formation volume factor
- solution gas
- oil viscosity
How to define bubble point pressure for undersaturated reservoir?
it is the pressure at which the first bubble of gas comes out of solution
How to define bubble point pressure for saturated reservoir?
it is the pressure at the gas oil contact
when produced, the bubble point shall be defined as the pressure which all free gas could be dissolved or also called as the ______
“saturation pressure”
