8 Questions
Which property is crucial in determining the relative permeability values of water and oil?
Capillary number of the fluids
What is the significance of capillary trapping in flow through porous media?
It causes entrapment and immobilization of fluids
How does increasing the capillary number affect fluid flow through a porous medium?
Accelerates fluid flow due to reduced capillary resistance
In a water-wet system, how does the critical oil saturation compare to the critical water saturation?
Critical oil saturation is less than critical water saturation
During the migration stage, when oil displaces water in a porous medium, what happens to the oil and water in different types of pores?
Oil invades the large pores and leaves water in the small pores
What is capillary trapping primarily responsible for in a porous medium?
Reducing relative permeability
What does relative permeability represent in relation to the permeability of a porous medium?
It represents the effective permeability for a given phase
Why is it necessary to specify fluid saturation when defining effective permeability?
Relative permeability is a function of saturation
Study Notes
Two-Phase Relative Permeabilities
- Permeability is the ability of the rock to transmit fluid, with a unit of Darcy, which is a unit of length squared.
- Absolute permeability refers to a single-phase flow in the porous media with 100% saturation.
- In two-phase flow, the porous media transmits each fluid by its effective permeability, which is a function of saturation and wettability.
Effective Permeability
- Effective permeability is a function of fluid saturation and wettability.
- It is necessary to specify the fluid saturation when defining the effective permeability of a given fluid phase.
- Multiple distinct values of relative permeability exist, corresponding to a given saturation value.
Relative Permeability
- Relative permeability is a dimensionless value representing the ratio of the effective permeability to the absolute permeability.
- Relative permeability is a function of saturation and wettability.
- It is specified at a given fluid saturation value.
Water-Wet System
- In a water-wet system, critical oil saturation is less than critical water saturation.
- Oil needs less saturation to be mobile.
- When oil displaces water, oil invades the large porous and leaves the water disconnected in the smaller porous (Connate water).
Waterflooding
- In waterflooding, water will displace the oil, leaving some of it disconnected in the large porous (Residual oil).
Problem One
- A rock has an absolute permeability of 80 mD, 13.2% porosity, 6 in length, and 1.5 in diameter.
- The rock's dry weight is 126 g, and its weight at a certain stage of the experiment is 145.7 g.
- Water and oil are injected at rates of 0.23 cm3/min and 0.52 cm3/min, respectively.
- The outlet pressure is atmospheric, and the inlet pressure is 7 psig for both water and oil.
Problem Two
- A core is 2 ft long and has a cross-sectional area of 1 ft2.
- The pressure gradient is kept constant at 50 psi/ft when the core is 100% saturated with oil.
- The flow rate is 13.29 ft3/day when the core is 100% saturated with oil.
- The viscosity of the oil is 1.2 cP.
Test your understanding of relative permeability and porosity calculations based on a given rock sample's properties and experimental data from a two-phase steady state experiment. Calculate the permeability and porosity of the rock using the provided information.
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