Permeability in Geology

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Questions and Answers

What is the principle behind the unsteady state method in flow testing?

Saturating the core with water before using gas for displacement.

Injecting a displacing fluid at a constant rate while measuring outlet volumes. (correct)

Monitoring the pressure drop at constant volume.

Maintaining constant pressure while observing flow rates.

What effect arises from saturation discontinuity at the outflow face during a flow test?

Imbibition process

End effect (correct)

Relative permeability fluctuation

Capillary action

Which process involves decreasing the saturation of the wetting phase in a core sample?

Imbibition

Desaturation (correct)

Saturation maintenance

End effect management

What is the significance of the hysteresis effect in relative permeability measurements?

It affects the accuracy of saturation history duplication. Signup and view all the answers

What is the primary method to determine saturation history effects on relative permeability?

Gravimetric analysis using weights Signup and view all the answers

What happens during imbibition in a reservoir flow test?

Increasing saturation of the wetting phase. Signup and view all the answers

What is crucial for preventing end effect during flow tests according to the method used?

Inserting a dummy porous disc Signup and view all the answers

What defines a relative permeability curve in the context of fluid displacement?

The change in permeability with varying saturation levels. Signup and view all the answers

What is effective permeability?

The permeability of a rock to a specific fluid at saturations less than 100%. Signup and view all the answers

How is relative permeability defined?

As a quantity ranging from zero to the maximum absolute permeability. Signup and view all the answers

What happens to the relative permeability of the wetting phase as its saturation decreases?

It decreases rapidly. Signup and view all the answers

In a water-oil system, which phase is generally considered the wetting phase?

Water Signup and view all the answers

What is the likely effect of having a high viscosity for the non-wetting phase?

It could reduce the overall flow of the non-wetting phase. Signup and view all the answers

What is required to apply relative permeability data successfully?

Confirmation of base permeability definition used. Signup and view all the answers

What is a key consideration when measuring effective permeability in a lab?

Multiple fluids can affect the measurements significantly. Signup and view all the answers

Which of the following describes what relative permeability curves represent?

The permeability of each fluid phase relative to the total permeability of the rock. Signup and view all the answers

What does region A represent in terms of fluid saturation?

Pendular, immobile oil phase and mobile water phase Signup and view all the answers

What happens to oil saturation as water saturation increases past a certain point?

Oil becomes discontinuous at Sw Signup and view all the answers

In a two-phase relative permeability measurement, what is the primary purpose of the up-stream plug?

It serves as a mixing head for the injected fluid Signup and view all the answers

Which saturation state is characterized by small, isolated groups of pores for the non-wetting phase?

Insular saturation Signup and view all the answers

What is the main characteristic of finicular saturation for both wetting and non-wetting phases?

Both phases exhibit continuous flow paths Signup and view all the answers

What methodology is described for measuring two-phase relative permeability?

Steady state method using modified Penn-State method Signup and view all the answers

What indicates the highest relative permeability for a wetting phase in relation to the non-wetting phase?

Continuous flow paths at finicular saturation Signup and view all the answers

In reservoir engineering, which condition defines the discontinuity of oil in the presence of increasing water saturation?

When the oil threads break and form isolated pores Signup and view all the answers

Study Notes

Effective Permeability

Effective permeability is the permeability of a rock to a specific fluid when other fluids are also present (saturation less than 100%).
Measured in darcies or millidarcies.
Equivalent to absolute permeability in terms of dimensional analysis.
Represented by k_o, k_w, and k_g for oil, water, and gas respectively.
Individual values can range from 0 to the absolute permeability (k).

Relative Permeability

Relative permeability is a dimensionless quantity.
Defined as the ratio of effective permeability to absolute permeability (k_e/k).
Represented by k_ro, k_rw, and k_rg for oil, water, and gas respectively.
Values range between 0 and 1.

Laboratory Measurement of Permeability

Steady-State Method: A method to measure two-phase relative permeability. The apparatus (modified Penn-State) confines the sample between cores for uniform properties.
Unsteady-State Method: Faster method, saturates with one fluid then displaces with another fluid, measures pressure drops and fluid volumes.

Calculation of Effective and Relative Permeability

Absolute permeability can be calculated when the core is 100% saturated with one fluid. This method uses data where saturation is 100%.
Relative permeability is calculated with flow rate, area, viscosity, pressure differences, and length.

Hysteresis Effects

Saturation history affects relative permeability.
Drainage (oil displacing water) and imbibition (water displacing oil) processes demonstrate hysteresis.
Imbibition process saturates the core with water, then displaces water with oil.
Drainage process fills the core with oil, then displaces oil with water.

Relative Permeability Curves

Curves show the relationship between relative permeability and saturation.
Wetting phase (e.g. water) shows rapid decrease in relative permeability with decreasing saturation.
Non-wetting phase (e.g. oil) shows a more gradual change in relative permeability.
The curves are important for predicting multiphase flow behavior in reservoirs.

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Description

This quiz explores the concepts of effective and relative permeability in rocks, essential for understanding fluid flow in geology. Learn about their measurements, definitions, and the laboratory techniques used to determine these properties. Perfect for students studying geology or petroleum engineering.