What is relative permeability in oil and gas?

The relative permeability reflects the capability of a specific formation to produce a combination of oil, water or gas more accurately than the absolute permeability of a formation sample, which is measured with a single-phase fluid, usually water.

What is relative permeability oil?

Relative permeability to oil (Kro), gas (Krg), or water (Krw) is the ratio of effective permeability of oil, gas, or water to absolute permeability. Relative permeability can be expressed as a number between 0 and 1.0 or as a percent. Pore type and formation wettability affect relative permeability.

What is unsteady state flow?

Unsteady-state flow is a flow that occurs while the pressures and/or rate changes with time. Reservoir conditions that are not described by the steady-state flow above are described by unsteady-state flow.

How do you calculate relative permeability?

There are essentially five means by which relative permeability data can be obtained:

1. Direct measurement in the laboratory by a steady state fluid flow process.
2. Direct measurement in the laboratory by an unsteady state fluid flow process.
3. Calculation of relative permeability data from capillary pressure data.

What is the relative permeability of water?

Relative permeability must be between zero and one. In applications, relative permeability is often represented as a function of water saturation; however, owing to capillary hysteresis one often resorts to a function or curve measured under drainage and another measured under imbibition.

What is residual oil saturation?

Residual oil saturation (Srow) is the final value of oil saturation from laboratory waterflood displacement experiments and depends primarily on the flow rate (or differential pressure) applied, permeability and capillary end effects, test methodology and (in many cases) the test laboratory.

How do you calculate permeability from relative permeability?

Relative permeability is represented as µ₀. µᵣ = µ / µ₀ (1) where µr is the relative permeability and µ is the permeability of the medium (H/m).

What is relative permeability used for?

Relative permeability and capillary pressure defines relative permeabilities as dimensionless functions of saturation with values generally ranging between 0 and 1. Relative permeability is important for estimating the flow of reservoir fluids.

What is steady state and unsteady state?

Under Steady state conditions the temperature within the system does not change with time. Conversely, under unsteady state conditions the temperature within the system does vary with time. Unsteady state conditions are a precursor to steady state conditions. No system exists initially under steady state conditions.

What is steady and unsteady state flow?

• steady: A steady flow is one in which the conditions (velocity, pressure and cross- section) may differ from point to point but DO NOT change with time. • unsteady: If at any point in the fluid, the conditions change with time, the flow is described as unsteady.

What is relative permeability in Physics?

Relative permeability = (number of lines of magnetic induction per unit area in a material)/(number of lines per unit area in a vacuum)

Why is relative permeability calculated differently for UN-steady state runs?

The relative permeability calculated during one un-steady state run at a certain saturation level could be quite different from a run performed earlier. For this reason lower confidence is placed on the actual value determined from displacement tests.

What do you know about relative permeability of coal?

Measurement of Relative Permeability of Coal: Approaches and Limitations Measurements of Mobile Water Saturation in Oil Sands Measurements of Residual Gas Saturation under Ambient Conditions Mechanisms of Capillary Displacement of Residual Oil by Gravity Assisted Inert Gas Injection Mechanisms of Heavy Oil Recovery by Low Rate Waterflooding

What is the relationship between permeability to water and oil?

During this process the permeability to oil reduces to zero along the curve ACD, and the permeability to water increases along the curve BCE. Note that there is no further production of oil from the sample after kro= 0 at point D, and so point D occurs at the irreducible oil saturation, Sor.

How do you measure relative permeability?

The outlet fluid composition and flow rate is measured and used in determining the relative permeability. Figure 2‑80-b shows an example of such a curve from an unsteady state waterflood experiment.