p.1
Permeability Definition and Measurement
What is the equation used for calculating permeability for liquids?
k = (ΔV / ΔT) * (μ / (P_o - P_i)) * (L / A)
p.1
Permeability Definition and Measurement
What does ΔV represent in the permeability equation for liquids?
The volume of liquid flowed in time ΔT (cm³).
p.6
Well Productivity and Permeability Relationship
What is the relationship between well productivity and permeability?
Well productivity is proportional to permeability and the interval of production, with a constant fluid viscosity.
p.5
Relative Permeability and Fluid Saturation
What is trapped gas saturation?
The immobile fraction of gas in a reservoir.
p.6
Permeability Classification of Reservoir Rocks
How does the permeability of sandstone compare to that of carbonate in relation to porosity?
Sandstone permeability is well controlled by porosity, while carbonate shows a more diffuse cloud indicating other factors also influence permeability.
p.4
Relative Permeability and Fluid Saturation
What is absolute permeability?
The maximum permeability of rock when it contains only one fluid.
p.7
PoroPerm Relationships and Cross-Plots
What can be plotted together to form a map of poroperm relationships?
Poroperm trends for different lithologies.
p.7
Permeability Classification of Reservoir Rocks
Why do fractured rocks have high permeability despite low porosity?
Because they form very connected networks that allow efficient passage of fluids.
p.7
Relative Permeability and Fluid Saturation
What type of porosity is primarily found in clay cemented sandstones?
Micro-porosity filled with chemically and physically bound water.
p.2
Factors Affecting Permeability
What factors influence the connectivity of pore spaces?
Size and shape of grains, grain size distribution, and capillary forces.
p.1
Permeability Definition and Measurement
What does P_o and P_i represent in the permeability equations?
P_o is the outlet fluid pressure and P_i is the inlet fluid pressure (both in atmospheres absolute).
p.7
Factors Affecting Permeability
What is the significance of pore throats in relation to permeability?
Smaller pore throats constrain fluid flow more than larger pore throats.
p.9
Empirical Approximations for Calculating Permeability
What does the Wyllie and Rose equation I calculate?
k = 2.25 × (S_wi)^2 / (100 - φ), where k is permeability (mD), φ is porosity (fraction), and S_wi is irreducible water saturation (fraction).
p.8
Directional Permeability and Its Implications
How is permeability described in terms of direction?
It is a directional quantity affected by heterogeneous or directional properties of pore geometry.
p.6
PoroPerm Relationships and Cross-Plots
Why are poroperm cross-plots best constructed for defined lithologies?
To avoid a disappointing cloud of data and to reveal individual trends.
p.11
Permeability Definition and Measurement
What does permeability measure in rocks?
The ease with which the rock permits the passage of fluids.
p.3
Klinkenberg Effect and Gas Slippage
What is the Klinkenberg Effect?
It refers to the overestimation of permeability due to gas slippage in smaller pores at low pressures.
p.3
Klinkenberg Effect and Gas Slippage
How is gas slippage corrected in permeability measurements?
By measuring permeability at multiple pressure differences and plotting apparent permeability against the reciprocal of mean pressure.
p.2
Permeability Definition and Measurement
What does 'k' represent in the context of permeability?
The permeability of the sample (millidarcy, mD).
p.1
Permeability Definition and Measurement
What is the significance of μ in the permeability equations?
It represents the dynamic viscosity of the fluid (centipoise, cP).
p.4
Relative Permeability and Fluid Saturation
What happens to effective and relative permeability as fluid saturation decreases?
Both effective and relative permeability decrease as the saturation of that fluid decreases.
p.11
Empirical Approximations for Calculating Permeability
What experimental setup did Darcy use to develop his permeability formula?
A vertical sand pack through which water flowed under gravity.
p.11
Empirical Approximations for Calculating Permeability
What is the significance of the difference in fluid pressures in Darcy's experiments?
It can be calculated from the heights of manometers, providing the density of the fluid is known.
p.11
Empirical Approximations for Calculating Permeability
What is Darcy's formula used for?
To calculate permeability based on flow rate and pressure differences.
p.9
Empirical Approximations for Calculating Permeability
What is the equation for permeability in a solution channel?
k = 2.0 × d^2 × 10^8, where k is permeability (D) and d is channel diameter (inches).
p.9
Empirical Approximations for Calculating Permeability
What does the Van Baaren equation calculate?
k = 3.64 × (D_d)^2 / (3.64 + C), where k is permeability (mD), φ is porosity (fraction), D_d is modal grain size (microns), and C is sorting index.
p.8
Empirical Approximations for Calculating Permeability
What has research shown about the relationship between permeability and pore geometry?
There is no fundamental law linking the two, only empirical approximations.
p.8
Factors Affecting Permeability
What is the role of pore geometry in permeability?
Pore geometry affects permeability in a complex way.
p.3
Permeability Definition and Measurement
Why is measuring permeability with liquids considered straightforward?
Because laminar flow and incompressibility are almost always met at surface geological conditions.
p.10
Permeability Definition and Measurement
What are the two systems of units that can be used for permeability measurements?
c.g.s system and S.I. units.
p.11
Fluid Flow Equations for Liquids and Gases
What fundamental physical law governs fluid flow in rocks?
The Navier-Stokes equation.
p.11
Relative Permeability and Fluid Saturation
How does permeability differ for single and multiple fluid phases?
Permeability to a single fluid is different from permeability with multiple fluid phases; relative permeability is used for multiple phases.
p.3
Well Productivity and Permeability Relationship
Why is the Klinkenberg permeability important in the oil industry?
It approximates the permeability of the sample measured with liquid flowing through it.
p.3
Factors Affecting Permeability
What can happen if the Klinkenberg correction is ignored?
It can lead to corrections of up to 100%, especially in tight rocks.
p.4
Relative Permeability and Fluid Saturation
What is the significance of threshold saturation for fluid movement?
There is a threshold value of saturation needed for a fluid to move, indicating that fluids can become trapped in the rock.
p.9
Empirical Approximations for Calculating Permeability
What does the Morris and Biggs equation represent?
k = C × (S_wi)^2, where k is permeability (mD), φ is porosity (fraction), S_wi is irreducible water saturation (fraction), and C is a constant.
p.8
Factors Affecting Permeability
What does permeability depend on?
Porosity, connectivity of flow paths, and pore geometry of the rock.
p.5
Relative Permeability and Fluid Saturation
What is residual oil saturation?
The amount of oil that remains in a reservoir after production, typically less than 20%.
p.8
PoroPerm Relationships and Cross-Plots
What is the significance of grain size in permeability?
Grain size influences permeability as shown in poroperm cross-plots.
p.5
Relative Permeability and Fluid Saturation
What is irreducible water saturation?
The immobile fraction of water in a reservoir.
p.3
Permeability Definition and Measurement
What is the primary distinction made in permeability measurements?
Between the use of gaseous fluids and liquids.
p.6
PoroPerm Relationships and Cross-Plots
What does a plot of permeability against porosity typically show?
A clear trend with some scatter due to other influences on permeability.
p.5
Relative Permeability and Fluid Saturation
How does oil saturation affect permeability?
As oil saturation increases, permeability to oil increases while permeability to water decreases, and vice versa.
p.4
Permeability Definition and Measurement
What is the nature of permeability in rocks?
Permeability is generally anisotropic due to depositional effects and the in-situ stress field.
p.5
Well Productivity and Permeability Relationship
Why is it important to avoid water production in oil reservoirs?
Water production does not generate revenue and increases water cut, reducing the permeability of the reservoir to oil.
p.3
Klinkenberg Effect and Gas Slippage
What complication arises when using gas as the fluid in permeability measurements?
Gas is a compressible fluid, leading to slower travel at high pressure compared to low pressure.
p.4
Permeability Definition and Measurement
How does permeability differ when measured parallel versus perpendicular to bedding?
Permeability perpendicular to bedding is about a third to half of that parallel to bedding.
p.5
Well Productivity and Permeability Relationship
What controls a well's productivity?
Permeability and the interval of the borehole that is open for production.
p.6
Factors Affecting Permeability
What can high porosities in carbonates indicate about permeability?
High porosities may not lead to high permeabilities if the pore spaces are poorly connected.
p.5
Well Productivity and Permeability Relationship
What is the relationship between well productivity and permeability?
Higher permeability generally leads to higher well productivity.
p.11
Fluid Flow Equations for Liquids and Gases
What assumption simplifies the equations for flow in rocks?
Assuming that the flow is laminar.
p.10
Permeability Definition and Measurement
How is permeability defined in terms of a sample's dimensions and flow conditions?
One darcy is the permeability of a sample 1 cm long with a cross-sectional area of 1 cm², causing a fluid with a dynamic viscosity of 1 poise to flow at a rate of 1 cm³/s under a pressure difference of 1 dyne/cm².
p.4
Relative Permeability and Fluid Saturation
What are effective permeabilities?
Permeabilities of each fluid present in the rock when two or more fluids are present, always less than absolute permeability.
p.3
Klinkenberg Effect and Gas Slippage
What does the Klinkenberg permeability represent?
The permeability at which gas behaves like a near perfect liquid under infinite pressure.
p.10
Permeability Definition and Measurement
What is the relationship between darcy and square meters?
1 D = 0.9869 × 10^-12 m².
p.4
Relative Permeability and Fluid Saturation
How are relative permeabilities defined?
Relative permeabilities are expressed as a fraction of the absolute permeability of the rock to either of the fluids present at 100% saturation.
p.2
Factors Affecting Permeability
How does porosity affect permeability?
Higher porosity generally leads to higher permeability.
p.10
Permeability Definition and Measurement
Why is the darcy often considered too large for practical geological applications?
Because it is commonly too large, so the millidarcy (mD) is used.
p.1
Permeability Definition and Measurement
What is the equation used for calculating permeability for gases?
k = (ΔV / ΔT) * (μ / (P_o - P_i)) * (L / A) (adjusted for gas pressures).
p.7
Factors Affecting Permeability
How does grain size affect permeability?
Smaller grain sizes produce smaller pores and pore throats, which constrain fluid flow more than larger grains.
p.2
Permeability Classification of Reservoir Rocks
What is the permeability range for granites, shales, and clays?
From 1 nanodarcy (nD) to 1 microdarcy (μD).
p.7
PoroPerm Relationships and Cross-Plots
What does the poroperm cross-plot for a carbonate reservoir show?
It shows the relationship between grain size, porosity, and permeability for each core taken.
p.9
Empirical Approximations for Calculating Permeability
What is the Kozeny-Carman equation used for?
k = (φ^3) / (c × (1 - φ)^2), where k is permeability (mD), φ is porosity (fraction), c is a constant, and d is median grain size (microns).
p.3
Factors Affecting Permeability
How does permeability correction vary with rock type?
The correction is generally smaller for higher permeability rocks with larger pores.
p.4
Relative Permeability and Fluid Saturation
What is the relationship between oil saturation and its mobility?
Oil becomes immobile until its saturation is about 20%.
p.2
Permeability Definition and Measurement
How is permeability measured in the laboratory?
By flowing a fluid of known viscosity through a core sample and measuring the pressure drop or flow rate.
p.9
Empirical Approximations for Calculating Permeability
What factors are included in the fracture permeability equation?
k = 0.544 × h^3 × w^8 × 10^8, where k is permeability (D), h is fracture width (inches), and w is fracture aperture (inches).
p.9
Empirical Approximations for Calculating Permeability
What is the RGPZ equation used for?
k = 1000 × (d^2) / (φ^2), where k is permeability (mD), d is weighted geometric mean grain size (microns), φ is porosity (fraction), and m is Archie cementation exponent.
p.7
Permeability Classification of Reservoir Rocks
What is the relationship between grain size and permeability?
Rocks with smaller grain sizes have smaller permeabilities than those with larger grain sizes.
p.1
Permeability Definition and Measurement
What does L represent in the permeability equations?
The length of the sample (cm).
p.1
Permeability Definition and Measurement
What is the area (A) in the context of permeability calculations?
The area of the sample (cm²).
p.9
Empirical Approximations for Calculating Permeability
What is the formula for the Timur equation?
k = 4.4 × (S_wi)^2 × 136, where k is permeability (mD), φ is porosity (%), and S_wi is irreducible water saturation (%).
