PETE 311 Petrophysics Final Review

Explain 2 methods to correct errors due to end effect in the relative permeability function.

-Measure saturation far away from the outflow face - Use high flow rates to make error negligible

Name 2 factors that affect the permeability of rocks and explain how they affect it.

-The shape and size of the grains affects permeability, large and round grains lead to higher permeabilities than small irregular grains. -Lamination by minerals such as shale as muscovite act as barriers lowering vertical permeability. -Cementation can lower permeability in certain locations of the pore space. -Fracturing and solution increase the permeability of a rock.

slope of q/A vs pressure gradient

-k/u

Name 2 factors that affect laboratory measurement of permeability and how they affect it.

1) Adding water may lead to clay swelling which decreases permeability. 2) Fracturing of the core will increase permeability.

Briefly describe the operation of a sonic log.

A transmitter is placed above various receivers in a well. As the transmitter generates sound the receivers mark the time at which it is received. The elapsed time between receiver receptions is then used to calculate densities and porosities.

Explain the difference between effective permeability and absolute permeability.

Absolute permeability represents the permeability of a medium that is only saturated with one phase. Effective permeability refers to the permeability of a specific phase in a medium saturated by more than one immiscible fluid.

Explain one advantage and disadvantage of the retort distillation method for calculating saturation.

Advantage: Results are obtained fast. Disadvantage: Destroys core and provides faulty oil saturation.

Which of the following determines how quickly ground water flows?

All of them: -water pressure -permeability -elevation

Name two factors that affect the amount of adsorbed gas and how.

As moisture increases adsorbed gas decreases. As temperature increases adsorbed gas decreases. As pressure increases adsorbed gas increases.

Briefly explain how dolomitization affects porosity.

Dolomitization increases porosity when dolomite is created by replacing the Ca ions in Calcite with Mg ions.

Define Drainage and Imbibition and give an example

Drainage: The increase of the non-wetting fluid saturation. (Gas injection of a water wet reservoir) Imbibition: Increase of the wetting fluid saturation. (Waterflooding a water wet reservoir)

Describe elastic deformation and Hooke's law.

Elastic deformation is a deformation that isn't permanent and will return to its original shape if load is released. Hooke's law is the linear relationship between stress and strain.

At constant temperature the density of the gas decreases with an increase in pressure.

False

Clastic sedimentary rocks consist primarily of carbonate minerals.

False

In highly cemented materials and most carbonates effective porosity is equal to total porosity.

False

In uniaxial strain compaction test, pressure is applied in all directions and strain occurs in response in all directions.

False

Porosity __________ as the range of particle size decreases and __________ as compaction increase.

Increases, Decreases

Briefly explain the mercury injection method for capillary pressure, give advantages and disadvantages.

Injecting mercury, the nonwetting fluid, and air , wetting fluid. Pressure required to inject additional mercury is measured. NWT Saturation is then calculated with mercury volumes and pore volume. Advantages: Fast Accurate Disadvantages: Ruins Core Conversion to reservoir values required.

Give 2 examples of non-darcy flow and briefly explain.

Non Darcy flow may occur if flow of the fluid is turbulent which violates the conditions. At low temperature gas slippage will occur creating non-darcy flow.

Define phase saturation using equations and words.

Phase saturation of a fluid is the fraction of total pore volume that is occupied by the specific phase. S(o)=Vo/Vp

Briefly explain how the presence of gas affects porosity readings in a density log and in a sonic log.

The presence of gas in density logs leads to a porosity value that is too high. Sonic logs aren't affected by the presence of gas.

Give a qualitative definition of isothermal compressibility.

The relative volume change of matter per unit pressure change under isothermal conditions of constant temperature.

Define total porosity and effective porosity using equations and words.

Total Porosity is the total pore volume over the bulk volume. Effective porosity is the volume of interconnected pores over the bulk volume. Total Porosity= Vp/Vb Effective Porosity= Vp(interconnected)/Vb

A water wet system will exhibit greater oil recovery under water flooding.

True

Oil moves easier in water wet rocks.

True

Describe difference between absorption and absorption.

Unlike absorption, in which gas particles enter the volume of the solid, in adsorption the gas particles only stick to the surface area.

Wettability

Wettability is the tendency of one fluid to spread on or adhere to a solid surface in the presence of other immiscible fluids.

Define Anistropy

When horizontal and vertical permeabilities are not equal.

Name three factors that affect the resistivity of rocks

cementation clay rheology geometry

Fluid flows

from areas of high potential to areas of low potential.