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Terms and Vocabulary

fresh water

пресная вода

fluid flow equation

уравнение течения флюидов (Дарси)

primary (matrix) permeability

первичная проницаемость

secondary (induced) permeability

вторичная проницаемость

fracturing

трещиноватость

conduit

выводящий канал

tight reservoir

непроницаемый пласт

directional (anisotropic) permeability

неодинаковая по различным направлениям (анизотропная \ двоякопреломляющаяся) проницаемость

anisotrophy

анизотропия

subsequent compaction

последовательное \ постепенное уплотнение

vertical permeability

вертикальная проницаемость

horizontal permeability

горизонтальная проницаемость

be interbedded

впластованный (залегающий между пластами)

immiscible

несмешивающийся

interface

поверхность контакта

equilibrium

равновесие

curvature

искривление

(non-)wetting

(не)смачивание

preferential wetting

избирательное смачивание

saturation

насыщенность

(non-)wetting phase

(не)смачивающая фаза

18. Read the text “Permeability” and do the exercises. Permeability

Permeability is easiness with which fluid can move through porous rock.

High permeability means numerous channels for oil and gas migration.

A reservoir rock must have the ability to allow petroleum fluids to flow through its interconnected pores. This rock property is termed permeability. The permeability of a rock depends on the effective porosity. Therefore, permeability is affected by the rock grain size, grain shape, grain size distribution (sorting), grain packing and the degree of consolidation and cementation. Permeability is affected by the type of clay present, especially where fresh water is present.

French engineer Henry Darcy developed a fluid flow equation that since has become one of the standard mathematical tools of the petroleum engineer. One Darcy is a relatively high permeability and the permeability of most reservoir rock is less than one Darcy. The common measure of rock permeability is in millidarcies (mD) or μm2 in SI units.

The term absolute permeability is used if the porous rock is 100% saturated with a single fluid (phase), such as water, oil or gas. When two or more fluids are present in the rock, the permeability of the rock to the flowing fluid is called effective permeability.

Because fluids interfere with each other during their movement through the pore channels in the rock, the sum of effective permeability will always be less than the absolute permeability. The ratio of effective permeability of one phase during multiphase flow to the absolute permeability is the relative permeability to that phase.

Classification of permeability

Petroleum reservoirs can have primary permeability, which is also known as the matrix permeability and secondary permeability. Matrix permeability originated at the time of deposition and lithification (hardening) of sedimentary rocks. As with secondary (induced) porosity, secondary permeability resulted from the alteration of the rock matrix by: compaction, cementation, fracturing and solution. Whereas, compaction and cementation generally reduce the primary permeability; fracturing and solution tend to increase. In some reservoir rocks, particularly low-porosity carbonates, secondary permeability provides the main conduit for fluid migration.

Fig. 4. Effects of clay cementing material on porosity and permeability

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