Reservoir KNW3

displacement efficiency factors

• capillary pressure

• relative permeability

interfacial tension

the work that is required to increase the interfacial area [N/m] = tension between two fluids

surface tension

the tension of a liquid-air interface

capillary pressure

the pressure difference across the interface between two immiscible fluids.

wetting phase

When two immiscible fluids are in contact with a solid surface, one fluid is usually attracted more strongly than the other fluid. The more strongly attracted phase is the called the wetting phase.

wetting classification

• 𝜃 = 0 → we have a complete water wet system

• 𝜃 < 90° → water wet

• 𝜃~90° → the system is intermediate or neutral wet

• 𝜃 > 90° → oil wet system

wetting factors

• temp

• fluid composition

Effect of Heterogeneity and Permeability on primary drainage of Pc

• lower permeability = smaller pores => higher Pc

• higher heterogeneity = wider range of pore => wider range of Pc

hysteresis

the result differs depending on whether water is displacing oil

reasons of hysteresis

• contact angle hysteresis

• trapping mechanism

• irreversible changes of interfacial area

trapping curve

the relationship between the initial and residual fluid phase saturation

MICP measurement

1. Sample is placed in the equipment and the sample chamber is evacuated

2. Pressure is increased in steps and the mercury intrusion volume is measured

3. Measurement up to 60,000 psi mercury pressure

miscible displacement

both fluids are miscible in all proportions

immiscible displacement

in ideal immiscible displacement, there is no mutual phase participation and an interfacial tension (IFT) between the fluids

relative permeability

the ratio of the effective permeability of that phase to the absolute permeability

effective permeability

a measure of the ability of that phase to flow in the presence of other fluid phases.

absolute permeability

the measurement of the permeability, conducted when a single fluid, or phase, is present in the rock

Effect of Wettability on Relative Permeability

• Water wet → more favorable oil mobility

• Oil wet → lower residual oil saturation

Wettability

property influencing the interactions between reservoir rock components and pore filling fluids, affecting fluid distribution and flow dynamics during production processes.

Water wet

the rock/mineral surface is coated with water, while oil and gas occupy the central position of the largest pores

Oil wet

the rock/mineral surface is coated with oil, while water occupy the central position of the largest pores