Wettability
This document was uploaded by user and they confirmed that they have the permission to share it. If you are author or own the copyright of this book, please report to us by using this DMCA report form. Report DMCA
Overview
Download & View Wettability as PDF for free.
More details
- Words: 631
- Pages: 12
Immiscible Phases • Earlier discussions have considered only a single fluid in the pores – porosity – permeability • Saturation: fraction of pore space occupied by a particular fluid (immiscible phases) Sw+So+Sg=1 – • When more than a single phase is present, the fluids interact with the rock, and with each other
DEFINITION OF INTERFACIAL TENSION • Interfacial (boundary) tension is the energy per unit area (force per unit distance) at the surface between phases • Commonly expressed in milliNewtons/meter (also, dynes/cm)
DEFINITION OF WETTABILITY • Wettability is the tendency of one fluid to spread on or adhere to a solid surface in the presence of other immiscible fluids. • Wettability refers to interaction between fluid and solid phases. • Reservoir rocks (sandstone, limestone, dolomite, etc.) are the solid surfaces • Oil, water, and/or gas are the fluids
DEFINITION OF ADHESION TENSION • Adhesion tension is expressed as the difference between two solid-fluid interfacial tensions.
AT = σ os − σ ws = − σ ow cos θ
• A negative adhesion tension indicates that the denser phase (water) preferentially wets the solid surface (and vice versa). • An adhesion tension of “0” indicates that both phases have equal affinity for the solid surface
CONTACT ANGLE Oil
σ ow Oil
σ os
θ
Water
Oil
σ ws
σ os
Solid
AT = adhesion tension, milli-Newtons/m or dynes/cm)
The contact angle, θ , measured through the denser liquid phase, defines which fluid wets the solid surface.
θ = contact angle between the oil/water/solid interface measured through the water, degrees σos = interfacial energy between the oil and solid, milli-Newtons/m or dynes/cm σws = interfacial energy between the water and solid, milli-Newtons/m or dynes/cm σ = interfacial energy (interfacial tension) between the oil and water, milli-Newtons/m or dynes/cm
OIL-WET RESERVOIR ROCK • Reservoir rock is oil-wet if oil preferentially wets the rock surfaces. • The rock is oil-wet under the following conditions: ∀ σ os > σ ws • AT > 0 (i.e., the adhesion tension is positive) • 90° < θ < 180° If θ is close to 180°, the rock is considered to be “strongly oil-wet”
OIL-WET ROCK Water
σ ow Oil
θ
σ os
σ ws
σ os Solid
• 90° < θ < 180° • The adhesion tension between water and the rock surface is less than that between oil and the rock surface.
WATER-WET
OIL-WET Air
OIL
θ
θ
θ
θ
WATER
θ < 90°
SOLID (ROCK)
FREE WATER
OIL
Oil
GRAIN
WATER
WATER
WATER
θ > 90°
SOLID (ROCK)
OIL GRAIN
OIL RIM BOUND WATER
FREE WATER Ayers, 2001
WATER-WET
OIL-WET Oil
Air
θ θ
WATER
WATER
WETTABILITY CLASSIFICATION • Strongly oil- or water-wetting • Neutral wettability – no preferential wettability to either water or oil in the pores • Fractional wettability – reservoir that has local areas that are strongly oil-wet, whereas most of the reservoir is strongly water-wet - Occurs where reservoir rock have variable mineral composition and surface chemistry • Mixed wettability – smaller pores area water-wet are filled with water, whereas larger pores are oil-wet and filled with oil - Residual oil saturation is low - Occurs where oil with polar organic compounds invades a water-wet rock saturated with brine
IMBIBITION • Imbibition is a fluid flow process in which the saturation of the wetting phase increases and the nonwetting phase saturation decreases. (e.g., waterflood of an oil reservoir that is water-wet).
• Mobility of wetting phase increases as wetting phase saturation increases – mobility is the fraction of total flow capacity for a particular phase
WATER-WET
OIL-WET Air
OIL
θ
θ
θ
θ
WATER
θ < 90°
SOLID (ROCK)
FREE WATER
OIL
Oil
GRAIN
WATER
WATER
WATER
θ > 90°
SOLID (ROCK)
OIL GRAIN
OIL RIM BOUND WATER
FREE WATER Ayers, 2001
DEFINITION OF INTERFACIAL TENSION • Interfacial (boundary) tension is the energy per unit area (force per unit distance) at the surface between phases • Commonly expressed in milliNewtons/meter (also, dynes/cm)
DEFINITION OF WETTABILITY • Wettability is the tendency of one fluid to spread on or adhere to a solid surface in the presence of other immiscible fluids. • Wettability refers to interaction between fluid and solid phases. • Reservoir rocks (sandstone, limestone, dolomite, etc.) are the solid surfaces • Oil, water, and/or gas are the fluids
DEFINITION OF ADHESION TENSION • Adhesion tension is expressed as the difference between two solid-fluid interfacial tensions.
AT = σ os − σ ws = − σ ow cos θ
• A negative adhesion tension indicates that the denser phase (water) preferentially wets the solid surface (and vice versa). • An adhesion tension of “0” indicates that both phases have equal affinity for the solid surface
CONTACT ANGLE Oil
σ ow Oil
σ os
θ
Water
Oil
σ ws
σ os
Solid
AT = adhesion tension, milli-Newtons/m or dynes/cm)
The contact angle, θ , measured through the denser liquid phase, defines which fluid wets the solid surface.
θ = contact angle between the oil/water/solid interface measured through the water, degrees σos = interfacial energy between the oil and solid, milli-Newtons/m or dynes/cm σws = interfacial energy between the water and solid, milli-Newtons/m or dynes/cm σ = interfacial energy (interfacial tension) between the oil and water, milli-Newtons/m or dynes/cm
OIL-WET RESERVOIR ROCK • Reservoir rock is oil-wet if oil preferentially wets the rock surfaces. • The rock is oil-wet under the following conditions: ∀ σ os > σ ws • AT > 0 (i.e., the adhesion tension is positive) • 90° < θ < 180° If θ is close to 180°, the rock is considered to be “strongly oil-wet”
OIL-WET ROCK Water
σ ow Oil
θ
σ os
σ ws
σ os Solid
• 90° < θ < 180° • The adhesion tension between water and the rock surface is less than that between oil and the rock surface.
WATER-WET
OIL-WET Air
OIL
θ
θ
θ
θ
WATER
θ < 90°
SOLID (ROCK)
FREE WATER
OIL
Oil
GRAIN
WATER
WATER
WATER
θ > 90°
SOLID (ROCK)
OIL GRAIN
OIL RIM BOUND WATER
FREE WATER Ayers, 2001
WATER-WET
OIL-WET Oil
Air
θ θ
WATER
WATER
WETTABILITY CLASSIFICATION • Strongly oil- or water-wetting • Neutral wettability – no preferential wettability to either water or oil in the pores • Fractional wettability – reservoir that has local areas that are strongly oil-wet, whereas most of the reservoir is strongly water-wet - Occurs where reservoir rock have variable mineral composition and surface chemistry • Mixed wettability – smaller pores area water-wet are filled with water, whereas larger pores are oil-wet and filled with oil - Residual oil saturation is low - Occurs where oil with polar organic compounds invades a water-wet rock saturated with brine
IMBIBITION • Imbibition is a fluid flow process in which the saturation of the wetting phase increases and the nonwetting phase saturation decreases. (e.g., waterflood of an oil reservoir that is water-wet).
• Mobility of wetting phase increases as wetting phase saturation increases – mobility is the fraction of total flow capacity for a particular phase
WATER-WET
OIL-WET Air
OIL
θ
θ
θ
θ
WATER
θ < 90°
SOLID (ROCK)
FREE WATER
OIL
Oil
GRAIN
WATER
WATER
WATER
θ > 90°
SOLID (ROCK)
OIL GRAIN
OIL RIM BOUND WATER
FREE WATER Ayers, 2001
Related Documents
Wettability
November 2019 2
