Changes

Jump to navigation Jump to search
157 bytes added ,  15:11, 24 January 2022
m
Line 41: Line 41:     
If a liquid wets a surface, it tends to spread and cover that surface. Observed on a microscopic scale, the edge of the liquid has a characteristic shape. A knife edge shape indicates wetting, while a beaded edge shape indicates nonwetting. This is shown quantitatively in [[:file:wettability_fig1.png|Figure 1]], which shows a drop of water surrounded by oil and contacting a solid surface. If the edge of the drop forms an acute angle (θ<sub>e</sub> 5.)
 
If a liquid wets a surface, it tends to spread and cover that surface. Observed on a microscopic scale, the edge of the liquid has a characteristic shape. A knife edge shape indicates wetting, while a beaded edge shape indicates nonwetting. This is shown quantitatively in [[:file:wettability_fig1.png|Figure 1]], which shows a drop of water surrounded by oil and contacting a solid surface. If the edge of the drop forms an acute angle (θ<sub>e</sub> 5.)
Several techniques used to measure this angle are described by Adamson.<ref name=pt05r2 /> The measurements are generally made on a polished surface that simulates the reservoir material. For sandstones, glass slides or polished quartz are often used. Polished marble is usually chosen to simulate a carbonate reservoir. An adaptation of the technique uses a drop of liquid confined between two surfaces.<ref name=pt05r39>Craig, F. F., 1971, The reservoir engineering aspects of waterflooding: Dallas, TX, Society of Petroleum Engineers Monograph No. 3, 120 p.</ref>
+
Several techniques used to measure this angle are described by Adamson.<ref name=pt05r2 /> The measurements are generally made on a polished surface that simulates the reservoir material. For sandstones, glass slides or polished [[quartz]] are often used. Polished marble is usually chosen to simulate a carbonate reservoir. An adaptation of the technique uses a drop of liquid confined between two surfaces.<ref name=pt05r39>Craig, F. F., 1971, The reservoir engineering aspects of waterflooding: Dallas, TX, Society of Petroleum Engineers Monograph No. 3, 120 p.</ref>
    
Contact angle measurements can be precise, but even for ideal systems, measurements can show significant variation. Variations are related to surface preparation, equilibration of the solid and liquids, and surface roughness.
 
Contact angle measurements can be precise, but even for ideal systems, measurements can show significant variation. Variations are related to surface preparation, equilibration of the solid and liquids, and surface roughness.
Line 66: Line 66:  
If a sample spontaneously imbibes only brine, it is considered water wet. Similarly, if it imbibes only oil, it is considered oil wet. If the sample imbibes neither, it is described as neutrally wet.
 
If a sample spontaneously imbibes only brine, it is considered water wet. Similarly, if it imbibes only oil, it is considered oil wet. If the sample imbibes neither, it is described as neutrally wet.
   −
A modification of the test in general use first prepares the sample by centrifuging it in brine. This is followed by centrifuging in oil to irreducible water saturation. The Amott procedure is then followed, but a combined index—the Amott-Harvey wettability index<ref name=pt05r26>Boneau, D. F., Clempett, R. L., 1977, A surfactant system for the oil wet sandstone of the North Burbank unit: Journal of Petroleum Technology, v. 29, p. 501–506., 10., 2118/5820-PA</ref> is calculated by subtracting the displacement by oil ratio from the displacement by water ratio. Figure 2 shows these volumes, and Equation 2 gives the calculation:
+
A modification of the test in general use first prepares the sample by centrifuging it in brine. This is followed by centrifuging in oil to [http://petrowiki.org/Glossary%3AIrreducible_water_saturation irreducible water saturation]. The Amott procedure is then followed, but a combined index—the Amott-Harvey wettability index<ref name=pt05r26>Boneau, D. F., Clempett, R. L., 1977, A surfactant system for the oil wet sandstone of the North Burbank unit: Journal of Petroleum Technology, v. 29, p. 501–506., 10., 2118/5820-PA</ref> is calculated by subtracting the displacement by oil ratio from the displacement by water ratio. Figure 2 shows these volumes, and Equation 2 gives the calculation:
   −
:<math>\mbox{Index} = \overline{BC}/\overline{BD} - \overline{DE}/\overline{DB}</math>
+
:<math>\mbox{Index} = \frac{\overline{BC}}{\overline{BD}} - \frac{\overline{DE}}{\overline{DB}}</math>
    
The range of values and the corresponding wettability characteristics are listed in Table 1.
 
The range of values and the corresponding wettability characteristics are listed in Table 1.
Line 78: Line 78:  
! || Water Wet || Neutrally Wet || Oil Wet
 
! || Water Wet || Neutrally Wet || Oil Wet
 
|-
 
|-
| Contact angle || || ||
+
| colspan=4 align=center | Contact angle
 
|-
 
|-
 
| Minimum || 0° || 60 to 75° || 105 to 120°
 
| Minimum || 0° || 60 to 75° || 105 to 120°
Line 86: Line 86:  
| USBM wettability index || W near 1 || W near 0 || W near -1
 
| USBM wettability index || W near 1 || W near 0 || W near -1
 
|-
 
|-
| Amott wettability index || || ||
+
| colspan=4 align=center | Amott wettability index  
 
|-
 
|-
 
| Displacement by water ratio || Positive || Zero || Zero
 
| Displacement by water ratio || Positive || Zero || Zero
Line 119: Line 119:  
|+ {{table number|2}}Alternative wettability measurement techniques
 
|+ {{table number|2}}Alternative wettability measurement techniques
 
|-
 
|-
! Method
+
! Method || Observation
! Observation
   
|-
 
|-
| Microscopic examination
+
| Microscopic examination || Visual examination of the fluid surrounding grains
| Visual examination of the fluid surrounding grains
   
|-
 
|-
| Flotation method
+
| Flotation method || Distribution of grains at water/oil interface or air/water interface
| Distribution of grains at water/oil interface or air/water interface
   
|-
 
|-
| Glass slide method
+
| Glass slide method || Displacement of the nonwetting fluid from a glass slide
| Displacement of the nonwetting fluid from a glass slide
   
|-
 
|-
| [[Relative [[permeability]]]] method
+
| [[Relative permeability]] method || Location and relative magnitudes of ''k''<sub>ro</sub> and ''k''<sub>rw</sub> curves
| Location and relative magnitudes of ''k''<sub>ro</sub> and ''k''<sub>rw</sub> curves
   
|-
 
|-
| Reservoir logs
+
| Reservoir logs || [[Basic open hole tools#Resistivity|Resistivity logs]] before and after injection of a reverse wetting agent
| [[Basic open hole tools#Resistivity|Resistivity logs]] before and after injection of a reverse wetting agent
   
|-
 
|-
| Nuclear magnetic resonance
+
| Nuclear magnetic resonance || Changes in the longitudinal relaxation time
| Changes in the longitudinal relaxation time
   
|-
 
|-
| Dye adsorption
+
| Dye adsorption || Adsorption of a water soluble dye
| Adsorption of a water soluble dye
   
|}
 
|}
   Line 169: Line 161:     
[[Category:Laboratory methods]]
 
[[Category:Laboratory methods]]
 +
[[Category:Methods in Exploration 10]]

Navigation menu