Chapter 2

Chapter 2 Principles of Waterflooding
2.3 Overall Recovery Efficiency

1

2.3 Overall Recovery Efficiency

Displacement Efficiency
Areal Sweep Efficiency
Vertical Sweep Efficiency

2

2.3 Overall Recovery Efficiency

The micromodel saturated with oil

The micromodel after water flooding
3

2.3 Overall Recovery Efficiency
• overall recovery factor (efficiency) RF
Def: the fraction of oil produced from the initial oil in place at the start of the flood.

RF  ED E A EV
ED

displacement efficiency

EA

areal sweep efficiency

EV

vertical sweep efficiency

E A  EV

Volumetric sweep efficiency

4

2.3 Overall Recovery Efficiency
• Displacement efficiency ED
– the fraction of movable oil that has been displ aced from the swept zone at any given time or pore volume injected.
Volume of oil at start of flood-Remaining oil volume
ED 
Volume of oil at start of flood
 Soi
 S o 
 S oi 
So
 Pore volume      Pore volume  

 
 
B
B
B
Bo oi o oi 








 Soi
 S oi
 Pore volume   


 Boi
 B oi
5

2.3 Overall Recovery Efficiency
• Displacement efficiency ED
• Assuming a constant oil formation volume factor d uring the flood life,

ED 

 Soi


B
 oi






 Soi


B
 oi

S o

B
 o

 

Boi  Bo  Cons tan t

Soi  So
ED 
Soi

 So  1  S w


 Soi  1  S wi

S w  S wi
ED 
1  S wi
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2.3 Overall Recovery Efficiency
• Example 2-1
– A saturated oil reservoir is under consideration to be waterfloode d immediately after drilling and completion. Core analysis tests i ndicate that the initial and residual oil saturations are 70 and 35
%, respectively. Calculate the displacement efficiency when the oil saturation is reduced to 65, 60, 55, 50, and 35%. Assume that
Bo will remain constant throughout the project life.

• Step 1. Calculate initial water saturation

S wi  1  0.7  0.3
• Step 2. Calculate ED from Equation

S w  S wi
ED 
1  S wi

So

Sw

ED

0.65

0.35

0.071

0.60

0.40

0.142

0.55

0.45