Page 191 - Fundamentals of Enhanced Oil and Gas Recovery

179
Thermal Recovery Processes

• Ignoring nonidealities at T of system distillation starts when sum of vapor pressure
equals total pressure:
P 5 P V 1 P W (V, volatile; W, water/steam)
P V V V 5 n V RT and P W V W 5 n W RT (V v 5 V W )

5.2.12.2 Myhill and Stegemeier Model (MS Model) [75]
Myhill and Stegemeier [75] introduced an average thermal efficiency of combined
steam-hot water zones, resulting in a uniform displacement model.
1
E h 5
t D
( " p )
ffiffiffi
ð t cD u
12f h;v Uðt D 2t cD Þ p ffiffiffiffiffi p e erfc u p ffiffiffi
t D 2t cD 2
Gt D 1 p 2 t D 2212f h;v ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi p ffiffiffiffiffiffiffiffiffiffiffiffi du2 πGt D
ðÞ
ðÞ
π 0 t D 2u
ffiffiffi
(5.126)
U 5 0 for t D . t cD and U 5 1 before critical time t D # t cD , f h,v 5 fraction of inj.
energy that is latent heat.
5.2.12.3 MS Uniform Model Limitations
The coefficient (1 2 f h,v ) is empirical. It is the fraction of injected energy that is in
the form of sensible heat. MS uniform model fails at low-quality steam drive
(f sd , 0.2) because it does not predict the oil displacement of HW zone adequately.

5.2.12.4 Capture Factor and Steam-to-Oil Ratio (SOR)
In reality, more oil is displaced than produced. To account for this, capture factor
(E c 5 70% 100% in field) is introduced:

W s;eq
F SOR 5 (5.127)
N p
where F SOR is the steam-to-oil ratio (SOR), W s,eq is the vol. of steam inj. N p is the
vol. oil produced.

5.2.12.5 Steam-to-Oil Ratio
In the definition of W s,eq , it is assumed that steam leaving boiler has 1000 Btu/lbm
energy, so
3
W s;eq 62:4 lbm=ft 350 lbm=bbl 1000 Btu=lb 5 _m s H ws 2 H wA 1 f sb λ s Þ
ð
(5.128)
26

W s;eq 5 2:854 3 10 ð _ m s H sbA Þ (5.129)