Page 167 - Fundamentals of Enhanced Oil and Gas Recovery

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Thermal Recovery Processes

• There will always be water vapor produced if gas is being produced.
•If p wv . p w , water will be flashed to vapor at production well. In this case, the
above equation fails.
• Boberg Lantz model need parameter tuning for any formation to account for
WOR over time.

Example 5.1: Calculation of mean temperature at a zone shut-in after steam
stimulation

Steam with temperature of 400 F is injected to the reservoir to give a heated zone

of 25 ft. The reservoir temperature, thickness, and conductivity are 120 F, 40 ft,
and 1.6 Btu/h ft 2 F/ft. The mean heat capacity for overburden and formation is
3
33 Btu/ft F. Calculate the mean temperature of the heated zone for 100,200,300 days
after reaching the reservoir temperature to 400 F. The reservoir has no production.

α should be determined to calculate T Dr and T Dz
2
2
a 5 k h /M 5 (1.6 Btu/h ft 2 F/ft)/(33 Btu/ft 3 F) 5 0.0484 ft /h 5 1.163 ft /D
For radial dimensionless temperature component,
T Dr 5 T Dr ðt Dr Þ
2 2
½
ð
ð
ð
ðt Dr Þ 5 α t 2 t i ފ=r h 5 ½ð1:163 ft =DÞ t 2 t i ފ=ð25 ftÞ 5 0:00186 t 2 t i Þ
2
At ð t 2 t i Þ 5 100 days and t Dr 5 0.186 T Dr 5 0:66; at ð t 2 t i Þ 5 200 days
t Dr 5 0:372 and T Dr 5 0:53; and at t 2 t i Þ 5 300 days, t Dr 5 0:558 T Dr 5 0:45. For
ð
the thickness-averaged temperature, T Dz :
2 2 2
ð
T Dz 5 α t 2 t i ފðh=2Þ 5 ½ð1:163 ft =DÞ t 2 t i ފ=ð20 ftÞ 5 0:0029 t 2 t i Þ
ð
ð
½
At ð t 2 t i Þ 5 100 days and t Dz 5 0:29 T Dz 5 0:78; at ð t 2 t i Þ 5 200 days
t Dz 5 0:58 and T Dz 5 0:64; and at ð t 2 t i Þ 5 300 days, t Dz 5 0:87 and
T Dz 5 0:56
Average heated zone temperature after
shut-in ( F)

ð t 2 t i ÞDays T Dr T Dz T D T ð FÞ
100 0.66 0.78 0.48 251.1
200 0.53 0.64 0.31 206.2
300 0.45 0.56 0.23 184.2
5.2.3 Fire Flood and In Situ Combustion
The process of ISC includes exothermic reactions which lead to increasing the final
temperature of the reservoir. For instance, the temperature increase may reach to

300 400 C which leads to phase change. Though there are complex reactions embedded
in this process, the engineers study on the mechanisms due to advantages of this process.