Page 476 - Enhanced Oil Recovery in Shale and Tight Reservoirs

440 Enhanced Oil Recovery in Shale and Tight Reservoirs

Figure 13.22 Temperature profiles for the base case and the adiabatic case.

temperature at the injection end (block (35 1 1)) decreases because sweeping
air takes heat away.
Huang and Sheng (2018) used the base model having heat loss consid-
ered to have done sensitivity analyses. The cumulative oils produced from
air injection and nitrogen injection are compared and found they are similar,
indicating that thermal effect is not significant; increasing the frequency
factor or reducing the activation energy can only increase the peak temper-
ature near the injector by 5e8 C; injection of pure oxygen leads a peak

temperature near the injector to 38 C increase; doubling the enthalpy

due to higher injection pressure increases the peak temperature near
the injector by less than 20 C. All these results indicate that a very high

temperature cannot be achieved, and thus spontaneous ignition cannot
occur, if the heat loss exists. Such sensitivity analyses should have been
extended to the adiabatic case to see whether spontaneous ignition is
possible under the adiabatic condition.
Huang and Sheng (2018) also used a field model to investigate the spon-
taneous ignition and thermal effect. The field model is a modified version of
Tingas’s (2000) model. The thermal properties are same as those presented in
Table 13.8. The field model shows that the temperature increase in the
middle layer is about 20 C, higher than 10 C in the above base laboratory

model and lower than 20 C in the adiabatic laboratory model. The result