Page 478 - Enhanced Oil Recovery in Shale and Tight Reservoirs

442 Enhanced Oil Recovery in Shale and Tight Reservoirs

Figure 13.23 Calculated time delay in ignition as a function of temperature at various
air injection pressure (Dietz, 1970).
system temperature from T r to T SI , with the subscript f here representing the
formation system.
Spontaneous ignition may be expected when the reservoir temperature is
higher than 60e70 C (Turta, 2013). If the delay of spontaneous ignition is

practically too long, artificial ignition needs to be considered. Artificial igni-
tion includes electrical heating, injection of steam, injection of chemicals like
linseed oil (Turta, 2013) and benzene (Gjini et al., 1999). Linseed oil can
start ignition at 33 C. But our tests in laboratory did not experience a

very low ignition temperature when linseed oil was used somehow. It might
have caused a significant heat loss in the tests. S. Ren (October 5, 2017, per-
sonal communication) also found the ignition temperature was still high
(250e300 C) when linseed oil was used.

It can be understood that there is also a delay in artificial ignition. It may
not be too important to know exactly ignition delay for spontaneous igni-
tion. But it is important for artificial ignition because extension of ignition
expenditure is expensive.