A semiopen hydrocarbon generation
thermal simulation experiment
was conducted on the Chang 7 shale after chloroform extraction. The
characteristics of expelled, retained, and total generated oils were
analyzed. The influence of the free hydrocarbons (S1) was
ruled out after extraction, and the kerogen hydrocarbons (S2) dropped nearly 92.5%, which is the main source of oil generation.
The oil generation of the Chang 7 shale was divided into three stages:
300–320 °C is the slow hydrocarbon generation stage, which
is mainly the initial cracking of kerogen, and the amounts of expelled
and retained oils are small; 320–360 °C is the rapid hydrocarbon
generation stage, which is mainly the second cracking of kerogen,
resulting in a rapid increase in expelled, retained, and total generated
oils; and 360–420 °C is mainly the cracking of the retained
oil generated in the early stage. The cumulative total generated oil
before 360 °C is larger than that generated after 360 °C,
which suggests that a large amount of oil was generated before 360
°C; however, this part of the oil is mainly the retained oil.
At this stage, as the pyrolysis temperature continues to rise, C14+ in the retained oil generated in the early stage begins
to crack. C6–14 and C14+ have a correlation
similar to the “zero-sum game”, suggesting that there
is an inherent transformational relationship between them. A semiopen
hydrocarbon generation thermal simulation experiment was first conducted
on the chloroform extraction of the Chang 7 shale. This study confirms
that the increase in pyrolysis temperature (>360 °C) is beneficial
to generating more expelled oil, which has practical implications
for the in situ conversion of shale oil.