Key;
Laboratory;
of;
Organic;
Geochemistry,;
Guangzhou;
Institute;
of;
Geochemistry,;
Chinese;
Academy;
of;
Sciences,;
Guangzhou;
510640,;
China;
Key;
Laboratory;
of;
Heavy;
Oil,;
China;
Petroleum;
University,;
Beijing;
102249,;
China;
Petroleum;
Exploration;
and;
Development;
Ltd.;
(CNPC),;
Guangzhou;
510240,;
China;