Influence of Provenance and the Sedimentary Environment on the Formation of High-Quality Source Rocks in the Paleocene Lishui Sag, China

Organic matter (OM)
is the material basis for hydrocarbon generation.
Its type and abundance determine the hydrocarbon generation ability
of source rocks, which is closely related to the provenance and sedimentary
environment of source rocks. The tectonic backgrounds of the eastern
and western subsags (ESS and WSS) of the Lishui Sag in the East China
Sea Shelf Basin are significantly different and their influence on
the OM in the source rocks is worthy of attention. This paper comprehensively
analyzes the provenance and environmental characteristics and their
influence on the features of the OM of Paleocene source rocks in the
ESS and WSS. The study finds that the source rocks in the ESS have
multiple sources. During the deposition period, as the salinity and
paleoproductivity of the water column increased, the proportion of
OM in the autochthonous components of the water column continued to
increase, but the overall water column was in an oxidizing environment,
resulting in a generally low abundance of OM. The provenance of the
source rocks in the WSS was relatively simple and terrestrial. Also,
the sedimentary environment had little effect on the type of OM. However,
the whole water column of the WSS was in an anoxic environment, so
the OM was better preserved, resulting in a higher abundance. Due
to the influence of provenance and the sedimentary environment in
different areas of the sag, the characteristics of OM in the source
rocks are different, so relevant exploration strategies need to be
adopted in actual exploration.