As petroleum exploration advances and as most
of the oil–gas reservoirs in shallow layers have been
explored, petroleum exploration starts to move toward deep
basins, which has become an inevitable choice. In this
paper, the petroleum geology features and research progress
on oil–gas reservoirs in deep petroliferous basins
across the world are characterized by using the latest
results of worldwide deep petroleum exploration. Research
has demonstrated that the deep petroleum shows ten major
geological features. (1) While oil–gas reservoirs have been
discovered in many different types of deep petroliferous
basins, most have been discovered in low heat flux deep
basins. (2) Many types of petroliferous traps are developed
in deep basins, and tight oil–gas reservoirs in deep basin
traps are arousing increasing attention. (3) Deep petroleum
normally has more natural gas than liquid oil, and the
natural gas ratio increases with the burial depth. (4) The
residual organic matter in deep source rocks reduces but
the hydrocarbon expulsion rate and efficiency increase with
the burial depth. (5) There are many types of rocks in deep
hydrocarbon reservoirs, and most are clastic rocks and
carbonates. (6) The age of deep hydrocarbon reservoirs is
widely different, but those recently discovered are predominantly
Paleogene and Upper Paleozoic. (7) The
porosity and permeability of deep hydrocarbon reservoirs
differ widely, but they vary in a regular way with lithology
and burial depth. (8) The temperatures of deep oil–gas
reservoirs are widely different, but they typically vary with
the burial depth and basin geothermal gradient. (9) The
pressures of deep oil–gas reservoirs differ significantly, but
they typically vary with burial depth, genesis, and evolution
period. (10) Deep oil–gas reservoirs may exist with or
without a cap, and those without a cap are typically of
unconventional genesis. Over the past decade, six major
steps have been made in the understanding of deep
hydrocarbon reservoir formation. (1) Deep petroleum in
petroliferous basins has multiple sources and many different
genetic mechanisms. (2) There are high-porosity,
high-permeability reservoirs in deep basins, the formation
of which is associated with tectonic events and subsurface
fluid movement. (3) Capillary pressure differences inside
and outside the target reservoir are the principal driving
force of hydrocarbon enrichment in deep basins. (4) There
are three dynamic boundaries for deep oil–gas reservoirs; a
buoyancy-controlled threshold, hydrocarbon accumulation
limits, and the upper limit of hydrocarbon generation. (5)
The formation and distribution of deep hydrocarbon reservoirs
are controlled by free, limited, and bound fluid
dynamic fields. And (6) tight conventional, tight deep, tight
superimposed, and related reconstructed hydrocarbon reservoirs
formed in deep-limited fluid dynamic fields have
great resource potential and vast scope for exploration.
Compared with middle–shallow strata, the petroleum
geology and accumulation in deep basins are morecomplex, which overlap the feature of basin evolution in
different stages. We recommend that further study should
pay more attention to four aspects: (1) identification of
deep petroleum sources and evaluation of their relative
contributions; (2) preservation conditions and genetic
mechanisms of deep high-quality reservoirs with high
permeability and high porosity; (3) facies feature and
transformation of deep petroleum and their potential distribution;
and (4) economic feasibility evaluation of deep
tight petroleum exploration and development.