Unconventional hydrocarbon resources, which
are only marginally economically explored and developed
by traditional methods and techniques, are different from
conventional hydrocarbon resources in their accumulation
mechanisms, occurrence states, distribution models, and
exploration and development manners. The types of
unconventional hydrocarbon are controlled by the evolution
of the source rocks and the combinations of different
types of unconventional reservoirs. The fundamental distinction
between unconventional hydrocarbon resources
and conventional hydrocarbon resources is their nonbuoyancy-
driven migration. The development of the microto
nano-scale pores results in rather high capillary resistance.
The accumulation mechanisms of the unconventional
and the conventional hydrocarbon resources are also
greatly different. In conventional hydrocarbon resources,
oil and gas entrapment is controlled by reservoir-forming
factors and geological events, which is a dynamic balance
process; while for unconventional hydrocarbon resources,
the gas content is affected by the temperature and pressure
fields, and their preservation is crucial. Unconventional and
conventional hydrocarbons are distributed in an orderly
manner in subsurface space, having three distribution
models of intra-source rock, basin-centered, and source
rock interlayer. These results will be of great significance
to unconventional hydrocarbon exploration.