This paper discusses the reservoir space in carbonate
rocks in terms of types, combination features, distribution
regularity, and controlling factors, based on core
observations and tests of the North Truva Oilfield, Caspian
Basin. According to the reservoir space combinations,
carbonate reservoirs can be divided into four types, i.e.,
pore, fracture–pore, pore–cavity–fracture, and pore–cavity.
Formation and distribution of these reservoirs is strongly
controlled by deposition, diagenesis, and tectonism. In
evaporated platform and restricted platform facies, the
reservoirs are predominately affected by meteoric fresh
water leaching in the supergene–para-syngenetic period
and by uplifting and erosion in the late stage, making both
platform facies contain all the above-mentioned four types
of reservoirs, with various pores, such as dissolved cavities
and dissolved fractures, or structural fractures occasionally
in favorable structural locations. In open platform facies,
the reservoirs deposited continuously in deeper water, in an
environment of alternative high-energy shoals (where
pore–fracture-type reservoirs are dominant) and low-energy
shoals (where pore reservoirs are dominant).