High-frequency sequences

generally formed in basins with stable subsidence settings and correspond well to astronomical Milankovitch cycles

are vivid records of high-frequency eustatic flucturation.Such sequences developed in epicontinental platforms of non-coastal sedimentary environment are both representative and special in certain ways.By combining core observations

thin section analyses and logging facies studies with such factors as energy environment

eustatic fluctuation and sea water salinity cycle as well as reservoir genesis types under high-frequency sequential framework

we classified high-frequency sequences in the epicontinental carbonate platform of the Jia 2 member of the Moxi gas field into the following three types:platform flat type

intraplatform shoal type and lagoon type.The sequences are found to be characterized by widely-distributed gypsiferous rocks and grainstone with all kinds of exposure marks.As a whole

they consist of stratigraphic assemblages of shallowing upwards sequences.Within the framework

sequences are separated by clear boundaries and stratigraphic assemblages are stable and highly comparable.The paper also discussed the mechanisms behind the formation of early reservoirs in the high-frequency sequence framework and proposed that the high-frequency sequences controlled the order of lithofacies development and the syngenetic karstification

and thus controlled the development of different genetic types of reservoirs.