Sequence Stratigraphic Features of Weathered Carbonate Residuum Reservoirs

Studies on the sequence stratigraphic features of carbonate weathered residuum reveal that the key factor which makes the karstification possible is the permeability paths that occurred, controlled by the exposure events which resulted from drops in the sea level. The formation of carbonate weathered residuum was diagenetically associated with different interfaces of syndepositional sequences. Studies on the weathering degree (diagenetic maturation) of the parasequences in the sedimentary systems have come to the conclusion that the development maturation of the weathered residuum basically represents the increase or decrease of accommodation space. Ideally, a relevant model between sequence stratigraphy and weathered residuum is established. Introducing the theory of sequence stratigraphy into the study of the carbonate reservoirs within the weathered residuum led to the belief that sequence stratigraphic feature analysis of the carbonate weathered residuum is actually a relationship between the different interface natures and reservoir physical properties. By comparing relevant information all over the world, the authors hold that parasequences of neritic carbonates usually represent a small part of sedimentation, and the exposure period makes up about half the period of cycling. Weathered residuum reservoirs occurred dominantly within two temporal ranges: 30–120 Ma, corresponding to megasequences or mesosequences; and 0.01–0.5 Ma, corresponding to parasequences.