Abstract:

The Yellow River Mouth Sag is located in the southeastern part of the Bohai Bay Basin, China. The large scale shallow water lacustrine delta developed in Neogene became profitable geologic conditions for the formation of concealed hydrocarbon reservoirs in this area. The authors take the sequence SQ1 as an example, totally 10 parasequence sets are divided to the sequence SQ1 of lower member of Minghuazhen Formation in Block B34 of the Yellow River Mouth Sag. Lithologic statistics show that the lithology is dominated by sandstone and mudstone. Thick sandstones are mainly distributed in PSS1 and PSS10, while thinbedded sandstones mainly developed in other parasequence sets. The developing character of sandstones is related with where they are developed in the same sequence. The studies include root mean square(RMS) amplitude in different parasequence sets and well lithology, onedimensional forward simulation of 7 kinds of lithology associations. The results indicate that lithology and its association  are correspondent to the amplitude  as follows: strong amplitude corresponds to thick sandbodies, weak amplitude corresponds to nondevelopment of sandbodies, and medium amplitude corresponds to a large set of mudstone intercalated with mediumthinbedded sandstone. The fine description of sandbodies was made taking the PSS1 as an example. It is quite difficult to quantitatively identify the thickness of sandstone although the relationship between lithology and amplitude is established. As a result, the thickness of sandstone is qualitatively determined according to the amplitude.

Key words:  high frequency sequence, root mean square (RMS) amplitude, geologicalgeophysical model, the Yellow River Mouth Sag