Abstract:

The Carboniferous(only exists in Huanglong Formation)is the most important set of resevoir among carbonate rock strata in eastern and northeastern Sichuan and western Hubei.It is discovered that the distribution of the Carboniferous in unstable and present in some areas in scattered pattern or even completely absent.The Permian in surrounding outcrop areas of Tongnanba structure is in diredct unconformity contact with the Silurian where the Carboniferous can not be found.However,reflection distribution in the seismic cross section,below reflection of TP 1(bottom of the Permian)and above weaker reflection of the Silurian,appears to be in uncontinuously pattern and corresponds to higher impedance area of odd distribution of wave impedance>230?10⁵(kg/m²·s,these features indicate that the Carboniferous exists in the center of Tongnanba structure.

Key words: wave impedance, inversion, Carboniferous, Tongnanba