Abstract：The velocity-field-built method, generally using seismic velocity spectrum as the basis, often leads to decrease the precision of structural mapping because of affected by quality of velocity spectrum. Based on the relationship between propagation velocity of seismic waves in rock formation and rock property, the paper presented attributes-model-based velocity-field-built method. The method first calibrates reflection horizons according to drilling, logging and VSP data; then, the divided unit formations, based on velocity attributes and the interfaces of formation and faults etc, are correlated and interpreted; these unit formations are divided into multiple layer sub-blocks based on cut of faults, found out the mechanism that the attributes feature of separate units (depths, planar variation of sand contents and rock property) controls the variation of velocities in both vertical and lateral directions, and built up mathematic relationship between separate attributes layer by layer; using above relationship and initiating from the wells, the reasonable velocity model is formed by interpolation and extrapolation, and finally, using this model to directly perform time-depth conversion in low-amplitude structural zone. The method was used in Tu-Ha oilfield and achieved good geologic results.
