Offset-dependent mis-tie analysis at seismic line intersections

Offset-dependent line-intersection displays can be of significant direct interpretive value. On our data set from a proprietary location. use of these displays permits a refined structural interpretation and im- proves the usefulness of amplitude and amplitude- versus-offset displays for direct hydrocarbon detec- tion. The degree of data reproducibility at each intersection may be exposed as a function of offset through the use of prestack and partial-range stack splice and difference displays. At a set of marine line intersections, after only cursory processing, the range of residual amplitudes found by subtracting strike traces from dip traces is from -20 dB to +6 dB relative to the input. The average is about -8 dB. The poorest line intersection ties occur below the edges of deep bright spots, where velocity anomalies leading to time mis-ties greater than IO ms can occur. Shallow near-surface velocity anomalies, out-of-plane arrivals including fault plane reflections, and, occasionally, water reverberation variations contribute locally to the data mis-ties. Lo- cation errors are ubiquitous but of secondary impor- tance, and random noise is more than 20 dB down. A simple and inexpensive routine splice display of line intersection data can be of significant value for quality control, for processing evaluation, and for interpretation. Issues of data reliability, such as screening of amplitude-versus-offset (AVO) anomalies by shallow gas and transmission-path problems for large CMP offsets, as well as other problems in oper- ational and research geophysics, may be addressed by analysis of line intersections in the offset domain.