The methods of vertical time to depth conversion

The final aim of seismic imaging is to position reflectors correctly in the depth domain. Depth imaging implies building up a velocity model of the subsurface. This velocity model must be chosen so that calculated traveltimes provide the closest approximation to real traveltimes. A correct and accurate estimate of depth and dips is required in many instances: structural interpretation of seismic data, well placement and design, rock volume assessment. This means that after time migration interpretive step is necessary for transforming times into depths. A operation that transforms a time-domain seismic data set into its corresponding depth-domain data set is referred to as time to depth conversion. The author is presenting an overview of different methods of converting time to depth using the set of seismic section from Wiszniów - Tarnoszyn survey and 10 number of wells with full set of borehole geophysical data and stratigraphic data. Inter alia: Single well and analytical Z — f(T) function, Several wells and single Z - Zsj- — f(T - Tsj) polynomial, Wells and average velocity maps, Wells and interpolation with seismic times, Wells and interpolation using calibrated stacking velocities, Wells and de-tended stacking velocities, Wells only and interval velocities, Wells and interpolation using calibrated interval seismic velocities, Wells and Vint = f(Zmid), Wells and Vo + kZ, Wells and normalized velocities. Examples of the methods' application were performed. They used building the velocity models on the basis of time to depth transformation. The results are presented on several graphs for comparison of outputs of different models.