A technique for matching seismic data in the depth domain to well control

Abstract A two-step depth conversion method that improves the accuracy and efficiency of seismic-to-well calibration was introduced, while also enhancing diagnostic capabilities for uncertainty analysis. Traditional seismic-to-well calibration — performed by scaling seismic velocities for time-to-depth conversion — can be time-consuming and labor-intensive, especially in complex velocity fields. The proposed two-step workflow addressed these challenges by streamlining the process of achieving an optimal fit between seismic data and well control. In the first step, an approximate velocity model was used to generate a geologically reasonable image through vertical depth conversion or depth migration. In the second step, an interval scaling field was defined and integrated in the depth domain to reposition the data, thereby achieving the desired fit to the well control. The second step acted as a perturbation of the initial velocity model but did not require access to the original velocity model or seismic data in time. This process is conceptually equivalent to scaling the velocity model used for time-to-depth conversion, followed by another depth conversion. The method improved depth accuracy, reduced interpretation time, and enhanced diagnostic capabilities for evaluating uncertainty. The utility of this workflow was illustrated with two examples: a synthetic data set and field data from the offshore North Sea. In both cases, close fits of the seismic-to-well markers were achieved, with significantly reduced residuals and negligible depth bias.