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The AAPG/Datapages Combined Publications Database

Indonesian Petroleum Association


25th Annual Convention Proceedings (Volume 1), 1996
Pages 385-391

2-D and Previous Hit3-DNext Hit Prestack Depth Migration for Complex Geologic Structures Offshore Indonesia

M. Murphy, R. Ottolini, R. Estill, E. Lumadyo, M. Mathias


Unocal Indonesia is using Previous Hit3-DNext Hit prestack depth migration to better image Indonesian prospects in difficult seismic areas. The goal is to delineate the deep fault geometry beneath image-distorting carbonates. Previous 2-D prestack depth migration has resulted in significantly better structural imaging, which is motivating the Previous Hit3-DNext Hit work.

Lateral velocity variations of 2 to 3 km/s within distances of less than 1 km make conventional time migration methods inadequate to accurately image structures and faulting. Iterative 2-D depth migration has provided better structural imaging in depth due to more accurate interval velocities and structural geometry resolution. Previous Hit3-DNext Hit prestack depth migration provides better migration velocity analyses and superior structural imaging, especially in comparison to 2-D lines acquired in directions oblique to major faults.

The most important step in depth migration is construction of a Previous Hit3-DNext Hit interval velocity model. All available data are used in constructing the model: Dip Moveout (DMO) stacking velocities, poststack time migration, well logs, check-shot surveys, gravity and magnetic data, seismic interpretations, and the Previous Hit3-DNext Hit prestack depth migration velocity analyses. The model is developed iteratively from the surface downward. Modeling packages such as GOCAD assist the data integration and Previous Hit3-DNext Hit visualization quality control. The Previous Hit3-DTop migration algorithm is a Unocal proprietary Kirchhoff migration with ray - trace traveltimes and migration computed on a 3 Gigaflop, 10 CPU Silicon Graphics Power Challenge.

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