Subsalt Imaging — Coherent Noise Removal and Steep Dip Enhancement in Support of Subsalt Exploration

Abstract

Abstract

In the Gulf of Mexico (GoM), coherent noises are commonly observed in the subsalt seismic data. Such noise is detrimental to subsalt exploration and appraisal as they often lead to incorrect interpretations. The coherent noise are related to converted waves, intra-salt multiples, residual free-surface multiples, and seismic data acquisition noise. At the same time, steep-dip events are usually imaged from far offsets and with limited illumination; therefore, the imaging amplitude is much weaker and easily contaminated by strong random or coherent noise.

Seismic processing from improved demultiple and noise attenuation will reduce post-migration coherent noise. Often we found that post-migration coherent noise attenuation was required to enhance the seismic data quality prior to structural and stratigraphic interpretation. Our approach is to decompose seismic images into dip ranges. If there is enough dip-separation, the coherent noise can be removed by applying a 3D filter to certain dip ranges.

For steep-dip events enhancement, partition image output and local horizon interpretation are required. Within the target steep-dip event area, the dip field is calculated based on the interpreted horizons. The dip field is also calculated for each image partition. The dip coherence between the interpreted horizons and the partition images will be used as the weight in the partition image stack.

Both the coherent noise removal and steep-dip enhancement are interpretation-driven; therefore, geological experience is required for optimal parameterization. In this presentation, we will show examples in Green Canyon and Walker Ridge to include Tonga, Ligurian, Heidelberg, Northwood and Shenandoah.

AAPG Datapages/Search and Discovery Article #90260 © 2016 AAPG/SEG International Conference & Exhibition, Cancun, Mexico, September 6-9, 2016