DEEP WATER SEQUENCE STRATIGRAPHY REVEALED USING 3D SEISMIC VISUALIZATION TECHNIQUES

The arsenal of methods for 3D seismic volume interpretation have increasingly been turned towards important new exploration areas; especially the high cost, deepwater areas of the world. These settings offer interpreters one of the most challenging scientific problems in the last 15 years; i.e. to make accurate pre-drill predictions of reservoir quality sand targets in deep water, often far from well control. Modern sequence stratigraphic architectural concepts for passive margin to deepwater settings add critical guidance to multi-screen, 3D seismic visualization, volume rendering, and seismic attribute interpretation techniques. Full analysis of the seismic data typically reveals the framework on three scales; the mega-architecture basin scale of 2nd order sea level rises and falls and tectonic events, the 3rd order ‘building block’ sequence scale of ~1-10 my, and the parasequence scale suitable for well prediction and reserve calculation.

Carefully designed seismic attributes can clarify fan morphologies in each sequence and resolve changing lithology assemblages, thick to thin-beddedness, and depositional style as sea level falls and rises. A cyclicity of attributes is often revealed on the seismic. As the seismic attributes tend to mimic the lithology/facies architecture, careful volume rendering and manipulation of voxels can effectively hide the shale-prone facies to reveal the full three-dimensional architecture of the sequence stratigraphic systems tracts and aid in proper identification of fan types. There are a number of tools now available to help interpret the most prospective targets for deep water drilling, the sheet-like fan types. These fans are the most vexing because they have the greatest laterally continuity, yet the fewest fan-forms on the seismic data. Analysis of various multi-attribute volumes that combine instantaneous amplitude, frequency and phase with the discontinuity attribute can help identify subtle sequence boundaries, allow for rapid identification of potential fan intervals, and help distinguish between high amplitude sand-prone facies and condensed sections. Combination attribute displays with specially designed color scales are useful to detect subtle cyclicities in the data and can enhance the plan view analysis of fan facies.