AAPG/GSTT HEDBERG CONFERENCE

“Mobile Shale Basins – Genesis, Evolution and Hydrocarbon Systems”

June 5-7, 2006 – Port-of-Spain, Trinidad and Tobago

Some Aspects of the Geometry and Fluid Dynamics of Diapiric Mud Systems

Rod Graham, Kelly Latter, Andy Pepper, Peter Mullin, and J.C. Wan

Amerada Hess Corporation

Structures associated with diapiric mud have both geometrical similarities and differences from those associated with salt. The cores of major anticlines like the western South Caspian, the Pedernales structure, and offshore Trinidad show the patchy destruction of coherent seismic reflectors which we associate with mobile mud, but we argue that they are first and foremost anticlinal folds formed in compression and that mud and volatile mobility is induced as a consequence of the folding process. Similarly, structures like Atlantis in the deep water Gulf of Mexico are almost certainly salt cored compressional folds. Mud- cored anticlines are pierced by pipes of diapiric mud which reach to the surface as volcanoes, comparable, geometrically at least, to the salt cored anticlinal folds of the Zagros or the Sierra Madre with their local salt diapirs. Structures associated with withdrawal and collapse occur in both mud and salt systems, but seem to be less common in mud systems. We cite examples from the South Caspian and the eastern Gulf of Mexico. Major gravity gliding is associated with mud mobility in many parts of the world, but we know of no mud analogue of the massive salt canopies and welds (withdrawn canopies) of the Gulf of Mexico and suggest that for various reasons these are unlikely or unlikely to be recognised. Opinions vary widely on the role of mud diapirs and volcanoes in petroleum charging and entrapment. A discussion of hydrodynamic principles is useful in constraining the possibilities, and therefore predicting the charge mechanisms and column-retention capacities in associated petroleum plays.