Observations from Structures Associated with Mud Diapirism and Their Role in Petroleum Charging and Trapping

Rod Graham¹ and Andy Pepper^2
1Hess, London, United Kingdom
²Hess, Houston, TX

There are both geometrical similarities and differences between the structures associated with mobile mud and those associated with salt(perhaps to be expected given the range of mud behaviour itself). Throughout the world, but especially in the gravity driven systems of the continental margins we see anticlines with cores that show the patchy seismic incoherence that we associate with mobile mud. Presumably these structures are fundamentally compressional anticlines, with mud mobility induced as a consequence of the folding process. As such, they are somewhat analogous with the salt cored compressional folds of the Perdido and Atwater fold belts of the deep water Gulf of Mexico, or the anticlines of the Zagros, and like the Zagros anticlines with their local salt diapirs, the mud cored anticlines are commonly pierced by pipes of diapiric mud which reach to the surface as volcanoes.

Structures associated with withdrawal and collapse seem to be less commonly associated with mud than they are with salt - we cite examples from the South Caspian, but know of few others. We know of only one example of a mud controlled minibasin province which might be analogous with salt related minibasin provinces such as those in the Gulf of Mexico. This is the Trinidad/Barbados fore-arc basin, a region where we suspect that the petroleum charge-migration story is strongly influenced by the mud tectonics.

As a generality, 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.

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