Abstract

World-wide, mud volcanoes have been documented in areas of overpressure where explosive expansion of trapped methane has occurred during argillokinesis. In an area with high sedimentation rate, such as the Gulf of Mexico or the South Caspian, there may be no time for fine-grained sediment to de-water before being covered by impermeable material.

In an accretionary wedge setting, such as Timor, this process is complicated by overthrusting of off-scraped material which increases the overburden pressure and provides many more avenues for the migration of fluids through the system. In some cases, such as is seen in the Caribbean, the fluids can escape directly to the seabottom through high permeability beds due to the subduction of coarser-grained material. When this happens there may be no diapirism. In other cases, such as in Venezuela, the fore-arc may be the site of rapid, laterally-derived, sedimentation and fluids from the overthrusted rocks may be forced to escape through several kilometers of recent deltaic sediments. Since these fluids may include petroleum, this has obvious exploration potential. Often, the source rock for the mud diapirism is the same source for the petroleum system. The overpressure which gives rise to the mud volcanism also causes increased expulsion efficiency and hydrocarbons sampled from mud volcanoes tend to be immature.

If there are no suitable reservoir rocks, there may be no commercial accumulations. However, many giant fields are associated with mud volcanoes, such as those in Azerbaijan.