ABSTRACT: Petroleum Potential of Active Convergent Margin Settings

Roland Von Huene

Models of constant accretion at convergent margins and certain exploration experiences would indicate generally unfavorable source rock, poor maturity, lack of reservoir, and chaotic structure at convergent plate boundaries. This is not the case at some less-explored Pacific convergent margins. Eocene and older rocks of the margin framework near some trench axes require accretion interspersed with erosion. The Eocene and older elements contain sediment with thermally mature hydrocarbons; in the presence of sufficient organic carbon, such rocks may provide sources. Off Peru, heat flow 20 km landward from the trench axis approaches continental levels. Potential reservoir horizons are found above regional unconformities. Changing convergence vectors or the collision of a mar in with topographic highs on the subducting plate can cause uplift to surf zone depths and can produce unconformities. One such unconformity off Japan is overlain by 100 m of shallow-water Oligocene sand. Similar erosional unconformities together with the tracts of open and well-organized structure have been observed as better seismic data becomes available. Tracts once thought to contain mostly chaotic structure from plate convergence show regular folding and organized fault patterns in reprocessed seismic record sections. Pacific convergent-margin tectonic history varies broadly, and some margins have favorable aspects for potential hydrocarbon resources.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990