The Miocene Tipping Point: Triggers for Rivers, Deltas, Deepwater Fans, and an Exceptional Global Hydrocarbon Endowment
Snedden, John W.
Examination of the global temporal distribution of oil and gas reserves shows a pronounced peak in the Miocene Epoch, a timeframe of just 18my in geologic history. Estimated ultimate recoveries from discoveries with Miocene reservoirs exceeds any other Cenozoic interval, and rivals better known Mid-Cretaceous and Late/Middle Jurassic intervals. This hydrocarbon endowment cannot be simply explained by source rock distribution, given the general absence of world-class source rocks in the Miocene.
Earlier studies have noted that the Miocene includes multiple, large-scale tectonostratigraphic events suggesting a large-scale deep earth process, such as development of a mantle super plume, drove increased plate motion on a global basis. But a direct connection between deep earth perturbations such as this and hydrocarbon systems seems tenuous at best.
One explanation that links both observations is that many petroliferous basins reached a tipping point of tectonostratigraphic conditions during the Miocene, including regional uplift and thus increased sediment input to fluvial, delta, and deepwater systems. Eustatic variations also accelerated in the Miocene, leading to seal rock deposition, organic enrichment and preservation as a function of changes in deep-water circulation with the closing of ocean gateways.
Illustrative examples are drawn from three key basins. In the Kutei Basin of Indonesia, uplift of central Borneo led to delta and deepwater reservoir deposition, including transport of terrestrial organic matter to charge deep-water reservoirs in this Type III petroleum system. Collapse of the SE Niger delta, formation of a major sequence boundary and top sealing by Qua Iboe shale, transformed what would have been a series of small fault-dependent traps into a large number of giant oil and gas fields. In the Gulf of Mexico Basin, rejuvenation of the Appalachians and Tennessee River system led to deposition of the large MCAVLU deepwater fan system, with continued salt withdrawal in turn setting up the conditions for development for several large discoveries.
These examples, combined with observations from other hydrocarbon-bearing basins, suggest that local, pre-existing conditions (the context) combined with one or more Miocene perturbations (the stimuli), caused these tectonostratigraphic systems to reach a tipping point in this Epoch, resulting in an exceptional hydrocarbon endowment in comparison to other parts of the Cenozoic.
AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013