AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Eolianites as Potential Reservoir Rocks
(1) Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin, Austin, TX.
(2) Department of Geology and Paleontology, Section of Earth Sciences and environment, University of Geneva, Geneva, Switzerland.
The recent discovery of a large scale, hydrocarbon producing eolianite in the South Pars gas field, (offshore Iran) confirmed the reservoir potential of these supratidal wind-driven carbonate deposits. Due to their very close sedimentary and petrographic features, eolianites are often misinterpreted as high-energy shallow marine deposits, especially on cores. As eolianites may be more represented in the fossil record then previously thought, their proper discrimination and understanding within a hydrocarbon field is a crucial issue for correct stratigraphic-sequencing, reservoir modelling and production planning. The correct differentiation of eolianites and high-energy shallow marine deposits will prevent the eventual neglecting of the other sedimentary system, which may, if present, represent valuable targets in a hydrocarbon field. The key factor influencing the reservoir potential and characteristics of eolianites is their supratidal deposition. It controls their spatial extent and thickness, petrotexture, and petrophysical properties through early diagenesis, dolomitization, pedogenesis and karstification. The proper identification of one or the other deposit will help issue a better field model. Finally and even though classic sequence-stratigraphic rules are not applicable to supratidal deposits, correlations between coastal eolian systems and coeval marine deposits can be achieved regarding the position of the eolianites on the eustatic curve. Eolianites display all the prerequisites to be good hydrocarbons reservoirs. Like all other reservoir bodies, their potential depends on their post-depositional history. Reconsidering the eventual presence of eolianites in the fossil record may open the door to better exploitation and understanding of shallow-marine / littoral carbonate systems.