Causes of the Worldwide Association Between Salt, Oil and Gas

Abstract

The importance of the evaporite-hydrocarbon association is clearly seen in a compilation of giant oil and gas discoveries across the period 2000-2012. Of the 120 giant oil and gas fields discovered in that period some 50% were hosted in marine carbonates and 15% in lacustrine carbonates, meaning about a third of new giant discoveries were in siliciclastic reservoirs. Some 56% of the oil and gas giants had an evaporite seal, with 82% of the marine carbonates having an evaporite seal and 91% of the lacustrine carbonates having an evaporite seal. Clearly, carbonate reservoirs with evaporite seals constitute the majority of the giant oil and gas discoveries in the period 2000-2012, and the proportions of this association are likely to increase in conventional discoveries across the next decades. Predicting the position and quality of potential reservoirs in evaporite terranes is difficult without integrating notions of feedback between deposition, diagenesis and structural evolution. Therein lies the difficulty in placing evaporite-associated reservoirs and traps in classic terms of structural, stratigraphic and diagenetic traps. When classifying a field with an evaporite trap, the fact that salt is so mobile, so soluble, and so diagenetically active, separates it from other trap styles in a petroleum system. It means that a salt unit, by its comings and goings, plays ongoing and multiple roles in generating reservoirs and traps from the time of deposition through diagenesis to structuring. Tying oil and gas field occurrences to a static and categoric breakdown is near impossible as salt-induced structuring, diagenesis and deposition are often penecontemporaneous and in a state of intimate feedback with adjustments continuing through out the mesogenetic and telogenetic realms.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016