Geochemical Preconditions of Oil-gas-bearing Capacity of the Alboran Basin

Elena Poludetkina, and E. Kozlova
Moscow State University, Moscow, Russia

Neogene basin of the Alboran Sea corresponds to the westernmost Mediterranean extensional basin located within a Miocene arc-shaped thrust belt formed by Betic and Maghrebian Cordilleras (Multidisciplinary study of Geological processes on the NE Atlantic and Western Mediterranean margins, UNESCO 2000). It has been the site of a vigorous program of oil and gas exploration since 1970`s and attracts attention nowadays as a potential oil-gas-generating basin. Materials to research work are obtained during TTR-9 and TTR-12 UNESCO cruises. Four mud volcanic structures were discovered, investigated and subsampled (Kalinin and Perejil on the Spanish margin, Dhaka and Granada on the Morocco margin). Cores from mud volcanic structures are characterized by relatively high concentrations of hydrocarbon gases as comparing with background concentrations represented by set of alkanes from methane to butanes with prevailing of alkanes under alkenes that implies on input of HC inflow from the inside. Geochemical data show that sedimentary sequence of the Alboran Sea includes middle- and high oil-potential strata able to generate HC fluids. These are Upper Miocene claystones sediments accumulated in anoxic subbasin (TOC=7,37%, S2=43,5 HC,mg/rock,g; HI=622 HC,mg/TOC,g); Upper Paleocene carbonates (TOC=0,68%, S2=1,27 HC,mg/rock,g; HI=186 HC,mg/TOC,g); Upper Carboniferous siltstones (TOC=2,94%, S2=17 HC,mg/rock,g; HI=577 HC,mg/TOC,g). Most of the samples are of marine origin with an input of terrigenous consistuent. Thus hydrocarbon gas content and composition allows us to suppose thermogenic inflow of hydrocarbons from the interior. Highly HC-potential strata are identified within the sedimentary sequence. Presence of source rocks and HC inflow testifies on being Alboran Sea a potential oil-bearing basin. These geochemical compilations will prove to be a critical guide for future exploration and thorough investigation in the Basin.

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece