Bleaching induced by migration of hydrocarbons in Los Chihuidos High, Neuquén Basin, Argentina

YENEALEM, YAREGAL; RAINOLDI, ANA LAURA

Ivry sur Siene

Congreso; 11 éme colloque du Groupe Français de Argiles; 2013

Groupe Francais des Argiles

The Neuquén Group consists of synorogenic red beds deposited during the Late Cretaceous (Cenomanian-Campanian). The Huincul Formation -one of the formal unit of this Group- outcrops on the east flank of the Los Chihuidos high, a main structure of the Neuquén basin. In this area, the red sandstones are interbedded with bleached sandstones. Two general diagenetic events are identified: burial diagenesis and the alteration due to hydrocarbons migration and interaction with clasts and authigenic minerals. Paragenetic relationships and relative timing of the alteration events were also identified. Burial diagenesis resulted in hematite coatings, albite and quartz overgrowths, kaolinite precipitation as pore filling mineral, and late calcite cement. Alteration of the red beds due to hydrocarbons migration resulted in the dissolution of hematite and partial dissolution of unstable clasts and kaolinite, precipitation of smectite and late carbonate due to the oxidation of hydrocarbons. Bleaching of red sandstones due to hydrocarbon-bearing fluids migration increased its porosity and permeability, thus, enhanced the petrophysical properties of the reservoir.