Mineralogical and chemical variations in clay minerals as key to decipher hydrocarbon migration in siliciclastic rocks, Neuquén Basin (Argentina)

ANA LAURA RAINOLDI; DANIEL BEAUFORT; PATRICIA PATRIER; FRANCHINI MARTA; JOSEFINA M. PONS; AGNES IMPICCINI,

Edinburgo

Congreso; Euroclay2015; 2015

The Clay Minerals Group of the Mineralogical Society of Great Britain & Ireland and The Clay Minerals Society.

The Late Cretaceous (Cenomanian-Campanian) deposits of the Neuquén Group comprisesa thick continental red-bed sequence which is an important reservoir for hydrocarbons in the northern part of the Neuquén Basin. Along Los Chihuidos and Huincul highs, two of the most important morphostructural units of the basin, the red-bed sequence is bleached and the clay mineralogy is furthermodified were the hydrocarbons have passed through.The objective of this contribution is to decipher the clayvariations at basin scale, including mineralogy and chemical transformations after the circulation of hydrocarbons through the basal units of the Neuquén Group (Candeleros and Huincul Formations). The behavior of clay minerals plays an important role in the study of thehydrocarbon paleo-migrations. Thechemical reactions between reducing fluids and diagenetic minerals were controlled in part by inherited depositional conditions (early diagenesis) and provenance. Afte rearly-diagenesis a variety of processes, in addition to hematite dissolution, occurred associated with the circulation of reducing basinal fluids through red-bed successions. In units that have early hematite cements it is easy to document the migration of such reducing pore waters. However, if early hematite is not present, then the migration of reducing pore waters could easily be overlooked. In this context,dissolution features of previous clay minerals, cation exchange, and precipitation of new clay minerals could be used to trace hydrocarbons migration.