Análisis diagenético de la Formación Springhill (Santa Cruz, Argentina).

SPALLETTI, L.A.; MATHEOS, S.D.; SÁNCHEZ, E.; OYARZÁBAL, F.

Mar del Plata

Congreso; VI Congreso de Exploración y Desarrollo de Hidrocarburos; 2005

Instituto Argentino del Petróleo y Gas

ABSTRACT The Upper Jurassic-Lower Cretaceous sandstones of the Springhill Formation are the main hydrocarbon reservois of the Austral Basin (southernmost Argentina). Conventional and CL petrographic studies in core samples from several oil fields located in the central and eastern Santa Cruz Province allowed to define the diagenetic features and proceses of the Springhill sandstones. Initial compaction and glauconitization were the main eogenetic processes. During mesogenesis a complex set of processes (such as pressure dissolution, quartz and calcite cementation, burial compaction and stylolitization, and kaolinite and chlorite neoformation) occurred. However, preservation of the reservoir-rock quality is related to overpressure, coating and location of hydrocarbons that inhibited total closure of the porous space. The sequenciality of mesogenetic processes is closely controlled by burial depth. Towards the east, where the Springhill Formation is located at shallow depths (less than 2,500 m), a few and weak mesogenetic processes are recognized. Instead, towards the west, where burial depths are between 2,500 and 6,000 m, quartz overgrowth and recrystallization, pressure dissolution and stylolitization, kaolinite cementation, and migration of hydrocarbons are commonly recognized. Bivariate age-burial depth diagrams were employed to illustrate the ranks of burial depth and temperature for each of the above mentioned mesogenetic proceses.