Paleogeography of the Early-to-Middle Miocene in the Tácata Oilfield (Capaya and Carapita Formations), Eastern Venezuelan Basin, North of Anzoátegui and Monagas States

Sánchez, Dennis, Manuel Delgado, Solange Angulo, PDVSA E&P, Puerto La Cruz, Venezuela

The studied area has an extension of 800 km2 and is located in the Eastern Venezuelan Basin, Maturín Sub-Basin, north of Anzoátegui and Monagas States.

A paleoenvironmental distribution scheme for the early to middle Miocene in the Tácata area was established by means of biostratigraphycal and sedimentological data from cores, well cuttings and subsurface log data.

Macroscopic core description allows identification of fourteen sedimentary lithofacies: Seven sandy lithofacies (A2/A1H/A1R/A1L/A2M/A3X/A3GL) and their bioturbated counter­parts (A1B/AOB); two heterolithic lithofacies (H/HB); two shaly lithofacies (L/L1); and a coal to coaly shale lithofacies (C).

This sedimentary facies can be grouped in four distinctive sedimentary facies associa­tions: lower shoreface, medium to upper shoreface, storm deposits (tempestites) and tidal channels.

This scheme allows, even in the absence of biocronostratigraphic markers, to carry out detailed stratigraphycal correlations in accordance with the paleoenvironmental and paleo­bathymetrical synchronised variations. Data of benthic foraminiferal studies in modern sed­iments and an aggressive campaign of core acquisition can enhance this “Paleoenvironmental Distribution Scheme”.

Paleogeographycal maps constructed using this paleoenvironmental scheme, evidence the transgressive character of the Miocene sedimentary cycle, as well as the progressive deepening of the sedimentary environments from the west to the east. In the same way, this sedimentary cycle is represented to the west by the coastal to transitional clastic sediments of Capaya Formation, while to the east the marine condition becomes more noticeable, rep­resented by the external neritic to bathyal sediments of the Carapita Formation.