ANALISIS MICROTECTÓNICO DE BANDAS DE DEFORMACIÓN EN ARENITAS DE LA FORMACIÓN BAJO BARREAL, CUENCA DEL GOLFO SAN JORGE

MÉNDEZ, FACUNDO L.; ALLARD, JOSÉ O.; OLAZÁBAL SABRINA XIMENA; BUETI, SEBASTIÁN A.

Mendoza

Congreso; 11° Congreso de Exploración y Desarrollo de Hidocarburos; 2022

IAPG

ABSTRACT Deformation bands are tabular discontinuities that affect porous and permeable rocks, modifying their petrographic properties. This contribution aims to quantify the variation of these properties on deformation band-bearing sandstones belonging to the Bajo Barreal Formation. This formation is the most important reservoir rock of the Golfo San Jorge Basin. The characterization was achieved through a multiscale analysis: i) topologic outcrop analysis of the observed network of bands, ii) air permeability measurements on hand samples, iii) microscopic characterization of deformation mechanisms and iv) visual porosity - clastic fraction size quantification. Two types of deformation bands were recognized, shear and dilation bands. Deformation mechanisms like inter-intragranular fracturing and ductile deformation of pyroclastic clasts were recognized on the shear band, generating a decrease in visual porosity from 7.11% (protolith) to 0.32% (band core), along with a decrease of the measured air permeability with Kair: 180.07 mD (protolith) and Kair: 101.75 mD (band core). The dilation band shows an increase in visual porosity going from 1.12% (protolith) to 20.22% (band core), along with an equivalent increase in air permeability, from Kair: 286.15 mD (protolith) to Kair: 5025 mD (band core). None of the recognized deformation mechanisms in the shear band were observed in the dilation band. The quantified variations on all of the analyzed parameters show that these structures can act as a fluid conduct or barrier depending on the deformation mechanisms that affect them, evidencing the importance of their analysis when characterizing oil-bearing reservoirs.