Dual pore system evaluation of Albian grainstone carbonates from Brazil using effective elastic media theory models

Abstract

Carbonates represent a significant portion of the Brazil's deepwater oil production, whose importance has increased with recent discoveries in the post-salt and pre-salt oil deposits. Often carbonates are characterized by a heterogeneous pore system, displaying a complex pore structure with wide range of pore sizes and shapes. This work aims towards investigating grainstone carbonates (Albian-age) of the offshore Campos Basin, Brazil by laboratorial evaluation and rock physics modeling to predict interparticle aspect ratio and quantitative fractions of a dual pore system approach under ultrasonic and dry conditions. The goal is to estimate elastic moduli considering intergranular porosity expected in oncolytic/oolitic grainstones using Effective Elastic Media (EEM) theories - KT (Kuster-Toksöz), SC (Self-consistent) and DEM (Differential Effective Medium), and either a spherical inclusions or a microporosity dominated pore system. The results show that the KT and DEM give a best compatibility with the texture of the Albian grainstone carbonates. Interparticle aspect ratio estimation and a quantitative prediction of the inclusion effects helped us to understand the elastic properties of Albian carbonates.