Application of effective elastic media models for pore system evaluation of Albian grainstone carbonates from Campos Basin, Brazil

Abstract

Carbonate reservoirs have great economic significance at worldwide. Carbonates represent a significant portion of the Brazil's deepwater oil production, whose importance has increased with new discoveries in the post-salt and pre-salt oil deposits. In contrast to the sandstones, often carbonates display a complex pore structure with a wide range of pore sizes and shapes, which are characterized by a heterogeneous pore system. This study aims to research grainstone post-salt carbonate samples (Albianage) of the offshore Campos Basin, Brazil by laboratorial evaluation and rock physics models application to predict interparticle aspect ratio and quantitative fractions of dual pore system approach under ultrasonic and dry conditions. The goal is to estimate elastic moduli considering intergranular porosity expected to oncolytic/oolitic grainstones by use of Effective Elastic Media (EEM) theory models: KT (Kuster-Toksöz), SC (Self-consistent) and DEM (Differential Effective Medium), and spherical or microporosity dominant inclusions. The Albian carbonate data set was evaluated in laboratory and pore aspect ratios were determined by comparing measured P-wave velocity data to EEM models. Thus, this study provides a methodology to predict intergranular porosity expected to oncolytic/oolitic Albian grainstone carbonates, and characterizes the interparticle aspect ratio applying EEM models and a quantitative fraction of inclusions according to dual pore system approach under ultrasonic and dry conditions. The results allowed interparticle aspect ratio estimation and a quantitative impact of inclusions by EEM models application, and help us to understand the elastic properties of the Albian carbonates.