Petrophysics and Petrography of Aptian Tight Carbonate Reservoir, Araripe Basin, NE Brazil

Abstract

Summary In recent decades, the exploitation of hydrocarbon reserves in carbonate reservoirs has motivated increasing numbers of investigations into their petrophysical characteristics due to their importance in fluid flow predictions. For tight reservoirs that are mainly composed of carbonate and fine-grained rocks, the determination of the petrophysical and petrographic parameters that affect the framework and their importance for fluid flow are key to determining the reservoir’s exploitation potential. Analysis of porosity, permeability, grain and bulk density, elastic wave velocities, and petrographic characteristics were made on an Aptian limestone from the Araripe Basin (NE Brazil), which has been used as an analogue for naturally fractured carbonate reservoirs. This study focuses on quantification of petrophysical and petrographic parameters in order to include the results in numerical simulations to combine the fracture network permeability and porosity and the rock matrix properties (double-porosity and/or double-permeability problems) to build more reliable geomechanical models. The lithofacies analyzed were laminated limestone (matrix) and recrystallized calcite (fracture fill). Crato Formation presents an intergranular porosity and average of porosity and permeability values of 12% and 0.04 mD, respectively that allowed us to classify this unit as an analogue of unconventional tight carbonate reservoir.