Relationship between porosity type and petroelastic properties for a complex carbonate reservoir

The focus of this Thesis is to study the reservoirs of the Sapinhoá Field , located in the Santos Basin on the southeastern Brazilian continental margin. The Santos Basin is a huge hydrocarbon province (Faria et al 2017) with a great variety of oil discoveries in the early 2000s at ultra-deep waters carbonate reservoirs. These discovered reservoirs are known as the Pre-Salt province. The carbonate reservoirs usually are very complex to understand and characterize. Normally they have a great variety of geological facies, diverse composition and distinct petrophysical properties. Particularly, the porosity permeability relationship is one of the greatest uncertainties related to these rocks, and have strong implications in reservoir management. The purpose of this thesis is to investigate the porosity types and pore geometries, by using the petroelastic properties, with the intention to fully understand the porosity-permeability relation. To investigate these characteristics of these reservoirs, two sets of data from three different vertical wells were evaluated. The first set of data are the wireline logs that went through a petrophysical formation evaluation in order to identify the rock mineralogy, estimate the porosity and classify the porosity types. In addition, laboratory analysis were used to apply the petroleastic model and also to validated the log analysis. From that a Petroelastic model was developed, applying the theory of elasticity, to proper understand the variation of velocities of the present rocks and its properties. Particularly, models of pore stiffness that appreciate the variety of pore space geometries showed and differentiate diverse features of the reservoir rocks. The prediction of pore space geometry by the pore stiffness assessment generated a proposition of three diverse Petroelastic facies. These facies represent different porosity types associations, diverse log identities and mostly important, three unique equations to predict the permeability of the reservoir.