A Chemical Approach to Prevent Asphaltenes Flocculation in Light Crude Oils: State-of-the-art

Abstract

Abstract This paper describes the state-of-the-art of the phenomena associated to the flocculation and precipitation of asphaltenes as well as the chemical solution used to prevent these problems in the production tubing of light crude oil(42°API) offshore wells in Santos Basin, Brazil. It is also provided a detailed discussion on the efforts to diagnose this light crude tendency to flocculate its low concentration (0.3 %) asphaltenes and on the approach to chemically-inhibit the phenomena. To assess the so-called asphaltenes deposition envelope of the light crude a mono-phase crude oil sample was collected and a suite of experiments was performed in a PVT analysis cell equipped with a solid detection system. As per this study, it was possible to evidence the reversibility of the asphaltenes flocculation process above the bubble point, meaning that these asphaltenes behave much as macromolecules in solution as predicted by the Hildebrand theory. It is also described the laboratory procedures used to select commercial asphaltenes flocculation inhibitors (AFI) and how the selected ones were evaluated in the field. Within the scope of the field test the following issues were addressed: - how the AFI injection is performed; -how the AFI-free oil samples are collected for the tests on the well site and; - how the existing analytical procedures had to be adapted and enhanced to evaluate the AFI performance in crude oils with so low asphaltenes concentration. The lessons learned from this pioneer study and the field test are being incorporated to Petrobras newer light-crude oil exploration and production projects.