Luiz Carlos do Carmo Marques

A study of asphaltene-resin interactions

A study was carried out to investigate the interaction between asphaltenes (in toluene solutions) and resins (in n-heptane solutions). To better understand the type of interaction between these fractions, it was quantified the resin uptake when asphaltenes (dissolved in toluene) were precipitated by a resin-containing n-heptane solution. These results indicated the asphaltene precipitation occurs together with a reduction in the resin concentration. The binding isotherm profiles indicated that saturation occurred in one case, while collective association following an initial plateau was observed for the other two samples. These results confirmed the hypothesis that resins can adsorb on asphaltenes but cannot prevent asphaltenes from flocculating and precipitating. Furthermore, microcalorimetric results suggested that the resin and asphaltene interact by weak van der Waals forces. These results are in stark contrast with the school of thought prevalent since the 1940s that resins can peptize and stabilize asphaltenes.

A preliminary study on the magnetic treatment of fluids

ABSTRACT Although the influence of magnetic fields on paraffin deposition is still dimly understood, magnetic devices have been exploited by the petroleum industry to mitigate this problem. In this study, a series of experiments were carried out using a lab-scale magnetic conditioner and two kind of samples: paraffin mixture and crude oil. The investigated parameters were: exposition time, temperature, magnetic field intensity. paraffin type and content in the fluid and the reversibility of the observed alterations. The results indicate that magnetic fields, up to 1 Tesla applied at a temperature close to the Wax Appearance Temperature (WAT), reduce the apparent viscosity of the samples. This effect has been ascribed to changes in the paraffin crystal morphology promoted by the magnetic field. Scanning Electronic Microscopy (SEM) was fundamental to confirm this hypothesis.

Asphaltenes Flocculation in Light Crude Oils: A Chemical Approach to the Problem

This article describes the state‐of‐the‐art of the phenomena associated to the flocculation and precipitation of asphaltenes as well as the solutions used to prevent this kind of phase behavior problem in a Brazilian light (420 API) crude oil. A discussion on how to diagnose this light crude tendency to flocculate its low concentration (0.3%) asphaltenes and on the approach to (chemically) mitigate the phenomena also are provided. To address the problem a comprehensive study was carried out as follows: 1) Scoping trials to assess the so‐called asphaltenes deposition envelope (ADE) of the crude, a key parameter to design the chemical injection system and to production management. To accomplish that a mono‐phase crude oil sample was collected and tests were performed on a PVT cell equipped with a solid detection system. These PVT results enabled us to evidence the reversibility of the asphaltenes flocculation process—above the bubble point pressure—which is in agreement with the Hildebrand theory for macromolecules in hydrotopic solutions and; 2) A suite of field experiments to address the following issues: asphaltenes flocculation inhibitor dosage optimization; how to collect inhibitor‐free oil samples for well site evaluation; adaptation of the existing analytical methods for well site analysis and: setting up guidelines against which measure the inhibitor performance in this low‐asphaltenes concentration crude oil. The engineered solutions that ended up being developed from this comprehensive study are now incorporated to Petrobras flow assurance solutions portfolio.

Pitfalls of CO2 Injection in Enhanced Oil Recovery

The intent of this paper is to offer a comprehensive understanding of the pitfalls associated with CO2-rich gas injection during enhanced oil recovery (EOR) operations. An emphasis is placed, however, on the interactions between this gas and crude oil asphaltenes, because these later compounds are heavy organic molecules which can destabilize, flocculate and precipitate in CO2-rich environments, thus triggering a major field problem: injectivity loss due to near-wellbore (inflow) formation damage: an Achilles heel for any EOR process.