Avaliação experimental dos efeitos da pressão e da presença de gases na deposição de parafinas de um petróleo do pré-sal brasileiro

Abstract

The growing global demand for energy and fossil fuels highlights the challenge of balancing energy efficiency with environmental concerns. Petroleum, in addition to being a primary energy source, plays a crucial role in the production of industrial feedstocks. Global investments in deepwater production systems have increased, posing significant challenges due to the extreme operating conditions involved, such as high pressures and low temperatures. The discovery of reserves in deep and ultra-deep waters has introduced additional technological challenges, including long tie-backs and high gas–oil ratios, particularly in the exploitation of Brazilian pre-salt fields. Production under these conditions faces the issue of undesirable deposit formation, mainly paraffin waxes, which can compromise operational efficiency and safety. This study, developed as part of an R&D project in partnership between UNIFEI and Petrobras, aims to characterize, analyze, and propose solutions for paraffin deposition during oil production and gas reinjection in deepwater wells. Experimental tests were conducted to investigate the mechanisms of deposit formation using Brazilian pre-salt crude oil and to develop chemical solvent-based cleaning techniques. Two deposition loops were developed: one operating at high flow rate and low pressure, and another operating at low flow rate and high pressure. These tests were carried out to qualitatively investigate the deposition mechanisms of pre-salt crude oil. In addition to the deposition loop experiments, microcalorimetry analyses were performed using different gases and pressures up to 200 barg, aiming to provide a deeper understanding of the effects of pressure and gas composition (N2, CO2, and natural gas) on the Wax Appearance Temperature (WAT). The low-pressure loop tests indicated a tendency for deposition under both single-phase and two-phase flow conditions, suggesting that the presence of gas in the system can influence the characteristics of the deposits formed. In the high-pressure loop tests, differences were observed in the deposits formed in the presence of N2 and CO2. The microcalorimetry results showed that N2 injection increases the WAT, whereas natural gas injection reduces it. In the case of CO2, different pressure ranges led to either an increase or stabilization of the WAT. Similar behavior was also observed for the crystallization temperature of the second event.