石油および環境バイオテクノロジージャーナル

概要

Evaluation of Asphaltene Deposition - A Systematic Study and Validation of Online Focused Beam Reflectance Measurement FBRM® at Reservoir Conditions

Ruidiaz EM, Koroishi ET, Kim NR, Trevisan OV, Soares-Bassani G and Merino-Garcia D

The production of crude oil from a reservoir is a challenging task. The handling of solids is one of the foremost assignments that operators may face during the life of a field. These solids may have the characteristics of both forms: inorganic material and organic material. The first one can be classified as salts and sand and the second comes from the crude oil that includes: waxes, asphaltenes, hydrates, and naphtenates. Apart from sand, the rest of the solids usually precipitate due to changes in composition (Commingling of fluids), temperature, or pressure. Asphaltenes precipitation is regarded to main issues referred to narrower mitigation strategy. Precipitate solid can produce reservoir blockage and in situ wettability change, decreasing well productivity widely. Know the operational conditions (PTx) under which the precipitation phenomena has been occurred is decisive, mainly the precipitation initial pressure (onset) and its velocity of formation. The purpose of this work consists in the experimental study of the asphaltenes precipitation from a crude oil sample under specific pressure and temperature representative of Brazilian pre salt reservoirs. In order to evaluate the impact of the operational conditions on solids formation and their relevant consequence to be used for petroleum exploration methods. The evaluation of solid formation was performed with Focused Beam Reflectance Measurement (FBRM®) at high pressure conditions, working with crude oil and live oil. The first stage involved the validation of asphaltenes precipitation for a batch system using crude oil and heptane at room conditions. The second one consisted in dynamic test carried out in a loop able to support pressures nearing 300 bars and temperatures up to 70°C. Furthermore, an experimental methodology was developed in order to charge live oil into loop system. The measurements were monitored by online Focused Beam Reflectance Measurement FBRM®. It was verified a greater count of asphaltene particles for range of 100-75 bars. There was more evidence in the asphaltenes precipitation in this period. It was possible to identify a pressure range combined to asphaltenes precipitation of target oil during depressurized system performed in successive stages. The pressure range combined with asphaltenes precipitation was revealed during the depressurization process that occurred in successive stages. Furthermore, the asphaltenes appearance was corroborated in the period of decrease from 100 to 75 bars. FBRM measurements allowed the asphaltenes appearance and growth for each stage of depressurization.