Morgan Vinícius G, Sad Cristina M S, Leite Juliete S D, Castro Eustáquio R V, Barbosa Lúcio L
Nanotechnology Engineering Program - COPPE, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
Department of Chemistry, Federal University of Espírito Santo, Vitoria, Brazil.
Magn Reson Chem. 2022 Oct;60(10):996-1004. doi: 10.1002/mrc.5301. Epub 2022 Aug 12.
During the oil production and processing stages, the asphaltene precipitation is one of the great operation problems of oil industry. It can precipitate in the formation, tubing, or surface, causing operating problems, such as reduction in oil recovery by changing the reservoir permeability and wettability, clogging of the pipelines, and difficulty in separations process. The quantification of asphaltenes in petroleum by ASTM D6560 standard method is very laborious and use of a larger solvent volume than necessary. The present work proposes the use of time domain nuclear magnetic resonance (TD-NMR) as new methodology to quantify the asphaltene precipitated in crude oil. Three (light, medium, and heavy) crude oils with asphaltenes content of 0.97, 1.88, and 7.00 wt% were mixed with n-heptane in different R (ml of solvent/g of oil) values and analyzed by means of transverse relaxation time (T ). According NMR results, the R values enough for complete asphaltene precipitation for the oils A, B, and C were, respectively, equal to 16.50, 23.00, and 39.50 ml g . These outcomes represent a reduction of 58.75%, 42.50%, and 1.25% in the solvent volume per mass of oil for the oil A, B, and C, respectively, compared to the ASTM D6560 method, which imposes 40 ml g . Therefore, it has been shown that TD-NMR can be applied to estimate the amount of asphaltene precipitated in petroleum and have potential to be applied in routine analysis with advantages of saving time and costs.
在石油生产和加工阶段，沥青质沉淀是石油工业中一个重大的操作问题。它会在油层、油管或地面沉淀，引发操作问题，比如通过改变储层渗透率和润湿性降低采收率、堵塞管道以及分离过程困难。采用美国材料与试验协会（ASTM）D6560标准方法对石油中的沥青质进行定量分析非常繁琐，而且使用的溶剂量远超必要量。本研究提出使用时域核磁共振（TD-NMR）作为一种新方法来定量原油中沉淀的沥青质。将三种沥青质含量分别为0.97 wt%、1.88 wt%和7.00 wt%的（轻质、中质和重质）原油与正庚烷按不同的R（溶剂毫升数/油克数）值混合，并通过横向弛豫时间（T）进行分析。根据核磁共振结果，对于A、B和C三种原油，使沥青质完全沉淀所需的R值分别等于16.50、23.00和39.50 ml/g。与要求40 ml/g的ASTM D6560方法相比，这些结果表明，对于A、B和C三种原油，每克油的溶剂量分别减少了58.75%、42.50%和1.25%。因此，已证明TD-NMR可用于估算石油中沉淀的沥青质含量，并且有潜力应用于常规分析，具有节省时间和成本的优势。
