Liu Shuang, Wu Jianxun, Xu Zhiming, Zhang Linzhou, Zhao Suoqi
State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, P. R. China.
ACS Omega. 2023 Jul 26;8(31):28866-28876. doi: 10.1021/acsomega.3c04098. eCollection 2023 Aug 8.
The viscosity of heavy oil hinders its cold production, posing a major challenge to its exploitation. The high viscosity of heavy oil can be attributed to the content of asphaltene. However, during the collection of heavy oil samples from various regions in China, we observed that heavy oils with high total acid number (TAN) but low asphaltene content also exhibit relatively high viscosity. Hence, the viscosity mechanism of high-acid crude oil, the influence of petroleum acid on heavy oil viscosity, should be investigated. In this study, Xinjiang Chunfeng heavy oil was selected for analysis, possessing a viscosity of 16,886 mPa·s at 50 °C and a high total acid number (TAN) of 17.72 mg KOH/g. Separation was performed on the deacidified oil and the acid component using an alkali-modified silica gel column. The viscosity changes of the deacidified oil and its blends with varying proportions of the acid component were determined, along with the viscosity changes of the deacidified oil and acid components in a toluene solution. The molecular composition was analyzed using a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS). The findings indicated successful separation of petroleum acid from the heavy oil, the acid component yield being 16.65 wt %. Furthermore, the viscosity of the petroleum acid was significantly higher than that of the deacidified oil. The rate of viscosity change of the acid component in the toluene solvent exceeded that of the deacidified oil, and the viscosity of the deacidified oil notably increased upon the addition of acid. In conjunction with the viscosity data, it was observed that the deacidified oil exhibited the removal of O2 and O4 compounds, resulting in a 43.11% viscosity reduction at 30 °C compared with crude oil. Thus, the monoacid and diacid components considerably affected the viscosity of heavy oil.
稠油的高粘度阻碍了其冷采，给开采带来了重大挑战。稠油的高粘度可归因于沥青质的含量。然而，在从中国不同地区采集稠油样品的过程中，我们发现总酸值（TAN）高但沥青质含量低的稠油也表现出相对较高的粘度。因此，应研究高酸原油的粘度机理，即石油酸对稠油粘度的影响。本研究选取新疆春风稠油进行分析，其在50℃时的粘度为16886 mPa·s，总酸值（TAN）高达17.72 mg KOH/g。使用碱改性硅胶柱对脱酸油和酸组分进行分离。测定了脱酸油及其与不同比例酸组分混合物的粘度变化，以及脱酸油和酸组分在甲苯溶液中的粘度变化。使用傅里叶变换离子回旋共振质谱仪（FT-ICR MS）分析分子组成。结果表明已成功从稠油中分离出石油酸，酸组分产率为16.65 wt%。此外，石油酸的粘度明显高于脱酸油。酸组分在甲苯溶剂中的粘度变化速率超过脱酸油，加入酸后脱酸油的粘度显著增加。结合粘度数据观察到，脱酸油中O2和O4化合物被去除，与原油相比，在30℃时粘度降低了43.11%。因此，单酸和二酸组分对稠油的粘度有很大影响。
