Sun Guangyu, Sheng Fujun, Li Qingyi, Li Chuanxian, Yang Fei, Yao Bo
College of Pipeline and Civil Engineering, China University of Petroleum (East China), Qingdao, Shandong 266580, People's Republic of China.
Shandong Key Laboratory of Oil & Gas Storage and Transportation Safety, Qingdao, Shandong 266580, People's Republic of China.
ACS Omega. 2024 Dec 16;9(52):51337-51348. doi: 10.1021/acsomega.4c08172. eCollection 2024 Dec 31.
With the gradual application of enhanced oil recovery by CO (CO-EOR), the rheological behavior of produced fluid is altered due to CO dissolution and degassing. This work focuses on the composition, physical properties, gelation and yield characteristics, and viscosity-temperature properties of crude oil containing paraffinic wax after CO treatment. Special attention is given to the effect of the phase state of CO. It is found that the contents of light hydrocarbons (C-) and liquid paraffin (C-C) decrease by 1.24% and 0.89%, respectively, while the contents of paraffin and microcrystalline wax increase by 1.90% and 1.71%, respectively, as the treatment pressure is increased to 25 MPa from atmospheric pressure. Besides, the content of the saturates decreases by 5.31%, while that of the aromatics, resins, and asphaltenes increases by 2.83%, 1.83%, and 0.65%, respectively, due to the extraction effect of CO on light hydrocarbons. In terms of wax precipitation characteristics, the wax appearance temperature (WAT) and wax precipitation content (WPC) increase with increasing pressure. Particularly, when the pressure increases from 5 to 15 MPa, the WAT and WPC increase by 4 °C and 1.27%, respectively, obviously greater than the other conditions due to the phase transition of CO. Moreover, the morphology of the wax crystals becomes tinier after supercritical CO (scCO) treatment because of the increase in the polarity of the crude oil. Likewise, considering the gelation and yield characteristics, the storage modulus, gelation temperature, and yield stress increase more obviously than the other pressure change conditions as the pressure increases from 5 to 15 MPa. All of the above structural enhancements are owing to the effect of CO treatment, especially scCO treatment, on the content and morphology of the precipitated wax crystals. Last, the apparent viscosity/viscosity also increases with the treatment pressure. The viscosity increases by 1.1 to 2.0 times with the pressure increasing from 5 to 15 MPa, again obviously greater than the other pressure change conditions due to the interior structural changes of the crude oil induced by scCO treatment..
随着二氧化碳驱油（CO-EOR）技术的逐步应用，由于二氧化碳的溶解和脱气，采出液的流变行为发生了改变。本工作聚焦于经过二氧化碳处理后的含石蜡原油的组成、物理性质、凝胶化和屈服特性以及黏温性质。特别关注了二氧化碳相态的影响。研究发现，随着处理压力从常压增加到25MPa，轻质烃（C-）和液态石蜡（C-C）的含量分别降低了1.24%和0.89%，而石蜡和微晶蜡的含量分别增加了1.90%和1.71%。此外，由于二氧化碳对轻质烃的萃取作用，饱和烃含量降低了5.31%，而芳烃、树脂和沥青质的含量分别增加了2.83%、1.83%和0.65%。就蜡析出特性而言，析蜡点温度（WAT）和析蜡量（WPC）随压力升高而增加。特别是当压力从5MPa增加到15MPa时，析蜡点温度和析蜡量分别升高了4℃和1.27%，由于二氧化碳的相变，明显高于其他条件。此外，超临界二氧化碳（scCO）处理后蜡晶形态变得更细小，这是由于原油极性增加所致。同样，考虑到凝胶化和屈服特性，当压力从5MPa增加到15MPa时，储能模量、凝胶化温度和屈服应力的增加比其他压力变化条件更明显。上述所有结构增强均归因于二氧化碳处理，特别是scCO处理对析出蜡晶含量和形态的影响。最后，表观黏度/黏度也随处理压力增加。随着压力从5MPa增加到15MPa，黏度增加了1.1至2.0倍，同样由于scCO处理引起的原油内部结构变化，明显高于其他压力变化条件。
