Chen Dong, Gao Yingxin, Sun Dejun, Li Yujiang, Li Feng, Yang Min
State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences Beijing 100085 China
University of the Chinese Academy of Sciences Beijing 100019 China.
RSC Adv. 2019 May 21;9(28):16044-16048. doi: 10.1039/c9ra01801h. eCollection 2019 May 20.
It is of great significance to know the fate of the polymers and surfactants used for enhanced oil recovery (EOR) in oil reservoirs at a relatively high temperature/pressure. In this paper, the changes of the properties of a polymer (partially hydrolyzed polyacrylamide, HPAM) and a surfactant (petroleum sulfonate, PS) were investigated under simulated oil reservoir conditions (a temperature of 45, 60 or 75 °C and a pressure of 10, 15 or 20 MPa). The impacts of the property changes to emulsion stability were also highlighted. The results showed that the hydrolysis degree of HPAM increased from 24.3% to 28.9%, 29.7% and 35.4%, whereas the molecular weight ( ) decreased from 7.60 × 10 g mol to 5.43 × 10 g mol, 4.49 × 10 g mol and 2.87 × 10 g mol as a function of raising the temperature to 45, 60 and 75 °C with 20 MPa, respectively, for a duration of one week. However, the increased pressure showed obvious prevention effects on the degradation of HPAM in the investigated pressure range of 10-20 MPa. There were no changes in the oil-water interfacial tension for PS solutions after high temperature/pressure treatment. The stabilization ability of HPAM to the emulsion decreased markedly after treatment because of the decreased viscosity attributed to the reduction of molecular weight, while that of PS did not change. It is reasonable to speculate that the influence of back produced HPAM to the stability of EOR produced water will be quite different in different oil reservoirs because of the differences in reservoir temperature, pressure and retention time, and therefore different strategies should be considered in treating the produced water from EOR.
了解用于提高油藏采收率（EOR）的聚合物和表面活性剂在相对高温/高压油藏中的命运具有重要意义。本文研究了一种聚合物（部分水解聚丙烯酰胺，HPAM）和一种表面活性剂（石油磺酸盐，PS）在模拟油藏条件下（温度为45、60或75°C，压力为10、15或20 MPa）的性能变化。还强调了性能变化对乳液稳定性的影响。结果表明，在20 MPa压力下，随着温度分别升至45、60和75°C并持续一周，HPAM的水解度从24.3%增加到28.9%、29.7%和35.4%，而分子量从7.60×10⁶ g/mol降至5.43×10⁶ g/mol、4.49×10⁶ g/mol和2.87×10⁶ g/mol。然而，在所研究的10 - 20 MPa压力范围内，压力升高对HPAM的降解有明显的抑制作用。高温/高压处理后，PS溶液的油水界面张力没有变化。处理后，由于分子量降低导致粘度下降，HPAM对乳液的稳定能力显著降低，而PS的稳定能力没有变化。可以合理推测，由于油藏温度、压力和停留时间的差异，回注的HPAM对EOR采出水稳定性的影响在不同油藏中会有很大不同，因此在处理EOR采出水时应考虑不同的策略。
