Mousapour M S, Simjoo M, Chahardowli M, Shaker Shiran B
Faculty of Petroleum and Natural Gas Engineering, Sahand University of Technology, Tabriz, Iran.
NORCE Norwegian Research Center, Bergen, Norway.
Sci Rep. 2024 Nov 20;14(1):28720. doi: 10.1038/s41598-024-74790-x.
Polymer flooding is a prominent chemical enhanced oil recovery (CEOR) method that involves the injection of polymer solution into the oil reservoirs to improve the sweep efficiency and maximize the ultimate oil recovery. Selecting an appropriate polymer type, molecular weight, and concentration is crucial for success of any polymer flooding project. This paper studies the flow behavior of HPAM-based EOR polymers with different molecular weights through porous media. Dynamic adsorption and injectivity tests were performed through 5 Darcies sandpacks using polymer solutions prepared with low (LM; 8-10 MDa) and high (HM; 20-25 MDa) molecular weight polymers. Polymer solutions with different target viscosity values of 7, 15 and 30 cP were flooded through sandpacks at the reservoir temperature of 80 ºC and pore pressure of 1000 psi. The results showed that HM solutions with different target viscosity have higher polymer retention through sandpacks compared to LM solutions. Furthermore, results of residual resistance factor (RRF) measurements were in line with dynamic adsorption tests results. That is, permeability reduction due to irreversible polymer retention was higher when HM polymer solutions were injected. Furthermore, the results showed that although the resistance factor (RF) and in-situ viscosity of HM and LM polymers are in the same range, however, shear thickening regime becomes pronounced in the case of HM polymer with higher target viscosity. Polymer relaxation time measurements, and consequently, Deborah number calculations were performed to describe the shear thickening behavior by polymers viscoelastic characteristics. Results demonstrate that occurrence of shear thickening regime is controlled by Deborah number which is a function of polymer molecular weight, polymer concentration and injection rate. These results shed light on the importance of the selection of optimal polymer molecular weight and concentration during the design of polymer flooding projects.
聚合物驱油是一种重要的化学强化采油（CEOR）方法，该方法通过向油藏注入聚合物溶液来提高波及效率并使最终采收率最大化。选择合适的聚合物类型、分子量和浓度对于任何聚合物驱油项目的成功都至关重要。本文研究了不同分子量的基于部分水解聚丙烯酰胺（HPAM）的强化采油聚合物在多孔介质中的流动行为。通过5达西砂柱进行动态吸附和注入性测试，使用由低分子量（LM；8 - 10兆道尔顿）和高分子量（HM；20 - 25兆道尔顿）聚合物配制的聚合物溶液。将目标粘度值分别为7、15和30厘泊的不同聚合物溶液在80℃的油藏温度和1000磅力/平方英寸的孔隙压力下驱过砂柱。结果表明，与低分子量溶液相比，具有不同目标粘度的高分子量溶液在砂柱中的聚合物保留量更高。此外，残余阻力系数（RRF）测量结果与动态吸附测试结果一致。也就是说，注入高分子量聚合物溶液时，由于不可逆聚合物保留导致的渗透率降低更高。此外，结果表明，尽管高分子量和低分子量聚合物的阻力系数（RF）和原地粘度处于相同范围，然而，在目标粘度较高的高分子量聚合物情况下，剪切增稠现象更为明显。通过聚合物松弛时间测量以及相应的德博拉数计算，利用聚合物的粘弹性特性来描述剪切增稠行为。结果表明，剪切增稠现象的发生受德博拉数控制，德博拉数是聚合物分子量、聚合物浓度和注入速率的函数。这些结果揭示了在聚合物驱油项目设计过程中选择最佳聚合物分子量和浓度的重要性。
