Associative polymer-based fluids for enhanced oil recovery using produced saline water

在加拿大，目前正在实施化学驱油，以提高阿尔伯塔省东部和萨斯喀彻温省西部劳埃德明斯特地区一些中型和稠油油藏的采收率。根据艾伯塔省政府的创新能源技术计划，化学提高石油采收率(CEOR)可能会在未来20年为艾伯塔省和萨斯喀彻温省的储量增加8000万立方米的石油。虽然仅在美国就有大约10亿磅的聚合物被用于cEOR，但在非常规致密油中化学驱油的潜力在很大程度上仍未得到勘探。在三次采油作业中，向油井中注入各种化学物质，如聚合物、表面活性剂、碱或其组合，以提高石油采收率。然而，不同的储油层运行条件(例如，pH、温度、盐度、溶解的铁和氧以及碱和/或表面活性剂的存在)会影响聚合物的结构和尺寸。具有少量疏水性质的水溶性聚合物(称为缔合聚合物)即使在采出水或盐水中也具有巨大的提高采收率效率的潜力。尽管近年来实验室研究取得了选择性的成功，但回答关键问题的全面和预测性知识仍然难以捉摸。这项建议侧重于了解缔合聚合物驱在常规和致密油藏中的应用机理，并创建预测模型。由于聚合物线圈的膨胀，盐水和智能水可以对缔合聚合物的注入性和传输性能产生积极的影响。缔合聚合物、表面活性剂和离子相互作用之间的协同效应可导致提高采油效率，即使对碳酸盐岩储层也是如此。缔合聚合物驱的机理和矿化度效应尚未明确区分，因此无法实现最优设计。此外，用剪切粘度和表观粘度计算的常规毛细管数不能解释这些缔合粘弹性聚合物溶液在不同矿化度下表现出的不同的剩余油采收率。此外，当毛细管数低于临界毛细管数时，粘弹性聚合物的快速驱油开始发生。因此，迫切需要修正传统的毛细管数定义，建立粘弹性缔合聚合物基流体的毛细管脱饱和曲线，从而重新确立毛细管的概念。总之，离子溶液、疏水基团含量和表面活性剂之间的协同效应除了影响其他机理外，还对粘度、拉伸性能和/或润湿性有巨大的潜在影响，从而提高采收率和水力压裂效率。拟议的研究计划将解决使用缔合聚合物基液提高采收率方面的关键技术空白。

In Canada, chemical flooding is currently being applied to increase recovery from a number of medium and heavy oil pools in the Lloydminster region of eastern Alberta and western Saskatchewan. According to the Government of Alberta's Innovative Energy Technologies Program, chemical-enhanced oil recovery (cEOR) could potentially add 80 million m3 of oil to Alberta and Saskatchewan's reserves in the next 20 years. While in the U.S.A. alone approximately 1 billion pounds of polymers were used for cEOR, the potential of chemical flooding in unconventional tight oil remain largely unexplored. In cEOR operations, various chemicals such as polymers, surfactants, alkali or combinations thereof are injected into wells to increase oil recovery. However, different reservoir operating conditions (e.g. pH, temperature, salinity, dissolved iron and oxygen, and presence of alkali and/or surfactant) affect polymer structure and size. Water-soluble polymers with a small amount of hydrophobic character (referred to as Associative Polymers) have huge potential for EOR efficiency even with produced or saline water. Despite selective success in laboratory research in recent years, a comprehensive and predictive knowledge to answer key questions remains elusive. This proposal focuses on understanding mechanisms during associative polymer flooding for applications in conventional and tight oil reservoirs and creating a predictive model. Saline water and smart water can have a positive effect on associative polymer injectivity and transport properties due to polymer coil expansion. Synergistic effects between associative polymer, surfactants, and ionic interactions can lead to increased EOR efficiency even for carbonate reservoirs. The mechanism due to associative polymeric flooding and the salinity effect haven't been clearly distinguished; therefore, optimal design cannot be achieved. Moreover, the conventional capillary number calculated using the shear viscosity and apparent viscosity does not explain the various residual oil recovery shown by these associative viscoelastic polymer solutions at different salinity. Also, rapid oil mobilization for viscoelastic polymers begins to occur at a capillary number lower than the critical capillary number. Therefore, there is a strong need to re-establish capillary concept by modifying the conventional definition of capillary number and developing a capillary desaturation curve for viscoelastic associative polymer--based fluids. In summary, the synergistic effects between ionic solution, hydrophobic group contents and surfactants have huge potential influences viscosity and extensional properties and/or wettability, besides other mechanisms, and thereby EOR and fracking efficiency. The proposed research program will address key technological gaps in EOR using associative polymer based fluids.