Arekhov Vladislav, Hincapie Rafael E, Clemens Torsten, Tahir Muhammad
OMV Russia Upstream GmbH, 197046 St. Petersburg, Russia.
OMV Expl. & Production GmbH, New Technologies, Trabrennstraße 6-8, 1020 Vienna, Austria.
Polymers (Basel). 2020 Sep 29;12(10):2241. doi: 10.3390/polym12102241.
The injection of chemicals into sandstones can lead to alterations in wettability, where oil characteristics such as the TAN (total acid number) may determine the wetting state of the reservoir. By combining the spontaneous imbibition principle and the evaluation of interfacial tension index, we propose a workflow and comprehensive assessment to evaluate the wettability alteration and interfacial tension (IFT) when injecting chemical-enhanced oil-recovery (EOR) agents. This study examines the effects on wettability alteration due to the application of alkaline and polymer solutions (separately) and the combined alkali-polymer solution. The evaluation focused on comparing the effects of chemical agent injections on wettability and IFT due to core aging (non-aged, water-wet and aged, and neutral to oil-wet), brine composition (mono vs. divalent ions); core mineralogy (~2.5% and ~10% clay), and crude oil type (low and high TAN). Amott experiments were performed on cleaned water-wet core plugs as well as on samples with a restored oil-wet state. IFT experiments were compared for a duration of 300 min. Data were gathered from 48 Amott imbibition experiments with duplicates. The IFT and baselines were defined in each case for brine, polymer, and alkali for each set of experiments. When focusing on the TAN and aging effects, it was observed that in all cases, the early time production was slower and the final oil recovery was longer when compared to the values for non-aged core plugs. These data confirm the change in rock surface wettability towards a more oil-wet state after aging and reverse the wettability alteration due to chemical injections. Furthermore, the application of alkali with high TAN oil resulted in a low equilibrium IFT. By contrast, alkali alone failed to mobilize trapped low TAN oil but caused wettability alteration and a neutral-wet state of the aged core plugs. For the brine composition, the presence of divalent ions promoted water-wetness of the non-aged core plugs and oil-wetness of the aged core plugs. Divalent ions act as bridges between the mineral surface and polar compound of the in situ created surfactant, thereby accelerating wettability alteration. Finally, for mineralogy effects, the high clay content core plugs were shown to be more oil-wet even without aging. Following aging, a strongly oil-wet behavior was exhibited. The alkali-polymer is demonstrated to be efficient in the wettability alteration of oil-wet core plugs towards a water-wet state.
向砂岩中注入化学物质会导致润湿性发生改变，其中诸如总酸值（TAN）等原油特性可能决定储层的润湿状态。通过结合自吸原理和界面张力指数评估，我们提出了一种工作流程和综合评估方法，以评估注入化学强化采油（EOR）剂时的润湿性改变和界面张力（IFT）。本研究考察了单独注入碱性溶液和聚合物溶液以及联合注入碱-聚合物溶液对润湿性改变的影响。评估重点在于比较化学剂注入对润湿性和IFT的影响，这些影响因岩心老化情况（未老化、水湿以及老化且从中性变为油湿）、盐水成分（单价离子与二价离子）、岩心矿物学（约2.5%和约10%的粘土）以及原油类型（低TAN和高TAN）而异。对清洁的水湿岩心塞以及恢复为油湿状态的样品进行了阿莫特实验。对IFT实验进行了300分钟时长的比较。从48次重复的阿莫特自吸实验中收集了数据。在每组实验中，针对盐水、聚合物和碱分别定义了IFT和基线。当关注TAN和老化效应时，观察到在所有情况下，与未老化岩心塞的值相比，早期产量较低且最终原油采收期较长。这些数据证实了老化后岩石表面润湿性向更油湿状态的变化，并扭转了因化学剂注入导致的润湿性改变。此外，将碱与高TAN原油一起使用会导致较低的平衡IFT。相比之下，单独使用碱无法驱替被捕获的低TAN原油，但会导致润湿性改变以及老化岩心塞变为中性湿状态。对于盐水成分，二价离子的存在促进了未老化岩心塞的水湿性和老化岩心塞的油湿性。二价离子充当矿物表面与原位生成的表面活性剂的极性化合物之间的桥梁，从而加速润湿性改变。最后，对于矿物学效应，即使未老化，高粘土含量的岩心塞也显示出更油湿的特性。老化后，表现出强烈的油湿行为。碱-聚合物被证明在将油湿岩心塞的润湿性改变为水湿状态方面是有效的。
