Liao Yubin, Jin Jicheng, Du Shenglin, Ren Yufei, Li Qiang
College of Construction Engineering, Jilin University, Changchun 130026, China.
No. 4 Oil Production Plant, PetroChina Qinghai Oilfield Company, Mangya 816400, China.
Polymers (Basel). 2024 Jan 31;16(3):397. doi: 10.3390/polym16030397.
Clean fracturing fluid has the characteristics of being environmentally friendly and causing little damage to reservoirs. Meanwhile, its backflow gel-breaking fluids (GBFs) can be reutilized as an oil displacement agent. This paper systematically evaluates the feasibility and EOR mechanism of a GBF based on a polymer surfactant as an oil displacement system for reutilization. A rotating interfacial tensiometer and contact angle measuring instrument were used to evaluate the performance of reducing the oil-water interfacial tension (IFT) and to change the rock wettability, respectively. Additionally, a homogeneous apparatus was used to prepare emulsions to evaluate GBF's emulsifying properties. Finally, core flooding experiments were used to evaluate the EOR effect of GBFs, and the influence rules and main controlling effects of various properties on the EOR were clarified. As the concentration of GBFs increases, the IFT first decreases to the lowest of 0.37 mN/m at 0.20 wt% and then increases and the contact angle of the rock wall decreases from 129° and stabilizes at 42°. Meanwhile, the emulsion droplet size gradually decreases and stabilizes with increases in GBF concentration, and the smallest particle size occurs when the concentration is 0.12-0.15 wt%. The limited adsorption area of the oil-water interface and the long molecular chain are the main reasons that limit the continued IFT reduction and emulsion stability. The oil displacement experiment shows that the concentration of GBF solution to obtain the best EOR effect is 0.15 wt%. At this concentration, the IFT reduction and the emulsification performance are not optimal. This shows that the IFT reduction performance, reservoir wettability change performance, and emulsification performance jointly determine the EOR effect of GBFs. In contrast, the emulsifying performance of GBFs is the main controlling factor for the EOR. Finally, the optimal application concentration of GBFs is 0.15-0.20 wt%, and the optimal injection volume is 0.5 PV.
清洁压裂液具有环境友好、对储层损害小的特点。同时，其返排破胶液（GBFs）可作为驱油剂再利用。本文系统评价了基于聚合物表面活性剂的GBFs作为驱油体系再利用的可行性及提高采收率的机理。分别使用旋转界面张力仪和接触角测量仪来评估降低油水界面张力（IFT）的性能和改变岩石润湿性。此外，使用均相装置制备乳液以评估GBFs的乳化性能。最后，通过岩心驱替实验评估GBFs的提高采收率效果，并阐明了各种性质对提高采收率的影响规律和主要控制作用。随着GBFs浓度的增加，IFT先降低至0.20 wt%时的最低值0.37 mN/m，然后升高，且岩壁的接触角从129°减小并稳定在42°。同时，乳液液滴尺寸随着GBFs浓度的增加逐渐减小并稳定，当浓度为0.12 - 0.15 wt%时粒径最小。油水界面有限的吸附面积和长分子链是限制IFT持续降低和乳液稳定性的主要原因。驱油实验表明，获得最佳提高采收率效果的GBF溶液浓度为0.15 wt%。在此浓度下，IFT降低和乳化性能并非最佳。这表明IFT降低性能、储层润湿性改变性能和乳化性能共同决定了GBFs的提高采收率效果。相比之下，GBFs的乳化性能是提高采收率的主要控制因素。最后，GBFs的最佳应用浓度为0.15 - 0.20 wt%，最佳注入体积为0.5 PV。
