Abstract

In recent years, a polymer-free fracturing fluid is under research to minimize the conductivity damage in formation and fracture during and after fracturing. Through extensive experiments, we prepared CO₂-sensitive wormlike micelles (WLMs) based fracturing fluid system using anionic surfactant NaOA (Sodium Oleate-C₁₈H₃₃NaO₂) and TMTAD (2,6,10-trimethyl-2,6,10-triazaundecane-C₁₁H₂₇N₃). Rheological results from viscosity variation with steady shear rate using CO₂/pH/time-response after CO₂ bubbling confirm that the 3NaOA-TMTAD (3:1) was found as the best one in the properties of WLMs structure and the intermolecular interactions when comparing to 1NaOA-TMTAD and 2NaOA-TMTAD. Further, the surface tension after CO₂ bubbling shows a good capability to decrease about 27.01 mN·m⁻¹ at a CMC of 0.543 mM. The cryo-TEM test justifies the occurrence of spherical and WLMs in the fluid, before and after CO₂ injection. The fluid system presents an outstanding sand suspension and gel breaking property, which are the positive features during the fracturing and flow back period; respectively. Good response with the alternative changes in CO₂ pressures possesses an effective influence on shear viscosity using different temperatures (25 and 85 °C) and shear rates (20, 170, and 200 s⁻¹). Also, the results of a linear relationship and low filtration coefficients verify that the fluid system has good filtration property. Such an easy and environmentally benign fluid system may be involved as a potential candidate in fracturing in unconventional hydrocarbon reservoirs, to reduce the formation damage which is usually very common in the polymer-based fracturing fluid.

摘要

近年来，正在研究一种无聚合物压裂液，以最大限度地减少压裂过程中和压裂后对地层和裂缝的导流损伤。通过大量实验，我们使用阴离子表面活性剂NaOA（油酸钠-C ₁₈ H ₃₃ NaO ₂）和TMTAD（2,6,10-三甲基-2,6,10）制备了基于CO ₂敏感的蠕虫胶束（WLMs）的压裂液体系-三氮杂十一烷-C ₁₁ H ₂₇ N ₃ )。使用 CO _{2 /pH/CO 2}后的时间响应，粘度随稳定剪切速率变化的流变学结果冒泡证实，与 1NaOA-TMTAD 和 2NaOA-TMTAD 相比，3NaOA-TMTAD (3:1) 在 WLM 结构和分子间相互作用方面是最好的。_{此外，CO 2}鼓泡后的表面张力显示出在0.543mM的CMC下降低约27.01mN·m ^{-1的良好能力。}_{cryo-TEM 测试证明在注入 CO 2}之前和之后流体中出现了球形和 WLM 。流体体系具有突出的悬砂破胶性能，是压裂返排过程中的积极特征；分别。_{对 CO 2}的替代变化反应良好使用不同的温度（25 和 85 °C）和剪切速率（20、170 和 200 s ^-1），压力对剪切粘度具有有效影响。此外，线性关系和低过滤系数的结果验证了流体系统具有良好的过滤性能。这种简单且对环境无害的流体系统可作为非常规油气藏压裂的潜在候选者，以减少在聚合物基压裂液中通常非常常见的地层损害。