Dissymmetric beauty: A novel design of heterogemini viscoelastic surfactant for the clean fracturing fluid

Herein, a new heterogemini surfactant (YS-18), which has a novel structure with two different hydrophobic chains, was designed and easily synthesized with excellent yields. When YS-18 was employed as a thickening agent for the clean fracturing fluid, the results of laboratory evaluation obviously showed that it has much better tolerance of salt and thermostability than the corresponding symmetrical surfactants (YS-YS and 18-18). This not only could prove the dissymmetric beauty, but also provides an alternative way to prepare high-functional materials. The fluid system with a formula of 5 wt% of YS-18 and 0.6 wt% of KCl could maintain high fluid viscosity (more than 100 mPa s) for 60 min under a share rate of 170 s−1 at 110 °C. Meanwhile, the fluid could also provide good support to achieve proppant suspension. The SEM study and rheology test revealed that the fluid system has good network structure, and exhibits good elastic fluid properties. Furthermore, the YS-18/KCl fluid system could be easily and thoroughly broken by reservoir brines and hydrocarbon.