Supramolecular Fluid of Associative Polymer and Viscoelastic Surfactant for Hydraulic Fracturing

Abstract

Summary This paper details the study of a new fracturing fluid that is based on a supramolecular complex between associative polymer and viscoelastic surfactant (VES). The crosslinked complex gel was based on weak physical attractive forces, such as van der Waals, hydrogen bonding, and electrostatic interaction between associative polymer and wormlike micelles of VES. The concentration of surfactant in the new fluid is 10 times less than that of VES fracturing fluid. The combination of VES and associative polymer synergistically enhances the viscosity to several times more than that of the individual components alone. The fluid system was optimized by experimental design. The microstructure of wormlike micelles and complex formation was verified by electron microscopy. The fluid is shear stable at high temperature for 1 hour. The dynamic rheological properties of the supramoleulcar fluid show high viscoelasticity, in which the elastic moduli are higher than the loss moduli below an angular frequency of 0.1 rad/s. The proppant-transport test in a large-scale fracture simulator showed good proppant-suspension ability. The fluid has 50% lower formation damage than conventional guar. The fluid was prepared with fewer additives, formed gel instantly, and can be mixed on the fly in the field. The gel can be completely broken with almost no residue. Field application of the new fracturing fluid in a gas well showed the enhancement of gas production by more than 100%. The fluid has 20% lower friction pressure than guar fluid. Hence, the new supramolecular fluid is an effective fracturing fluid.