The properties of novel supramolecular complex fracturing fluid are discussed in this paper. Based on the supramolecular polymer thickener (SMPT), the thickening system forms a gel with viscoelastic surfactant (VES) wormlike micelles through experimental design. The resultant gel contains very efficient cross-links between the wormlike micelles and polymer chains that can be advantages in elastic and viscous properties of the fluid.
The fracturing fluid contains nearly twentieth of conventional surfactant fracturing fluid. Both VES and SMPT synergistically enhance the shear-tolerant property in high-temperature much more than the single. The electron microscopy photos of the solution microstructure and rheological results reveal the suitable ratio of SMPT and VES forms a supramolecular network honeycomb structure, which is built by strong hyper-branched compound structures through noncovalent interactions. Meanwhile, the physical model can legitimately expound the gelation mechanism of the supramolecular viscoelastic gel. Moreover, proppant suspension behavior, gel breaking test and the permeability damage rate of core matrix were studied.
Laboratory data showed that the viscosity of new fluid could be maintained above 50 cp with the formation of 0.8%SMPT and 0.5%VES. The steady shear viscosity test has been conducted for 2 hours at 150 °C and 170s−1. Shear restoration experiment proved the new supramolecular viscoelastic fluid was in high viscosity at low shear rate and a strong reversible shear thinning behavior. The dynamic rheological properties showed high viscoelasticity, while elastic modulus was higher than loss moduli at an oscillation frequency 0.01Hz. The result of sand sedimentation experiment with 20% sand ratio was well. The supramolecular viscoelastic fluid was completely broken and gel breaking liquid was transparent with no water insoluble residue. The permeability damage rate of core matrix caused by this fracturing fluid was 20% less than guar fluid.
The supramolecular viscoelastic fluid presents in this paper could be a total or partial alternative to VES and guar for hydraulic fracturing whose price is subjected to harvest areas. Results show that the new supramolecular viscoelastic fluid is an effective fracturing fluid satisfies high temperature tight gas reservoir.