Review on High-Temperature-Resistant Viscoelastic Surfactant Fracturing Fluids: State-of-the-Art and Perspectives

A viscoelastic surfactant (VES) fluid is an importantpart of awater-based fracturing fluid. As oil and gas exploration expands intodeep, high-temperature, low-permeability reservoirs, the conventionalVES fracturing fluid has shown great limitations. The high-temperature-resistancemechanisms of the high-temperature-resistant VES fracturing fluidsin publicly available literature were analyzed from five aspects:single-chain surfactant system, oligomeric surfactant system, counterioneffect, blended surfactant system, and nano-enhanced VES system. Thefriction-reduction performance, sand-carrying performance, gel-breakingperformance, and core-damage performance of these systems were summarized.The results show that oligomeric surfactants with a monounsaturatedhydrophobic long chain (>C21) are most likely to be used for VESfracturingfluids in high-temperature reservoirs, but the loading of the surfactantsis still relatively high (3-5 wt %). By reducing the repulsionamong polar headgroups to effectively decrease the area of head groups,or/and penetrating into the nonpolar cores based on hydrophobic interactionto increase the average hydrophobic volume of hydrophobic tails, counterionsaffect the performance of VESs. The aromatic counterion salts arepreferred choices for improving the temperature resistance, frictionreduction, and suspended sand performance of VES fluids. The blendedsurfactant/synthetic polymer systems based on noncovalent interactionimprove the temperature resistance of VES fluids and reduce the loadingof the surfactants to a certain extent. Based on the "pseudo-cross-linking"of nanomaterials and wormlike micelles, a very small amount of nanomaterialscan improve the temperature resistance of VES fluids and reduce theloading of the surfactants. The most essential and effective methodto improve the temperature resistance of VES fluids for fracturingis the molecular structure design based on the packing parameter theory.However, the synthesis process or route still needs further optimizationto reduce production costs. In addition, given the excellent performanceof VES fluids enhanced by nanomaterials, further research should beconducted on the influence mechanism of nanomaterial type and geometricfeatures on the performance of VESs, as well as the potential harmfulnessof nanomaterials, to promote the field-scale application of nano-enhancedVES fluids.