A High Temperature Shear-resistant Association Supramolecular Polymer Weak Gel Fracturing Fluid

Supramolecular polymer chemistry is a new interdiscipline of supramolecular chemistry and polymer chemistry. Based on the research work previously done on supramolecular fracturing fluid, a high temperature shear-resistant supramolecular polymer viscosifer, SPM-2, has been synthesized with a zwitterionic surfactant ASF-1 (having good solubilization to hydrophobic monomers), a synthesized long-chain unsaturated cationic monomer, LCM, and another synthesized high temperature monomer HTM, through micelle copolymerization. By compounding the synthesized SPM-2 and PCA-1 (a physical crosslinking agent with worm-like micelle), an association supramolecular polymer fracturing fluid (0.8% SPM-2+0.5% PCA-1) with weak gel has been developed. This fracturing fluid has supramolecular "honeycomb" grid structure, and apparent viscosity that increase with increase in the concentration of PCA-1. It has been proved that ASF-1 and LCM formed strong physical crosslinking. Sheared at 150℃ and 170 s^-1 for 2 h, the apparent viscosity of the fracturing fluid was maintained at about 58 mPa.s, higher than the apparent viscosity of the SPM-2 solution itself by 30 mPa.s. Increased the shear rate frst from 40 s^-1 to 170 s^-1, and then reduced the shear rate to 40 s^-1 again, the viscosity of the fracturing fluid was reduced and resumed sharply, showing good resistance to shearing. Scanned at frequency of 0.01-10 Hz, the elasticity of the fracturing fluid was better than its viscosity. The settling rate of proppant in the fracturing fluid was less than 8×10^-3 mm/s. Compared with the supramolecular polymer SPM-2, this fracturing fluid has suspending capacitythat is an order of magnitude higher. The fracturing fluid, after gel-breaking at 90℃ for 2 h, had viscosity less than 2 mPa·s, and no residue had been found therein. Core experiment indicated that core damage by the fracturing fluid was lower than 10%. Laboratoryexperiments showed that this fracturing fluid can satisfy the needs for fracturing high temperature tight sand gas reservoirs.