Construction and synergistic mechanism of self‐assembled nano‐unit clean fracturing fluid system

Conventional viscoelastic surfactant based clean fracturing fluids suffer from insufficient temperature tolerance and poor proppant carrying capacity, which restrict their application in medium deep oil gas reservoirs. In this work, a quaternary ammonium salt surfactant ODHAB‐18 was synthesized via a one‐step reaction. Nano silica (SiO 2 ‐16) was further modified by hexadecyltrimethoxysilane, and sodium salicylate (NaSal) was introduced as the counter ion additive to construct a novel nanocomposite clean fracturing fluid system. The optimal formulation was determined to be 3 wt.% ODHAB‐18, 0.1 wt.% modified SiO 2 ‐16, and 0.2 wt.% NaSal. Comprehensive performance evaluation and rheological tests were carried out for the composite system. Experimental results demonstrate that the nanocomposite system exhibits remarkably improved thermal tolerance compared with single component systems, reaching 70.5°C. At 25°C, the static proppant settling rate of the composite system is 0.044 mm · s −1 . Meanwhile, the system possesses favourable shear stability, and its gel breaking performance complies with industrial standards. Core damage test shows that the core permeability damage rate of composite system is 12.5%, which still satisfies the requirement of low damage fracturing fluid. Rheological analysis reveals that negatively charged SiO 2 ‐16 nanoparticles form electrostatic driven pseudo crosslinking with cationic ODHAB‐18 worm like micelles, which reinforces the compactness and stability of micellar network. This nanocomposite fracturing fluid exhibits promising application prospects for fracturing stimulation of medium deep oil and gas reservoirs.