Viscoelasticity and microstructural properties of zwitterionic surfactant induced by hydroxybenzoate salt for fracturing

摘要

The viscoelasticity and microstructural behaviors of wormlike micelles (WLMs) solutions induced by different organic salts are interesting. However, the influence of different hydroxybenzoate salts on zwitterionic surfactant, erucylamidopropyl carboxybetaine (EDAB) is unknown. The effects of hydroxybenzoate salts; sodium 2-hydroxybenzoate (oBen), sodium 3-hydroxybenzoate (mBen), on sodium 4-hydroxybenzoate (pBen) on EDAB were studied. The rheological and micelle aggregates transformation of the zwitterionic-hydroxybenzoate system were investigated by rheology, dynamic light scattering, and cryo-microscopy transmission electron (Cryo-TEM) measurements. The properties of the EDAB-hydroxybenzoate solutions as fracturing fluid were evaluated based on viscoelasticity, temperature and shear tolerance, sand suspension, gel breaking, and core permeability damage. The micellar development in EDAB-hydroxybenzoates was governed by intramolecular interactions within EDAB molecule, hydrophobic interactions, and electrostatic interactions. Apart from these interactions, the position of the hydroxyl group relative to the carboxyl group in hydroxybenzoates induced hydrogen bonding which was responsible for varied rheological properties of EDAB-hydroxybenzoate fluids. It was found that EDAB-oBen (EoBen) demonstrated higher viscoelasticity than other EDAB-hydroxybenzoates. Switching pH values alters acidity around the carboxylate head groups of EDAB causing structural transformations of EDAB-hydroxybenzoate solutions. EoBen and EDAB-mBen (EmBen) solutions demonstrated a viscoelastic fluid characteristic at pH 7 and a viscous behavior at pH 2. Moreover, the EoBen, EmBen, and EDAB-pBen (EpBen) as fracturing fluids maintained a viscosity of 50, 35.7, and 32.2 mPa.s respectively for 2 h at 90 degrees C and 170 s(-1), these viscosities indicate that all solutions can effectively transport sand during fracturing. The settling velocities in EoBen, EmBen, and EpBen at 90 degrees C were 0.0018, 0.0035, and 0.0066 cm/s respectively after 5 h. The viscosity of the studied EDAB-hydroxybenzoates breaks to <5 mPa.s within half an hour. The residual content and core permeability damage for EoBen were 9.5 mg/L and 5.5% respectively. Thus, compared to EmBen, and EpBen, the EoBen is the best prospect for the development of pH-responsive viscoelastic fracturing fluid. (C) 2020 Elsevier B.V. All rights reserved.