Preparation And Performance Evaluation Of A Hydrophobic Association Thickener For A Fracturing Fluid

With the continuous development of prospecting and exploitation in oil and gas field, Hydraulic fracturing, as an important technology of reservoir reconstructions, has played an increasing significant role in enhancing the production of oil and gas. As the main additive of fracturing system, the property of thickener was directly effect to the fracturing. The paper based on developing fracturing fluid thickener with heat and shearing resistance, good viscoelasticity, no residue as well as low damage. So a fracturing fluid thickener named PAAD-16 was design and prepared, also it showed an excellent performance. The main works accomplished in this paper were list as follows.The intermediate product of amino propyl intermediates dimethyl methyl acrylamide (DMAPMA) was synthesized by amidation reaction, using N, N-dimethyl-1,3-propylene amide and methyl methacrylate (MMA) as raw material. The chemical structure of DMAPMA was characterized by hydrogen infrared spectrum (IR) and nuclear magnetic spectroscopy (’HNMR). Then, the intermediate product was reacted with cetyl bromide to get a hydrophobic monomer named DHAB, also it was characterized by Hydrogen IR and’HNMR. Finally, the hydrophobic association polymer called PAAD-16 was synthesized by free radical polymerization in aqueous solution, using acrylamide (AM),2-acrylamide-2-methyl propane sulfonic acid (AMPS) and DHAB as monomers. The optimal synthetic conditions were determined by the single factor experiment. And conditions were that the initiator dosage was 0.15%(total mass of monomers), pH value was 7, the total concentration of monomers was 25.0%(mass fraction), n(AM):n(AMPS):n(hydrophobic monomers)=89.8:10.0 :0.2, reaction temperature was 70.0℃ and the reaction time was 6.Oh. The structure of PAAD-16 was characterized by hydrogen IR and 1HNMR. The results showed that the synthesized product was the target product.The association concentration (CAC) of PAAD-16 was 0.32% though the preliminary exploration experiment. Meanwhile, it had good salt resistance and heat-resistant. And the kinds and concentrations of surfactants were optimized. The formulation of PAAD-16/SDBS composite fracturing fluid system was determined, and the optimal formulation was: 0.5%PAAD-16+0.05%SDBS+2% KC1.The corresponding performance testing of PAAD-16/SDBS composite fracturing fluid system was carried out according to evaluation criterion of water-based fracturing fluid evaluation. The results showed that the using temperature of the system could reach 120℃, so it had good temperature resistance. The continuous high-speed shear and alternating shear experiment showed that the fracture system had good shear thinning and shear recovery. The rheological tests showed that, between 0.1 Hz and 10Hz, the storage modulus G’ was greater than the energy consumption modulus G". And rheological index ’n’was between 0.1989～0.2295, thickening coefficient ’K’was 16.39～24.62. It showed that the fracturing fluid was pseudoplastic fluid. The sedimentation experiments indicated that the fracturing fluid system could satisfy the requirement of carrying sand. Meanwhile, it contained no residues after the fracturing fluid gel breaking, and gel breaking liquid viscositywas was less than 5 mPa·s, surface tension was less than 27mN/m, the interfacial tension was less than 1mN/m. Also it was easy to flowback as well as had small damage to the reservoir.