Preparation And Performance Evaluation Of Supramolecular Self-Assembly Fracturing Fluid Viscosifier

As the commonly used thickener,guar gum contains higher insoluble content,can not break completely and damage reservoirs.This paper puted forward a supramolecular polymer as thickener of fracturing fluid,basing on self-assembly principle,under the condition of not adding cross-linking agent,satisfying the requirement of fracturing fluid viscosifier.The main works of this paper are as follows:Making the choice that vinyl modified β-cyclodextrin as the host unit,N-phenyl ethyl-methyl acrylamide as the guestt unit,throughing redox initiator system,making them copolymerization with acrylamide,acrylic acid and synthesis of supramolecular polymer HMPAM.The optimum conditions determined by single faxtor analysis:0.2%vinyl modifiedβ-cyclodextrin,0.4%N-phenyl ethyl-methyl acrylamide,25%acrylic acid,25%monomers concentration,0.2%initiator;reaction temperature was 40℃ and reaction time was 5h.Fourier transform infrared spectrometry,nuclear magnetic resonance,were used to prove the products were the same as expected.Oligomeric zwitterionic surfactant N,N’,N"-dodecyl-divinyl-triamine-pentacetate was synthesized and characterized by FTIR,then surface active agent SS was prepared by compounding with sodium oleate.Finally,the constuitute of supramolecular self-assembly fracturing fluid viscosifier was determined as0.3%～0.5%HMPAM+0.04%～0.12%SS.At 90℃,118℃ and shear rate of 170s-1,thickening system still remained 124.9mPa·s and 60.54mPa·s after beening sheared for 120min.In the range of 0.1～10Hz of frequency oscillation,thickening system showed gel properties with strong elastic structure with G’>110Pa,G">4Pa.At 60℃ and 90℃,the value of flow index "n" and consistency coefficient"K’were 0.20028,0.18627 and 11.191 Pa sn,12.053 Pa·sn,the area of thixotropic loop were 171.5Pa/s and 68.8Pa/s,proppant settling velocity were 0.00662cm/min and 0.01076cm/min,filtration rate was(4.24～9.351)×10-4m/(?)and(4.24～9.351)×10-5m/min.Supramolecular self-assembly fracturing fluid viscosifier breaking performance was good,after breaking,the viscosity of system was between 2.7 mPa·s and 4.8mPa·s,its surface and interfacial tension with kerosene were 0.52-0.59 mN/m and 26.1-26.9 mN/m,moreover,system don’t contain residues.The damage of permeability was 12.01%～16.12%,does low damage.Floccules and precipitation were not generated after gel breaking liquid mixed with simulated formation.The research achienements further perfected the water-based fracturing fluid system and provided technical support for the development of uncrosslinked gelled fracturing fluid system.