| In order to carry out the delay, high temperature and shear resistance fracturing fluid for 2500~3000 m deep well, a new type of terpolymer thickening agent HMPAM was researched and in this paper. In this study, acrylamide(AM) polymerize with acrylate(AA), N,N-diethylacrylamide(DEAM), and the related influencing factors were studied. The chemical structure and rheological properties of its solution were tested. In addition, an organic titanium crosslinker with excellent delay performance was synthesized, and the related influencing factors were studied. Furthermore, a laboratory evaluation of the fracturing gel of the organic titanium agent crosslinking HMPAM was researched. The fracturing fluid with delay time, high temperature and shear resistance, low damage was obtained successfully. Main conclusions were obtained as follows:Terpolymer thickening agent HMPAM was obtained by the free radical emulsion polymerization of AM, AA, DEAM. The influence of the content of monomer, initiator, emulsifier was discussed, and the best synthesis process was determined: m(AM):m(Na AA):m(DEAM)=15:4:6, the dosage of emulsifier SDS is 2% of total monomers, the dosage of initiator K2S208 is 0.5% of total monomers, the reaction temperature is 60 ℃, the reaction time is 3 h.The chemical structure of HMPAM was characterized by infrared spectroscopy(FT-IR), 1H nuclear magnetic resonance(1H NMR) and thermogravimetric analysis(TGA). The microstructure of HMPAM solution was tested by fluorescence spectra. The results show that DEAM will be formed in the HMPAM. The determination of molecular weight of HMPAM was about 600 million. In addition, through the power law model, thixotropy, temperature resistance, the rheological properties of HMPAM solution are studied. The results show that, when HMPAM concentration increased from 0.1% to 0.5%, the k was raised from 0.960 to 5.872, the viscosity become higher, n values of solution are less than 1, so the solution is non-Newtonian fluid. HMPAM solution has the obvious thixotropy and excellent temperature resistant performance.Using tetrabutyl titanate as the main agent, ethylene glycol as the solvent, glycerol and lactic acid as complexing agent, through the complexation reaction, a type of organic-titanium cross-linking agent was synthesized. The best synthesis process as follows: the concentration of solvent ethylene glycol is 60%, the concentration of tetrabutyl titanate is 4%, complexing agent m(glycerol):m(lactic acid)=1:3, p H=4~5, the reaction temperature is 80 ℃, the reaction time is 2 h. Then the organic titanium/ HPAM fracturing fluid was obtained, the optimum concentration of HMPAM solution is 0.5%, the cross-linking ratio is m(HMPAM):m(organic titanium)=100:0.4~100:0.6.Through static suspension sand test, static rheological test, dynamic rheological test and gel breaking test, the laboratory evaluation of the fracturing gel of the organic titanium agent crosslinking HMPAM was researched. The results indicate that: the fracturing gel has an excellent performance of suspended sand, and when the temperature rise, the suspended sand ability increased. The viscosity of the system was still higher than 50 m Pa·s after shearing for 90 min at the temperature of 95 and the shearing rate of 170℃ s-1, so the fracturing fluid possessed good temperature tolerance and shearing resistance. The viscoelastic test proved that the fracturing gel is a typical viscoelastic system, has an excellent elasticity. At the temperature of 60 ℃, 80 ℃, 100 ℃, adding different mass ratio of breaking agent, the residue content of gel breaking fluid is far below the plant gum fracturing fluid, the surface tension is below 30 m N.m-1, the interfacial tension at about 0.8 m N.m-1, so the fracturing fluid is easy to flow back and low damage for the layer. |
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