Development Of A High Temperature Resistant Fracturing Fluid Thickening Agent

Hydraulic fracturing has been the effective method of reforming formation which can not only boost production of oil field but also augment injection of injection wells.The fracturing fluid has capacity of carrying proppant,transferring pressure and creating the new fissure in formation during the fracturing execution.The thickening agents are the main additives of water-based fracturing fluids,whose ability seriously affect the effect of fracturing treatment.With the increase of reservoir temperature,therefore,it is important to do the research on the development for temperature-resistant thickening agent.A novel kind of temperature-resistant thickening agent was synthesized by the free radical copolymerization of Acrylamide,Acrylic Acid,Sodium p-styrene Sulfonate PS and dimethyl diallyl ammonium chloride.The polymerization conditions were optimized by the single factor method.The optimization of experimental conditions are as follows:the ratio of AM:AA:PS:DMDAAC on mole is 9:1:0.1:0.4,monomer weight concentration is 25%of water,the initiator concentration(Ammonium persulfate)is 0.1%,the solution value pH is 5,reaction temperature is 50? and reaction time is up to 24h.The intrinsic viscosity of the copolymer is 1047 mL/g under this condition.Subsequently,the structure of the copolymer was characterized through Fourier transform infrared(FTIR)spectroscopy.The result shows that all functional groups are present in the LK.Thermal gravimetric analysis demonstrates that the thickening agent LK has a strong ability of temperature-resistance and its degradation temperature is higher than 300?.The properties of the thickening agent solution and the overall performence of the fracturing gel system were researched.The results indicate that:The thickening agent has better solution property,viscosity property and salt resistance property.The organic zirconium crosslinking agent was optimized and viscosity was up to 950mPa·s when the cross-linking ratio is 100:0.5 and the value pH is 4.Under the conditions of 170s-1 and 180?,the temperature resistance and shear resistance properties was tested and the final viscosity still maintains 114 mPa·s after shearing for 2h.So the fracturing fluid possessed good temperature tolerance and shearing resistance.The viscoelastic test proved that the fracturing gel is a typical viscoelastic system and has an excellent elasticity.The sedimentation rate was 0.24mm/min in 90? water bathe,which indicates that the fracturing gel has an excellent performance of suspended sand.The gel breaking liquid has a lot of excellent characteristics such as easily gel broken,less residue,low surface tension and little filtration,which could satisfy the construction requirement of operated fracturing.The ant-temperature and suspended sand mechanism of fracturing gel system was investigated through thermogravimetry,TOC analyzer and scanning electron microscopy.The results show that it is significant for resisting high temperature that the temperature resistant functional group-SO3H connects with C-C? main chain carbon atom and much stronger cross-links were developed after the crosslinking agents was added.The membrane-like structure,throats resulting from membrane wrinkling,the filamentous networks and electric attraction improves its ability to suspend the proppant.In conclusion,the thickening agent LK has the strong ability of viscosity property and salt resistant.The fracturing gel system has better overall performence,which shows its good practical application prospect.