Study On Semi-dry Process Of Carboxymethyl Hydroxypropyl Guar Gum And Pilot-scale Research

Our country has a huge reserve of shale gas resources,and guar gum as a water-based fracturing fluid is widely used in shale gas and other areas of mining.Guar gum itself has defects,such as poor dispersion,instable viscosity.Therefore,modified products of guar gum are used in a practical application.Carboxymethyl hydroxypropyl guar gum(CMHPG)as fracturing fluid has better performance than other modified guar gum.At present,the double modification of guar gum mainly adopts organic solvent method.The use of much organic solvent and high energy consumption of the solvent recovery lead to high cost.Besides,the solvent evaporation in the production process not only causes environmental pollution but also increases production risk.In this paper,we use water instead of organic solvents.Carboxymethyl hydroxypropyl guar gum is synthesized by semi-dry method in a kneader,and its pilot study is carried out.The effects of some factors on the degree of substitution(DS)and viscosity are discussed,such as the amount of catalyst,sodium chloroacetate consumption,propylene oxide consumption,water consumption,alkalization time,reaction temperature and reaction time.In addition,the optimum amount of reactants is determined.The amount of the catalyst,sodium chloroacetate,propylene oxide and water are 10,60,40,350 respectively when the amount of guar gum is 200.The alkalization time,reaction time and reaction temperature are determined as 20 min,4 h,35 ℃respectively in the reaction conditions.The results show that the modified guar gum has a viscosity of up to 38 cps,and it can reach 90%viscosity at 3min and maintain a high viscosity in high salinity and temperature.Lower concentrations of cross-linking agent can be associated with its cross-linking.At the same time,the structure was characterized by IR and NMR.The success of carboxymethyl and hydroxypropyl substitution was determined.In addition,this paper based on laboratory results has carried out a medium-scale production experiments,designed the process flow,selected the pilot equipment,guided the equipment installation and commissioning,and analyzed the reaction factors under the test conditions.The synthesis conditions were determined as alkalization time 20 min,reaction temperature 35 ℃,reaction time 5 h.A hydroxypropyl substitution is greater than 0.25 and a carboxymethyl substitution is larger than 0.2.The viscosity of carboxymethyl hydroxypropyl guar gum is about 38cps.