Reseach Of Modifed Guar Gum Used In Oil And Gas Fields

Guar gum(GG)is one of the best water-soluble polysaccharides currently known,which has the advantages of low cost,biodegradable,high viscosity,good water solubility and salt tolerance,resistance to high temperature etc..GG is widely used in oil and gas fields,cosmetic,food,sewage treatment and mining.The ratio of GG in oil and gas fields is 1/4 to 1/3 of the total amount.As the domestic research of modified GG used in gas and oil fields was started relatively late,the aqueous solution viscosity of domestic modified GG is lower than foreign products.High viscosity of GG still mainly relys on imports.Thus,with reference to the foreign product performances,the reaction conditions of modified GG are studied for reducing the dependence on foreign imports.Firstly,carboxymethyl guar gum(CMG)was prepared by the reaction of GG and monochloroacetic acid(MCA)and the influence factors affecting reaction were determind.The maximum degree of substitution(DS)reached 0.11 and the viscosity of CMG aqueous solution(1%,w/w)was up to 7750mPa·s,which met the foreign product standards.The synthesis time of CMG of the new process was greatly reduced.Secondly,the carboxymethyl hydroxypropyl guar gum(CMHPG)was prepared by using MCA and epoxypropane as etherification agents,and the optimum process was determined.The maximum carboxymethyl DS was 0.10,the maximum hydroxymethyl DS was 0.14,and the viscosity reached 6890mPa·s which also met the foreign product standards.Thirdly,the sulfohydroxypropyl guar gum(SHGG)was prepared by reacting of 3-chlorine-2-hydroxypropanesulfonate and GG,and the optimum process was determined.The maximum DS of the products was 0.10,and the etherification time was just 45 min which was shorter than that of foreign products(2~4h),while the viscosity of SHGG aqueous solution(1%,w/w)could be up to 4800mPa·s,which was correspondence to the same foreign products,and its transmittance was 88.5%.The surface tension of SHGG aqueous solution(0.6 %,w/w)was 70.32mN/m,which was lower than the same DS of CMG(74.87mN/m).With the increase of DS,the surface tension of SHGG decreased firstly and then increased.The minimum surface tension was 67.56mN/m when the DS was 0.06.Compared to titration method determined the DS of sulfonic group,energy dispersive spectrometry(EDS)analysis was more simple and quicker.Three kinds of guar gum derivatives were prepared without packing phenomen during the process of dissolution in favor of the further application of the guar gum fracturing thickener.Studying on rheological properties of guar gum derivatives showed that the properties of modified guar gum solution such as stability,salt tolerance,acid and alkali resistance were better than guar gum solution,while the thickening effect decreased slightly.The freezing-thaw stability of derivatives was improved.The structure was characterized by Fourier Transform Infrared Spectroscopy(FTIR)and solid-state Nuclear Magnetic Resonance.The changes of thermal stability were investigated by Thermal Gravity Analysis(TGA).