Study On Preparation And Application Conditions Of Fenugreek Gum Fracturing Fluid

Plant gum and its derivatives have been widely used in the fracturing operations at home and abroad, and it accounted for about 90% of the thickener market demand. The guar gum and hydroxypropyl or carboxymethyl derivatives were commonly used, in recent years, the import price of guar gum has been increased, resulting in the rise of fracturing cost, so it need to find a self-producted plant gum instead of guar gum. In the 1980 s, sesbania gum、 konjac gum and soap kernel glue was represented, but these plant glue have not been able to large-scale promotion, because of instability of gel performance. For the research of new plant gum fracturing system, this paper studied the following four parts of contents:(1) For fenugreek gum thickener, using sodium tetraborate, butyl titanate, triethanolamine, glycerin and glycol as raw materials, an organic titanium boron crosslinking agent was synthesized. The paper has studied the effects of the main agent and ligand material ratio, reaction temperature and reaction time on the properties of crosslinking agent gelling. The best technological conditions were as follows: the m(sodium tetraborate):m(butyl titanate)=1:4, m(triethanolamine):m(glycerin)=1:2, reaction temperature was 70℃, reaction time was 3 h.(2) The fenugreek gum fracturing fluid product performance was measured. When the w(fenugreek gum solution)=0.4%, crosslinking ratio m(fenugreek gum solution):m(titanium boron crosslinking agent)=100:(0.4~0.6), fenugreek gum fracturing fluid was prepared and its performance was tested. The result shows that: the delayed time was 150 s, the shearing resistance and temperature tolerance were good, under the condition of 90℃and 170 s-1, when the fenugreek gum fracturing fluid was sheared 60 min continuously, fracturing fluid viscosity remained above 50 m Pa·s, it achieved the requirement of the fracturing operation; Fenugreek gum fracturing fluid with instantaneous recovery belonged to the thixotropic fluid typical, and had good viscoelasticity. Under normal temperature, when the sand ratio was 30% in volume, the settling velocity was 0.009 mm·s-1, fracturing fluid had excellent carrier performance; The viscosity gel breaking liquid was lower than 5 m Pa·s, and residue content was 350 mg·L-1. The surface-interfacial tension of gel breaking liquid were 32.56 m N·m-1 and 1.07 m N·m-1, lower surface-interfacial tension, which promoted the flowback of gel breaking liquid and reduced the damage to the reservoir.(3) Carboxy methyl fenugreek gum was synthesized and the structure of carboxymethyl fenugreek gum was analysed. Using fenugreek powder, chloroacetic acid sodium, sodium hydroxide, anhydrous ethanol as raw material, carboxymethyl fenugreek gum was prepared. The study has studied the effects of the dosage of sodium hydroxide, the dosage of sodium chloroacetate, reaction temperature, the time of basification and reaction time on the the carboxymethyl substitution degree and apparent viscosity. The best technological conditions were as follows: 10 g fenugreek gum powder, 50 ml ethanol, 25 m L 1.5 mol/L Na OH, 25 m L 0.8 mol/L Cl CH2 COONa, alkalization time was 30 min, reaction temperature was 50℃, reaction time was 5 h. Carboxymethyl substitution degree was 0.52, the mass fraction of 0.4% carboxymethyl fenugreek gum solution viscosity was 80 m Pa·s. By FT-IR analysis, the wave number 1631.49 cm- 1 position appears obvious-C=O vibration absorption peak, the results showed that carboxymethyl functional groups was introduced successfully. By XRD analysis, modified products crystallinity was decreased and the performance was changed due to the carboxymethyl was introduced on the molecular branched chain. By TG analysis, with the increase of temperature, thermal decomposition was completed in 300℃,residual quantity of modified fenugreek gum was increased,the average weight loss rate was reduced. It showed that thermal stability of the modified products was improved.(4) The carboxy methyl fenugreek gum performance was studied. The result showed that: carboxymethyl fenugreek gum solution exhibits the properties of non Newtonian fluid, the viscosity was decreased with increasing shear rate; Using Arrhenius formula fitting, viscosity was dependent on temperature. Carboxymethyl fenugreek gum was compared with fenugreek collagen powder, we could see that dissolving time was shortened from 2 h to 50 min, the water insoluble matter content was decreased from 15% to 4%; By dynamic rheological test, under the influence of temperature, carboxy methyl fenugreek gum fracturing fluid elasticity and viscosity were greater than fenugreek gum fracturing fluid, and the viscoelasticity was changed obviously; By gel breaking liquid residue test, the gel breaking residue content of carboxy methyl fenugreek gum fracturing fluid was 170 mg·L-1, more better than the 350 mg·L-1 of fenugreek gum fracturing fluid; By surface-interfacial tension test, the surface tension of carboxy methyl fenugreek gum fracturing fluid was 25.29 m N·m-1, the interfacial tension was 0.71 m N·m-1, both better than the 32.56 m N·m-1 and 1.07 m N·m-1 of fenugreek gum fracturing fluid.