钻井液用交联-接枝淀粉的制备及性能

Preparation and Properties of Water-soluble Crosslink-graft Starch for Drilling Fluid

以N,N'-亚甲基双丙烯酰胺为交联剂,过硫酸铵为引发剂,采用"溶剂法"工艺合成了高粘度抗剪切丙烯酸钠接枝淀粉(St),考察了单体、引发剂和交联剂用量、丙烯酸中和度、反应时间及反应温度对合成交联丙烯酸钠接枝淀粉糊液粘度的影响。结果表明,其优化反应条件为:m(淀粉)∶m(丙烯酸)=1∶1.5,乙醇质量分数为80%,过硫酸铵的用量为单体总质量的1%,交联剂为单体总质量的0.6%,反应时间2.5 h,反应温度为55℃,丙烯酸中和度为70%。该交联接枝淀粉糊液具有良好的触变性,在4%盐水泥浆中的添加量为14.0 g/L时,表观粘度为26.0 mPa.s,滤失量为7.2 mL;在饱和盐水泥浆中添加量为23.5 g/L时,表观粘度为54.5 mPa.s,滤失量为3.1 mL;在80℃高温下老化16 h其表观粘度及滤失量等性能基本保持不变,表现出良好的增粘、降失水作用和抗盐、抗老化性能。

The starch（St） graft sodium acrylate was synthesized by solvent method.It has a high viscosity and a strong shear-resistance.The copolymerization was carried out using N,N′-methylene bisacrylamid as the crosslinker and ammonium persulfate as the initiator.Effects such as the amount of monomer,initiator and crosslinking agent,neutralization degree of the acrylic acid（AA）,reaction time and temperature on the apparent viscosity were discussed.Through orthogonal experiment,the optimum graft copolymerization condition was obtained as the follows： the mass ratio of starch to acrylic acid is 1∶ 1.5,the mass fraction of alcohol is 80%,initiator is 1% and crosslinker is 0.6% on the basis of the mass of starch,the reaction time is 2.5 h,the reaction temperature is 55 ℃,and the neutralization degree of the acrylic acid is 70%.The experiments showed that the graft starch paste has an excellent thixotropy.When 14.0 g/L slurry was dissolved in 4% salt water and base fluid,the apparent viscosity of the slurry was 26 mPa·s and the filtration loss was 7.2 mL.When the dosage of slurry was added up to 23.5 g/L in saturated salt water and base fluid,the apparent viscosity of the slurry was 54.5 mPa·s and the filtration loss was 3.1 mL.Additionally,the apparent viscosity and the filtration loss of the slurry were essentially remained the same after the slurry was treated for 16 h at 80 ℃.The experimental results show that the graft starch copolymer has good capacities of increasing viscosity and depressing the filtration loss,and it has excellent properties of aging-resistance and salt-resistance.