pH对羟丙基瓜尔胶压裂液性能影响研究

发布时间：2018-04-16 07:10

本文选题：压裂液 + 瓜尔胶　；参考：《西南石油大学》2016年硕士论文

【摘要】：随着低渗透储层的不断开发,水力压裂对其进行改造是提高产能的必要手段,而压裂液体系是决定压裂施工是否成功的关键因素。常规瓜尔胶压裂液配方中,pH调节剂发挥着重要作用,然而pH在稠化剂溶胀、交联、携砂、破胶等不同压裂施工阶段所起的作用国内外还没有认识清楚。本文从流变学和微观结构上解释不同pH导致瓜尔胶性能的差异,明确不同施工阶段最佳pH范围,优选压裂全过程最佳pH调节剂。以瓜尔胶溶液表观黏度随时间变化关系作为评价指标,研究不同pH下瓜尔胶溶胀规律变化。结果表明pH=9-11为瓜尔胶由快速溶胀向缓慢溶胀过渡的阶段,且溶液中OH-离子吸附于瓜尔胶链上阻碍其溶胀,金属钠离子降低瓜尔胶水动力学体积,降低溶液的最终黏度。进一步运用激光散射仪、扫描电镜进行研究,结果表明瓜尔胶的溶胀规律与不同溶胀阶段瓜尔胶分子粒径及微观构象的变化有关。运用黏度分析方法和流变学方法对不同pH下瓜尔胶溶液结构和流变性能开展研究。pH=7-12.5时瓜尔胶具有较低的临界重叠浓度和较高的特性粘数。Zeta电位测试研究表明,随着pH的增加,瓜尔胶的所带电荷量先增加后减小,从而影响瓜尔胶的分散状态。结合Cross流变模型,求取了不同pH下的零剪切黏度,基于Ostwald-Dewaele方程求取了不同pH下瓜尔胶溶液n、K值,表明pH=8.5-12时瓜尔胶易于溶胀,溶液增黏性能最好。基液表观黏度随着pH增加先增加后减小,其黏度的变化与瓜尔胶微观构象的变化有关。运用流变学方法明确了pH对于冻胶交联时间、冻胶黏度的影响。采用变剪切实验研究pH对冻胶抗剪切性能的影响,pH=8.5-11.5时,瓜尔胶之间有强氢键作用,使其抗剪切性能较强。黏弹性实验及触变性实验验证了不同pH下冻胶最大弹性模量范围及最佳触变性范围。pH=7-12时,冻胶静态携砂性能和破胶性能最好。结合实验结果和现场实际综合分析,为保证压裂液发挥最佳性能,整个施工过程瓜尔胶压裂液的最佳pH范围为9.5-11.5。
[Abstract]:With the continuous development of low permeability reservoirs, hydraulic fracturing is a necessary means to improve productivity, and fracturing fluid system is the key factor to determine the success of fracturing.The pH regulator plays an important role in the formulation of Guar gum fracturing fluid, but the role of pH in different fracturing stages such as thickener swelling, crosslinking, sand carrying and gel breaking is not well understood at home and abroad.This paper explains the difference of guar gum performance caused by different pH in rheology and microstructure, determines the optimal pH range in different construction stages, and optimizes the optimal pH regulator in the whole fracturing process.The relationship between the apparent viscosity of guar gum solution and time was used as the evaluation index to study the swelling law of guar gum at different pH.The results show that pH=9-11 is the transition stage of guar gum from rapid swelling to slow swelling, and the adsorption of OH- ions on Guar gum chain hinders its swelling, and the metal sodium ion decreases the dynamic volume of guar glue and reduces the final viscosity of the solution.The results show that the swelling law of Guar gum is related to the changes of the molecular particle size and the microconformation of Guar gum in different swelling stages.The structure and rheological properties of guar gum solution at different pH were studied by viscosity analysis and rheology method. The results showed that the solution structure and rheological properties of guar gum had lower critical overlap concentration and higher intrinsic viscosity. Zeta potential test showed that with the increase of pH value, the gel had lower critical overlap concentration and higher intrinsic viscosity.The charge of guar gum increases first and then decreases, which affects the dispersion of guar gum.Combined with the Cross rheological model, the zero shear viscosity at different pH was obtained, and the K value of guar gum solution at different pH was obtained based on Ostwald-Dewaele equation. The results showed that guar gum was easy to swell and the viscosity increasing property of the solution was the best when pH=8.5-12 was used.The apparent viscosity of base solution increased first and then decreased with the increase of pH, and the change of viscosity was related to the change of Guar gum conformation.The effect of pH on gel crosslinking time and gel viscosity was determined by rheological method.The effect of pH on the shear resistance of gel was studied by variable shear experiment. When pH value was 8.5-11.5, there was a strong hydrogen bond between guar gum, which made the shear resistance of guar gum stronger.The viscoelastic and thixotropic tests show that the static sand carrying and breaking properties of the gel are the best in the range of maximum elastic modulus and optimum thixotropic range of pH 7-12 at different pH.Combined with the experimental results and field practice, in order to ensure the best performance of the fracturing fluid, the optimum pH range of Guar gum fracturing fluid is 9.5-11.5.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TE357.12

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