黏弹性转向酸转向性能研究

发布时间：2018-05-24 07:56

本文选题：转向酸 + 微观结构　；参考：《西南石油大学》2015年硕士论文

【摘要】：目前低渗透、特低渗透油藏已成为油气田开发的主战场,酸化是低渗透储层开发和增产的重要措施之一,近年来发展了以黏弹性表面活性剂为基础的转向酸化体系,可以满足均匀布酸目的,有效提高了酸化施工效果。然而该转向酸化技术转向理论问题在国内外还没有认识清楚,制约了这项技术优势的更好发挥。本文在广泛调研国内外转向酸研究现状及表面活性剂溶液微观结构表征方法的基础上,研究了转向酸溶液的微观结构及宏观黏弹性能与转向性能之间的关系。通过稳态黏度测试、黏弹性能测试和触变性测试研究了酸浓度、钙离子、表面活性剂浓度以及醇浓度对转向酸流变特性的影响。实验结果及由相关模型求取流变参数显示不同酸浓度下转向酸黏度差异并不大,随着酸浓度的降低,弹性模量G与结构参数λ都大致呈现出先增加后降低的趋势,在12%-15%时达到最大。而在酸浓度为8%-10%时,转向酸溶液出现相分离,流变性质发生突变,但剪切作用、钙离子以及醇存在能促使体系形成较为稳定的结构,溶液弹性模量以及体系的结构弛豫时间τ均明显增大。采用动态光散射实验和透射电镜扫描对转向酸溶液内部聚集体尺寸及微观结构变化进行了观测。结果表明随着酸浓度从高到低,胶束平均粒径先升高后降低,在高酸浓度下,体系主要以长蠕虫状胶束相互缠绕形成网络结构为主且随着酸浓度的降低,网状结构间网眼大小明显变小,结构逐渐变得均一、连续、致密。转向酸溶液微观结构的变化与不同酸浓度流变性能的改变一致,同样在不同醇浓度以及表面活性剂浓度下二者也显示出同步变化的规律,表明溶液中胶束聚集形态的变化是引起体系弹性特征以及结构强度差异的内在原因。使用微孔滤膜模拟油藏的多孔介质研究了封堵转向性能。发现随着酸浓度的减小,转向酸溶液封堵能力先增强后减弱,通过计算体系流经变径孔道过程中弹性黏度发现,转向酸封堵转向性能不仅与体系静态黏度、黏弹性有关,同样与液体通过多孔介质时动态黏弹性以及由此产生的附加弹性黏度有关,而数值模拟结果表明采用考虑由弹性黏度引起的拉伸压降的模型模拟结果更接近真实情况。
[Abstract]:At present, low permeability and ultra-low permeability reservoirs have become the main battlefield of oil and gas field development. Acidizing is one of the important measures to develop and increase production of low permeability reservoirs. In recent years, a turning acidizing system based on viscoelastic surfactants has been developed. It can meet the purpose of uniform acid distribution and effectively improve the effect of acidizing construction. However, the theory of turning to acidizing technology has not been clearly understood at home and abroad, which restricts the better exertion of this technology advantage. On the basis of the investigation of the present situation of the study on steering acid at home and abroad and the methods of characterization of the microstructure of the surfactant solution, the relationship between the microstructure of the acid solution and the macroscopic viscoelastic energy and the steering property is studied in this paper. The effects of acid concentration, calcium ion, surfactant concentration and alcohol concentration on rheological properties of turning acid were studied by means of steady viscosity test, viscoelastic property test and thixotropy test. The experimental results and the rheological parameters obtained from the model show that the viscosity of the turning acid is not different at different acid concentrations. With the decrease of acid concentration, the modulus of elasticity G and the structural parameter 位 tend to increase first and then decrease. Reach maximum at 12- 15%. However, when the acid concentration was 8- 10%, the phase separation appeared in the acid solution and the rheological property was abrupt. However, shearing, calcium ion and alcohol could promote the formation of a stable structure of the system. The elastic modulus of the solution and the relaxation time 蟿 of the structure of the system increase obviously. Dynamic light scattering experiments and scanning electron microscopy were used to observe the size and microstructure of the aggregates in the acid solution. The results showed that the average particle size of micelles first increased and then decreased with the acid concentration from high to low. At high acid concentration, the long wormlike micelles formed a network structure and the structure decreased with the decrease of acid concentration. The size of mesh between reticular structures became smaller, and the structure became uniform, continuous and compact. The change of the microstructure of the turning acid solution is consistent with the change of the rheological properties of different acid concentration, and the change law of the two changes is also shown at different concentration of alcohols and surfactants. It is shown that the change of micelle aggregation morphology in solution is the internal cause of the difference of the elastic characteristics and the structural strength of the system. The performance of plugging steering was studied by using microporous membrane to simulate the porous media of reservoir. It is found that with the decrease of acid concentration, the plugging ability of the turning acid solution increases first and then weakens. By calculating the elastic viscosity of the system in the process of flowing through the variable diameter channels, it is found that the steering performance of the turning acid plugging is not only related to the static viscosity of the system, but also to the viscoelasticity of the system. It is also related to the dynamic viscoelasticity of liquid passing through porous media and the additional elastic viscosity. The numerical simulation results show that the model considering the tension pressure drop caused by elastic viscosity is closer to the real situation.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE357.2

【参考文献】