胶凝酸稠化剂在方解石中的滞留伤害研究

发布时间：2018-04-19 11:49

本文选题：碳酸盐岩 + 聚丙烯酰胺　；参考：《西南石油大学》2017年硕士论文

【摘要】：胶凝酸是目前碳酸盐岩酸化压裂中使用最广泛的改造工作液,其稠化剂聚丙烯酰胺在储层岩石中的吸附和堵塞,将严重降低储层渗透率。为提高酸化后裂缝的导流能力,弄清胶凝酸稠化剂对孔隙的堵塞伤害机理,有必要开展系统研究。本文以碳酸盐岩主要成分—方解石作为滞留介质,研究聚丙烯酰胺在其中的的静态吸附机理和动态滞留规律,以此对复杂矿物组成的岩石中的稠化剂滞留问题进行了细致解构。在所得认识基础上,测试研究结果对降低灰岩岩心伤害的效果,证实了该研究思路和方法的科学性。采用紫外分光法研究聚丙烯酰胺浓度、液固比、方解石粒径、温度、背景离子的种类和浓度等对吸附量影响,实验结果表明,吸附平衡的移动影响了体系吸附量的变化趋势。使用傅立叶变换红外光谱、Zeta电位测试等实验方法细致探究了聚丙烯酰胺-方解石吸附体系中可能的吸附作用力的强度,发现使用尿素处理可以使吸附量减少60%以上,从而证实稠化剂与方解石之间主要作用力为氢键作用。采用Langmuir单分子层吸附模型拟合实验数据,证实氢键吸附位点的存在和吸附界面聚丙烯酰胺的分子形态共同决定了该体系的吸附规律。为弄清聚丙烯酰胺在孔隙中的滞留机理,分析了渗透率伤害程度和滞留量随驱替流量、返排流量、返排时间的变化规律,结果显示聚丙烯酰胺在方解石中的堵塞存在一定的强度上限。以絮团形态和方解石介质孔隙结构为基础研究了聚丙烯酰胺堵塞行为。结合静态吸附机理和絮团堵塞条件对聚丙烯酰胺在方解石中的动态滞留现象进行分析,划分出滞留量和伤害率随聚丙烯酰胺浓度变化的三个典型阶段,并发现在岩石孔径与稠化剂絮团粒径一定情况下,在滞留伤害的组成中,吸附居次要((?)20%)而堵塞居主要((?)50%)。使用压汞法对比了未经处理的岩心和受到滞留伤害的岩心的孔隙结构,证实聚丙烯酰胺滞留将同样造成岩中孔径缩小和堵塞。在分析单矿物和岩心矿物滞留伤害联系的基础上,论证了尿素和氟碳表面活性剂对降低聚丙烯酰胺滞留伤害的可行性。进而使用方解石灰岩岩心进行伤害降低实验,发现尿素可降低滞留伤害10%以上,加入氟碳表面活性剂伤害减少率较小但可以在短时间(约30min)内取得明显效果。
[Abstract]:Gelling acid is the most widely used modification fluid in acidizing fracturing of carbonate rock at present. The adsorption and plugging of polyacrylamide in reservoir rock will seriously reduce reservoir permeability.In order to improve the conductivity of the fracture after acidizing and clarify the mechanism of plugging and damage caused by the gelling acid thickener, it is necessary to carry out a systematic study.In this paper, the static adsorption mechanism and dynamic retention law of polyacrylamide in carbonate rock, which is the main component of carbonate rock, is studied, and the problem of thickener retention in rock with complex mineral composition is deconstructed in detail.On the basis of the knowledge obtained, the results of the test and research are effective in reducing the damage of limestone core, which proves the scientific nature of the research idea and method.The effects of polyacrylamide concentration, liquid-solid ratio, calcite particle size, temperature, type and concentration of background ions on the adsorption capacity were studied by UV spectrophotometry. The experimental results showed that the shift of adsorption equilibrium affected the change trend of adsorption capacity.The strength of possible adsorption force in polyacrylamide calcite adsorption system was investigated by Fourier transform infrared spectroscopy (FTIR) and Zeta potential measurement. It was found that urea treatment could reduce the adsorption capacity by more than 60%.It is proved that the main force between thickener and calcite is hydrogen bond.The Langmuir monolayer adsorption model was used to fit the experimental data. It was proved that the existence of hydrogen bond adsorption sites and the molecular morphology of polyacrylamide at the adsorption interface jointly determined the adsorption law of the system.In order to understand the retention mechanism of polyacrylamide in pores, the change of permeability damage degree and retention amount with displacement flow rate, back discharge flow rate and reflux time were analyzed.The results show that there is a certain upper limit of the strength of polyacrylamide plugging in calcite.The plugging behavior of polyacrylamide was studied on the basis of floc morphology and pore structure of calcite medium.The dynamic retention of polyacrylamide in calcite was analyzed based on static adsorption mechanism and flocculation plugging condition. The three typical stages of the change of retention and damage rate with the concentration of polyacrylamide were divided.It is also found that in the case of rock pore size and thickener flocs size, in the composition of residual damage, adsorption occupies the secondary position, and the blockage occupies the main position of 50%.The pore structure of untreated core and damaged core is compared by mercury injection method. It is proved that polyacrylamide retention will also cause pore size reduction and blockage in rock.Based on the analysis of the relationship between single mineral and core mineral retention damage, the feasibility of urea and fluorocarbon surfactant in reducing the retention damage of polyacrylamide was demonstrated.The damage reduction experiment with calcite limestone core shows that urea can reduce the residual injury by more than 10%, and the damage reduction rate of fluorocarbon surfactant is small, but the obvious effect can be obtained in a short time (about 30 min).
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE39

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