表面改性玻化微珠增强地热保温固井水泥研究

Research on surface modified vitrified microbeads for enhanced geothermal insulation cement

摘要:

在地热开采井上部非储层段采用保温水泥固井，将有利于提高出口温度，改善能量利用效率。玻化微珠因其质轻、价廉、导热系数低等优势，已广泛应用于建筑外墙保温中。但由于其钝化表面与水泥基质结合性较差，随其掺量的增加，复合水泥的强度呈线性降低。本文利用酸腐蚀、高温灼烧、喷涂硅烷偶联剂等方式，开展玻化微珠表面改性，并利用改性后的玻化微珠制备了地热保温固井水泥。通过SEM，XRD等微观测试手段，对改性前后微珠的表面形态进行了表征，测试了改性前后微珠对水泥石的强度、水化产物、微珠与水泥基质界面形貌等的影响研究。得出了以下结论：密度较小的微珠，等质量与水泥混合后，水泥基质对微珠表面覆盖不足，导致其掺入后强度的迅速降低；60 ℃养护后，改性玻化微珠水泥试块抗压强度提升了173.5%，掺入氟硅酸镁使得强度进一步提升；改性后，微珠表面活性提高、其中的无定型SiO₂与CH火山灰反应增强，生成了起主要强度作用的C-S-H凝胶；微珠表面粗糙度增加，水化产物的附着增多并参与水泥整体的硬化过程中，水泥基质与微珠表面的粘结改善，共同提高了水泥石强度。

Abstract:

Using thermal insulation cement in the upper non reservoir section of geothermal extraction wells will be beneficial for increasing outlet temperature and improving energy utilization efficiency. Vitrified microbeads have been widely used in building exterior wall insulation due to their advantages of light weight， low cost and low thermal conductivity. However， due to its poor adhesion between the passivated surface and the cement matrix， the strength of the composite cement decreases linearly with the increase of its dosage. This article uses methods such as acid corrosion， high-temperature burning and spraying silane coupling agents to carry out surface modification of vitrified microspheres， and uses the modified vitrified microspheres to prepare geothermal insulation cementing cement. The surface morphology of vitrified microspheres before and after modification was characterized， the effects of modified and unmodified microspheres on the strength， hydration products， and interface morphology between microspheres and cement matrix were studied by micro testing methods such as SEM， XRD， etc. The following conclusion can be drawn： for microspheres with lower density， when mixed with cement of equal mass， the cement matrix does not cover the surface of the microspheres enough， resulting in a rapid decrease in the strength of the cement stone after its addition； After curing at 60 ℃， the compressive strength of the modified vitrified microsphere cement increased by 173.5%， and the addition of magnesium fluorosilicate further enhanced the strength； After modification， the increase in surface roughness of microbeads promotes the adhesion of hydration products， enhances the activity of microbeads involved in the overall hardening process of cement， and improves the bonding between cement matrix and microbead surface， collectively improving the strength of cement stone.