导热填料对地热井固井材料性能及结构的影响

Effect of Thermal Conductive Filler on Cementing Material Property and Structure for Geothermal Well

固井是地热开发过程中重要的一步,向地热井固井材料中掺入导热填料能够有效提升其导热性能,有利于地热能高效开采。通过试验研究了石墨、铁粉和石英砂对固井材料导热系数和抗压强度的影响,并借助扫描电子显微镜(SEM)、X射线衍射仪(XRD)、压汞仪(MIP)等设备,研究了不同导热填料对固井材料微观结构的影响。结果表明,随着填料掺量增加,固井材料的导热系数增大,48 h抗压强度逐渐减小;与铁粉、石英砂相比,石墨对固井材料性能的影响最为显著;石墨、铁粉、石英砂均对固井材料的微观形貌、水化产物以及孔隙结构产生较大影响;填料使固井材料导热性能发生变化的原因是导热填料取代了水泥基体,而使抗压强度发生变化的原因是填料对材料微观结构的改变。

Cementing is an important step in the process of geothermal development. Adding thermal conductive filler to the cementing material of geothermal well can effectively improve its thermal conductivity and is conducive to the efficient exploitation of geothermal energy. The effects of graphite, iron powder and quartz sand on the thermal conductivity and compressive strength of cementing materials were studied through experiments. The effects of different thermal conductive fillers on the microstructure of cementing materials were studied by means of scanning electron microscope(SEM), X-ray diffraction(XRD) and mercury injection porosimeter(MIP). The results show that with the increase of filler content, the thermal conductivity of cementing material increases and the 48 h compressive strength decreases gradually. Compared with iron powder and quartz sand, graphite has the most significant effect on the properties of cementing materials. Graphite, iron powder and quartz sand all have great effects on the micro morphology, hydration products and pore structure of cementing materials. The main reason for the change of thermal conductivity of cementing materials caused by fillers is that thermal conductive fillers replace cement matrix, while the main reason for the change of compressive strength is that fillers change the microstructure of materials.