[目的]研究硅藻土对硅酸钠的吸附效果,探讨油井水泥环微裂缝的修复问题.[方法]采用硅酸钠作为自愈合剂,硅藻土为载体,利用真空浸渍法制备硅藻土基自愈合材料;借助扫描电子显微镜(scanning electron microscope,SEM)、红外光谱仪(infrared spectrometer,FTIR)、全自动表面积和孔结构分析仪(automatic surface area and pore structure analyzer,BET)进行分析;通过对比分析掺入硅藻土基自愈合材料前、后水泥石的抗压强度、恢复率和渗透率等,对自愈合效果进行评价;通过对水泥石裂缝表面物质进行X射线衍射分析(X-ray diffraction,XRD)、热重分析(thermal analysis,TG)和SEM分析评价材料的自愈合机制.[结果]利用真空浸渍法能够成功制得硅藻土基自愈合材料;硅藻土基自愈合材料在油井水泥中最佳掺量为9％(质量分数),该试样劈裂造缝后自愈合14 d的抗压强度比纯水泥的提高99.57％,自愈合14 d后渗透率为0.42 mD,渗透率降低率达到75.44％,比纯水泥试样的高40.94％,且自愈合14 d后裂缝表面已经闭合.[结论]硅藻土基自愈合材料制备工艺简单,在油井水泥浆中具有良好的分散性和稳定性,可以促进油井水泥石微裂缝自愈合.
Preparation and characterization of oil well cement self-healing materials based on sodium silicate and diatomite
Objective The expansion of micro-cracks in oil well cement seriously affects the safe exploitation of oil and gas.Self-healing cement slurry can respond timely to repair these micro-cracks.When micro-cracks form,the self-healing agent activates to repair them.As a potential self-healing agent in cement-based materials,sodium silicate reacts with calcium hydroxide(CH)to form calcium silicate hydrate(C-S-H).Microcapsule technology is usually used to encapsulate sodium silicate.However,these microcapsules have poor compatibility with cement paste.To overcome this problem,this paper aims to use diatomite,an inorganic porous mineral with an intricate pore structure and excellent physical and chemical properties,to adsorb sodium sili-cate to prepare diatomite-based self-healing materials.Also,the paper explores their effect on the self-healing properties of oil well cement.Methods Diatomite-based self-healing materials were prepared using the vacuum impregnation method.The materials were characterized by scanning electron microscopy(SEM),Fourier-transform infrared spectroscopy(FTIR),and an automatic sur-face area and pore structure analyzer(BET).The self-healing effect was evaluated by comparing and analyzing cement stone's compressive strength,recovery rate,and permeability before and after the incorporation of diatomite-based self-healing materi-als.The self-healing mechanism was analyzed using X-ray diffraction(XRD),thermal analysis(TG),and SEM.Results and Discussion After adsorption,it was found that the number of pores on the sample surface was significantly reduced compared to pre-adsorption,and most of the pores were filled.BET analysis also showed that the pore volume and aver-age pore size were smaller after adsorption.FTIR analysis confirmed that sodium silicate filled the pores of diatomite.Then,diatomite-based self-healing materials were added to cement at different mass fractions of 0％,3％,6％,9％,and 12％.The 14-day compressive strength of the sample with 9％content was(39.56±1.98)MPa,17.95％higher than that of pure cement.At the same time,the self-healing experiment of cement stone after the Brazilian splitting method was carried out.After 14-day self-healing,the compressive strength of the 9％cement sample reached(36.90±l.85)MPa,99.57％higher than that of pure cement.Its permeability was 0.42 mD after 14-day of self-healing,and the permeability reduction rate was 75.44％,40.94％higher than that of pure cement.XRD analysis of the cracked sample surface showed a lower CH content in diatomite-based self-healing material compared to pure cement.TG analysis further confirmed that CH content was lower,and C-S-H content was higher than that of the pure cement.SEM analysis confirmed that the self-healing product of the diatomite-based self-healing material at the cement stone cracks was C-S-H.Conclusion The preparation and characterization of a sodium silicate and diatomite-based self-healing material for oil well cement were reported in this paper.The prepared samples were analyzed by SEM,FTIR,and BET.The diatomite-based self-healing materials could be successfully prepared using vacuum impregnation method.At the same time,the diatomite-based self-healing material was added to the cement to explore its effect on the self-healing performance of the oil well cement stone.The optimum content of the material in cement was 9％(mass fraction).Diatomite-based self-healing materials exhibited good dispersibility and stability in cement slurry,which could promote the self-healing of micro-cracks in oil well cement stone.Their simple preparation process and compatibility with cement paste suggest that inorganic porous materials can provide a refer-ence for further research on the repair of micro-cracks in cement sheath.
sodium silicatediatomiteoil well cementmicro-crackself-healing
万方数据
维普
