Study On The Effect Of AC Foaming Agent On The Self-Degrading Alkali-Activated Cement Of Geothermal Well And Its Performance

In this paper,the development and research of degradable cement for medium-high temperature geothermal Wells are carried out.The ideal cement formula should have a high strength at 85?,and the strength drops sharply to achieve the effect of self-degradation when it meets water at medium-high temperature.Alkali excitation current cement research in geothermal well temperature on the high side,all above 150?,so in this paper,on the basis of CMS alkali excitation cement,select AC foaming agent and foam activator,through the screening of different particle sizes of the freedom of AC foaming agent and activator add ratio,effective in reducing alkali excitation cement density,improve the flow performance of the slurry,developed for 120?150?high temperature geothermal well in alkali cement.The main research methods and conclusions are as follows:The thermal decomposition characteristics of five kinds of AC foaming agents were measured by thermal weight loss test method.The results showed that the AC foaming agents treated by 85?filtrate began to degrade at 90?,and the weight loss rate was about 10%at150?.The thermal decomposition products are H₂O,CO₂,NH₃,CO and other gases.The two selected AC foaming agents were added to the CMS alkali stimulated cement to measure the basic properties of the cement slurry.Two kinds of AC foaming agents were selected by compressive strength,and the optimal dosage of AC foaming agents in 120?and150?geothermal Wells were respectively selected.The optimal dosage of AC-4(DN4)is0.06%,and that of AC-12(DN12)is 0.04.Activator ZnO was added on the basis of the optimized amount of AC to explore the optimal ratio of two kinds of AC foaming agents and ZnO.The experiment showed that the addition of activator ZnO could improve the strength of alkali activated cement at 85?,120?and 150?,but had little effect on the strength of alkali activated cement after high temperature water contact.The ratio of AC foaming agent to activator ZnO of 4:1 and 3:1 is better than that of 2:1.On the basis of the optimal addition amount of AC foaming agent and the optimal ratio of AC foaming agent and activator ZnO,orthogonal test with four factors and three levels was carried out to select the optimal formula.Among them,AC,CMS,ZnO,W/B(water-cement ratio)were the four factors.Finally,the optimal formula at 120?and 150?was optimized as follows:2.5%CMS,0.04%AC-12(DN12),3:1 AC:ZnO and 0.7 water-cement ratio.Through XRD,FTIR and polarizing microscope,it is found that AC foaming agent has little effect on the hydration process of alkali excited cement,while CO₂ generated by thermal degradation can promote the generation of hydration product CaCO₃.The study showed that after alkali excited cement was cured at 120?and 150?,OH-in alkaline environment would promote the hydrorigidity of cement,improve the generation of CaCO₃ and C-S-H cementification,and thus improve its strength,but had little influence on the strength after water contact.Based on the above experimental analysis,AC foaming agent is a kind of foaming agent suitable for application in medium-high temperature geothermal Wells,which can effectively reduce the density of cement and promote the self-degradation of alkali stimulated cement.