掺超细矿渣油井水泥抗碳化腐蚀情况及其机理OA

To improve the ability of set cement to resist carbonation-induced corrosion,the mobility,the strength of set cement and the depth of carbonation-induced corrosion in supercritical CO2 environment were measured of a cement slurry in which ultrafine slag was substituted for oil-well cement.This measurement was aimed to determine the appropriate amount of the slag to substitute cement.Using low-field NMR,XRD and SEM with energy dispersive spectroscopy,the mechanisms with which the substituting ultrafine slag affects the ability of the set cement to resist carbonation-induced corrosion was studied.It was concluded that when the substituting amount of the ultrafine slag is less than 40%,it helps improve the mobility of the cement slurry;when increasing the substituting amount of the ultrafine slag,the strength of the set cement first increases and then decreases,and the depths of the carbonation-induced corrosion first decrease and then increase.Compared with the reference sample,the cement slurry sample with substituting amount of 10%ultrafine slag has more gel pore developed while the number of capillary pores decreases.The cement slurry sample with substituting amount of more than 50%ultrafine slag has less gel pores and more capillary pores.The cement slurry sample with substituting amount of 30%-50%ultrafine slag has basically gel pores and no evident capillary pores.By associating the pore structure of the sample with the depth of the carbonation-induced corrosion,it was found that the sample containing substituting amount of 30%-50%ultrafine slag showed no significant corrosion,and this is relevant to the fact that it has no evident capillary pores.The sample containing substituting amount of 40%ultrafine slag has compact structure and no evident pores in the micromorphology.The hydration product of this sample is mainly fine fluffy-shaped CSH gel with low Ca/Si ratio,and contains less Ca(OH)2 mineral phase which is easily being corroded.Therefore,it is recommended that the appropriate substituting amount of ultrafine slag be around 40%.