Research Of Retarders For Modified High Aluminate Cement System

The stratum carbon dioxide corrosion on portland cement sheath has greatly influenced the production life of oil well.Modified High Aluminate Cement（MHAC）is a kind of hydraulic cementing materials with good CO₂-resistant performance,but thickening time of MHAC slurry is only 4 minutes at atmospheric pressure and 75℃.In order to make thickening properties of MHAC slurry meet the requirements of cementing engineering,studying to select a kind of retarder that is suitable for MHAC is essential.On the basis of studying and analyzing silicate cement commonly used retarder,the article has carried on the optimization experiment.Optimization research suggests that,hydroxyl carboxylic acid,organic phosphate and several kinds of inorganic salts have no retarding effect on MHAC slurry.Sodium tetraborate,boric acid,sodium lignosulphonate and GH-9 have obvious setting retarding effect,but the unfavourable result is that those retarders have observably reduced the compression strength,and sodium lignosulphonate,GH-9 will make the slurry aberrant gelation.The retarding action of sodium tetraborate and boric acid is extremely unstable and lack of reproducibility.Through theoretical analysis and experimental study,the article has discovered that GH-9 chelating aluminum sulfate can eliminate the aberrant gelation of MHAC slurry with retarder GH-9.The composite retarder is compounded by GH-9 chelating aluminum sulfate and sodium tetraborate,its optimal proportion is 3:1:0.6.The cement slurry with composite retarder has the favorable behaviors of rheology,right-angle-set property,minimal-impact on compressive strength and good retarding effect under the high pressure,but there is a serious problem that the compound proportion of composite retarder is too sensitive.Therefore,on the basis of optimization study of synthesis conditions,regarding salt and temperature tolerant AMPS and SSS,DMDAAC that can form associated structure with retarded groups and IA with double carboxylic acid groups as polyfunctional unsaturated monomers,polymer retarder SDGLHN-1 has been developed.MHAC slurry with polymer retarder has the favorable behaviors of rheology,no phenomenon of aberrant gelation,short transition time from 30 Bc to 100 Bc,right-angle-set property and minimal impact on compressive strength,and the relation between thickening times of MHAC slurry and dosages of retarder has been confirmed as a linearity curve.What’s more,the polymer retarder can apply to high temperature and pressure,in 75℃ and 20 MPa,the thickening properties of MHAC slurry can meet the requirements of cementing operation.At last,the article preliminary reveals the mechanism of the polymer retarder and eliminating the aberrant gelation of MHAC slurry,and lays the foundation for application of modified alumina cement in CO₂ corrosion resistant cementing requirements.