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Application of Polyacrylamide in cementing
Cementing is the annular space between the casing and the casing to be injected into the mud and let it return to a certain height, and then the cement slurry is then turned into cement. When the drilling fluid density and leakage loss is adopted, it is necessary to cut down the drilling fluid density and leakage, and seal it with other complex layers. If the drilling fluid can be drilled, it is easy to have a high pressure oil layer, and the high pressure oil layer can be protected, and the high pressure oil layer is needed. In addition, the casing outside the cement Shi Ke to reduce the bottom of the pipe extrusion, play a role in protecting the pipeline. Cement slurry is a working fluid used in cementing, which is composed of water, cement, admixture and admixture. The added amount is less than or equal to 5% of the cement quality. The addition of material is 5% of cement quality.Polyacrylamide flocculant used in drilling fluid is non hydrolyzed polyacrylamide and hydrolyzed polyacrylamide. The former belongs to the whole flocculant, which belongs to the selective flocculant. There is a great difference between the electric charge and the degree of the high quality soil. The negative charge of the high quality soil is big, the cation exchange capacity is large, the water dispersion is strong, and the film thickness is thick. The cuttings with the electronegativity of less, thin water film. Only polar amide groups in the molecule of NPAM, which are not negatively charged, and the hydration film is thinner, and the repulsion force between the high quality soil and inferior soil are small. When meet with two kinds of particles, adsorption and bridging can occur. Therefore, NPAM flocculant can not only the drilling fluid in the drilling fluid, but also the high quality soil in the drilling fluid. HPAM reached a certain degree of hydrolysis with a high negative charge density, also has a thicker hydration film. When the particles are close to the high quality soil, it is difficult to absorb the high quality soil particles when they are close to each other, and when they are close to the drilling cuttings, they are easy to produce. The average molecular weight of HPAM is more than 200X104, and the degree of hydrolysis is better than 30%.
In order to meet the construction requirements, the need to adjust the curing time of cement paste with retarder. Cement retarder mainly through adsorption and chelation mechanism retarding effect; adsorption mechanism, the cement retarder can be adsorbed on the surface of the cement particles, hindering its contact with water, can also be adsorbed on the surface of cement hydration saturation precipitation, affect the curing stage and hardening stage in the formation rate of the network structure, retard coagulation; chelation mechanism, cement retarder and Ca2 + by chelating formed stable five membered ring or six membered ring structure and the influence of cement hydrate saturation precipitation rate, retarding effect.AM, Na and copolymer of HPAM - AA and Na - AMPS can be used as cement retarder.
Due to the high solid content of cement slurry, the flow resistance is very large, and can be used to reduce the flow resistance of mud. Cement slurry reduced drag reducer mechanism and drilling fluid thinner with the same mechanism, they are by adsorption, and increasing the water layer thickness and improve the electronegativity of the surface of the cement particles, so that cement particle formation structure apart and drag reduction effect.
3.Cement slurry filtration reducing agent
Similar to the drilling fluid, there is also the phenomenon of fluid loss. The filtration loss theory and its influence factors are the same as the drilling fluid.
4.Cement slurry plugging agent
Drilling fluid and cement slurry are also similar, leakage phenomenon. Leakage theory of cement slurry and its influence factors are same as that of drilling fluid.