Experiment Study On The Law Of Change Of Casing Axial Tension In Process Of Well Cementation

The process of solidification is an important part in cementing engineering. Whether cement slurry solidified well or not has a direct effect on the cementing quality, afterwards on the whole drilling engineeringand the cost. The decrease of cement slurry pressure will make the pulling force exerted on the top casing increase, which is also the main reason of oil, gas or water channeling and casing early broken.In the process of slurry gelation, the temperature of slurry will be up because of hydration reaction of silicates, and at the same time cement slurry will be weight loss. Plastic defomation will be happen on the casing by the mutual action of weight-loss, temperature and pressure.Along with slurry gelation, the defomation will be solidified in the cement. With the changing of temperature and pressure, the casing in the cement may be in bad stress and strain.which is likely to become the key factor affecting the useful life of the casing.In the past process of casing damage study, the research just aimed at that well cementation was completed, after cement solidified and the later period of oil field production.Under the influence of high temperature and pressure, construction and so on, people mainly foucsed on the mechanical and chemical action, but rarely thought about the changing of the casing condition in process of slurry solidified. Therefore, it is necessary to study the stress and defomation law of the casing in the process of slurry gelation and weight loss.Through the measure of laboratory testing, in this paper, the experimental apparatus of measuring casing load during the primary cementing is designed, and different downhole behaviors are simulated. The conditions of casing force and its change under the effect of cement slurry density, cement mantle length, different additive, and formation environment and so on are analysed. The law that the axial pulling force of the casing takes on step increment and finally tending to decline as the slurry gelation is obtained. Experimental study provides a good reference for the foundation for cement slurry system and formula selection, improving the cementing practice technology, the research of casing damage latterly and so on.