Study On Affection Factor Of Toughess And Strength Cement

With the exploration and drilling technology is evolving, the number of complicated well is increasing, The well cementation quality has become one of the most concern. Meanwhile, in order to yield, the oil usually take fracturing, acidizing, and fill holes to increase production pressure to increase yield. Because of the toughness and strength of the cement, it easily lead to cement cracks, and even make sealed reservoir failure of the cement, causing the water oil and gas channeling and the damage corrosion of the casing. Therefore, the toughness and strength of the cement have a great significance on production oil wells and the long life of it.Firstly, this paper study the cement stress distribution by finite element simulation.secondly, the paper study strength and toughness in experimental laboratory. And observed the micro structural of the cement, by above all we further explained the reasons for cement that the toughness of cement is performance and the strength of cement is the changed.From the finite element simulation, The paper more comprehensive analyse the cement stress distribution in which different stress environment and different shapes cement. The results showed that: the different stress has great influence on stress distribution on the cement, when the ratio is less than 1.1 between formation of the maximum principal stress and minimum principal stress, the cement on the stress distribution is more uniform, With the increase of stress ratio, the cement stress inequality is increasing , which makes the cement more easily broken. The shape of the cement also impact the stress distribution, with the cement ellipticity is increaseing, the stress nonuniformity first is decreasing and then is increasing; the casing decenter in the cementing also increases the asymmetry of the stress, Because of the oval-shaped cement is can to improve its mechanical condition. We should take the advantage of this feature, in the drilling should be appropriately reduced fluid density, so that an appropriate degree of wall surrounding the release of stress, prompting the formation of certain borehole ellipticity. From the laboratory experiment, the paper have been optimised the various additives's ratio in slurry system. the toughening of cement system not only be good at rheological property but also has a zero free water content features, It's not only fully able to satisfaction the requirements of the cementing but also can improve cementing quality. By cement mechanical properties studying, fluid channeling layer capabilities studying and anti-corrosion hydrochloric acid experiments studying, the results showed that: the toughness and strength of the cement significantly improved, under room temperature and pressure, after 48h, on the non-uniform loading which loading rate 2MPa, the compression strength of up to 70MPa, the axial deformation capacity can be increased about 3 times, axial deformation capacity of the increase reflects the improvement of cement toughness and toughness increased and it helps declines the stress inequality of the cement, the rate of decline is up to 10%; while the layer of the fluid channeling ability and hydrochloric corrosion are greatly increased.With electronic scanning microscope, through the microstructure observation of the cement.We find that the internal structure is more densify, plasticizer take part in reaction in the cement. There inlaid with amount of toughening agent in the stone surface, A great quantity of small latex pellet mixed with in crystalline solid. Makes the non-permeability of cement is increasing and is improving corrosion proof capability, in the compression experiments, it absorb some of the stress not only to improve the cement's compressive strength but also to improve the deformation capacity.