Note The Steam Casing Theoretical Study Of Thermal Stress And Residual Stress

The production of heavy oil mainly through steam huff and puff and steam drive. But the casing will produce large heat stress for the injection of steam, and can make heavy casing failure. It is very important that In the process of steam injecting accurately forecast well bore temperature field and the loads of casing and reduce the failure of casing to the completion and production of the thermal production well.Applying the basic theory of heat transfer, this paper have established the well bore and formation temperature field model of steam injection step, and have established the casing temperature change model of the steam soak step. And the model established through conversation of energy, conservation of momentum, and conservation of mass.After getting well bore and formation temperature field model, this paper using the basic theory of heat stress establish the model of casing heat stress. And consider the casing was snap in the thermal production well; this paper introduced the generalized Saint-Venant model. At the same time this paper consider the effect of one-way cumulative effect, have analyzed the casing elastoplasticity mechanical behavior when the casing get along with the several cycle of steam injecting. This paper presented the mechanism of producing the residual stress, and gets the calculated model of the residual stress.It has been proved by oil field practice example that this model can use to dynamic prediction and simulate thermal production well in oil field. At the same time this model can optimize process parameter of the thermal production well and can calculate the casing heat stress and the residual stress.Considering the use of directional well and horizontal well in the thermal production of heavy oil, this paper has established the relationship of casing under force balance in the process of drawing casing. This model has considered the effect of friction to well head drawing force; especially curved portion must take friction into account. Combine the analyses method of casing heat stress thismodel can get the heat stress distribute rule induced by steam injection after drawing casing.Because it is difficulty to describe the effect of the eccentric tubing to well bore and formation temperature field by analytic method. This paper use finite element method to analyze the well bore and formation temperature field. Especially, this paper using the finite element method to simulate the operating mode of eccentric tubing in the well bore, and having get the effect relationship of eccentric distance to the well bore and formation temperature field.N80 and TP90H grade casing are common used in the thermal production well. This paper has calculated and compared the two type casings. And point out that the TP90H grade casing is superior to N80 grade casing in the face of performance of the thermal production. The TP90H grade casing has the advantage of resisting the residual stress. This have proved in theory that in the oil field the failure of N80 grade casing is more often, and after changing to use TP90H grade casing the casing failure phenomenon is evidently decrease.