What Causes the Strength of the Oil Casing to Change

The strength and quality of oil casings are always the concern of everyone, because the quality of oil casings is one of the important factors affecting the production of crude oil in China. In fact, the causes of its damage include uneven stress, corrosion and the formation of sand in the reservoir. And high pressure water injection. As for the strength of oil casing, API standard does not clearly point out the influence of uneven stress, geometrical defect of oil casing and residual stress on the bearing capacity of casing. Therefore, the influence of these unpredictable conditions makes it difficult for designers to determine the influence of these factors on tank strength.


Now, casing manufacturers understand that existing data have analyzed the effects of geometric defects, residual stress, uneven ground stress and other factors on casing strength. Most literatures are limited to the finite element numerical simulation. In the actual engineering, the squeeze pressure distribution of oil casing is uneven. It is important that the formation of sand, slip, expansion, cement channeling and so on will cause uneven distribution of casing pressure. Therefore, considering the nonuniform distribution of the load on the outer wall of the shell, a variety of nonuniform modes have been adopted. The following is an example of decomposing the non-uniform load into two parts: uniform load and non-uniform load. In practice, the bearing unevenness of the oil casing greatly reduces the bearing capacity of the oil casing, so it shows these factors. It is of great significance to the influence of casing strength.


When the load distribution on the outer wall of the oil tank is not uniform, the stress at the point on the circumference of the same radius is different. The smaller the uniform compression pressure of the oil tank, the greater the degree of non-uniformity. These are the reasons that affect the strength of oil casing.