Non-Uniform Bearing of Oil Casing Reduces its Bearing Capacity

Oil casing damage is one of the important factors affecting China's crude oil production. The reasons for its damage include non-uniform stress, corrosion, sand formation in oil layers, and high-pressure water injection. As for the strength of petroleum casing, the API standard does not
clearly indicate the effects of non-uniform stress, geometrical defects of petroleum casing, and residual stress on the bearing capacity of the casing on the bearing capacity of petroleum casing.Therefore, it is difficult for the designer to determine the influence of these factors on the strength of the oil casing.

In practice, the non-uniform bearing of oil casing and other factors greatly reduce the bearing capacity of oil casing, which reveals that these factors have very important practical significance in the impact of the strength of oil casing.

At present, petroleum casing manufacturers understand that the existing literature has analyzed the effects of geometric defects, residual stress, non-uniform ground stress and other factors on the strength of petroleum casing. Most literature is limited to finite element numerical simulations. In actual engineering, the squeezing force of oil casing is unevenly distributed. Formation sand,
slippage, swelling, cement channeling, etc. will cause uneven distribution of casing squeezing force. Therefore, considering the non-uniform distribution of the load on the outer wall of the casing, a variety of non-uniform modes have been adopted. For example, the non-uniform load is
decomposed into two parts: uniform load and non-uniform load. Assuming the casing diameter radius is ? and the wall thickness is ?, the radial dimension of the casing is much smaller than the axial dimension, which can solve the problem of plane strain.

When the load distribution of the outer wall of the oil casing is not uniform, the stresses at the points on the circumference of the same radius are different. The smaller the uniform compression pressure of the oil casing, the greater the unevenness of the load.

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