Design method for strength of casing string

Abstract

The invention discloses a design method for the strength of a casing string. The method includes the steps of determining the steel grade and wall thickness of the first section of a casing, determining the length of the first section of the casing tripping in a well, carrying out internal pressure strength check on the first section of the casing, computing the length of the first section of the casing tripping in the well, and designing the second section of the casing, the third section of the casing and the like according to the steps until the designed casing reaches the well depth. The design method can be successfully applied to the strength design for the casing strings, the design method and process are simple, and the design cost is greatly reduced.

Description

technical field [0001] The invention relates to a strength design method of a casing string. Background technique [0002] With the continuous deepening of exploration and development, the number of directional wells, horizontal wells and extended-reach wells is increasing, especially for the development of beach and offshore oil fields, due to the limitation of platform location and the needs of later management and production, all Directional wells and horizontal wells are used for development. In recent years, with the development of offshore oilfield exploration to shallow sea and deep sea, extended-reach wells have been increasingly adopted by oilfields due to their cost advantages, and more requirements have been put forward for the casing string strength design of extended-reach wells. high demands. Due to the large inclination angle, long open hole section, and deeper and deeper casing, the load acting on the casing of oil and gas wells has become larger and more c...

AI Technical Summary

Problems solved by technology

However, with the development of drilling technology and the needs of exploration and development, the drilling depth is getting deeper, the geological conditions are becoming more and more complex, and the working conditions of oil wells are getting worse and worse. The uniaxial stress design and biaxial stress design can no longer meet the needs of drilling And the requirements of oil and gas well development often cause the early damage of oil and gas well casing

The problem with the biaxial stress method is that when using the biaxial stress method to design, although the interaction of external extrusion force, internal pressure and axial force is considered, the influence of radial stress is ignored

According to the experimental data in the relevant literature, the experimental data of the specimens with collapsed damage are far from the theoretical curve of the biaxial stress ellipse, and the degree of agreement between the two is not high. This experimental result shows that the biaxial stress design method has flaws