Casing compensator for thermal recovery well

Abstract

The invention discloses a special casing compensator for thermal recovery wells used in the petroleum industry, which is connected to casing strings of heavy oil thermal recovery wells, and is used for elongation of the casing strings of thermal recovery wells caused by steam injection technology. The shrinkage of the pipe string caused by carbon dioxide injection or other measures can provide effective compensation to prevent the deformation and damage of the casing due to elongation or shrinkage. The invention includes an outer cylinder and a central pipe, the outer cylinder is connected with the bottom cap, the central pipe and the outer cylinder are connected by splines, and a locking mechanism is also provided between the outer cylinder and the central pipe. The invention has the advantages of reliable operation, simple structure, short tool length, low cost and long compensation distance, and is suitable for the design of various thermal recovery well completion processes, and can be placed in any required position without being affected by the angle of well inclination. Ensure that the completion string is intact during steam injection in heavy oil thermal recovery wells and will not be damaged by temperature changes. After construction, no follow-up operation measures are required. conditions of.

Description

technical field [0001] The invention relates to downhole tools for heavy oil thermal recovery wells in the petroleum industry, in particular to special casing compensators for thermal recovery wells, which are connected The elongation caused by the steam process, or the shrinkage of the pipe string caused by carbon dioxide injection and other measures provide effective compensation to prevent the deformation and damage of the casing due to elongation or shrinkage. Background technique [0002] Existing casing compensators for thermal recovery wells are mainly composed of upper and lower sections of casing compensators, heat insulation pipes, inner pipes, sealing elements, upper and lower compression plugs, etc., and their principles are basically similar, mostly through mechanical shears. Controls when the casing compensator starts working. This type of casing compensator mainly has two insurmountable defects in principle. One is to install a small amount of shear nails, so...

AI Technical Summary

Problems solved by technology

This type of casing compensator mainly has two insurmountable defects in principle. One is to install a small amount of shear nails, so that the casing compensator can start working before the casing is damaged, and the safety factor of the casing in the downhole is improved. However, this situation increases the difficulty of actual construction. If you do not pay attention during the lowering process, the shear nails will be easily cut off in advance, causing the compensation distance to be occupied in advance and lose its compensation function; another situation is to install more shear nails to increase the The safety of the casing compensator in the construction process, but this situation is easy to cause the casing to be damaged before the casing compensator works

The two situations contradict each other, it is difficult to choose a reasonable number of shear nails

In addition, the internal structure of the casing compensator commonly used at present is relatively complex, with dozens of parts and dozens of parts, which is prone to problems in actual field application

At the same time, the existing bushing compensator can only compensate the expansion and elongation of the bushing in one direction, but cannot compensate the shrinkage of the bushing, and cannot realize two-way compensation

Therefore, it can be concluded that the existing casing compensators for thermal recovery wells have the following defects: 1. There are contradictions in the working principle, so that the probability that the casing compensators can work normally is very small; It cannot compensate for the shrinkage of the casing string caused by the carbon dioxide injection process; 3. The length of a single tool is long, and if multiple tools need to be lowered, it will occupy too long a section of the oil layer and increase the input cost; 4. The structure is complex , it is prone to failure when used underground; 5. It is suitable for conventional thermal recovery wells, not suitable for complex well completion processes such as thermal recovery horizontal wells

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