Wear-resistant and anti-reflux double rubber plug system for well cementing and its application method

Abstract

The invention discloses a wearproof and anti-backflow double-rubber-plug system for well cementation and a using method. The system comprises a wearproof and anti-backflow upper rubber plug, a lower rubber plug, a bump pressure holder and a leak-off basket. A rib and a sealing head are arranged on the wearproof and anti-backflow upper rubber plug, a self-locking tooth is arranged on the sealing head, and the rib is provided with a caster angle. A rib provided with a caster angle is arranged on the lower rubber plug. The bump pressure holder comprises a shell and a self-locking bump pressure seat, the shell and the self-locking bump pressure seat are both arranged in an axial penetrating mode, the self-locking bump pressure seat is fixed in the shell, and a self locking structure matched with the self-locking tooth on the sealing head is arranged on the inner wall of the self-locking bump pressure seat. After the rib of the lower rubber plug deforms, the maximum outer diameter at the rib of the lower rubber plug is shorter than the inner diameter of the self-locking bump pressure seat. The leak-off basket is matched with the lower rubber plug to form a fluid flow channel in the construction process of well cementation. According to the wearproof and anti-backflow double-rubber-plug system for well cementation and the using method, effective separation of cement paste from mud infront and back can be achieved in a casing pipe.

Description

technical field [0001] The invention discloses a wear-resistant and anti-reflux double rubber plug system and a use method for oil and gas field cementing operations, and belongs to the technical field of oil and gas field downhole operation tools manufacturing and use. Background technique [0002] After the drilling work is completed, in order to ensure smooth production in the future, it is necessary to carry out cementing operations, but before the implementation of the cementing operation, because there is still drilling mud in the well that has not returned to the ground, the conventional cementing operation is carried out, and the cementing operation is carried out. Before and after, it is necessary to use a rubber plug to separate the mud in the casing, the injected cement slurry and the displaced mud to avoid mixing the drilling mud and the cementing slurry, so as to prevent the cementing slurry from being polluted by the drilling mud problem occurs. Pushed by the ...

AI Technical Summary

Problems solved by technology

[0006] Both single and double rubber plugs currently used have technical deficiencies. During field cementing, due to various reasons, sometimes the floating hoop fails, and because the density of the annular cement slurry is higher than that of the mud, the annular The air pressure is higher than the pressure in the casing, the cement slurry will flow back, and the rubber plug will retreat, resulting in an excessively long cement plug and increasing the drilling time of the plug. At the same time, the cement slurry in the upper part of the annulus is missing, leaking seals, and the cementing quality is poor.

When cementing with a single rubber plug, the front part of the cement slurry will form a large amount of mixed slurry in the pipe, and it will run to the upper part of the annulus, which will also affect the quality of the floating hoop

The above situation will bury hidden dangers for future oil well production, and even cause cementing accidents

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