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How to Improve the Collapse Resistance of Oil Casing Pipe?

Date:2020-11-26    keywords:casing pipe, collapse resistance
In fact, oil casing collapse is a common form of damage to oil casing, but although it is common, how can oil casing pipe damage be prevented? The anti-collapse performance of oil casing has always been the focus of attention, and the prediction and application of the anti-collapse strength of petroleum special pipelines has always been a hot research topic.
It can be seen from the model that when D/S is in the plastic collapse and transitional collapse zone, the ellipticity is very obvious, and the ellipticity becomes the process control factor that affects the main size and quality of the anti-pressure value; when D/S is in the elastic collapse zone or yield collapse When the residual stress is not obvious, the nominal yield strength should be controlled as much as possible. The K-T model better predicts the anti-fragmentation performance of the current oil casing, but its formula coefficient depends on the level of each enterprise.

In fact, in deep wells, not only the influence of high temperature on the strength of oil casing, but also the influence of high temperature on the elastic modulus and Poisson's ratio of the pipe material must be considered. These factors will eventually affect the collapse resistance of the pipeline under service conditions. Ultra-thick wall casing is an effective method to solve the problem of formation collapse in deep wells with abnormally high pressure.

The anti-collapsing oil casing should adopt temperature adjustment heat treatment process, try to increase the tempering temperature to meet the yield strength requirements, increase the straightening temperature, and reduce the residual stress. It is recommended to use the external heat treatment technology and internal spray synchronous phase change technology. Improve the quenching depth and uniformity of the tube body.

However, due to the directionality and anisotropy of the formation pressure, the stress environment of the J55 oil casing is very harsh, and the casing collapse is more serious. In fact, it is recommended to increase the safety factor of oil casing pipe collapse resistance, but the casing collapse resistance strength is its inherent engineering property and cannot be changed with the characteristics of formation stress distribution. The above is how to improve the collapse resistance of oil casing.

Tips: In case ASTM A53 Grade B in ERW (electric resistance welded) pipe, the weld seam shall be done the heat treatment with a minimum 1000°F [540°C]. In this way the no untempered martensite remains.

In case ASTM A53 B pipe in cold expanded, then expansion should not exceed 1.5% of the required OD.

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