A casing suitable for diameter expansion and deformation and its processing method

Abstract

The invention provides a sleeve applicable to diameter expansion deformation and a processing method. The sleeve comprises a sleeve body, an internal threaded joint and an external threaded joint, wherein the internal threaded joint and the external threaded joint form a whole with the sleeve body; the thread profiles of the internal threaded joint and the external threaded joint are mutually matched deviated arc-shaped threads; the flank angle of the bearing surface of the thread profile is a negative angle; the flank outline of a guide surface is a natural curve approximate to a sine curve; the height of thread of the internal threaded joint is greater than that of the external threaded joint; and after the screwing and buckling, crest of the internal threads is in contact with root of the external threads. During sleeve diameter expansion, the external threads extrude the internal threads from the inside to the outside; the axial shrinkage quantity of the internal threads is greater than that of the external threads; arc-shaped threads are more favorable for the metal flowing of threaded metals in the plastic deformation process; during the diameter expansion, gaps between the guide surfaces of the internal and external threads can be more easily filled; gaps originally existing between the internal and external threads can disappear after the joint diameter expansion; in addition, the tight contact is generated at the flank surfaces of the internal and external threads for achieving an auxiliary sealing effect; and the sealing performance of a sleeve joint is improved.

Description

technical field [0001] The invention belongs to the technical field of well construction and workover of oil and gas wells, and relates to the oil expansion casing technology, in particular to a casing suitable for diameter expansion and deformation and a processing method. Background technique [0002] After the oil and gas well is drilled, it is necessary to run steel casing into the wellbore to reinforce the wellbore. The length of a single casing is usually about 10 meters, and the casings are usually connected by pipe threads to form a length of several thousand meters. casing string. [0003] In recent years, a new technology has emerged, which is called the expansion casing technology. The core of this technology is to expand the diameter of the casing string in the wellbore, so that the inner and outer diameters of the casing change by about 10% to 20%. % plastic deformation, this kind of expansion deformation is usually realized by liquid pressure in the casing str...

AI Technical Summary

Problems solved by technology

During the expansion process of the casing string, the pressure of the expansion liquid required by this threaded joint is roughly the same as that of the pipe body, and typically requires a pressure of about 20-40 MPa. At the same time, since the wall thickness of the joint is the same as that of the pipe body, there is no thickening , so the connection strength of this kind of joint is also relatively low, and generally can only reach about 50% of the strength of the pipe body at most. Caution may also cause the sealing rubber ring to break away from the sealing groove and fail to achieve the proper sealing effect.

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