Special Thread Joint for Casing Pipe

The casing pipe can be divided into two categories: one is the API connector, that is, according to the API standard production and inspection of the joints; the other is non-API connector, also known as special thread joints. The special thread joint is the new type of joint design which is designed to overcome the shortcomings of the API joint. This kind of joint breaks through the frame of the API joint in the structural design, generally has the advantages of high connection strength and good sealing performance. Because the special thread joint solves the structural integrity and seal integrity of the oil pipe joint, the scope of its application is expanding and has a broad market space. In China, the development of special high-tech value-added oil pipe casing, has been the majority of casing pipe manufacturers attach great importance to and has been a certain application, so that China's special thread joint research into a new stage.

At the same time, due to foreign oil casing processing plants generally do not want to process low-tech API casing, making China a large part of the API casing is also exported to foreign countries. However, China's special threaded joint casing, regardless of the yield, variety, or quality, are far from meeting the needs of the oil field, the required special thread products are basically dependent on imports. It can be seen that China's production of special thread joint casing is still far from meeting the needs, this has a high value-added products have not been foreign and even domestic users recognized. At the same time, with the further increase in China's natural gas production, good sealing performance of the special thread joint casing will increase the amount, which also requires China's oil casing manufacturers to increase the intensity of development.

Threaded tubing casing currently has the following problems
(1) Production is far behind the use of demand.
(2) Including imports, the use of special threaded joint casing is far from the international level.
(3) The domestic production of special thread joint casing of the small number of enterprises, production is also low.
(4) Domestic enterprises special thread joint casing product series is small, available for oil field selection button type limited.
(5) By the steel series of restrictions. Special thread joint casing is usually used in acid gas wells, CO2 gas wells, oil and gas mixed wells, heavy oil thermal recovery wells, high pressure gas wells, deep wells, ultra-deep wells, low pressure and low permeability gas wells, which requires oil casing material itself to have Anti-H2S corrosion, anti-CO2 corrosion, anti-squeeze, ultra-high strength and other properties.
(6) Basic research work is not in place. The development of the domestic special oil joint casing is still in the process of introduction from the introduction to the independent development of the special thread joint design principles, such as sealing design, strength design, anti-stick design and other aspects of the lack of deep understanding.
(7) Do not have short section processing capacity. Some domestic enterprises, from abroad to introduce a very high precision machining lathe, the ability to process special thread joint casing, but in the production line processing short section and supporting accessories are very difficult, sometimes unable to process, sometimes although Processing but inefficient.

Therefore, according to the user to reflect, some domestic special thread joints in the use of the process there are still many problems, highlighted in: ` sealing performance is not reliable, due to improper sealing structure and tolerance selection, or because the thread is too large, Buckle in place, in the course of the use of the joints prone to leakage; a clasp, due to thread interference or metal / metal seal interference improper selection, resulting in thread gluing or main sealing surface bonding.