High-toughness and ultra-high strength seamless steel pipe for oil well and manufacturing method thereof

Abstract

The invention discloses a high-toughness and ultra-high strength seamless steel pipe for oil well and a manufacturing method thereof. The steel contains the following chemical components of: by weight, 0.15-0.27% of C; Si being less than or equal to 0.30%; 0.20-0.50% of Mn; 0.85-1.45% of Cr; 0.40-1.2% of Mo; 0.08-0.20% of V; 0.01-0.05% of Als; P being less than or equal to 0.012%; S being less than or equal to 0.005%; H being less than or equal to 0.00015%; N being less than or equal to 0.0050%; O being less than or equal to 0.0040%; As+Sn+Pb+Sb+Bi being less than or equal to 0.0080%; and the balance being Fe. By a specific manufacturing process, the low alloy steel provided by the invention is prepared into a steel pipe, which is characterized by a mechanical property that the ratio of transverse notch CVN to yield strength is greater than or equal to 0.1, therefore raising the security of applying the ultra-high strength oil-well pipe with strength level of more than Q125 in deep wells and ultra-deep wells.

Description

technical field [0001] The invention belongs to the field of low-alloy steel manufacturing, and in particular relates to a super-high-strength seamless steel pipe with high toughness, which can be used for drilling oil and natural gas in oil and gas fields. Background technique [0002] With the large-scale exploitation of crude oil and natural gas in the world year by year, the exploitation of shallow oil layers can no longer meet the increasing huge demand. The drilling depth of oil and gas fields is continuously deepening. In some places, the drilling depth has reached 6, 7,000 meters, or even deeper. . With the increase of well depth, the geological conditions become complex and harsh, coupled with the high temperature and high pressure downhole environment, put forward higher requirements for the strength and toughness of oil well pipes, the highest API grade Q125 oil well pipes can no longer meet these deep wells, The use requirements of ultra-deep wells. At present,...

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Problems solved by technology

[0003] Generally speaking, the higher the strength of the steel, the lower the toughness, and the two are trade-offs. According to the theory of fracture mechanics strength, the critical size and K IC with σ y It is related to the square of the ratio, that is, the higher the strength of the oil well pipe, the higher the toughness that needs to be matched. The guidance technical document of the British Department of Energy shows that when the transverse notch CVN (unit J) of the oil well pipe (unit J) and the yield strength (unit MPa) When the ratio is greater than or equal to 0.1, the notch sensitivity of the steel pipe can ensure the safety of use, that is, the oil well pipe with a yield strength greater than 140ksi (980MPa) needs to match the transverse CVN of more than 98J, and the ultra-high strength oil well pipe currently on the market, It is difficult to meet this requirement

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