METHOD FOR LIGHTENING A RISER PIPE WITH OPTIMIZED WEARING PART

• US 20110209878A1
• Filed: 09/23/2009
• Published: 09/01/2011
• Est. Priority Date: 10/29/2008
• Status: Active Grant

• Current Assignee: IFP Energies Nouvelles
• Original Assignee: IFP Energies Nouvelles
• Inventors: Guesnon, Jean
• Granted Patent: US 8,800,666 B2
• Time in Patent Office: Days
• US Class Current: 166/367
• CPC Class Codes: E21B 17/01 Risers
• CPC Class Codes: E21B 17/0853 Connections between sections of riser provided with auxiliary lines, e.g. kill and choke lines
• CPC Class Codes: E21B 17/1035 for plural rods, pipes or lines, e.g. for control lines

Abstract

A riser pipe for drilling an offshore well comprises a main tube extending the well up to a floating support, an auxiliary line being arranged parallel to main tube (4a, 4b). The auxiliary line comprises tubular sections (7a, 7b) made of steel and assembled end to end with a sliding fit by means of a tubular end part (25). According to the invention, a material, a titanium alloy for example, having an elastic limit at least 25% higher than that of the steel tubular sections (7a, 7b), is selected to manufacture said end part (25), and the end part as well as the end of said sections are dimensioned by taking account of the elastic limit of said material so as to reduce the sealing section of the end part.

Claims

1. ) A method for lightening the weight of a riser for offshore well drilling, the riser comprising a main tube extending well up to a floating support, at least one auxiliary line being arranged parallel to the main tube, the auxiliary line comprising tubular steel sections assembled end to end, each one of said sections being connected to the adjacent section by means of an end part, said end part being secured to the end of a section and mounted with a sliding fit in the end of another section, seal means being arranged between the end part and the section at the level of the sliding fit. The method is characterized in that a material having an elastic limit at least 25% higher than the elastic limit of the steel of the tubular sections is selected to manufacture said end part, and in that end part and the end of said sections are dimensions by taking account of the elastic limit of said material so as to reduce the outer section of the end part at the level of seal means.

2. ) A method as claimed in claim 1, characterized in that the inside diameter of the end part is selected smaller than the inside diameter of the tubular sections of the auxiliary line.

3. ) A method as claimed in claim 1, characterized in that a material having an elastic limit at least 49% higher than the elastic limit of the steel of the tubular sections is selected to manufacture said end part.

4. ) A riser obtained by means of a method as claimed in claim 1, characterized in that said material consists of a metal alloy comprising at least 80 wt. % titanium.

5. ) A riser as claimed in claim 4, characterized in that said material is selected from among the following titanium alloys:

Ti-6-4 and Ti-6-6-2.

6. ) A riser obtained by means of a method as claimed in claim 1, characterized in that said material consists of steel and in that at least the inner surface of said end part is coated with an anti-corrosion protective layer.

7. ) A riser as claimed in claim 1, characterized in that each one of said tubular sections comprises a metallic tubular body hooped by fiber windings coated with a polymer matrix.