Abstract

The Cameron/TOTAL Usan project team brought one of the first High-Pressure Drill Pipe Riser for Intervention Systems (DPRISi) to the African deepwater market in 2009.

Since July 2010, the string has been used offshore Nigeria. A total of 20 runs have been performed with this DPRIS, resulting in the safe and efficient installation of four trees. These trees have had no cleaning issues and no rust debris impacting operations.

Proper operating procedures implemented by field personnel have allowed for safe and efficient subsea DPRIS runs to date and provide confidence in future runs (38 more trees are planned).

Before DPRIS, most operators used conventional drill pipe available on rigs to install and retrieve the production adapter base and tree cap. While success varied, difficulties and risks arose using a hydraulic umbilical inside the riser, making it evident that technological improvement was needed to minimize interference between the pipe and the hydraulic lines.

The pipe delivered as part of this project, from VAM Drilling, are drill pipe risers with a propriety double shoulder connection and featuring a gas-tight metal-to-metal seal on the inner shoulder.

The standard offer for high-pressure DPR is 6-5/8" 0.5" wt and X-95 grade. VAM Drilling suggested this be changed to have a thick wall for corrosion allowance and higher grade for tensile strength, 6-5/8" 0.625" wt and G-105 grade.

The qualification program additionally covered all remaining requirements for full compliance to ISO-13628-7, which is believed to be a good certification level for such demanding and challenging operations.

The DPRIS system delivered in West Africa is a cost-efficient solution for subsea operations, workover applications and well intervention. This successful project, which provides technical and commercial value, is an example of how to implement a successful deepwater intervention business, not only in Africa but throughout the world.

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