簡介：最近，瑞典技術公司Swelleborg AB Group推出了可用于高溫高壓環境下的泡沫包裹新技術，通過應用此技術，可以防止海上油井套管由于環空壓力恢復發生故障。
Swedish technology company Swelleborg AB Group recently announced a new high-temperature, high-pressure crushable foam wrap (CFW) technology for mitigating subsea well casing failure. The company’s Trelleborg CRP division says that the technology known as CFW+ incorporates 3M’s Glass Bubbles product to prevent casing failure due to annular pressure buildup or trapped annular pressure.
Trelleborg’s CFW technology, which was originally introduced to the market in the early 1990s, is a polymeric foam material with a honeycomb microstructure designed to disperse annular fluid pressure increases during production. The product is installed around the inner drillstring casing, which is subsequently immersed in the annulus fluid.
During production of hot hydrocarbon, the fluid in the sealed annuli is denied thermal expansion, resulting in an increase in annular pressure which may lead to eventual rupture of the outer casing of the annuli. In extreme cases, this can lead to leaking of fluid or complete collapse of the inner casing, which will restrict or completely stop production.
CFW helps prevent this scenario by collapsing at a predetermined pressure/temperature combination, thus allowing the annulus fluid to expand and dispersing any pressure increases. The polymeric nature of the foam gives it a thermal softening point that is formulated to be below the maximum operating temperature of the annulus, which ensures that the foam will not fail to collapse before the maximum operating temperature is reached.
CFW is available as quarter cylinders, typically 1 m in length, and are installed on the inner drill casing in opposing pairs using a high-performance adhesive. The number of quadrant pairs installed is dictated by the collapse volume required within the annulus, which is defined as the calculated volume increase of the annulus fluid during thermal expansion between the installation temperature and the operating temperature.
The total volume of foam required for a particular job is calculated using this collapse volume and the crush percentage, which is the volume percentage of foam available for compression. Crush percentage is defined as the amount of compression under isostatic load that the foam will allow over the collapse pressure band?typically 30?50%?depending on the particular foam formulation.
The total volume of foam actually installed is typically increased by 20% of that calculated from the collapse volume and crush percentage to cover any losses during installation or deployment and to provide a safety factor in the event that fluid expansion exceeds the calculated amount.
“Until now, the operating range of our CFW solution has had typical performance in excess of 4,000 psi at 60?80ºC, which has been sufficient to meet the needs of most projects,” said Guy Downie, Manager of the Subsea Group for Trelleborg CRP. “However, due to trends in drilling more complex wells, sometimes much deeper and further offshore, we have developed CFW+ which can provide an annular pressure buildup solution for these more demanding situations to temperatures in excess of 110ºC and much greater pressures.”
The incorporation of 3M’s Glass Bubbles technology, which are hollow, low-density, low-viscosity glass beads, provide increased strength and chemical inertness to the substrates to which they are added. In the CFW+ foam, the Glass Bubbles technology increases resistance to water absorption, which increases the foam lifetime downhole before utilization.
Downie pointed to this new formulation’s ability to match the required collapse volume and pressure collapse range for more demanding deep subsea wells, and said, “This is the only commercially available solution to operate on temperature and pressure triggers, rather than just pressure alone.”
Trelleborg aims to introduce this new technology to drilling operations in the coming year, and projects potential use in over 100 field developments worldwide between 2009 and 2011.
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