Sumitomo Metals Develops VAM®21, the World’s Highest-performance Threaded Connection

Sumitomo Metal Industries, Ltd. (Sumitomo Metals) has co-developed with Vallourec S.A.(*2) VAM®21, the latest high-performance VAM®(*1) threaded connection for Oil Country Tubular Goods (OCTG). VAM®21 enables the development of ultra-deep oil & gas wells, which had previously been difficult to complete.

Thanks to its highest performance in the world, VAM®21 is a super high-end product that delivers stable performance even in ultra-deep oil and gas wells.

1. Development background
When oil and gas wells are developed by using OCTGs, these tubes are connected with threaded connections. These OCTGs connected with threaded connections and buried in the earth have to withstand diverse loads imposed by underground pressure from outside of the tube, the pressure of oil or natural gas within the tube, and tension and compression caused by their own weight in its length direction. In the case of ultra-deep oil and gas wells, a big challenge is to withstand the compression load of the weight of the OCTGs in their length direction, in addition to underground pressure.

Performance verification tests for threaded connections include checking leakage of the tube-connected areas under heavy loads (sealability.) The most rigorous ISO standards(*3) include a procedure to repeatedly apply compression loads as heavy as close to the point that the OCTGs start to break. Up to now, no threaded connections have passed this rigorous test in all sizes.

Another important factor is ease of use for sealing at actual worksites. When the OCTG and a threaded connection are sealed together, failure to tightly fit the crest and root of the thread causes troubles (i.e., smashing or burning the crest) and would require work such as cutting off the tips of OCTGs and refabricating the thread, which could also incur extra costs.

2. Features of VAM®21
(1) VAM®21 threaded connections have an unprecedented high sealing performance.

VAM®21 features an extended lip called VAM Stabilizer™ at the tip of the seal face, an area to prevent leakage by firmly attaching an internal thread with an external thread at the edge of the OCTG. The seal face at the tip of the OCTG is slightly larger than the coupling (a short tube with internal threads on both ends that connects to the OCTG with external threads.) This design ensures air tightness of both seal faces.　

Excluding the tip area, VAM Stabilizer™ creates a gap between the OCTG and the coupling so that they are not in contact with each other. Owing to the presence of the VAM Stabilizer™, the seal face of the external thread of the OCTG is slightly misaligned inside. This makes sealing tighter, as a reaction force to return to the original status is generated not only on the seal face but also on the VAM Stabilizer™.

Thanks to such superior sealing performance that has been realized for the first time in the world, VAM®21 can pass the most rigorous ISO standards, in all sizes of its commercialized products.

(2) VAM®21 facilitates sealing work for thread connections and prevents troubles.

When a threaded connection is stabbed to the OCTG with some misalignment, the root and crest of the thread cannot fit each other. In order to solve this problem, conventional threaded connections have tilted the slope of the crest thread to the tube longitudinal axis so that the crest top surface of the OCTG’s external thread and the coupling’s internal thread hit and adjust to fit each other. However, in cases where the surfaces cannot engage well with each other, cross-threading (where the root and crest of threads cannot fit with each other and become jammed) could occur.

In the case of VAM®21, the crest top surface of the thread is set parallel to the pipe’s longitudinal axis and the edges of the thread slope are cut off. This design is based on the idea to prevent cross-threading not by aligning the tube and the coupling at first, but conversely by giving some space allowance between the tube and the coupling. This new method has resulted in a reduction in the occurrence of cross-threading at worksites and improvement in the ease of sealing work.

Moreover, having VAM Stabilizer™ at the tip of the tube means that the seal face is no longer positioned at the tip of the tube and will therefore not be damaged even if the tube tip bangs some object. Thus, even rough handling at worksites will not damage sealing performance.

VAM®21’s high sealing performance has enabled the development of ultra-deep oil and gas wells. It is attracting the attention of major oil companies and other customers as a product that facilitates oil and gas development, with its sealing workability.

3. Future development
In May 2009, VAM®21 was first deployed for exploration of natural gas wells in a North Sea oilfield, which presents adverse development conditions. The customer commended the product for its high sealability and superior sealing workability at the worksite. Since then, VAM®21 has been sold to customers in Southeast Asia, Western Australia, and the Middle East.

VAM®21 is currently available in 22 sizes from 9-5/8” to 13-3/8” in outer diameter, to be used for casings(*4) and large-diameter tubing(*5). We will continue to expand the line-up and respond to requests from our customers.

<Reference figures>

Figure1: VAM Stabilizer™

Figure2: Ease of sealing work

Figure 3: Oil and gas well fields with sales history of VAM®21

＜Terms＞
*1 VAM®
The brand name of seamless pipe threaded connection jointly developed by Sumitomo Metals and Vallourec. It ranks number one with about a 40% market share for high-grade OCTG Premium Connection in the world. The best service network existing in the world, with over 137 thread repair shops in 46 countries.

*2 Vallourec S.A.

(1) Head office:	France
(2) Representative:	Philippe Crouzet
(3) Business activities:	Manufacturing and sales of steel pipe and tube for oil & gas industries and others
(4) Capital:	229,123,000 Euro
(5) Number of employees:	Approximately 18,600 (as of Dec. 31, 2009)

Sumitomo Metals and Vallourec have a business alliance extending over 30 years for VAM®, the world renowned brand for threaded connections for seamless pipe

*3 The most rigorous standard for threaded connections
ISO13679 CAL-IV. This is the international standard detailing testing procedures for threaded connections for OCTG. It was established by an international standards committee that included both OCTG users (i.e., oil majors) and about a dozen Pipe manufacturers.

*4 Casing
A large-diameter pipe that is stabbed into a recently drilled section of a borehole of oil and gas wells, to prevent the collapse of the wall. Pipe size varies from 20” to 5” in outer diameter.

*5 Large-diameter tubing
A small-diameter pipe is held within the above-mentioned casing, in order to pipe up production fluids. Conventionally, OCTG with an outer diameter of 2-3/8” to 7” is used. However, in order to improve the production efficiency of wells, large OCTGs measuring 9-5/8” in diameter are also used.