Gas Wells especially high-temperature and high-pressure ultra-deep gas Wells, put forward a series of strict and demanding requirements on completion technology. Due to severe downhole conditions, the design of gas well completion string and the selection of tubing coupling are important factors to be considered. Premium connection threaded on casing and tubing for gas tightness and high compression resistance. It features a special buckle with a reverse angle on the load flank, allowing it to resist fatigue fracture. The oil and gas production under deep, high temperatures and high pressure has proved that the trapezoidal threaded coupling, that’s the VAM type oil tubing without sealing grease can meet the harsh environment and work well.
What are Vam couplings?
A steel pipe coupling is a cylinder used to connect two lengths of threaded casing or tubing. Couplings come in three types of buckle: EU, NU and Vam. Couplings are available in different types to match specific application requirements. For example, some are designed to resist bending and compression forces more than others. Others might be optimized for gas tightness or repeated make/break cycles. Premium couplings also have unique features, such as a special wedge effect and a dual-sealing surface.
As the name suggests, VAM couplings are used to leak-tightly connect casing and tubing in oil wells. The casing is a pipe permanently cemented into the well, while the tubing is the retrievable pipe through which oil/gas flows. Occasionally, it’s also used for “landing strings” — temporary pipes that convey other tubing in and out of the well. The VAM thread has a rectangular cross-section, equal pitch intervals and little taper, which results in high connecting strength. Vam couplings are usually manufactured with a seamless type, material grade the same as the casing or tubing pipe body and have API threads on both ends. Vam coupling oil tubing is a premium connection in the tubing and casing size range, offering excellent gas-tight seal performances under combined loads (pressure, bending, compression). A unique reverse angle on the torque shoulder enhances the wedge effect of the metal-to-metal seal. It’s also optimized to resist combined external pressure, bending and compression loads. This feature improves tensile strength, resistance to compression and a minimized risk of galling even when the thread lubricants are poorly applied. The special-clearance (reduced outside diameter Wc) couplings for buttress casing and external upset tubing have a bevel on both sides of the bearing face. The inside and the outside of the coupling bearing faces shall be rounded or beveled and the ends (or root face when the bevel is on the tubing side) are faced at right angles to the axis.
Advantages of VAM oil Casing and Tubing
- Metal-to-metal seal. It uses a reverse angle torque shoulder that provides a positive power-tight make-up and minimizes hoop stresses. This unique metal-to-metal seal connection also protects against galling even when lubricants are not used properly. The metal-to-metal seal of the VAM premium connection resists the most severe combined loads, minimizing the risks that can lead to failures such as gas pressure, temperature, bending and compression.
- High tensile strength. It has high tensile strength, excellent resistance to internal and external stress, and can be used in all kinds of environments. The trapezoidal thread of Vam tubing has higher tensile strength than the API standard tubing of the same size, and the radial force generated during stretching is smaller due to the small load surface Angle. At the same time, the torque shoulder has better anti-pressure effect.
- Good adhesion resistance. The trapezoidal thread and conical surface sealing design of VAM tubing reduce the compressive stress on the contact surface, so it has better anti-adhesion performance.
- Smooth diameter. The joint erosion caused by eddy current in the tube can not be ignored. The inner diameter of vam tubing is smooth at the collar after forming the pipe string, and it is not easy to produce eddy erosion. Its long internal shoulder and a tight tolerance on the coupling center minimize turbulence and energy loss in the tubing/casing joint. The smooth bore makes it easy to run completion tools even in deviated Wells.
Applications of VAM coupling oil tubing
VAM coupling oil tubing can prevent the accident of oil well pipe string break effectively, due to the structure design, stress concentration is smaller than conventional casing coupling. The connection stress is distributed over a larger area, which makes it less likely to cause fatigue fracture or other damage. The coupling can prevent the accident of oil well pipe string break effectively. The VAM coupling is a good choice for applications that require the highest levels of reliability, such as wells with high gas loads or in deviated formations.
WiHo Industrial is a leading supplier and manufacturer of EU, EU, VAM, and other premium connections for both casing and tubing. The VAM product line also includes specific designs with increased performance in torque (VAM HT) or compression (VAM HC). These couplings can be used in all OCTG applications, including workover and production operations. They are also designed to withstand a wide range of API tests, include tensile test, flattening tests, hydrostatic tests and sulfide stress corrosion cracking tests. Contact WIHO for your oil and gas production need!