Gas Lift Manufacturer -Tubing Nipples

 Tubing Nipples – Selective According To Profile & Top No-Go

The RPT Plug/Mandrel uses a profile nipple in conjunction with a top no-go restriction to locate and set. It is especially suited for large-bore production strings. The plug can withstand a 10000 psi differential from either direction. The RPT is available for tubing sizes ranging from 2 3/8” to 7”

It can be used as a receptacle for a plug when installed above the subsurface safety valve. This prevents the safety valve from being used as a pressure barrier should work on the tree be required. It’s bore is larger than the rest of the production nipples so the RPT doesn’t “get in the way” of other wireline- associated operations.

Otis X & R equipment are examples of nipples and associated lock mandrels which are selective due to the functions of the running tool.

Unlike S equipment,X Unlike S equipment,X nipples do not have To be installed in the tubing in any

particular order since there is no difference in the profile of any X nipple as compared to another and the same is true for the R equipment.

Although X & R equipment is similar in its functioning, the R equipment is designed for high pressure service.

Setting the X lock in the top nipple is accomplished as seen in the first animation. The tool string is lowered to the nipple and the locking keys locate in the nipple. Downward jarring sets the mandrel in the nipple. Upward jarring shears a pin in the running tool and the tool string is retrieved.

The second animation illustrates the procedure used to set a lock mandrel in a lower nipple. The running tool is run in the “cocked” position and locates the nipple with the  locator  keys.  The  tool  string  will  momentarily  “sit down” and then alls through the nipple.

The tool string is lifted back up through the nipple and the  running  tool  “uncocks” which  allows  the  locking keys to protrude. The tool string is then lowered and the lock mandrel locates in the nipple. The mandrel is then set in the nipple as explained above.

Tubing Nipples – No-Go Nipples

NoGo nipples are the lowermost nipples in the production string and as such, have the smallest internal diameter.

Like other lock mandrels, a wide variety of flow control devices can be installed on the No-Go mandrel and set in the No-Go nipple

If an N nipple is to be installed in the  tubing  string,  it’ s  installed before Position 1 S nipple.

Otis X & R equipment incorporates an equalizing sub in its No-Go assembly as seen below. And like the Otis S equipment, the XN or RN nipple is installed in the production string before the first X or R nipple.

Tubing Movement During Production, Testing and Stimulation

There are four factors that tend to cause a change in the length or force in the tubing string:

  1. Temperature effect, which is directly influenced by a change in the average temperature of the string
  2. Piston effect, caused by a change in the pressure in the tubing or annulus above the packer acting on a specific affected area
  3. Ballooning effect, caused by a change in average pressure inside or outside the tubing string
  4. Buckling effect, which occurs when internal tubing pressure is higher than the annulus pressure

Buckling will shorten the tubing string; however, the other effects may tend to lengthen or shorten the string depending on the application of the factors. As long as the tubing is allowed to move in the packer bore, the temperature and ballooning effects will only have an impact on tubing-length changes, but, if movement is prevented (or restrained) at the packer, these two factors would then createa force.

It is important to remember that a string of tubing landed in any packer is initially in a neutral condition, except for any subsequent mechanical strain or compression loads applied by the rig operator. After the tubing is landed, the factors that cause changes in length or force are always the result of a change in temperature and pressure.

Design considerations must be made for the potential temperature and pressure changes the tubing string could be subjected to over its’ service life.

A Polished Bore Receptacle (PBR) used in combination with an Extra Long Tubing Seal Receptacle (ELTSR) will act as an expansion joint, allowing the tubing to change length while maintaining it’s barrier properties without damage to the wellbore or tubing string


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