Subsea pig launcher

Abstract

A multiple pig subsea pig launcher is disclosed. The pig launcher can be assembled on a production pipeline subsea with the aid of an ROV. In the preferred embodiment, the pigs are connected to each other and spaced apart by a spine. The pig launcher is configured to capture the next pig to be launched in such a manner that the spine behind it is in alignment with a shearing valve; for example, coiled tubing or wireline. Sequential valve operation shears the spine and applies pressure behind the pig to launch it from the launcher past the pig detector and onto a platform for recapture.

1 . A pig launching apparatus comprising: 
 a housing;    a plurality of pigs initially attached to each other for placement in said housing; and    a separator device to release one pig for launching.    
     
     
         2 . The apparatus of  claim 1 , wherein: 
 said pigs are attached to each other at a predetermined distance.    
     
     
         3 . The apparatus of  claim 2 , wherein: 
 said housing is configured to stop the advancement of lowermost pig at a location where said separation device can separate one pig from 4 another.    
     
     
         4 . The apparatus of  claim 3 , wherein: 
 said configuration of said housing comprises a taper.    
     
     
         5 . The apparatus of  claim 4 , wherein: 
 said pigs are separated from each other by a member which is exposed between each pair of pigs.    
     
     
         6 . The apparatus of  claim 5 , wherein: 
 said separation device selectively severs said member.    
     
     
         7 . The apparatus of  claim 6 , wherein: 
 said separation device is operable form a closed position where it supports all unlaunched pigs followed by an open position where it allows for one pig to drop onto said taper, followed by a closed position where said member is severed behind the pig resting on said taper.    
     
     
         8 . The apparatus of  claim 7 , further comprising: 
 a weight on said pigs to assist them into dropping down toward said taper.    
     
     
         9 . The apparatus of  claim 8 , further comprising: 
 at least one connection on said housing which can be made or released with an ROV.    
     
     
         10 . The apparatus of  claim 1 , wherein: 
 said attachment of said pigs is accomplished by a member, a portion of which is exposed between said pigs.    
     
     
         11 . The apparatus of  claim 10 , wherein: 
 said member is aligned with said separation device after said separation device is retracted which allows said pigs to advance in tandem by a predetermined amount.    
     
     
         12 . The apparatus of  claim 11 , wherein: 
 said separation device shears said member above the lowermost pig to allow said lowermost pig to be launched.    
     
     
         13 . The apparatus of  claim 12 , further comprising: 
 a taper on said housing to stop the lowermost pig with said member aligned with said separation device.    
     
     
         14 . A pig launching apparatus, comprising: 
 a housing;    a plurality of undirectional pigs insertable in said housing for launching one at a time.    
     
     
         15 . The apparatus of  claim 14 , further comprising: 
 a separating device to separate one pig from other pigs for launching.    
     
     
         16 . The apparatus of  claim 15 , wherein: 
 said separating device functions as a pressure isolation valve.    
     
     
         17 . The apparatus of  claim 16  further comprising: 
 attaching a plurality of pigs to each other.  
 
     
     
         18 . The apparatus of  claim 17 , wherein: 
 said separation device selectively breaks the attachment between two pigs.    
     
     
         19 . The apparatus of  claim 14 , further comprising: 
 a cartridge to support said pigs which can be inserted by an ROV into said housing to load said pigs therein.