Dart launcher for well cementing operations

Abstract

Modular apparatus for remotely activating a wiper plug launching tool or other down-hole equipment by launching a dart or other projectile along tubing to the subsea equipment. A dart is loaded into a basket prior to launch and subsequently loaded into a modular tool piece. The pre-loaded tool pieces are configurable prior to use dependent on operational requirement and furthermore may be independently removable from the remaining equipment facilitating maintenance and serving of individual tool pieces.

1 . A dart launcher for use in well cementing operations comprising:
 body having a bore which can be arranged to communicate with the well;   a valve element located in the body and operable to open or close the bore;   a dart receiver positioned in the body above the valve element for housing a dart that can be launched through the valve element into the well;   the dart receiver being dimensioned to receive a dart sleeve, into which the dart is pre-loaded, the sleeve comprising formations on its outer surface which engage in corresponding formations in the inner surface of the receiver to prevent the sleeve from passing through the valve element when the dart is launched wherein the dart comprises an elongate core with a series of flexible fins projecting therefrom, and a head section for engaging a plug launching tool, the head section being connected to a core by means of a resilient damping system   
   
   
       2 . A dart launcher as claimed in  claim 1 , wherein the body, valve element and dart receiver form a launcher module, the launcher comprising several modules connected together one above the other such that the part of the body through which the dart is launched is connected to the top of the dart receiver of the module below. 
   
   
       3 . A dart launcher as claimed in  claim 2 , wherein each module also comprises a sleeve loaded with a dart. 
   
   
       4 . A dart launcher as claimed in  claim 3 , further comprising a ball dropper positioned below the lowermost module. 
   
   
       5 . A dart sleeve for use in a dart launcher as claimed in  claim 1 , comprising a sleeve for housing a dart in a compressed form, wherein formations are provided on the outer surface of the sleeve which can engage in corresponding formations in the inner surface of the dart receiver to hold the sleeve in place as the dart is launched. 
   
   
       6 . A dart sleeve as claimed in  claim 5 , further comprising a dart in compressed form housed inside the sleeve. 
   
   
       7 . A dart for use with a dart sleeve as claimed in  claim 6 , comprising an elongate core with a series of flexible fins projecting therefrom, and a head section for engaging a plug launching tool, the head section being connected to a core by means of a resilient damping system. 
   
   
       8 . A dart as claimed in  claim 7 , wherein the resilient damping system comprises a spring. 
   
   
       9 . A method of providing a dart launching assembly on a well in a cementing operation, comprising:
 installing a number of darts in compressed form, each in an associated sleeve;   installing the sleeves in respective dart receivers of dart launchers as claimed in  claim 1 ;   connecting the dart launchers together in an end to end fashion to form an assembly; and   connecting the assembly to the top of the well to be cemented.