Perforating gun spacer
Perforating gun connectors are provided with a small diameter inner tube to house the detonating cord and an outer load-bearing tube that is ported to be in pressure balance. The inner tube controls the volume in the gun for the well fluids to enter after the guns are fired and the initial pressure surge dissipates. The smaller diameter also increases pressure rating and diminishes the chance of plastic deformation. Since the inner tube is inset even some deformation is tolerated without distorting the outer tube due to the space between the tubes. A bored rod is used as a housing member or a layered single outer wall.
1. A connector, for perforating guns having charges set off by a detonation cord, comprising:
a housing assembly having at least one end connector to accept a perforating gun;
at least one inner tubular connected to said end connector through which the detonation cord passes to the charges, said inner tubular forms part of an initially sealed conduit with respect to a surrounding annular space, said initially sealed conduit has fluids entering from a formation after the charges are set off at a time when said inner tubular is no longer sealed;
an outer tubular supported by said end connector and mounted over said inner tubular to define said annular space which is free of the charges, said annular space along the substantial length of said outer tubular is in pressure balance with surrounding well fluid in the wellbore at a time before said gun is fired.
2. The connector of claim 1 , wherein:
said outer tubular has at least one opening.
3. The connector of claim 2 , wherein:
said outer tubular has an outside diameter no greater than said end connector.
4. The connector of claim 2 , wherein:
any deformation of said inner tubular occurs in said annulus without deformation of said outer tubular.
5. The connector of claim 4 , wherein:
a volume inside said inner tubular is selected to provide a predetermined volume to control surge flow from the formation after the charges are set off.
6. The connector of claim 1 , wherein:
said annular space comprises fill material comprising at least one of metal, plastic, cement and organic material.
7. The connector of claim 6 , wherein:
any deformation of said inner tubular occurs in said annulus without deformation of said outer tubular.
8. The connector of claim 1 , wherein:
said outer tubular has an outside diameter no greater than said end connector.
9. The connector of claim 1 , wherein:
a volume inside said inner tubular is selected to provide a predetermined volume to accommodate surge flow from the formation after the charges are set off.
10. The connector of claim 1 , wherein:
said outer tubular has a diameter-to thickness ratio ranging 3.2 to 50 inclusive.
11. The connector of claim 1 , wherein:
said outer tubular has an outside diameter greater than said end connector.