Method and structure for protecting a crushable plug in a pipe section for hydrocarbon production, and use thereof

Abstract

A method to protect a crushable plug in a pipe section for hydrocarbon production against falling objects is described, and it is characterised in that one or more layers of a thick, viscous liquid is arranged on the topside of the crushable plug, where the topside of the thick, viscous liquid is given a completely covering protective layer to cover and seal the liquid layer on top of the plug, and in particular, several layers of viscous liquid are placed on top of the plug and between each layer of viscous liquid a completely covering protective layer is arranged to protect the plug. Also described is a construction of a plug unit comprising a crushable plug. The invention can be used to protect test plug units fitted in a section of casing tubing to carry out pressure testing.

1 .- 14 . (canceled) 
     
     
         15 . Method to protect a crushable plug in a pipe section against falling objects, wherein one or more layers of a thick, viscous liquid is arranged on the topside of the crushable plug, where the topside of the thick, viscous liquid is given a completely covering protective layer to cover and seal the liquid layer on top of the plug. 
     
     
         16 . Method according to  claim 15 , wherein several layers of viscous liquid are arranged on the top side of the plug, and a completely covering protective layer is arranged between each layer of viscous liquid. 
     
     
         17 . Method according to  claim 15 , wherein a thick, viscous liquid based on clay, different forms of gels with a paste-form are used, such as polymer-based gels, gel-formed lubricating means such as silicone lubricating means, glycerol, different forms of oil such as Castor oil, a thick oil corresponding to the gear oil with the designation W90, as the layer has a higher viscosity than common well fluids so that the layer, when completely fitted, remains lying on top of the crushable plug as a protecting layer. 
     
     
         18 . Method according to one of the  claim 15 , wherein the protective layer or layers is an elastic membrane or a disc movable in the axial direction of the pipe 
     
     
         19 . Method according to  claim 18 , wherein said elastic membrane is an elastic membrane of rubber or synthetic plastic materials such as polymers, such as polyethylene or polypropylene, is used which is leakproof and impermeable to a viscous liquid. 
     
     
         20 . Method according to  claim 18 , wherein said movable disc is a disc/plug of an inelastic material of metal, ceramic materials, stiffer plastic materials and glass are used, and the disc is prefabricated and adjusted to be placed on top of the viscous liquid layer by a movement in the axial direction of the pipe. 
     
     
         21 . Method according to one of the  claim 15 , wherein the uppermost protective layer that is exposed to the well fluids is leakproof and impermeable to well fluids and the viscous liquid layer used. 
     
     
         22 . Method according to  claim 15 , wherein the crushable plug and the one or more of the layers of viscous liquid and the in-between lying protective layer are fitted in advance in a separate pipe section which is then inserted in the production pipe in a suitable location with respect to its actual position in the well. 
     
     
         23 . Crushable plug unit for testing of a pipe section for oil and/or gas production, wherein the topside of the crushable plug unit comprises one or more layers of a thick (dilatant) viscous liquid and the topside of the viscous liquid layer comprises a completely covering protective layer to cover and seal the thick, viscous liquid layer on top of the plug, where said protective layer is movable in the axial direction of the pipe in response to blows from falling objects in the pipe. 
     
     
         24 . Crushable plug unit according to  claim 23 , wherein several layers of viscous liquid are placed on the topside of the plug and a completely covering protective layer is placed between each layer of viscous liquid. 
     
     
         25 . Crushable plug unit according to  claim 23 , wherein the thick, viscous liquid is based on clay, different forms of gels with a paste-form are used, such as polymer-based gels, gel-formed lubricating means such as silicone lubricating means, glycerol, different forms of oil such as Castor oil, a thick oil corresponding to gear oil with the designation W90, as the layer has a higher viscosity than common well fluids so that the layer, when completely fitted, remains lying on top of the crushable plug as a protecting layer. 
     
     
         26 . Crushable plug unit according to one of the  claim 23 , wherein
 the protecting layer is an elastic membrane of rubber or synthetic plastic materials such as polymers, such as polyethylene or polypropylene, and which is leakproof and impermeable to a viscous liquid, or   the protecting layer is a disc/plug of an inelastic material of metal, ceramic materials, stiffer plastic materials and glass, and the disc is prefabricated and can be placed on top of the viscous protective layer by a movement in the axial direction of the pipe.   
     
     
         27 . Crushable plug unit according to  claim 23 , wherein the top protecting layer that is exposed to the well fluids is leakproof and impermeable to well fluids and the applied viscous liquid layer. 
     
     
         28 . Crushable plug unit according to  claim 23 , wherein the crushable plug and the one or more layers of viscous liquid and the in-between lying protecting layer are fitted in advance in a separate pipe section for insertion in a production pipe at a suitable location with respect to the actual position down in the well. 
     
     
         29 . A method of protecting a test plug unit fitted in a section of casing tubes to carry out pressure testing comprising the steps:
 fitting a glass plug set into a casing tubing section;   arranging at least one layer of a thick, viscous liquid on the topside of the plug set in the section;   arranging a completely covering protective layer over the liquid layer on the topside to create a test plug unit; and   inserting the test plug unit into a separate section of casing tubing section to carry out pressure testing.