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A method of subsurface lubrication facilitates well completion, re-completion and workover while increasing safety and reducing expense. The method involves using a subsurface lubricator mounted to a wellhead of the cased wellbore to lubricate a downhole tool string into the cased wellbore by runnin

A method of subsurface lubrication facilitates well completion, re-completion and workover while increasing safety and reducing expense. The method involves using a subsurface lubricator mounted to a wellhead of the cased wellbore to lubricate a downhole tool string into the cased wellbore by running a subsurface lubricator through the wellhead and into an upper section of a production casing of the cased wellbore.

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I claim: 1. A method of subsurface lubrication into a cased wellbore, comprising: running a bottom end of a subsurface lubricator downward through a wellhead into an upper section of production casing supported by the wellhead until the subsurface lubricator is in a lubricated-in position in which

I claim: 1. A method of subsurface lubrication into a cased wellbore, comprising: running a bottom end of a subsurface lubricator downward through a wellhead into an upper section of production casing supported by the wellhead until the subsurface lubricator is in a lubricated-in position in which a top end of the subsurface lubricator remains above the wellhead, the upper section of the production casing being larger than and connected to a lower section of production casing of the cased wellbore; and securing the subsurface lubricator in the lubricated-in position; whereby full-bore access to the lower section of the production casing of the cased wellbore is provided by the subsurface lubricator. 2. The method as claimed in claim 1 wherein running the bottom end of the subsurface lubricator down through the wellhead further comprises running the bottom end of the subsurface lubricator down through a pressure control gate mounted above the wellhead. 3. The method as claimed in claim 2 wherein running the bottom end of the subsurface lubricator down through the pressure control gate comprises running the bottom end of the subsurface lubricator through a blowout preventer or a high pressure valve. 4. The method as claimed in claim 1 further comprising mounting a coil tubing blowout preventer or a wireline blowout preventer to a top end of the subsurface lubricator prior to running the bottom end of the subsurface lubricator down through the wellhead. 5. The method as claimed in claim 4 further comprising mounting a coil tubing injector to a top of the coil tubing blowout preventer, or mounting a grease injector to a top of the wireline blowout preventer. 6. The method as claimed in claim 5 further comprising running a coil tubing string through the coil tubing injector and the coil tubing blowout preventer and connecting the downhole tool string to an end of the coil tubing string, or running a wireline through the grease injector and the wireline blowout preventer and connecting the downhole tool string to an end of the wireline. 7. The method as claimed in claim 6 wherein prior to running the bottom end of the subsurface lubricator down through the wellhead, the method further comprises drawing the downhole tool string into the subsurface lubricator using the coil tubing or the wireline. 8. The method as claimed in claim 6 further comprising operating the coil tubing injector or a wireline unit to run the downhole tool string into the lower section of the production casing. 9. A method of lubricating a downhole tool string into a wellbore cased with an upper section of production casing of a first diameter and a lower section of production casing of a second, smaller diameter than the diameter of the upper section of production casing, the method comprising: mounting a subsurface lubricator containing the downhole tool string above a pressure control gate mounted above a wellhead of the cased wellbore; and opening the pressure control gate and running a bottom end of the subsurface lubricator through the wellhead of the cased wellbore and into the upper section of the production casing until a top end of the subsurface lubricator is adjacent a top end of the wellhead. 10. The method as claimed in claim 9 wherein prior to opening the pressure control gate, the method further comprises mounting a coil tubing blowout preventer or a wireline blowout preventer to a top of the subsurface lubricator. 11. The method as claimed in claim 10 further comprising mounting a coil tubing injector to a top of the coil tubing blowout preventer or a grease injector to a top of the wireline blowout preventer. 12. The method as claimed in claim 11 further comprising running a coil tubing string through the coil tubing injector and the coil tubing blowout preventer and connecting the coil tubing string to the downhole tool string, or running a wireline through the grease injector and the wireline blowout preventer and connecting the wireline to the downhole tool string. 13. The method as claimed in claim 12 further comprising operating the coil tubing injector to run the downhole tool string into the lower section of the production casing, or operating a wireline unit to run the downhole tool string into the lower section of the production casing after the subsurface lubricator has been run into the upper section of the production casing. 14. The method as claimed in claim 13 further comprising operating the downhole tool string to perform one of a well completion, recompletion and workover operation. 15. A method of lowering a working height of equipment used for well completion, recompletion or workover of a cased wellbore, comprising: mounting a subsurface lubricator containing a downhole tool string to a wellhead of the cased wellbore; lubricating the downhole tool string in the subsurface lubricator into the cased wellbore by running the subsurface lubricator through the wellhead and into an upper section of a production casing of the cased wellbore until the subsurface lubricator is in a lubricated-in position in which a top end of the subsurface lubricator remains above the wellhead. 16. The method as claimed in claim 15 wherein running the subsurface lubricator through the wellhead comprises running the subsurface lubricator through a pressure control gate mounted above the wellhead. 17. The method as claimed in claim 16 wherein running the subsurface lubricator through the pressure control gate comprises running the subsurface lubricator through a blowout preventer or a high pressure valve. 18. The method as claimed in claim 15 further comprising operating a coil tubing injector or a wireline unit to lower the downhole tool string down the cased wellbore.