Shaft collar assembly and method

Abstract

Disclosed is an extended shaft collar comprising a reinforced concrete collar which extends from the surface to below a groundwater formation, providing an impenetrable barrier between the surrounding groundwater formations and the work area within the shaft. The extended shaft collar of the present invention provides a barrier to the ground and the work area of a shaft, including the prevention of contamination of shallow groundwater of the surrounding formations from the activities of the shaft, and may further be used for emergency shaft purposes. Concrete utilized in the extended collar may be comprised of conventional cements as well as specialty cements. The disclosed extended shaft collar supports a wide variety of scenarios for heavy civil construction projects, oil and gas production and mining, including subterranean oil recovery platforms and related products and services where shallow groundwater reservoirs are located.

What is claimed is: 
     
         1 . A shaft comprising an impermeable shaft collar extending from a surface continuously underground below a groundwater formation into a competent rock formation for groundwater isolation from the shaft for an underground drilling facility. 
     
     
         2 . The shaft of  claim 1 , further comprising a surface-oriented shaft collar pad for supporting surface equipment. 
     
     
         3 . The shaft of  claim 2 , wherein the shaft collar pad is comprised of reinforced concrete. 
     
     
         4 . The shaft of  claim 1 , wherein said shaft collar further supports a shaft, utility and piping supports for the underground drilling facility. 
     
     
         5 . The shaft of  claim 1 , wherein said shaft collar further prevents shaft production fluids from contaminating a groundwater formation. 
     
     
         6 . The shaft of  claim 1 , wherein said shaft is a large diameter shaft. 
     
     
         7 . The shaft of  claim 1 , wherein said shaft collar is comprised of concrete. 
     
     
         8 . The shaft of  claim 1 , wherein said shaft collar is comprised of reinforced concrete. 
     
     
         9 . The shaft of  claim 1 , wherein said shaft collar further comprises a retaining wall extending below the surface for supporting the extended sub-surface shaft collar. 
     
     
         10 . The shaft of  claim 1 , wherein a shaft liner further connects to the shaft collar below the competent rock formation, said shaft liner extending below the shaft collar substantially through the remaining portion of the shaft. 
     
     
         11 . A method of isolating subterranean shaft activities from a groundwater formation, comprising:
 excavating a pre-determined shaft for subterranean activities;   installing an impermeable shaft collar from the surface of the shaft to a competent rock formation below said groundwater formation;   placing a shaft liner impermeably connected below the installed shaft collar; and   extending said shaft liner below the shaft collar substantially through the remaining portion of the shaft.   
     
     
         12 . The method of  claim 11 , wherein said shaft collar comprises reinforced concrete capable of supporting surface equipment and piping suspension supports. 
     
     
         13 . The method of  claim 11 , further comprising applying flashing of supporting material to exposed raveling rock formations prior to installing said impermeable shaft collar. 
     
     
         14 . The method of  claim 11 , further comprising applying flashing of supporting material to exposed raveling rock formation prior to installing the shaft liner below said shaft collar. 
     
     
         15 . The method of  claim 11 , wherein installing said shaft collar further comprises installing a shaft collar pad capable of supporting surface equipment and piping suspension supports. 
     
     
         16 . The method of  claim 11 , further comprising installing a retaining wall below the shaft collar pad and external to the extended sub-surface shaft collar and further extending below the surface for supporting the extended sub-surface shaft collar. 
     
     
         17 . The method of  claim 11 , wherein the shaft is an emergency shaft comprising an impermeable shaft collar having an inner diameter comprised of a steel pipe liner extending from a surface continuously underground below a groundwater formation into a competent rock formation wherein said shaft collar isolates groundwater and hazardous gas from the emergency shaft. 
     
     
         18 . An emergency shaft comprising an impermeable shaft collar having an inner diameter comprised of a steel pipe liner extending from a top surface continuously underground below a groundwater formation into a competent rock formation wherein said shaft collar isolates groundwater and hazardous gas from the emergency shaft. 
     
     
         19 . The emergency shaft of  claim 18 , wherein said steel pipe liner incorporated into the inner diameter of the shaft collar extends from the shaft collar into the shaft liner, said shaft liner having said inner steel pipe liner extending through the remaining portion of the emergency shaft. 
     
     
         20 . The emergency shaft of  claim 1 , wherein said emergency shaft further serves as a ventilation shaft.