Cylinder Assembly For Snubbing And Drilling Applications

A cylinder assembly comprising:

• (a) an outer tubular housing having a top end and a base end;
• (b) a stationary piston sealing ring retained within said outer tubular housing between top end and said base end;
• (c) an inner tubular piston slideably positioned within said piston sealing ring, said tubular piston have an upper sealing flange creating an upper fluid chamber in said outer tubular housing between said upper sealing flange and said stationary piston and a lower fluid chamber between said lower sealing flange and said stationary piston;
• (d) an upper fluid conduit in said stationary piston sealing ring in fluid communication with said upper fluid chamber and a lower fluid conduit in said stationary piston in fluid communication with said lower fluid chamber;
• and
• (e) a first fluid line in communication with said upper fluid conduit and a second fluid line in communication with said lower fluid conduit whereby pressurized fluid may be selectively directed.

The method of snubbing a pipe through a BOP stack of a wellbore comprising the steps of:

• (a) providing a snubbing cylinder having an outer cylindrical tubular housing, a stationary piston sealing ring retained within said outer housing, said stationary piston sealing ring separating said outer housing into upper and lower outer housing segments, an inner tubular piston slideably positioned within said piston sealing ring, said tubular piston have an upper sealing end and a lower sealing end creating an upper fluid chamber in said upper housing segment and a lower fluid chamber in said lower housing segment;
• (b) attaching a bearing table to said upper sealing end of said tubular piston;
• (c) attaching a set of travelling slips to said bearing table;
• (d) providing stationary slips mounted to a BOP stack positioned over a wellbore containing a pipe string;
• (e) attaching said pipe string to said stationary slips;
• (f) moving said piston upward through said outer cylindrical housing by introducing pressurized fluid into said upper fluid chamber;
• (g) positioning a pipe segment through said inner tubular piston;
• (h) attaching said pipe segment to said travelling slips;
• (i) moving said inner tubular piston downward through said outer cylindrical housing by introducing pressurized fluid into said lower fluid chamber whereby said pipe segment is positioned for attachment to said pipe string;
• (j) rotating said pipe segment whereby said pipe segment and said pipe string are attached;
• (k) detaching said stationary slips from said pipe string;
• and
• (j) moving said inner tubular piston downward through said outer cylindrical housing by introducing pressurized fluid into said lower fluid chamber thereby pushing said pipe segment with said attached pipe string through said BOP stack.

A snubbing unit comprising:

• (a) an outer tubular housing defined by upper and lower outer tubular cylinders, said lower outer tubular cylinder attached to stationary slips mounted on a BOP stack positioned over a wellbore;
• (b) a stationary piston sealing ring separating said upper and lower outer tubular cylinders;
• (c) an inner tubular piston having an upper sealing end, a lower sealing end, and a central bore for receiving a length of pipe, said inner tubular piston slideably received in said piston sealing ring;
• (d) an upper annular fluid chamber defined by said stationary piston, said inner tubular piston, and said upper outer tubular cylinder and a lower annular fluid chamber defined by said stationary piston, said inner tubular piston, and said lower outer tubular cylinder;
• (e) fluid conduits in said piston sealing ring in communication with said upper and lower annular fluid chambers;
• (f) fluid selectively directed into said upper annular fluid chamber or said lower fluid annular chamber through said fluid conduits whereby said inner tubular piston may be selectively moved upward or downward;
• (g) a pipe guide positioned within said lower outer tubular cylinder;
• (h) a tubular spool having an upper end and a lower end, said lower end of said tubular spool attached to said upper sealing end of said inner tubular piston;
• (i) a bearing table positioned on said upper end of said tubular spool, said bearing table having a central opening;
• and
• (j) travelling slips mounted to said bearing table whereby a length of pipe may be supported to extend vertically through said central opening of said bearing table and said inner tubular piston.