Making up and breaking out of a tubing string in a well white maintaining continuous circulation

A method of assembling a tubing string projecting into a well, including the steps of:

• providing a top end connecting unit including at least one connector for connection to a tubular axially projecting from said at least one connector, and at least one main high pressure conduit communicating with said at least one connector for allowing circulation through a tubular connected to said at least one connector;
• providing a connecting shell below said top end connecting unit, said shell bounding a connecting chamber and having an upper passage and a lower passage coaxial therewith for receiving tubulars, seals for sealing off said passages against tubulars extending through said passages, a preventer for separating an upper portion of said connecting chamber from a lower portion of said connecting chamber, and a back-up high pressure conduit communicating with said lower portion of said connecting chamber;
• lowering said at least one connector and a tubing string connected thereto into said connecting shell until a position at least partially within said connecting chamber of said connecting shell;
• disconnecting said at least one connector from said tubing string;
• lifting said at least one connector into a position in which a lowest portion thereof is located above said preventer;
• closing off said preventer;
• removing feeding pressure from said at least one main high pressure conduit and from said upper portion of said connecting chamber and withdrawing said at least one connector from said connecting chamber;
• connecting a tubular to one of said connectors and lowering said tubular into said upper passage;
• bringing one of said at least one main high pressure conduits in communicating with said tubular and said upper portion of said connecting chamber under pressure and opening said preventer;
• and
• further lowering said tubular and making up a connection between said tubular and said tubing string;
• characterized in that, after said step of lowering said tubular into said upper passage, pressure in at least one pressure chamber is maintained at a level corresponding to pressure in said upper portion connecting chamber, axially urging said tubular towards said connecting chamber and at least partially balancing out upward pressure exerted to said tubular towards said connecting chamber and at least partially balancing out upward pressure exerted to said tubular by the pressure applied to said upper portion of said connecting chamber.

A method of disassembling a tubing string projecting into a well, including the steps of:

• providing a top end connecting unit including at least one connector for connection to a tubular axially projecting from said at least one connector for allowing circulation through a tubular connected to said at least one connector;
• providing a connecting shell below said top end connecting unit, said shell bounding a connecting chamber and having an upper passage and a lower passage coaxial therewith for receiving tubulars, seals for sealing off said passages against tubulars extending through said passages, a preventer for separating an upper portion of said connecting chamber from a lower portion of said connecting chamber, and a back-up high pressure conduit communicating with said lower portion of said connecting chamber;
• lowering said at least one connector into said connecting shell until a position at least partially within said connecting chamber of said connecting shell;
• bringing one of said at least one main high pressure conduit in communication with said connector under pressure and opening said preventer;
• further lowering said connector and making up a connection between said tubular and said tubing string;
• connecting said at least one connector to said tubing string (2);
• lifting said at least one connector and a tubular connected thereto into a position in which a lowest portion of said tubular is located in said lower portion of said connecting chamber;
• breaking up a connection between said tubular and said tubing string;
• lifting said at least one connector and a tubular connected thereto into a position in which a lowest portion of said tubular is located in said upper portion of said connecting chamber and above said preventer;
• closing off said preventer;
• removing feeding pressure from said at least one main high pressure conduit and from said upper portion of said connecting chamber and withdrawing said tubular from said connecting chamber;
• characterized in that, after said step of lowering said at least one connector into said connecting shell, pressure in at least one pressure chamber is maintained at a level corresponding to pressure in said upper portion of said connecting chamber, axially urging said connector towards said connecting chamber and at least partially balancing out upward pressure exerted to said connector by the pressure applied to said upper portion of said connecting chamber.