System and method for performing well operations

Abstract

System and associated method for performing well operations in a plurality of hydrocarbon wells ( 120 a , 120 b , 120 c ) of a wellhead cluster ( 104 ), has a main drilling rig ( 106 ) with a main drilling unit ( 107 ) displaying a drill floor ( 108 ) and having a drilling and hoisting system ( 109 ) arranged to operate on the drill floor about a well center ( 110 ), wherein the main drilling unit is positioned at least partially vertically above the wellhead cluster enabling the drilling and hoisting system to perform well operations in the plurality of hydrocarbon wells. A plurality of secondary drilling units ( 105 a , 105 b ), each having its own drilling equipment for performing drilling operations, are positioned on the wellhead cluster below the main drilling unit for performing well operations in the plurality of hydrocarbon wells, wherein the main drilling unit and at least one of the plurality of secondary drilling units are arranged for performing alternating well operations in at least one of the plurality of hydrocarbon wells.

1 . A system for performing well operations in a plurality of hydrocarbon wells of a wellhead cluster, which system comprises a main drilling rig comprising a main drilling unit displaying a drill floor and comprising a drilling and hoisting system arranged to operate on the drill floor about a well center, wherein the main drilling unit is positioned at least partially vertically above the wellhead cluster enabling the drilling and hoisting system to perform well operations in the plurality of hydrocarbon wells, wherein a plurality of secondary drilling units, each comprising its own drilling equipment for performing drilling operations, are positioned on the wellhead cluster below the main drilling unit for performing well operations in the plurality of hydrocarbon wells, wherein the main drilling unit and at least one of the plurality of secondary drilling units are arranged for performing alternating well operations in at least one of the plurality of hydrocarbon wells. 
     
     
         2 . The system according to  claim 1 , wherein the main drilling unit has a well operations capacity in at least one of said well operations which is higher than the well operations capacity of said at least one of the plurality of secondary drilling units. 
     
     
         3 . The system according to  claim 1 , further comprising at least one umbilical running from the main drilling unit to the wellhead cluster for providing drilling support to said plurality of secondary drilling units and/or for allowing control and operation of the plurality of secondary drilling units from the main drilling unit. 
     
     
         4 . The system according to  claim 3 , wherein the main drilling unit provides at least one of mud control, power supply, hydraulics supply to the wellhead cluster. 
     
     
         5 . The system according to  claim 1 , wherein the main drilling unit is movable in a plane above the wellhead cluster. 
     
     
         6 . The system according to  claim 1 , wherein the main drilling rig is any one of a jack-up rig, a drilling module, a drillship, a tension leg platform, a jacket, a land rig or a semi-submersible platform. 
     
     
         7 . The system according to  claim 1 , wherein said plurality of hydrocarbon wells comprise distributed well activities. 
     
     
         8 . The system according to  claim 1 , wherein said main drilling rig comprises a skiddable cantilever comprising a drilling mast and drilling machinery, wherein said main drilling unit is placed on the skiddable cantilever, wherein the wellhead spread is placed adjacent and below the cantilever of the main drilling unit, said wellhead spread comprising said secondary drilling units, where each secondary drilling unit has its own drilling equipment for performing drilling operations, and each secondary drilling unit is being arranged for simultaneously well operations in separate wells while being supported by the main drilling unit. 
     
     
         9 . The system according to  claim 8 , wherein the wellhead spread comprises distributed well centers comprising said secondary drilling units. 
     
     
         10 . The system according to  claim 8 , wherein the main drilling rig is a jack-up rig standing on support legs and comprising a barge that can be raised or lowered, the jack-up rig being further equipped with the cantilever supporting the main drilling unit, where the cantilever can be driven or skidded out over water, such that the main drilling unit is above an operational area to perform desired drilling operations. 
     
     
         11 . The system according to  claim 8 , wherein the secondary drilling units each comprises a mast, drill floor and BOP, which mast comprises a rotary drilling machine which is adapted to drive a tubular through the BOP and into a desired wellhead. 
     
     
         12 . The system according to  claim 8 , wherein the main drilling unit comprises a driller's cabin/control station connected by at least one umbilical to the equipment on the wellhead spread for control and operations of the secondary drilling units and equipment on the wellhead spread. 
     
     
         13 . A method of performing well operations in a plurality of hydrocarbon wells of a wellhead cluster, comprising the steps of:
 positioning a main drilling unit displaying a drill floor and comprising a drilling and hoisting system operating on the drill floor above the wellhead cluster,   positioning a plurality of secondary drilling units at wellheads on the wellhead cluster, and   alternatingly or simultaneously performing well operations in the hydrocarbon wells using the main drilling unit and at least one of said secondary drilling units.   
     
     
         14 . The method according to  claim 13 , comprising the steps of:
 positioning the main drilling unit above the wellhead cluster such that a well center of the drilling unit becomes positioned vertically above a first wellhead of a first hydrocarbon well of the wellhead cluster,   performing a well operation in the first hydrocarbon well using the main drilling unit,   repositioning the main drilling unit such that the well center of the drilling unit becomes positioned vertically above a second wellhead of a second hydrocarbon well of the wellhead cluster,   performing a well operation in the second hydrocarbon well using the main drilling unit and simultaneously performing a well operation in the first hydrocarbon well using a first secondary drilling unit positioned on the wellhead spread at the first wellhead.   
     
     
         15 . The method according to  claim 13 , wherein the step of positioning a plurality of secondary drilling units at wellheads on the wellhead cluster comprises deploying the plurality of secondary drilling units from a main drilling rig carrying the main drilling unit. 
     
     
         16 . The method according to  claim 13 , wherein the method is realised using a system comprising a main drilling rig comprising an elevated main drilling unit comprising a drill floor positioned on a skiddable cantilever, equipped with at least one main well center, and a wellhead spread placed adjacent and below the cantilever of the main drilling rig, wherein the method comprises the steps of:
 (a) deploying, from the main drilling rig, several secondary drilling units onto a well deck of the wellhead spread,   (b) running well operations in a first well from the main well center through a first secondary drilling unit on the wellhead spread,   (c) breaking the connection between the main well center and the first secondary drilling unit,   (d) proceeding with drilling operations in the first well using the first secondary drilling unit,   (e) moving the main drilling rig to a position above a second secondary drilling unit on the wellhead spread,   (f) running well operations in a second well from the main well center through the second secondary drilling unit on the wellhead spread,   (g) breaking the connection between the main well center and the second secondary drilling unit , and   (h) proceeding with well operations in the second well using the second secondary drilling unit.   
     
     
         17 . The method according to  claim 16 , wherein the main drilling unit performs preparations for the next activity, such as making up bottom hole assembly or rack up or down casing, while not supporting one of the secondary drilling units. 
     
     
         18 . The method according to  claim 16 , wherein the main drilling unit in step (b) is tripping in with bottom-hole assembly through the first secondary drilling unit's rotary bushing and BOP, and when reaching TD the drill string is landed in said secondary drilling unit's rotary bushing and an iron roughneck machine on the secondary drilling unit breaks the connection freeing the main drilling unit for other operations. 
     
     
         19 . The method according to  claim 16 , wherein the main drilling unit moves over immediately to the second secondary drilling unit, after breaking the connection between the main well center and the first secondary drilling unit, to assist the second secondary drilling unit while the first secondary drilling unit is drilling ahead using local pipe storage. 
     
     
         20 . The method according to  claim 16 , wherein the main drilling unit in step (f) is tripping in with the bottom hole assembly to TD through the second secondary drilling unit, and when reaching TD the string is landed out in the rotary bushing on the second secondary drilling unit and an iron roughneck breaks the connection releasing the drill string from the main well center, while the second secondary drilling unit starts drilling using its own local drill pipe storage. 
     
     
         21 . The method according to  claim 16 , wherein the main drilling rig prepares the casing section for the first secondary drilling unit, moves over and when ready pulls out the drill string from the first secondary drilling unit and then run in the casing section through the secondary drilling unit's rotary bushing and BOP. 
     
     
         22 . The method according to  claim 21 , wherein when the run is close to be completed, the casing landing string is transferred to the secondary drilling unit which is landing out the casing.