Early hydrocarbon production system

Abstract

A subsea hydrocarbon reserve is exploited by intially drilling a first well ( 4 ) from a floating drilling vessel ( 2 ). A tree ( 8 ) is then installed on the well ( 4 ) and a production riser ( 10 ) is established between the well and the vessel for transferring production fluid from the first well ( 4 ) to the vessel ( 2 ) from where an off-loading hose ( 12 ) conveys the production fluid to a tanker ( 18 ). Production fluid is then extracted from the first well ( 4 ) via the production riser ( 10 ) which is of sufficient flexibility and length to permit the drilling vessel ( 2 ) to move between appropriate locations to drill further wells ( 4′, 20 ).

1 . A method of exploiting a subsea hydrocarbon reserve, comprising the steps of drilling a first well ( 4 ) from a floating drilling vessel ( 2 ), establishing a production riser ( 10 ) for transferring production fluid from the first well ( 4 ) to the drilling vessel or production fluid reception means ( 18 ) closely associated with the vessel, and extracting production fluid from the first well ( 4 ) while drilling one or more further wells ( 20 ) from the drilling vessel ( 2 ), and characterised by the steps of: 
 (i) processing the production fluid with processing means ( 24 ) installed on the drilling vessel ( 2 );    (ii) subsequently installing the processing means ( 24 ) on the seabed; and    (iii) carrying out subsea processing of production fluid from the wells ( 4 , 4 ′, 20 ) by using the processing means ( 24 ).    
     
     
         2 . A method as claimed in  claim 1 , wherein the processing means ( 24 ) is in the form of a module for installation as part of a seabed processing system.  
     
     
         3 . A method as claimed in  claim 1 , wherein the processing means ( 24 ) separates the production fluid into different components.  
     
     
         4 . A method as claimed in  claim 1 , wherein the production riser ( 10 ) is sufficiently flexible to permit local excursions of the drilling vessel ( 2 ) while it is drilling a said further well ( 20 ).  
     
     
         5 . A method as claimed in  claim 1 , wherein the production riser ( 10 ) is of sufficient flexibility and length to permit the drilling vessel ( 2 ) to move between appropriate locations for drilling plural further wells ( 20 ) in order that output from two or more wells ( 4 , 4 ′) can be exploited while well drilling is still in progress.  
     
     
         6 . A method as claimed in  claim 5 , including the step of establishing at least one further well ( 4 ′) and transferring production fluid from the first well ( 4 ) and the at least one further well ( 4 ′) to the drilling vessel ( 2 ) or the production fluid reception means ( 18 ) closely associated with the vessel while drilling at least one additional well ( 20 ).  
     
     
         7 . A method as claimed in  claim 6 , including conveying the production fluid from the drilling vessel ( 2 ) to an off-loading buoy ( 12 ) for onward conveyance.  
     
     
         8 . A method as claimed in  claim 7 , wherein said production fluid reception means comprises a floating storage unit ( 18 ), and the method includes storing production fluid for a period of time in the buoy ( 12 ) while the floating storage unit ( 18 ) is removed for replacement by another floating storage unit.  
     
     
         9 . A method as claimed in  claim 1 , including conveying the production fluid from the drilling vessel ( 2 ) to a pipeline leading to a remote location via an off-loading buoy ( 12 ).  
     
     
         10 . A method as claimed in  claim 7 , wherein production fluid is conveyed from the drilling vessel ( 2 ) to the buoy ( 12 ) by means of an off-loading hose ( 16 ) extending from the drilling vessel ( 2 ) to the buoy ( 12 ).  
     
     
         11 . A method as claimed in  claim 10 , wherein fluid is conveyed from a said further well ( 4 ′) by an additional production riser ( 10 ′) to the drilling vessel ( 2 ) or production fluid reception means ( 18 ).  
     
     
         12 . A method as claimed in  claim 11 , wherein fluid is conveyed from a said further well ( 4 ′) by interconnecting said further well ( 4 ′) with at least one other well ( 4 ) so that the combined production flow from a number of wells ( 4 , 4 ′) is conveyed via a common production riser ( 10 ).  
     
     
         13 . A method as claimed in  claim 1 , wherein fluid is conveyed from a said further well ( 4 ′) by installing a manifold to which the further well or wells is/are attached and the combined production flow is conveyed to the drilling vessel ( 2 ) or production fluid reception means ( 18 ) via the production riser ( 10 ).