Apparatus and method for the disposition of drilling solids during drilling of subsea oilfield wellbores

Abstract

This invention provides apparatus and methods for controlling the particle size of the solid mass present in the circulating drilling fluid returning from an underwater wellhead during the drilling of a subsea wellbore. The system may include a separator at the sea floor adjacent the wellhead, which separates solids above a predetermined size from the wellstream. The wellstream then enters one or more underwater pumps, which pump the wellstream to the surface. A crusher, as a separate unit, integrated in the separator or in the pump, receives the separated solids and reduces them to relatively small-sized particles. The small particles are then pumped or moved to the surface by the pumps utilized for pumping the wellstream to the surface or by a separate underwater pump. Alternatively, the separated solids are collected from the separator into a container, which container is then transported to the surface by a suitable method. Solids reaching the surface are removed to obtain filtered fluid, which after conditioning by conventional methods is pumped back into the wellbore as the drilling fluid.

What is claimed:  
     
         1 . An apparatus for processing drilling fluid including solids therein (the “return fluid”) received at a subsea wellhead during drilling of a subsea wellbore, comprising: 
 (a) a subsea separator receiving said return fluid from the wellbore and separating at least solids from the drilling fluid; and  
 (b) a subsea device associated with said separator reducing size of the separated solids below a predetermined size.  
 
     
     
         2 . The apparatus according to  claim 1  further comprising a first subsea pump for pumping fluid from the separator to a surface location and a second subsea pump for pumping solids reduced by the device.  
     
     
         3 . The apparatus according to  claim 1  further comprising a common pump for pumping the drilling fluid from the separator and the solids reduced by said subsea device to a surface location.  
     
     
         4 . The apparatus according to  claim 3 , wherein the separator includes a selectively operable valve for discharging the separated solids to said pump.  
     
     
         5 . The apparatus according to  claim 2  further comprising a separator at the surface for separating solids from fluid pumped to the surface.  
     
     
         6 . The apparatus according to  claim 1 , wherein the subsea device reduces the size of the separated solids to a size that can be pumped to the surface by a subsea pump.  
     
     
         7 . The apparatus according to  claim 1 , wherein the subsea device includes a plurality of cooperating crushing members to reduce size of the separated solids.  
     
     
         8 . The apparatus according to  claim 1 , wherein the subsea device is one of (i) mechanically-operated; (ii) electro-mechanical; (iii) hydraulically-operated; and (iv) pneumatically-operated.  
     
     
         9 . The apparatus according to  claim 1 , wherein the separator comprises: 
 (i) a vessel having an inlet for receiving the drilling fluid;    (ii) a conical section for housing separated solids from the drilling fluid, said conical section having a discharge port of sufficient size to discharge the separated solids from the conical section; and    (iii) a control valve for opening the discharge port of the conical section to selectively discharge the separated solids from the vessel to the device.    
     
     
         10 . The apparatus according to  claim 4 , wherein the subsea device is remotely-operable from the surface.  
     
     
         11 . The apparatus according to  claim 1  further comprising at least one sensor for providing a measure of a parameter of interest relating to said apparatus.  
     
     
         12 . The apparatus according to  claim 11 , wherein the at least one sensor is selected from a group of sensors consisting of a: (i) level sensor; (ii) pressure sensor; and (iii) flow rate sensor.  
     
     
         13 . The apparatus according to  claim 12  further comprising a controller for controlling the operation of the apparatus in response to the measured parameter of interest.  
     
     
         14 . An apparatus for processing drilling fluid including solids therein received at a subsea wellhead during drilling of a subsea wellbore, comprising: 
 (a) a subsea separator separating solids from said drilling fluid into a container; and    (b) a pump for pumping the drilling fluid from the separator to the container to move the solids from the container to a surface location.    
     
     
         15 . A method for processing drilling fluid and solid mixture received at a subsea wellhead during drilling of a subsea wellbore, comprising: 
 (a) separating the solids and drilling fluid from the mixture and discharging said separated solids into a container; and    (b) transporting the separated solids to a surface location.    
     
     
         16 . The method of  claim 15 , wherein transporting the separated solids comprises transporting the container to the surface location.  
     
     
         17 . The method of  claim 15 , wherein transporting the separated solids comprises pumping the separated drilling fluid into the container to move the separated solids to the surface location via a suitable conduit.  
     
     
         18 . An apparatus for processing a mixture of drilling fluid and solids received at a subsea wellhead during drilling of a wellbore, comprising: 
 (a) a device receiving the mixture and reducing the size of the solids; and    (b) at least one pump receiving the drilling fluid and the reduced sized solids and pumping said received drilling fluid with the reduced sized solids to a surface location.    
     
     
         19 . The apparatus according to  claim 18 , wherein the at least one pump includes a plurality of pumping stages.  
     
     
         20 . A method of processing mixture of drilling fluid and solids received at a subsea wellhead during drilling a subsea wellbore, comprising: 
 (a) separating solids of sizes greater than a first predetermined size from said mixture; and    (b) transporting said separated solids to a surface location.    
     
     
         21 . The method of  claim 20  further comprising reducing size of the separated solids to a size smaller than a second predetermined size by a subsea crusher before transporting said solids to the surface location.  
     
     
         22 . The method according to  claim 21 , wherein transporting solids comprises pumping said reduced solids to a surface location of a subsea pump.  
     
     
         23 . The method according to  claim 21  further comprising pumping the reduced size solids and the drilling fluid to a surface location by a common subsea pump.