Downhole cleaning system

Abstract

The present invention relates to a downhole cleaning system for cleaning an element inside a casing in a wellbore comprising well fluid having a wellbore pressure, comprising the casing, a cleaning tool having a longitudinal direction and comprising a rotatable nozzle head having a plurality of nozzles, a tool housing having an inlet being in fluid communication with the nozzles for jetting well fluid into the tool, a flow hindering element arranged on an outside of the housing dividing the tool in a first and a second tool part and dividing the casing in a first and a second casing part and a rotatable shaft connecting the nozzle head with the housing, wherein the system further comprises a pumping device for pressurising the well fluid in the first part of the casing to a pressure substantially above the wellbore pressure and above a pressure in the second part of the casing so that well fluid is pumped in through the inlet and out through the nozzles. Furthermore, the invention relates to a wireline cleaning tool and to a cleaning method.

1 .- 28 . (canceled) 
     
     
         29 . A wireline cleaning tool ( 10 ) arranged in a casing downhole and having a longitudinal direction ( 11 ), comprising:
 a rotatable nozzle head ( 12 ) having a plurality of nozzles ( 13 ),   a tool housing ( 14 ) having an inlet ( 15 ) being in fluid communication with the nozzles for letting well fluid into the tool and out through the nozzles,   a flow hindering element ( 16 ) arranged on an outside ( 17 ) of the housing dividing the tool in a first ( 18 ) and a second ( 19 ) tool part and dividing the casing in a first ( 20 ) and a second ( 21 ) casing part, and   a rotatable shaft ( 22 ) connecting the nozzle head with the housing, the shaft being a hollow shaft for supplying the nozzles with well fluid, wherein the wireline cleaning tool further comprises a control device for controlling a rotational speed of the nozzle head.   
     
     
         30 . A wireline cleaning tool according to  claim 29 , wherein the tool further comprises a pumping device ( 32 ) for pressurising the well fluid in the first part of casing to a pressure substantially above the wellbore pressure and above a pressure in the second part of the casing so that well fluid is pumped in through the inlet and out through the nozzles. 
     
     
         31 . A wireline cleaning tool according to  claim 29 , wherein the control device is also configured for controlling which nozzle/nozzles is/are allowed to eject fluid. 
     
     
         32 . A wireline cleaning tool according to  claim 31 , wherein the control device is a hydraulic control unit arranged in the tool for controlling which nozzles are open and which nozzles are closed. 
     
     
         33 . A downhole cleaning system ( 1 ) for cleaning an element ( 2 ) inside a casing ( 3 ) in a wellbore ( 4 ) comprising well fluid ( 5 ) having a wellbore pressure (Pw), comprising:
 the casing, and   a wireline cleaning tool ( 10 ) according to  claim 29 , wherein the system further comprises a pumping device ( 23 ) for pressurising the well fluid in the first part of the casing to a pressure substantially above the wellbore pressure and above a pressure in the second part of the casing so that well fluid is pumped in through the inlet and out through the nozzles,   wherein the system further comprises a control device ( 24 ) for controlling a rotational speed of the nozzle head.   
     
     
         34 . A downhole cleaning system according to  claim 33 , wherein the control device ( 24 ) is also configured for controlling which nozzle/nozzles is/are allowed to eject fluid. 
     
     
         35 . A downhole cleaning system according to  claim 33 , wherein the control device is a hydraulic control unit ( 34 ) arranged in the tool for controlling which nozzles are open and which nozzles are closed. 
     
     
         36 . A downhole cleaning system according to  claim 33 , further comprising a control device ( 24 ) to control the rotation of the shaft and the nozzle head. 
     
     
         37 . A downhole cleaning system according to  claim 33 , wherein the control device is an electrical motor for rotating the shaft. 
     
     
         38 . A downhole cleaning system according to  claim 33 , wherein the control device comprises a gear, a motor brake or a centrifugal brake ( 25 ). 
     
     
         39 . A downhole cleaning system according to  claim 33 , wherein the nozzles are fixedly arranged in the nozzle head. 
     
     
         40 . A downhole cleaning system according to  claim 33 , wherein the shaft is hollow for supplying the well fluid to the nozzle head. 
     
     
         41 . A downhole cleaning system according to  33 , wherein the flow hindering element is a packer, an inflatable unit, a rubber element or an elastomeric element. 
     
     
         42 . A downhole cleaning system according to  claim 33 , further comprising a stroker ( 29 ) being a device providing a stroking reciprocating movement of the nozzle head in relation to the longitudinal direction of the tool, or a piston ( 26 ) interacting with a piston housing ( 27 ) in which a spring device ( 28 ) is arranged for providing a reciprocating movement of the nozzle head in relation to the longitudinal direction of the tool. 
     
     
         43 . A downhole cleaning system according to  claim 33 , wherein a filter ( 36 ) is arranged upstream of the inlet or inside the inlet. 
     
     
         44 . A downhole cleaning system according to  claim 33 , further comprising a downhole driving unit ( 37 ) driving the tool and itself in the casing. 
     
     
         45 . A downhole cleaning system according to  33 , further comprising a measuring device ( 38 ) measuring a rotational speed of the nozzle head. 
     
     
         46 . A downhole cleaning system according to  claim 45 , further comprising a control unit ( 39 ) to control the measuring device from surface. 
     
     
         47 . A downhole cleaning system according to  33 , wherein the nozzle head comprises a check valve ( 40 ). 
     
     
         48 . A cleaning method comprising the steps of:
 entering a cleaning tool according to  29  into a casing,   activating the pumping device and pressurising the first casing part,   turning the nozzle head, and   cleaning a casing element by letting well fluid in through the inlet in the pressurised first casing part and out through nozzles in the second casing part.