Method for cleaning drilling fluid in rock sampling drilling and a cleaning unit

Abstract

To recover drilling fluid used in sample drilling at a drilling machine, when the drilling fluid exits the drill hole, and to transport it to a separate cleaning unit wherein solid matter is separated from the drilling fluid. The cleaned drilling fluid is returned to the drilling machine and reused in sample drilling. The cleaning unit has an inlet connection and two or more precipitation basins, where the solid matter accumulates on the bottom of the basin. In the bottom part of at least one precipitation basin there is a valve arrangement for removing drilling fluid sludge containing solid matter from the precipitation basin, which drilling fluid sludge is filtered with a filter arrangement. In the top part of the precipitation basin there is a transfer connection between precipitation basins or an outlet connection for taking cleaned drilling fluid out from the cleaning unit back to the drilling process.

1 . A method for cleaning drilling fluid in rock sampling drilling, where a drilling machine ( 100 ) is used, which has a hollow drilling pipe ( 101 ), a cylindrical blade unit ( 401 ) in the drilling end of the drilling pipe, a protective pipe ( 201 ;  903 ), which surrounds the part of the drilling pipe which is close to the ground surface ( 103 ), so that there is empty space between the drilling pipe and the protective pipe, and in the method drilling fluid is fed into the drilling pipe, which drilling fluid lubricates the drilling event, and the drilling fluid flows between the drilling pipe and the wall of the drill hole toward the opening of the drill hole, simultaneously transporting solid matter formed in the drilling, characterised in that the method further has steps, where
 drilling fluid containing solid matter coming from between the protective pipe and the drilling pipe in the drilling machine is recovered with an arrangement in the drilling machine   the recovered drilling fluid is guided to a cleaning unit ( 501 )   the cleaning unit has two or more precipitation basins ( 604 ,  605 ,  606 ,  607 ) in series, where the solid matter is separated from the drilling fluid, and between the precipitation basins there is a transfer connection, which has an intake end and a discharge end, and the discharge ends of the transfer connections are closer to the bottom of the precipitation basins than the intake ends and   the drilling fluid cleaned in the cleaning unit is guided to the drilling machine and fed into the drilling pipe.   
     
     
         2 . The method according to  claim 1 , characterised in that drilling fluid sludge containing solid matter accumulating at the bottom of the precipitation basin ( 604 ,  605 ,  606 ,  607 ) is removed from the basin. 
     
     
         3 . The method according to  claim 2 , characterised in that the drilling fluid sludge removed from the bottom of the precipitation basin ( 604 ,  605 ,  606 ,  607 ) is filtered and returned to some precipitation basin. 
     
     
         4 . The method according to  claim 1 , characterised in that the drilling fluid is in the cleaning unit fed into the first precipitation basin through a nozzle ( 611 ), which nozzle has a throat part ( 803 ) and a curved flange part, and the curved flange part is arranged so that the fluid flow substantially follows the flange part and solid matters contained in the fluid detach from the flow. 
     
     
         5 . The method according to  claim 1 , characterised in that an ion charged polymer mixture, ferrous sulphate, ferric sulphate or some other chemical added to the drilling fluid, which assists the separation of solid matter from fluid, is used in the cleaning of the drilling fluid for boosting the process. 
     
     
         6 . The method according to  claim 1 , characterised in that new drilling fluid is, when necessary, added to the circulation of drilling fluid. 
     
     
         7 . The method according to  claim 1 , characterised in that substances or chemicals, which assist the drilling process, are added to the drilling fluid before the drilling fluid is returned to the drilling pipe. 
     
     
         8 . The method according to  claim 1 , characterised in that the cleaning unit ( 501 ) is placed in a container or another movable structure. 
     
     
         9 . A cleaning unit ( 501 ) for drilling fluid in sampling drilling, characterised in that the cleaning unit is placed in one or several containers or corresponding movable structures and the cleaning unit has
 a connection ( 701 ) for feeding uncleaned drilling fluid into the cleaning unit   at least two precipitation basins ( 604 ,  605 ,  606 ,  607 ), where solid matter contained in the drilling fluid is arranged to accumulate on the bottom of the basin as drilling fluid sludge, and in the bottom part of at least one precipitation basin there is a valve arrangement ( 703 ) for removing said drilling fluid sludge containing solid matter from the precipitation basin and   between the precipitation basins there is a transfer connection ( 610 ), which has an intake end and a discharge end, for moving the drilling fluid between precipitation basins, and the discharge ends of the transfer connections are closer to the bottom of the precipitation basins than the intake ends, and in the last precipitation basin of the series there is an outlet connection ( 611 ) for removing the cleaned drilling fluid from the cleaning unit.   
     
     
         10 . The cleaning unit ( 501 ) according to  claim 9 , characterised in that the drilling fluid sludge containing solid matter, which has been let through the valve arrangement ( 703 ), is arranged to pass through a filter arrangement ( 609 ) in order for the solid matter to be removed. 
     
     
         11 . The cleaning unit ( 501 ) according to  claim 10 , characterised in that the filter arrangement ( 609 ) is detachable for replacing and cleaning or is can be cleaned in its place. 
     
     
         12 . The cleaning unit ( 501 ) according to  claim 9 , characterised in that there is a point in the bottom of the precipitation basin ( 604 ,  605 ,  606 ,  607 ), which is lower than the rest of the bottom, and the valve arrangement ( 703 ) is placed in this point. 
     
     
         13 . The cleaning unit ( 501 ) according to  claim 9 , characterised in that the drilling fluid separated from the drilling fluid sludge with the filter arrangement ( 609 ) is arranged to be transported back to the precipitation basin ( 604 ,  605 ,  606 ,  607 ). 
     
     
         14 . The cleaning unit ( 501 ) according to  claim 9 , characterised in that beneath the precipitation basin or precipitation basins ( 604 ,  605 ,  606 ,  607 ) there is a lower basin ( 608 ), wherein the drilling fluid filtered from the drilling fluid sludge with the filtering arrangement ( 609 ) is arranged to be collected and from which lower basin there is a transfer arrangement for transferring drilling fluid to the precipitation basin. 
     
     
         15 . The cleaning unit ( 501 ) according to  claim 9 , characterised in that the uncleaned drilling fluid fed into the first precipitation basin is arranged to be fed through a nozzle ( 611 ), which nozzle has a throat part ( 803 ) and a curved flange part, and the curved flange part is arranged so that the fluid flow substantially follows the flange part and the solid matters contained in the fluid detach from the flow. 
     
     
         16 . The cleaning unit ( 501 ) according to  claim 9 , characterised in that the discharge ends of the transfer connections ( 610 ) between the precipitation basins are shaped to guide the drilling fluid substantially toward the bottom of the precipitation basin. 
     
     
         17 . The cleaning unit ( 501 ) according to  claim 9 , characterised in that an ion charged polymer mixture, ferrous sulphate, ferric sulphate or some other chemical, which assists the separation of solid matter from fluid, is arranged to be added to the drilling fluid. 
     
     
         18 . The cleaning unit ( 501 ) according to  claim 9 , characterised in that it has an arrangement for feeding substances which assist the drilling event into the drilling fluid before the drilling fluid is returned to the drilling process.