Method for continuous formation core sampling

Abstract

The present invention regards a method for performing core sampling during drilling of wells, comprising the steps of providing a dual bore drill pipe with drill bit in the end in the well bore, providing means to introduce a drill liquid into an annular space of the drill pipe and return it together with drill cuttings to the surface through centrally arranged return line in the dual bore drill pipe, removing larger cuttings at outlet of return pipe, and perform core testing on these cuttings, knowing where the cuttings come from in the well. The invention also regards a device for performing the invention.

1 . A method for performing core sampling during drilling of wells, comprising:
 providing a dual bore drill pipe with a drill bit at an end thereof in a well bore,   providing means to introduce a drilling liquid into an annular space of the drill pipe and return the drilling liquid together with drill cuttings to the surface through a centrally arranged return pipe in the dual bore drill pipe,   removing cuttings at an outlet of the return pipe, and   performing core testing on the removed cuttings.   
     
     
         2 . The method of  claim 1 , wherein the drilling liquid is introduced into the annular space at a velocity of more than 1 meter per second. 
     
     
         3 . The method of  claim 1 , wherein the cuttings are removed continuously or at intervals. 
     
     
         4 . The method of  claim 3 , wherein cuttings of a given size range are removed for testing. 
     
     
         5 . The method of  claim 1 , wherein the return pipe is provided with an equal inner diameter between the two ends of the return pipe. 
     
     
         6 . The method of  claim 1 , wherein the drilling liquid is lighter than conventional drilling mud and makes less contamination of the removed cuttings. 
     
     
         7 . The method of  claim 1 , wherein a flow of the drilling liquid in the dual bore drill pipe is set up in the drill pipe before the drilling liquid is guided to the drill bit. 
     
     
         8 . A device for performing core sampling during drilling of wells, comprising:
 a dual bore drill pipe with a drill bit on one end,   means for providing a drilling liquid to flow down the drill pipe in an annulus of the drill pipe and return through a return pipe centrally arranged in the drill pipe,   a cuttings sample arrangement at an outlet of the return pipe,   wherein the return pipe is formed with an equal inner diameter between the two ends thereof.   
     
     
         9 . The device of  claim 8 , wherein a cross over element is arranged between the drill bit and the dual bore drill pipe. 
     
     
         10 . The device of  claim 8 , wherein the sample arrangement is configured to remove cutting samples of a given size range continuously or at intervals. 
     
     
         11 . The device of  claim 8 , wherein the drill bit is a reverse circulation bit. 
     
     
         12 . The method of  claim 1 , further comprising separating out cuttings that are within a given size range and that traveled substantially the same velocity through the return pipe from the removed cuttings. 
     
     
         13 . The method of  claim 12 , wherein the core testing is performed on the separated out cuttings.