Formation Evaluation While Drilling

Abstract

A sample module for a sampling while drilling tool includes a sample fluid flowline operatively connectable between a sample chamber and an inlet, for passing a downhole fluid. A primary piston divides the sample chamber into a sample volume and a buffer volume and includes a first face in fluid communication with the sample volume and a second face in fluid communication with the buffer volume. A secondary piston includes a first face in fluid communication with the buffer volume having buffer fluid disposed therein and a second face.

1 . A sample module for a sampling while drilling tool positionable in a wellbore penetrating a subterranean formation, comprising: 
 a sample chamber having an inlet;    a sample fluid flowline operatively connectable to the sample chamber inlet for passing a downhole fluid thereto;    a primary piston slidably disposed within the sample chamber and dividing the sample chamber into a sample volume and a buffer volume, the primary piston having a first face in fluid communication with the sample volume and a second face in fluid communication with the buffer volume;    a secondary piston having a first face in fluid communication with the buffer volume and a second face; and    a buffer fluid disposed in the buffer volume.    
   
   
       2 . The sample module of  claim 1 , in which the secondary piston is slidably disposed in the sample chamber.  
   
   
       3 . The sample module of  claim 1 , further comprising a buffer chamber in fluid communication with the buffer volume, and in which the secondary piston is disposed in the buffer chamber.  
   
   
       4 . The sample module of  claim 3 , further comprising a second sample chamber in fluid communication with the buffer chamber.  
   
   
       5 . The sample module of  claim 3 , in which the secondary piston comprises a stepped piston.  
   
   
       6 . The sample module of  claim 3 , further comprising a dump chamber in fluid communication with the secondary piston first face and a fluid at substantially atmospheric pressure disposed within the dump chamber.  
   
   
       7 . The sample module of  claim 1 , in which the buffer fluid comprises a liquid.  
   
   
       8 . The sample module of  claim 7 , in which the secondary piston second face fluidly communicates with a fluid at substantially atmospheric pressure.  
   
   
       9 . The sample module of  claim 1 , in which the buffer fluid comprises a gas.  
   
   
       10 . The sample module of  claim 1 , further comprising a mud flowline fluidly communicating wellbore mud to the secondary piston second face.  
   
   
       11 . The sample module of  claim 10 , further comprising a mud passage through which wellbore mud passes, and in which the mud flowline fluidly communicates with the mud passage.  
   
   
       12 . The sample module of  claim 10 , further comprising a mud orifice in fluid communication with the wellbore, and in which the mud flowline fluidly communicates with the mud orifice.  
   
   
       13 . The sample module of  claim 1 , in which the sample chamber is inverted so that the sample chamber inlet is below the primary piston.  
   
   
       14 . The sample module of  claim 1 , further comprising a sensor operatively communicating with the sample volume.  
   
   
       15 . The sample module of  claim 1 , further comprising an agitator disposed in the sample volume for agitating the sample fluid.  
   
   
       16 . A sample module for a sampling while drilling tool positionable in a wellbore penetrating a subterranean formation, comprising: 
 a sample chamber having an inlet and a sealed end opposite the inlet;    a sample fluid flowline operatively connectable to the sample chamber inlet for passing a downhole fluid thereto;    a primary piston slidably disposed within the sample chamber and dividing the sample chamber into a sample volume and a buffer volume, the primary piston having a first face in fluid communication with the sample volume and a second face in fluid communication with the buffer volume; and    a buffer fluid at substantially atmospheric pressure disposed in the buffer volume, wherein the sample chamber is detachably coupled to the sample module.    
   
   
       17 . The sample module of  claim 16 , further comprising a sensor operatively communicating with the sample volume.  
   
   
       18 . A method of obtaining a fluid sample with a sampling while drilling tool, comprising: 
 lowering a tool in a wellbore penetrating a subterranean formation, the tool including a sample chamber having a first volume and a second volume;    flowing a sample fluid through an inlet of the tool into the first volume of the sample chamber;    moving a first piston disposed between the first and second volumes, thereby increasing the first volume;    moving a buffer fluid from a first position to a second position with at least one of the first and a second piston; and    moving the second piston disposed between the second and a third volume, thereby decreasing the third volume.    
   
   
       19 . The method of  claim 18 , wherein the third volume is disposed in the sample chamber.  
   
   
       20 . The method of  claim 18 , wherein the third volume is fluidly connected to one of a mud passage and a mud orifice.  
   
   
       21 . The method of  claim 18 , including removing the sample chamber from the tool with the sample fluid disposed therein.  
   
   
       22 . The method of  claim 18 , including agitating the sample fluid in the sample volume with an agitator.  
   
   
       23 . The method of  claim 18 , including restricting the flow of the buffer fluid.  
   
   
       24 . The method of  claim 23 , wherein restricting the flow includes regulating a flow of the buffer fluid within the second volume.  
   
   
       25 . The method of  claim 18 , including measuring a property of the sample fluid in the sample chamber.