Minimization of contaminants in a sample chamber

Abstract

A formation testing apparatus and method for obtaining samples with lower levels of contaminants is provided. Such a method can remove contaminants from at fluid sample, and can include the steps of obtaining fluid, from a formation and passing a first quantity of the fluid through a sample flow line. A connection between the sample flow line and a sample chamber can he opened, and a first portion of the first quantity of the fluid can be drawn into the sample chamber via a floating piston. The first portion can be forced out of the sample chamber, and this process can be repeated until sufficient contaminants have been removed. Finally, a second portion of the first quantity of the fluid can be drawn into the sample chamber as the fluid sample.

What is claimed: 
     
         1 . An apparatus that facilitates removal of contaminants from a fluid sample, comprising:
 an intake section configured to sealingly engage a borehole wail to obtain formation fluid, through the borehole wall;   a first flow line in fluid communication with the intake section, wherein at least a portion of the formation fluid obtained by the intake section passes through the first flow line; and   a sample chamber comprising a floating piston, wherein the floating piston is configured to draw at least a first quantity of the portion into the sample chamber from the first flow line, wherein the first quantity of the portion is forced out of the sample chamber, and wherein the floating piston is configured to draw at least a second quantity of the portion into the sample chamber for storage therein as the fluid sample.   
     
     
         2 . The apparatus of  claim 1 , wherein the floating piston is configured to draw the first quantity into the sample chamber through a front end of the sample chamber, and the floating piston is configured to force the first quantity out through a back end of the sample chamber. 
     
     
         3 . The apparatus of  claim 1 , further comprising a mechanical device configured to force out the first quantity from the sample chamber. 
     
     
         4 . The apparatus of  claim 3 , wherein the mechanical device comprises a spring. 
     
     
         5 . The apparatus of  claim 1 , further comprising:
 a pressure-based device configured to force the first quantity out of the sample chamber.   
     
     
         6 . The apparatus of  claim 5 , wherein the pressure-based device comprises a closed nitrogen charge. 
     
     
         7 . The apparatus of  claim 1 , wherein the floating piston is configured to draw at least a third quantity of the portion into the sample chamber from the first flow line before the floating piston draws at least the second quantity of the portion, wherein the third quantity of the portion is forced out of the sample chamber. 
     
     
         8 . The apparatus of  claim 7 , wherein the second quantity is drawn into the sample chamber based at least in part on a determination that insufficient contaminants have been removed. 
     
     
         9 . The apparatus of  claim 1 , further comprising:
 a second flow line in fluid communication with the intake section, wherein at least a second portion of the formation fluid obtained by the intake section passes through the second flow line, and wherein the second portion comprises more contaminants than the first quantity.   
     
     
         10 . The apparatus of  claim 1 , wherein the floating piston is automatically controlled. 
     
     
         11 . The apparatus of  claim 1 , wherein the intake section comprises a probe. 
     
     
         12 . The apparatus of  claim 1 , wherein the intake section comprises dual packers. 
     
     
         13 . A method of removing contaminants from a fluid sample, comprising:
 obtaining fluid from a formation;   passing a first quantity of the fluid through a sample flow line;   opening a connection between the sample flow line and a sample chamber:   drawing, a first portion of the first, quantity of the fluid into the sample chamber via a floating piston;   forcing the first portion out of the sample chamber; and   drawing a second portion of the first quantity of the fluid into the sample chamber as the fluid sample.   
     
     
         14 . The method of  claim 13 , wherein the drawing the first portion into the sample chamber comprises drawing the first portion in through a front end of the sample chamber, and wherein the forcing the first portion out of the sample chamber comprises employing the floating piston to force the first portion out of the back of the sample chamber. 
     
     
         15 . The method of  claim 13 , wherein the forcing the first portion out of the sample chamber comprises using a mechanical device to force the first portion out of the sample chamber. 
     
     
         16 . The method of  claim 15 , wherein the mechanical device comprises a spring. 
     
     
         17 . The method of  claim 13 , wherein the forcing the first portion out of the sample chamber comprises employing a pressure-based device to force the first portion out of the sample chamber. 
     
     
         18 . The method of  claim 17 , wherein the pressure-based device comprises a closed nitrogen charge. 
     
     
         19 . The method of  claim 13 , further comprising:
 determining whether sufficient contaminants have been removed from the first quantity.   
     
     
         20 . The method of  claim 19 , further comprising:
 drawing at least one additional portion of the first quantity of the fluid into the sample chamber via the floating piston prior to drawing the second portion; and   forcing the at least one additional portion out of the sample chamber.   
     
     
         21 . The method of  claim 20 , further comprising:
 selecting the number of additional portions drawn, wherein the number of additional portions is selected to remove sufficient contaminants from the first quantity.