Detecting gas compounds for downhole fluid analysis using microfluidics and reagent with optical signature

Abstract

A gas separation and detection tool for performing in situ analysis of borehole fluid is described. The tool operates by introducing a reagent to a test sample and causing the resulting mixture to flow through a microfluidic channel where optical testing is performed. The optical testing detects a change in a characteristic of the reagent in response to expose to one or more particular substances in the test sample. The test sample may be borehole fluid, a mixture of borehole fluid and scrubbing fluid subsequently mixed with reagent, a mixture of reagent and gas separated from borehole fluid, or a mixture of scrubbing fluid and gas separated from borehole fluid which is subsequently mixed with reagent. A membrane may be employed to separate one or more target gasses from the borehole fluid.

1 . Apparatus for detecting a substance of interest in a borehole fluid in a borehole comprising:
 a first port through which a test sample fluid is introduced;   a second port through which a reagent is introduced to the test sample fluid, thereby creating a mixed fluid, the mixed fluid exhibiting a characteristic change if the substance of interest is present in the borehole fluid;   a microfluidic device into which the mixed fluid is introduced;   a test module that detects, within the borehole, the characteristic change in the mixed fluid in the microfluidic channel; and   a transmitter that outputs a signal indicative of whether the characteristic change is detected.   
     
     
         2 . The apparatus of  claim 1  further including a component separator. 
     
     
         3 . The apparatus of  claim 1  further including a pressure compensator to balance fluid pressure inside and outside the apparatus 
     
     
         4 . The apparatus of  claim 1  further including a fluid delivery module to introduce each respective fluid. 
     
     
         5 . The apparatus of  claim 1  wherein the signal outputted by the transmitter is indicative of level of concentration of the substance of interest in the borehole fluid. 
     
     
         6 . The apparatus of  claim 1  wherein the test module includes an optical transmitter and optical receiver that detect differences in color or transmissivity. 
     
     
         7 . The apparatus of  claim 1  wherein the reagent is selected from the group consisting of fluorescein mercuric acetate, complexes of metal cation and organic compounds and organometallic materials, combined with various appropriate solvents, and combinations thereof, suitable for both ambient and borehole condition use. 
     
     
         8 . The apparatus of  claim 1  wherein the test sample fluid is borehole fluid. 
     
     
         9 . The apparatus of  claim 1  wherein the test sample fluid is borehole fluid mixed with scrubbing fluid 
     
     
         10 . The apparatus of  claim 1  wherein the microfluidic device includes an integrated mixer. 
     
     
         11 . The apparatus of  claim 1  wherein a target compound for analysis can be transferred from one phase at feed side to another phase at permeate side. 
     
     
         12 . The apparatus of  claim 1  wherein the microfluidic device and test module are integrated as one device. 
     
     
         13 . The apparatus of  claim 1  further including a membrane disposed between the borehole fluid and the first port, and wherein the test sample fluid is a fluid separated from the borehole fluid by the membrane. 
     
     
         14 . The apparatus of  claim 13  wherein the membrane includes capillary tubing. 
     
     
         15 . The apparatus of  claim 13  wherein the membrane capillary tubing is supported by a structure that increases diffusion area. 
     
     
         16 . The apparatus of  claim 14  wherein the capillary tubing is wound. 
     
     
         17 . The apparatus of  claim 14  wherein the membrane includes a thin film, multilayered micro porous or nano porous membrane 
     
     
         18 . The apparatus of  claim 1  wherein the test sample fluid is a mixture of scrubbing fluid and borehole fluid. 
     
     
         19 . The apparatus of  claim 1  further including a membrane disposed between the borehole fluid and the first port, and wherein the test sample fluid is a mixture of scrubbing fluid and gas separated from the borehole fluid by the membrane. 
     
     
         20 . The apparatus of  claim 1  wherein the first and second ports are part of a multi-port valve, and wherein a test loop is connected between ports of the valve in order to introduce a predetermined fixed volume of reagent. 
     
     
         21 . The apparatus of  claim 1  adapted to operate in a borehole. 
     
     
         22 . The apparatus of  claim 1  further including a piston for delivering at least one of the fluids in response to pumped pressure from another one of the fluids. 
     
     
         23 . The apparatus of  claim 1  further including a piston for delivering at least one of the fluids in response to borehole pressure. 
     
     
         24 . The apparatus of  claim 1  wherein the apparatus is pressure balanced with at least one of: a spring and piston, bellows, and diaphragm membrane. 
     
     
         25 . The apparatus of  claim 1  further including a combined passive mixer and membrane module. 
     
     
         26 . The apparatus of  claim 1  further including thin wall capillary tubing which functions as an optical waveguide, the tubing coupled to an optical source and detector. 
     
     
         27 . The apparatus of  claim 1  wherein multiple sample loops are disposed between the ports on a single chip. 
     
     
         28 . The apparatus of  claim 27  wherein the sample loops are operated by at least one of: multiposition switching valves; and one time use valves. 
     
     
         29 . A method for detecting a substance of interest in a borehole fluid comprising:
 introducing a test sample fluid via a first port;   introducing a reagent to the test sample fluid via a second port, thereby creating a mixed fluid, the mixed fluid exhibiting a characteristic change if the substance of interest is present in the borehole fluid;   causing at least some of the mixed fluid to flow into a microfluidic device;   detecting, within the borehole, the characteristic change in the mixed fluid in the microfluidic channel with a test module; and   transmitting an output signal indicative of whether the characteristic change is detected.   
     
     
         30 . The method of  claim 29  further including transmitting an output signal indicative of level of concentration of the substance of interest in the borehole fluid. 
     
     
         31 . The method of  claim 29  wherein the test module includes an optical transmitter and optical receiver, and further including detecting differences in color or transmissivity. 
     
     
         32 . The method of  claim 29  wherein introducing the test sample fluid includes introducing borehole fluid. 
     
     
         33 . The method of  claim 29  further including a membrane disposed between the borehole fluid and the first port, and wherein introducing the test sample fluid includes introducing a gas separated from the borehole fluid by the membrane. 
     
     
         34 . The method of  claim 29  wherein introducing the test sample fluid includes introducing a mixture of scrubbing fluid and borehole fluid. 
     
     
         35 . The method of  claim 29  further including a membrane disposed between the borehole fluid and the first port, and wherein introducing the test sample fluid includes introducing a mixture of scrubbing fluid and gas separated from the borehole fluid by the membrane. 
     
     
         36 . The method of  claim 29  wherein the first and second ports are part of a multi-port valve, and wherein a test loop is connected between ports of the valve, and wherein introducing reagent includes causing a predetermined fixed volume of reagent to flow into the test loop.