In-situ detection and analysis of methane in coal bed methane formations with spectrometers

Abstract

A measuring system for in-situ measurements down a well ( 1 ) by a spectrometer ( 4 ) is provided. The spectrometer ( 4 ) includes a radiation source ( 5 ) and a detector ( 6 ). A probe ( 15 ) optically connected to the spectrometer ( 4 ) and includes an optical pathway ( 7 ) for transmission of a radiation from the radiation source ( 5 ) and at least a second optical pathway for transmission of a characteristic radiation from a sample to the detector ( 6 ). A positioner is provided to position the probe ( 15 ) near a side surface ( 11 ) of the borehole ( 3 ) and to optically couple the optical pathways ( 7 ) to the side surface ( 11 ), wherein the probe ( 15 ) is traversable up and down the well ( 1 ) by way of a guide operatively connected to the probe ( 15 ) and to a fixed location at the wellhead. By use of the apparatus and method a concentration of methane or other substance of interest is obtained, and thereby, a potential production of a coal bed methane formation is obtained.

We claim: 
     
       1. A method of measuring methane using a spectrometer in a coal bed methane well with a borehole extending to at least a top surface of at least one coal bed and containing water, comprising:
 providing a spectrometer including a radiation source and a detector 
 providing a housing including a radiation source, a detector and a sample interface, 
 lowering the housing in the coal bed methane well to a depth down the well, 
 positioning the sample interface to a sample located outside of the housing, 
 irradiating the sample from the radiation source, 
 detecting a characteristic radiation of the methane from the sample with the detector of the spectrometer, and 
 processing a signal from the detector and spectrometer with a computer to calculate a concentration of the methane. 
 
     
     
       2. A method of measuring according to  claim 1 , wherein the sample is a face of the coal bed. 
     
     
       3. A method of measuring according to  claim 2 , wherein the a radiation source is selected to minimize a radiation from the coal. 
     
     
       4. A method of measuring according to  claim 2 , wherein a wavelength of the radiation source is lower than a wavelength producing maximum fluorescence in the coal. 
     
     
       5. A method of measuring according to  claim 1 , wherein the characteristic radiation is emitted, reflected or scattered radiation. 
     
     
       6. A method of measuring according to  claim 1 , wherein the sample is a volume of water in the well at or near the depth down the well. 
     
     
       7. A method of measuring according to  claim 1 , wherein the sample is a collected gas from the water which has been depressurized to release the gas. 
     
     
       8. A method of measuring according to  claim 1 , wherein the sample is chemically treated before the irradiating. 
     
     
       9. A method of measuring according to  claim 1 , wherein the sample is biologically treated before the irradiating. 
     
     
       10. A method of measuring according to  claim 1 , wherein the radiation source is selected to minimize fluorescence. 
     
     
       11. A method of measuring according to  claim 1 , wherein the sample interface includes at least one lens to focus the radiation from the radiation source, and a focal length of the sample interface is adjusted to mitigate a noise level or to increase the detected characteristic radiation. 
     
     
       12. A method of measuring according to  claim 1 , wherein the radiation source is a tunable laser located in the housing. 
     
     
       13. A method of measuring according to  claim 1 , wherein the radiation source is a diode laser with a wavelength between 450 nm and 580 nm. 
     
     
       14. A method of measuring according to  claim 1 , wherein the detector is an optical fiber transmitting the characteristic radiation to a charge-coupled device. 
     
     
       15. A method of measuring methane in at least one coal bed methane well, comprising:
 providing an instrument package in a housing, 
 lowering the package to a depth down the coal bed methane well, 
 positioning a radiation source to irradiate a sample and a detector to detect a characteristic radiation from the sample, 
 irradiating the sample which is located outside the housing with radiation from the radiation source to produce the characteristic radiation from the sample, and 
 measuring a concentration of methane in the sample by detecting the characteristic radiation from the sample with the detector, transmitting a signal from the detector to a signal processor and processing the signal to calculate the concentration of the methane in the sample. 
 
     
     
       16. A method of measuring according to  claim 15 , wherein the radiation source includes an optical fiber transmitting light waves from a spectrometer near a well head and connected to the housing. 
     
     
       17. A method according to  claim 15 , further comprising:
 lowering the package to at least a second depth down the well, and measuring a concentration of methane at the second depth, in order to obtain concentration of methane versus depth of the well. 
 
     
     
       18. A method according to  claim 15 , further comprising:
 obtaining concentration of methane versus depth of at least a second well, in order to obtain a potential production of a coal formation. 
 
     
     
       19. A method according to  claim 15 , wherein the instrument package is sealed against water and armored to withstand pressure down the well. 
     
     
       20. A method according to  claim 15 , wherein the package includes a radiation source for supplying a radiation to irradiate the sample. 
     
     
       21. A method according to  claim 15 , wherein the package includes the detector for detecting the characteristic radiation from the sample and transmitting the signal. 
     
     
       22. A method according to  claim 21 , wherein the package includes the signal processor for processing the signal from the detector. 
     
     
       23. A method according to  claim 15 , wherein the package includes a filter for filtering the radiation from the radiation source. 
     
     
       24. A method according to  claim 15 , wherein the package includes a filter for filtering the characteristic radiation before the detector. 
     
     
       25. A method according to  claim 15 , wherein the radiation source is a diode laser at a wavelength which minimizes a fluorescence of the coal. 
     
     
       26. A method according to  claim 15 , wherein the depth is at a top of a water column in the well. 
     
     
       27. A method according to  claim 15 , wherein the depth is at a top of a first coal bed. 
     
     
       28. A method according to  claim 15 , wherein the depth is at a top of a second coal bed. 
     
     
       29. A method according to  claim 15 , wherein the sample is water at or near the depth. 
     
     
       30. A method according to  claim 15 , wherein the sample is a bacterium or bacterial community. 
     
     
       31. A method according to  claim 15 , wherein the housing includes at least one window for transmitting the radiation from the radiation source and the characteristic radiation. 
     
     
       32. A method according to  claim 31 , wherein the window is positioned next to the sample. 
     
     
       33. A method according to  claim 15 , wherein the sample is a face of the wellbore. 
     
     
       34. A method according to  claim 33 , wherein a portion of the housing is pressed into the face of the wellbore. 
     
     
       35. A method according to  claim 33 , wherein the face of the wellbore is scraped or prepared to provide a sampling surface. 
     
     
       36. A method according to  claim 15 , wherein the sample is a face of the coal bed. 
     
     
       37. A method according to  claim 15 , further comprising selecting a wavelength of the radiation source to mitigate fluorscence. 
     
     
       38. A method according to  claim 37 , wherein the wavelength is selected to mitigate a radiation from entrained particle in the water. 
     
     
       39. A method according to  claim 37 , wherein the wavelength is selected to mitigate errors due to length of optical pathways transmitting the radiation from the radiation source and the characteristic radiation. 
     
     
       40. A measuring system for introduction into a well, comprising:
 a housing being traversable up and down the well, 
 a guide extending down the well from a fixed location and being operatively connected to the housing, 
 a spectrometer being located inside the housing and including a radiation source, a sample interface to transmit a radiation from the radiation source to a sample located outside of the housing, and a detector to detect a characteristic radiation emitted, reflected or scattered from the sample and to output a signal, and 
 a signal processor to process the signal from the detector and calculate a concentration of a substance in the sample. 
 
     
     
       41. A measuring system according to  claim 40 , wherein the probe has no moving parts. 
     
     
       42. A measuring system for in-situ measurements down a well with a borehole by a spectrometer, comprising:
 the spectrometer including a radiation source and a detector, 
 a probe being optically connected to the spectrometer and including an optical pathway for transmission of a radiation from the radiation source and at least a second optical pathway for transmission of a characteristic radiation from a sample to the detector, and 
 a positioner to position the probe near a side surface of the borehole and to optically couple the optical pathways to the side surface of the borehole sample, 
 wherein the sample is located outside of the probe, and 
 wherein the probe is traversable up and down the well by way of a guide operatively connected to the probe and to a fixed location at the wellhead. 
 
     
     
       43. A measuring system according to  claim 42 , wherein the sample is methane adsorbed to coal. 
     
     
       44. A measuring system according to  claim 42 , wherein the optical pathway for transmission of the radiation from the radiation source includes at least one lens for focusing the radiation from the radiation source onto the sample. 
     
     
       45. A measuring system according to  claim 42 , wherein the positioner includes an adjustable device which extends from the probe and presses a side of the wellbore. 
     
     
       46. A measuring system according to  claim 42 , wherein the radiation source is a diode laser at a wavelength of 450 nm to 580nm. 
     
     
       47. A measuring system according to  claim 42 , wherein a filter is located between the radiation source and the sample to filter the radiation from the radiation Source. 
     
     
       48. A measuring system according to  claim 42 , wherein at least one filter is located between the sample and the detector to filter the characteristic radiation. 
     
     
       49. A measuring system according to  claim 42 , wherein the probe includes the spectrometer. 
     
     
       50. A measuring system according to  claim 49 , wherein the probe is armored against pressure and sealed against liquids. 
     
     
       51. A measuring system according to  claim 49 , wherein the probe includes a high-pressure feed-through jacket for an optical fiber which interfaces between the enclosed spectrometer and the wellbore. 
     
     
       52. A measuring system according to  claim 49 , wherein the probe includes a reflector to direct the radiation from the radiation source to the sample and a second reflector to direct the characteristic radiation from the sample to the detector. 
     
     
       53. A measuring system according to  claim 42 , wherein an error corrector is provided to correct for inherent system noise and errors. 
     
     
       54. A measuring system according to  claim 42 , wherein the probe is optically connected to the radiation source via at least one optical fiber. 
     
     
       55. A measuring system according to  claim 42 , wherein the probe is optically connected to the detector via at least one optical fiber. 
     
     
       56. A measuring system according to  claim 42 , wherein the probe is streamlined so as not to substantially disturb the water in the well. 
     
     
       57. A measuring system according to  claim 42 , wherein the radiation source is a UV/Vis spectrometer. 
     
     
       58. A measuring system according to  claim 42 , wherein the radiation source is a near IR spectrometer. 
     
     
       59. A measuring system according to  claim 42 , wherein the radiation source is a Raman spectrometer. 
     
     
       60. A measuring system according to  claim 42 , wherein the radiation source is an infrared spectrometer. 
     
     
       61. A measuring system according to  claim 42 , wherein the radiation source is a fluorimeter. 
     
     
       62. A measuring system according to  claim 42 , wherein the detector is a charge-coupled device. 
     
     
       63. A measuring system according to  claim 42 , wherein the detector includes at least one of a photomultiplier tube, a photo-diode array, an avalanche photo-diode, a charge injection device and a complimentary metal-oxide semiconductor image sensor. 
     
     
       64. A method of measuring a side surface of a borehole using optical spectrometers, comprising:
 providing the optical spectrometer including a radiation source and a detector, 
 optically connecting the side surface of the borehole to the radiation source and the detector, 
 said side surface being located outside of the spectrometer, 
 irradiating the side surface of the borehole with radiation from the radiation source, 
 collecting a characteristic radiation emitted, reflected or scattered from an interaction between the side surface of the borehole and the radiation from the radiation source, 
 transmitting the characteristic radiation to the detector to thereby produce a signal, 
 transmitting the signal to a signal processor, and 
 calculating a concentration of a substance on the side surface of the borehole. 
 
     
     
       65. A method according to  claim 64 , wherein the side surface of the borehole is a face of a coal seam. 
     
     
       66. A method according to  claim 64 , wherein the side surface is optically connected by at least one lens which focuses the radiation from the radiation source onto the side surface. 
     
     
       67. A method according to  claim 64 , wherein the side surface is optically connected to the radiation from the radiation source by at least one fiber optic which is positioned near the side surface. 
     
     
       68. A method according to  claim 67 , wherein the fiber optic is pressed into the side surface. 
     
     
       69. A method according to  claim 64 , wherein the side surface is optically connected to the radiation from the radiation source via a window or lens in a housing. 
     
     
       70. A method according to  claim 69 , wherein the housing is pressed into the side surface. 
     
     
       71. A method according to  claim 69 , wherein the housing is lowered down the wellbore and is positioned near the side surface by an adjustable device extending from the housing. 
     
     
       72. A method according to  claim 69 , wherein the spectrometer is located in the housing. 
     
     
       73. A method according to  claim 64 , wherein the radiation source is a diode laser with a wavelength between 450 nm and 580 nm. 
     
     
       74. A method of analyzing a coal bed methane reservoir comprising,
 providing an instrument package in a well bore comprising a   detector and spectrometer in a housing and   measuring an amount of concentration of methane in the well bore dissolved in a wellbore fluid with the detector and spectrometer to thereby predict the amount of the concentration of methane in the coal bed methane reservoir.   
     
     
       75. A method according to claim 74, wherein the amount measured is a concentration of methane dissolved in the wellbore fluid. 
     
     
       76. A method of analyzing a coal bed methane well having a borehole extending to at least a top surface of at least one coal bed and containing water, comprising:
 providing a instrument package comprising a detector and spectrometer in a housing in the well including a detector and a water sample interface in a borehole,   positioning the sample interface to a sample located outside the housing,   detecting a characteristic of a dissolved methane from the sample with the detector, and   processing a signal from the detector by a computer to calculate a concentration of the dissolved methane in the water.   
     
     
       77. A method according to claim 76, wherein the concentration of dissolved methane predicts a production of the coal bed methane well. 
     
     
       78. A method according to claim 77, wherein the production is an amount of methane contained within the coal bed methane reservoir. 
     
     
       79. A method according to claim 77, wherein the measurement instrument is an optical spectrometer. 
     
     
       80. A method of analyzing a coal bed methane reservoir comprising:
 (a) drilling a well with a well boring machine to an appropriate depth;   (b) recording the depth of the water table if present;   (c) recording the depth of the top of the coal seam and the bottom of the coal seam;   (d) preparing the well head to receive the probe or instrument package;   (e) coupling the probe to a fiber-optic cable;   (f) coupling the fiber-optic cable to a spectrometer that contains a light source, dispersion element, detector and signal processing equipment and ancillary devices;   (g) connecting the spectrometer system to a computer that serves as an instrument controller, data collection and manipulation device; and   (h) outputting information from the spectrometer to the computer to be manipulated into information to be used to calculate the concentration and potential production of methane.   
     
     
       81. A method of measuring methane in a coal bed methane well with a borehole extending to at least a top surface of at least one coal bed and containing water, comprising:
 providing a spectrometer, a detector and a sample located outside the housing in a coal bed methane well,   irradiating the sample with the spectrometer,   processing a signal from the detector to calculate a concentration of the methane in the water, and   predicting a gas content of the coal bed using a computer.   
     
     
       82. A method of measuring according to claim 81, wherein the sample is a volume of water in the well at or near the depth down the well. 
     
     
       83. A method of measuring according to claim 81, wherein the sample is a collected gas from the water which has been depressurized to release the gas. 
     
     
       84. A method of measuring methane in at least one coal bed methane well, comprising:
 providing an instrument package in a well bore   comprising a detector and spectrometer in a housing,   lowering the package to a depth down the well, measuring a concentration of methane in a sample located outside the housing, and   calculating a concentration of the methane in the sample with a computer processor.   
     
     
       85. A method according to claim 84, further comprising:
 lowering the package to at least a second depth down the well, and measuring a concentration of methane at the second depth, in order to obtain concentration of methane versus depth of the well.   
     
     
       86. A method according to claim 84, further comprising:
 obtaining a reservoir characteristic of the well based upon the concentration.   
     
     
       87. A method according to claim 84, wherein the package includes a filter for filtering the sample from particles in the well. 
     
     
       88. A method according to claim 84, wherein the depth is at a top of a water column in the well. 
     
     
       89. A method according to claim 84, wherein the depth is at a top of a first coal bed. 
     
     
       90. A method according to claim 84, wherein the sample is water at or near the depth. 
     
     
       91. A method according to claim 84, wherein the sample passes through a filter and is brought inside the housing. 
     
     
       92. A method according to claim 84, wherein the sample is a gas produced from the water at or near the depth by depressurizing the water inside the housing and collected in a head-space.