AU2010290994A1

AU2010290994A1 - In-borehole gas monitor apparatus and method comprising a VOC concentration analyser and a VOC collector

Info

Publication number: AU2010290994A1
Application number: AU2010290994A
Authority: AU
Inventors: Steve Boult
Original assignee: Intelisys Ltd
Current assignee: Intelisys Ltd
Priority date: 2009-09-01
Filing date: 2010-08-03
Publication date: 2012-03-08
Also published as: CN102597766A; GB0915150D0; EP2473843A1; RU2012110978A; IN2012DN02476A; BR112012004245A2; ZA201202341B; JP2013504035A; MX2012002602A; CA2772744A1; WO2011027137A1; US20130036811A1

Abstract

In-Borehole Gas Monitor Apparatus and Method An in-borehole gas monitor (IGM) apparatus comprising a VOC concentration analyser and a VOC collector.

Description

WO 2011/027137 PCT/GB2010/051282 IN-BOREHOLE GAS MONITOR APPARATUS AND METHOD COMPRISING A VOC CONCENTRATION ANALYSER AND A VOC COLLECTOR Field of the Invention 5 The present invention relates to in-borehole gas monitor (IGM) apparatus and methods. Background to the Invention 10 The monitoring of gas concentrations, and in particular methane and carbon dioxide, generated by landfill and associated sites is becoming a more common legislative requirement due to the potential problems these gases pose, such as the risk of explosion and impacts as 15 greenhouse gases. At present, the majority of landfill gas analysis is achieved either through spot sampling or through the use of large expensive fixed position monitoring stations. More recently it has been recognised that gas production and migration responds to 20 environmental factors such as barometric pressure and groundwater movement, with the accompanying realisation that spot sampling will often miss such changes. It is known from WO 2007/141512 to provide a self 25 contained IGM apparatus comprising a detector for measuring a gas variable, and a controller configured to automatically periodically use the detector to measure a gas variable. 30 However, the apparatus and method disclosed in WO 2007/141512 do not deal with volatile organic compounds (VOCs).

WO 2011/027137 PCT/GB2010/051282 2 It is an aim of preferred embodiments of the present invention to address, overcome or obviate a disadvantage of the prior art, whether such prior art or disadvantage is referred to herein or otherwise. 5 Summary of the Invention According to the present invention in a first aspect, there is provided an in-borehole gas monitor (IGM) 10 apparatus comprising a VOC concentration analyser and a VOC collector. Suitably, the VOC concentration analyser is configured to provide a non-specific real-time concentration of VOCs. 15 Suitably, the VOC concentration analyser comprises a photo-ionisation detector. Suitably, the VOC collector is configured to provide a specific concentration by volume. Suitably, the VOC 20 collector comprises a sorbent material. Suitably, the apparatus further comprises a pressure sensor configured to measure atmospheric pressure. 25 Suitably, the apparatus further comprises a clock. Suitably, the apparatus comprises a pump for pumping gas past the VOC concentration analyser and the VOC collector in a downstream direction and the apparatus is configured 30 whereby the VOC concentration analyser determines a VOC concentration at a predetermined time by the pump pumping borehole gas past the VOC concentration analyser and the VOC collector for a pumping period. Suitably, the WO 2011/027137 PCT/GB2010/051282 3 apparatus is configured whereby the pumping period, a time of measurement and an atmospheric pressure at the time of measurement are recorded. 5 Suitably, the apparatus comprises a pump for pumping gas past the VOC concentration analyser and the VOC collector in a downstream direction and a filter for removing any of particulates or moisture from a gas input, wherein the VOC concentration analyser and the VOC collector are upstream 10 of the filter. Suitably, the apparatus comprises a pump for pumping gas past the VOC concentration analyser and the VOC collector in a downstream direction and there is a gas flow path 15 comprising a gas input, a first valve upstream of the pump and a pressure sensor, wherein the apparatus is configured whereby with the first valve closed the pump is activated for a predetermined period and if within the predetermined period a predetermined pressure is not exceeded, as 20 measured by the pressure sensor, a pump fail signal is generated. Suitably, the predetermined period is between 8 and 12 seconds and the predetermined pressure is 100mb. Suitably, the apparatus comprises a pump for pumping gas 25 past the VOC concentration analyser and the VOC collector in a downstream direction and there is a gas flow path comprising a gas input, a first valve upstream of the pump, a pressure sensor and a filter, wherein the apparatus is configured whereby with the first valve open 30 a first pressure sensor reading is taken, the pump is activated for a predetermined period after which a second pressure sensor reading is taken, and if the magnitude of the difference between the first pressure sensor reading WO 2011/027137 PCT/GB2010/051282 4 and the second pressure sensor reading is greater than a predetermined value, a filter fail signal is generated. Suitably, the predetermined period is between 2 seconds and 6 seconds. Suitably, the predetermined value is 5 250mb. Suitably, the time of sensing and the length of time for which the pump operates are recorded 10 Suitably the apparatus comprises a second valve downstream of the first valve and a gas outlet. Suitably, the apparatus is configured to have a borehole side and an atmospheric side, wherein there is a gas 15 outlet to the borehole side of the device and to the atmospheric side of the device. Suitably, the VOC concentration analyser and the VOC collector are in series in a gas flow path with a gas 20 analyser. Suitably, the gas analyser analyses one or more of hydrocarbons, carbon dioxide, oxygen and hydrogen sulphide. According to the present invention is a second aspect, 25 there is provided a method of operation of an in-borehole gas monitor apparatus, which method comprises the use of an in-borehole gas monitor apparatus according to the first aspect of the invention in a borehole. 30 Suitably, the VOCs collected by the VOC collector are quantified.

WO 2011/027137 PCT/GB2010/051282 5 Suitably, the apparatus comprises a pump for pumping gas from the borehole past the VOC collector and the VOC analyser, wherein the time of sensing and the length of time for which the pump operates are recorded to determine 5 the volume of gas passing through the apparatus. This enable the VOC concentration to be determined. Brief Description of the Drawings 10 The present invention will now be described, by way of example only, with reference to the drawings that follow; in which: Figure 1 is a schematic illustration of a borehole site 15 with an in-borehole gas monitor according to the present invention. Figure 2 is a schematic cross-sectional elevation of an in-borehole gas monitor apparatus according to the present 20 invention. Figure 3 is a schematic flow diagram illustrating a method of operation of an in-borehole gas monitor apparatus according to the present invention. 25 Description of the Preferred Embodiments Referring to Figure 1 of the accompanying drawings, there is shown a borehole 2 in ground consisting of a landfill 30 site. The borehole 2 is supported by a liner 4 in which a plurality of side-holes 6 are located to allow for sampling.

WO 2011/027137 PCT/GB2010/051282 6 Referring to Figure 2 of the accompanying drawings, there is shown an in-borehole gas monitor (IGM) apparatus 8 including a cap 10. The cap 10 comprises an inner bore 12 for receiving the IGM apparatus 8. The cap 10 includes an 5 exterior screw thread 14 for engaging with a corresponding interior screw thread (not shown) on liner 4. Alternatively, the cap can be made as part of the housing. A seal 16 is provided for fitting the IGM apparatus 8 in a borehole when a suitable screw thread is not available for 10 the cap 10 to be used. The IGM apparatus 8 consists of a body portion 17 which is a self-contained unit meeting environmental rating IP-68, i.e. essentially waterproof. The IGM apparatus 8 comprises 15 a top 30 and an external tube 32. The external diameter of tube 32 in this embodiment is approximately 40mm allowing for it to be inserted into a typical borehole liner. In this embodiment of the invention, the length of tube 32 is 800mm, but may be less. 20 The IGM apparatus 8 further comprises a gas inlet 36 connected to a first entry valve 38, which gas inlet leads to a volatile organic compounds ("VOC") detector 40 connected to a VOC collector 42, connected to a water and 25 particulate filter 44 for removing any excess moisture and/or particles from the ingressed gases. The filter 44 is connected to a first pressure sensor 46, connected to a pump 48 connected to a gas detector 50 comprising a plurality of gas analysers, in this case and H 2 S and CO 30 sensor 52, a C02 sensor 54, a CH 4 sensor 56 and an 02 sensor 58. The detector is connected to a second valve 60 which is connected to a return line (a first outlet) 62 back to the borehole and a branched connection to a third WO 2011/027137 PCT/GB2010/051282 7 valve 64 which is connected to a second pressure sensor 66 from which extends a second outlet 68, this time to atmosphere. 5 A suitable filter 44 is an in-line particulate and moisture filter such as that available from Geotechnical Instruments of Sovereign House, Queensway, Leamington Spa, United Kingdom. 10 The VOC detector 40 detects the presence and concentration of a range of VOCs but does not distinguish between the various VOCs. A suitable VOC sampler 40 is a photo ionisation detector. The VOC collector 42 is a sorbent and sorbs (that is, adsorbs or absorbs) VOCs passing 15 therethrough. A suitable VOC sampler 40 would be a GORESorb (trade mark) tube with a multiplicity of small sorbent balls therein. Any suitable gas variable can be measured in the detector 20 50, the analysers typically being used to monitor hydrocarbons (especially methane), carbon dioxide, oxygen carbon monoxide and hydrogen sulphide concentrations. The IGM apparatus 8 further comprises a combined 25 controller and memory 70 for controlling operation of the apparatus 8 and a power cell (battery) 72 making the operation of the apparatus 8 self-contained, i.e. not reliant on data communication with or power from an external source. The controller 70 includes a clock. 30 A vent pipe 74 is provided running through the apparatus 8 from the bore-hole end to an outlet 76 through the top 30 to atmosphere (the atmospheric end of the apparatus) . A WO 2011/027137 PCT/GB2010/051282 8 vent pipe valve 78 is provided for the vent pipe 64 to control whether it is open to atmosphere. Also shown is a water detector 80, which detects the 5 presence or proximity of liquid water in the apparatus and upon such detection transmits a signal to the controller 70. A conductance sensor is used to determine a liquid water presence. 10 Further, a water level detector (not shown) can be connected to the bottom of the IGM apparatus and suspended therebelow in use into the borehole. As wired pressure transducer can be used. 15 The top 30 includes a connector 82 allowing data communication with a remote device and unit activation. Additionally, a pressure sensor can be attached here for monitoring borehole water level. 20 The IGM apparatus 8 is mounted in a borehole 2, within a borehole liner with the cap 10 providing a gas-tight seal. Over time, gases will build up in the borehole 2. The IGM apparatus 8 is configured, specifically by programming of 25 the controller 70, to automatically and periodically test a gas sample from the borehole. The process by which this is undertaken will now be described. First (step 100) a pump test is carried out. With first 30 valve 38 shut, the pump 48 is started and first pressure sensor 46 must read 100mb within 10 seconds otherwise a FAIL warning is produced by controller 70 as the pump 48 may have failed.

WO 2011/027137 PCT/GB2010/051282 9 Next (step 102) a filter test is carried out. With first valve 38 open after 4 seconds first pressure sensor 46 takes a pressure reading BH. The pump 48 then runs for a 5 predetermined period and first pressure sensor 46 takes another pressure reading BHP. If BHP-BH>250mb a FAIL warning is produced by controller 70 as the filter 44 is likely to have become blocked. 10 Any FAIL warnings appear prominently as part of a data download from the apparatus. First and second valves 38 and 60 are opened (step 104) and pump 48 is activated (step 106) to pump gas from the 15 borehole through the gas flow path described above to ensure the sensors have an up to date gas sample from the borehole. The VOC detector 40 and VOC collector 42 precede the filter 44 which would otherwise remove the VOCs from the gas flow. VOC's collected by the VOC 20 collector can be quantified by removing the VOC collector and eluting the VOC's into an instrument such as a gas chromatograph. Measurements (step 108) of VOC concentrations are made by the VOC detector 40. Moisture and particulates are removed by the filter 44. 25 Borehole gas then passes through the detector 50 where it is analysed by (step 110) by gas analysers 57, 54, 56 and 58. 30 A concurrent gas pressure measurement (step 112) is made by first gas pressure sensor 38 and a reference measurement of atmospheric pressure is made by second pressure sensor 66. The time of the sensing and length of WO 2011/027137 PCT/GB2010/051282 10 time for which the pump is operated and recorded (step 114). Based on an empirical measurement or by calculation, the volume of gas passing through the apparatus 8 per unit time when the pump 48 is running can 5 be determined. Accordingly, it can be determined what volume of gas has passed through the apparatus in any given testing period. This data is stored in the controller/memory 70. The amount of VOC's collected by the VOC collector can then be divided by the volume of gas 10 passed over the collector giving a measure of VOC concentration. First and second valves 38 and 60 are then closed (step 116). The gas from the borehole is circulated back to the 15 borehole through the borehole end of the apparatus. Gas variable measurements are carried out by the gas analysers 52, 54, 56 and 58. Any appropriate variable can be monitored including one or more of the presence or 20 absence of a particular gas, a gas concentration level, a gas pressure, moisture content in a gas, etc. The data from the gas variable measurements is stored in the controller/memory 70. 25 A timer in the controller 70 is re-set (step 116) so that a subsequent periodic measurement can be made. The data stored in controller/memory 70 can be downloaded over a hard-wired connection via the connector 82 or by 30 wireless transmission. This connection can also be used to program the controller 70 to operate the apparatus 8 as desired. For instance, variables such as the frequency of sampling, whether sampling is regular or irregular, WO 2011/027137 PCT/GB2010/051282 11 whether there should be a periodic venting to atmosphere, etc can be set. On an ongoing basis if the water detector 80 detects the 5 presence of water in the apparatus, a water detection signal is sent to the controller 70 which can take an appropriate step, such as deactivating the apparatus 8, transmitting an alert signal, illuminating a warning light etc. This can both protect the apparatus 8 from damage 10 and avoid contaminated readings being made. As gases build up in the borehole over time, it can be useful to open the borehole to atmosphere to reduce the pressure therein, but also to provide the opportunity to, 15 in effect, re-start the sampling operation by allowing the borehole to equilibriate to atmosphere. Thus, the base line for any monitoring can be re-set and an analysis of the variation of gas variables over time can be undertaken. The apparatus 8 can be configured to vent the 20 borehole to atmosphere periodically or on instruction. Thus, there is provided a portable, self-contained IGM apparatus that can be conveniently deployed in a borehole to take periodic data readings of gas variables in the 25 borehole. In particular, preferred embodiments of the present invention enable VOCs to be monitored. The combination of the VOC detector together with the VOC collector and the 30 determination of the volume of gas passing through the apparatus enables a calculation to be made of the absolute concentrations of specific VOCs in the borehole and also how they vary over time. By time-stamping the results, WO 2011/027137 PCT/GB2010/051282 12 the variation of VOCs over time can be monitored enabling, for instance, comparisons with other time-variable phenomena, such as atmospheric pressure or weather conditions. 5 Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this 10 specification, and the contents of all such papers and documents are incorporated herein by reference. All of the features disclosed in this specification (including any accompanying claims, abstract and 15 drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. 20 Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each 25 feature disclosed is one example only of a generic series of equivalent or similar features. The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any 30 novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any WO 2011/027137 PCT/GB2010/051282 13 novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. An in-borehole gas monitor (IGM) apparatus comprising a VOC concentration analyser and a VOC collector. 5

2. The in-borehole gas monitor (IGM) apparatus of claim 1, wherein the VOC concentration analyser is configured to provide a non-specific real-time concentration of VOCs. 10

3. The in-borehole gas monitor (IGM) apparatus of claim 1 or claim 2, wherein the VOC concentration analyser comprises a photo-ionisation detector. 15

4. The in-borehole gas monitor (IGM) apparatus of any preceding claim, wherein the VOC collector is configured to provide a specific concentration by volume. 20

5. The in-borehole gas monitor (IGM) apparatus of any preceding claim, wherein the VOC collector comprises a sorbent material.

6. The in-borehole gas monitor (IGM) apparatus of any 25 preceding claim, wherein the apparatus further comprises a pressure sensor configured to measure atmospheric pressure.

7. The in-borehole gas monitor (IGM) apparatus of any 30 preceding claim, wherein the apparatus further comprises a clock. WO 2011/027137 PCT/GB2010/051282 15

8. The in-borehole gas monitor (IGM) apparatus of any preceding claim, wherein the apparatus comprises a pump for pumping gas past the VOC concentration analyser and the VOC collector in a downstream 5 direction and the apparatus is configured whereby the VOC concentration analyser determines a VOC concentration at a predetermined time by the pump pumping borehole gas past the VOC concentration analyser and the VOC collector for a pumping period. 10

9. The in-borehole gas monitor (IGM) apparatus of claim 8 wherein, the apparatus is configured whereby the pumping period, a time of measurement and an atmospheric pressure at the time of measurement are 15 recorded.

10. The in-borehole gas monitor (IGM) apparatus of claims 1 to 7, wherein the apparatus comprises a pump for pumping gas past the VOC concentration analyser and 20 the VOC collector in a downstream direction and a filter for removing any of particulates or moisture from a gas input, wherein the VOC concentration analyser and the VOC collector are upstream of the filter. 25

11. The in-borehole gas monitor (IGM) apparatus of claims 1 to 7, wherein the apparatus comprises a pump for pumping gas past the VOC concentration analyser and the VOC collector in a downstream direction and there 30 is a gas flow path comprising a gas input, a first valve upstream of the pump and a pressure sensor, wherein the apparatus is configured whereby with the first valve closed the pump is activated for a WO 2011/027137 PCT/GB2010/051282 16 predetermined period and if within the predetermined period a predetermined pressure is not exceeded, as measured by the pressure sensor, a pump fail signal is generated. 5

12. The in-borehole gas monitor (IGM) apparatus of claim 11, wherein the predetermined period is between 8 and 12 seconds and the predetermined pressure is 100mb. 10

13. The in-borehole gas monitor (IGM) apparatus of claims 1 to 7, wherein the apparatus comprises a pump for pumping gas past the VOC concentration analyser and the VOC collector in a downstream direction and there is a gas flow path comprising a gas input, a first 15 valve upstream of the pump, a pressure sensor and a filter, wherein the apparatus is configured whereby with the first valve open a first pressure sensor reading is taken, the pump is activated for a predetermined period after which a second pressure 20 sensor reading is taken, and if the magnitude of the difference between the first pressure sensor reading and the second pressure sensor reading is greater than a predetermined value, a filter fail signal is generated. 25

14. The in-borehole gas monitor (IGM) apparatus of claim 13, wherein the predetermined period is between 2 seconds and 6 seconds. 30

15. The in-borehole gas monitor (IGM) apparatus of claim 13 or claim 14, wherein the predetermined value is 250mb. WO 2011/027137 PCT/GB2010/051282 17

16. The in-borehole gas monitor (IGM) apparatus of claims 8 to 15, wherein the time of sensing and the length of time for which the pump operates are recorded. 5

17. The in-borehole gas monitor (IGM) apparatus of claims 11 to 15 wherein, the apparatus comprises a second valve downstream of the first valve and a gas outlet.

18. The in-borehole gas monitor (IGM) apparatus of any 10 preceding claim, wherein the apparatus is configured to have a borehole side and an atmospheric side, wherein there is a gas outlet to the borehole side of the device and to the atmospheric side of the device. 15

19. The in-borehole gas monitor (IGM) apparatus of any preceding claim, wherein the VOC concentration analyser and the VOC collector are in series in a gas flow path with a gas analyser.

20 20. The in-borehole gas monitor (IGM) apparatus of claim 19, wherein the gas analyser analyses one or more of hydrocarbons, carbon dioxide, oxygen and hydrogen sulphide. 25

21. A method of operation of an in-borehole gas monitor apparatus, which method comprises the use of an in borehole gas monitor apparatus according to any one of claims 1 to 20. 30

22. The method of operation of an in-borehole gas monitor apparatus of claim 21, wherein the VOCs collected by the VOC collector are quantified. WO 2011/027137 PCT/GB2010/051282 18

23. The method of operation of an in-borehole gas monitor apparatus of claim 21 or claim 22, wherein the apparatus comprises a pump for pumping gas from the borehole past the VOC collector and the VOC analyser, 5 wherein the time of sensing and the length of time for which the pump operates are recorded to determine the volume of gas passing through the apparatus. This enables the VOC concentration to be determined.