GB2437961A

GB2437961A - Inert drilling on landfill sites

Info

Publication number: GB2437961A
Application number: GB0608995A
Authority: GB
Inventors: Geoffrey Kevin Ellison; Francis Alan Hay
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-05-06
Filing date: 2006-05-06
Publication date: 2007-11-14
Anticipated expiration: 2026-05-06
Also published as: GB0608995D0; GB2437961B

Abstract

A landfill barrel auger apparatus 4 includes hollow drill rods 5 and barrel auger 6 at the lower end. The interior of the barrel auger 4 is in communication with the interior of the drill rods 5. An inert supply of gas 1 is connected to the upper end of the drill rods 5 and inert gas can therefore be supplied to the interior space of the barrel drill auger 4. The barrel auger 4 may include a temporary window 7 with a removable patch 8 which can be removed as the barrel 4 fills with material and therefore prevents over pressure of the barrel 4.

Description

ENVIRONMENTAL IMPROVEMENTS FOR DIRLLING ON LANDFILL SITES

Introduction

It is a requirement to install boreholes on landfill sites to enable the control and utilisation of landfill gas and leachate.

As landfill sites generate methane, as a result of the anaerobic degradation of biodegradable waste, it is inevitable that drilling activities will come in contact with landfill gas at a range of concentrations.

Landfill gas is typically composed of methane (up to 65%); carbon dioxide (up to 40%) and various trace contaminants. Some of the minor constituents are odorous and can result in complaints from residents regarding odour nuisance.

Methane is an explosive gas in the range 5 -15% vol/vol air. Carbon dioxide is an asphyxiant and hydrogen sulphide has a TLV of lOppm in air.

Activities that take place in areas that contain potentially hazardous properties, including flammability and explosions, are covered by the Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR).

This invention is concerned with the reduction in oxygen concentration within the borehole to minimise the development of a potentially explosive mixture of landfill gas. The invention may be used on its own or with other environmental control systems such as exhaust ventilation.

1. Drilling on landfill sites inevitable involves penetration of the drilling implement into the waste mass and the possible release of landfill gas into the working environment.

2. If the concentration of methane, a major constituent of landfill gas, is between 5 and 15% vol/vol, then there is a risk of explosion if the gas encounters a source of ignition. As a flammable gas there is also a risk of combustion.

3. In order to prevent a risk of explosion, a combined strategy of elimination of sources of ignition and control of the atmosphere to prevent methane levels reaching the lower explosive limit (LEL) is required. This invention is concerned with the creation of an inert gas atmosphere to prevent the formation of an explosive mixture of landfill gas and oxygen.

4. The drilling operation will take place at the surface of the landfill and involves the use of a barrel auger which will penetrate the waste and create a void.

5. As the barrel is made of steel there is a potential for the generation of a spark if the auger comes into contact with items capable of creating an impact spark such as metal or rock. If the atmosphere in the vicinity of the spark is within the explosive range then there is a possibility that there could be an explosion or fire.

6. The landfill gas within the landfill is usually under a slight positive pressure, amounting to some 8Ombar. This pressure is due to the interaction between bacteria generating methane as a bi-product of anaerobic decomposition and physical restriction within the waste mass or as part of containment engineering e.g. lining and capping works.

The pressure differential will also reflect atmospheric conditions. There will be a larger pressure differential between the waste mass and the environment during a fall in barometric pressure. Conversely during rising atmospheric pressure the pressure differential will be lower and the rate of release of landfill gas will be reduced.

7. Under conditions of "over pressure" there will be a tendency for landfill gas to enter the borehole being drilled and be released at the surface of the borehole. It is possible that the drilling tool could be in a potentially flammable environment at various points within the borehole being drilled.

8. As landfill gas is extracted for control, by combustion or utilisation for power generation, it is possible that the waste mass could be under a negative pressure due to gas extraction operations. The "under pressure" will be of the order of up to l5Ombar and under these conditions there will be a tendency for air to be drawn into the borehole.

This is potentially a more serious condition as the presence of oxygen within the borehole could extend deep into the waste and create conditions which are within the explosive range at depth. It would normally be considered that at such depths oxygen (with no pressure differential or a slight over pressurisation) would not be present and drilling conditions would be considered to be safe.

9. In addition to the explosion risk the presence of oxygen within the waste mass has a detrimental effect on methanogenic bacteria and can also lead to conditions which can result in subterranean fires.

10. As it is not possible to control the pressure within a landfill site and as the pressure can be negative or positive as a result of site activities and atmospheric conditions, additional control measures are required during drilling activities. This invention is concerned with the reduction in the presence of oxygen in the vicinity of the drilling tool to eliminate the development of conditions which could give rise to a potentially explosive atmosphere.

11. The objective for the invention is to create within the borehole being drilled, and specifically at the point of contact between the drilling tool and objects which could result in impact spark, an inert environment due to the displacement of oxygen by an inert gas.

It is known from US 5701963 to supply inert gas via a rotating or swivel fitting 27 to hollow square rotating shaft 20 and then out presumably via by-pass pipe 31 to what may be a quick-coupling 32 which somehow then re-directs inert gas to the interior of a hollow auger 22 which has helical flights along its outer length together with holes 24 between the flights and along the length of the drill auger 22 for the oufflow of inert gas.

The present invention is concerned with barrel augering or drilling with a barrel auger wherein the drill teeth are located around the lowermost annular end face of a cylindrical tube which receives the drilled waste material. When full, the barrel auger is subsequently raised and the waste removed normally sometimes via an aperture or "window" in the cylindrical side wall of the barrel auger provided also to prevent the barrel from becoming pressurised as waste is forced into it during drilling.

According to the present invention there is provided landfill barrel auger drilling apparatus including hollow drill or stem rods or a hollow drilling string carrying a barrel auger at the lower end with the interior space of the barrel auger being in communication with the interior of the drill rods, an inert gas reservoir or supply means connected to the upper end of the drill rods and operable to supply inert gas down the hollow interior of the drill rods to the interior space of the auger barrel.

Preferably any aperture or "window" in the side of the auger barrel will have a removable closure or seal applied thereto to ensure inert gas flows to the drill teeth and which closure will, preferably, be a temporary or sacrificial seal or patch.

Also according to the present invention there is provided a method of barrel auger drilling especially suitable for drilling landfill sites, comprising using hollow drill or stem rods communicating with their interior spaces with interior space of the barrel auger and supplying inert gas down the drill rods to the barrel auger during drilling. Preferably a temporary closure is provided in the window or wall aperture of the barrel and removed to discharge waste from the barrel.

A number of preferred features of an embodiment will now be disclosed:-The inert gas will be located in pressurised gas bottles (1) on the drilling rig.

The gas will normally be nitrogen but could be carbon dioxide or one of the noble gasses such as Argon.

The inert gas will be delivered by flexible pipework (2) to the hollow drive/swivel head (3) which is capable of the acceptance and transfer of gasses or liquids. It is the drive/swivel head which provides the mechanism for turning the drilling tool.

The drilling head will be connected to the barrel auger (4) by means of hollow stem rods (5). There will be, therefore, a conduit for the delivery of the inert gas from the gas storage cylinder to the cutting tool or shoe (6) on the bottom of the barrel auger.

The barrel auger is equipped with a "window" (7) which is an orifice in the side of the barrel which prevents the barrel becoming pressurised as waste is force into it during drilling. The window can be sealed, temporarily, using a sacrificial patch (8) prior to drilling operations commencing.

The drilling rig is positioned over the borehole to be drilled in the conventional way.

A sacrificial patch will be placed over the window to effect a temporary seal on the barrel auger. Any inert gas delivered to the barrel via the hollow stem rods and drilling head can only be released from the base of the barrel auger at the drilling shoe (9).

Inert gas is added to the rods and the barrel using the regulation valve (10) on the gas cylinders. When inert gas is detected at the drilling shoe then drilling can commence. As the pressure of the inert gas within the barrel is above the expected 350mbar "under pressure" level of the landfill site, during active gas abstraction, the inert gas will displace the gasses in the immediate area of the drilling shoe. This is the area where the teeth cut into the waste and impact sparks could result in a source of ignition if a flammable environment is present. The displacement of the oxygen by the inert gas renders the area safe for drilling activities.

Drilling operations continue with additional hollow rods being added to enable the barrel auger to drill the borehole to the required depth. The supply of inert gas will be temporarily suspended during rod addition.

When the barrel auger is full of waste, the barrel auger will be returned to the surface by the incremental removal or rods.

The temporary patch will be removed prior to waste extraction from the barrel.

On completion of waste extraction from the barrel, a further temporary patch will be applied to the barrel and the inert gas supply reactivated, prior to introducing the barrel auger back into the borehole.

The invention will be described further by way of example, with reference to the accompanying schematic drawing.

A barrel auger drilling apparatus is schematically illustrated comprising a number of hollow stem or drill rods 5 screw connectable or connected with the hollows/interior spaces communicating through the screw connector region. A barrel auger 4 with teeth 6 on the annular lower end is provided and has a window 7 in its sidewall closed by a temporary closure or seal or patch 8 which is sacrificed.

The barrel auger 4 is screw connected to the lowermost drill rod 5 and communicates, axially in the region of interconnection, its hollow interior with the interior space of the drill rods 5.

The uppermost drill rod 5 has a swivel connection 3 secured thereto and flexible pipe 7 leading to a source comprising gas bottle 1 of pressurised inert gas such as nitrogen with control means at regulator valve 10.

The drilling operation is as described above.

The apparatus and method of the present application is particularly suitable for use in combination with the apparatus described in our co-pending application 0524600.4.

Claims

CLAIMS

1. A landfill barrel auger drilling apparatus including hollow drill or stem rods or a hollow drilling string carrying a barrel auger at the lower end, with the interior space of the barrel auger being in communication with the interior of the drill rods, an inert gas reservoir or supply means connected to the upper end of the drill rods and operable to supply inert gas down the hollow interior of the drill rods to the interior space of the auger barrel.

2. Apparatus as claimed in claims 1, in which an aperture or "window" provided in the side of the auger barrel has a removable closure or seal applied thereto to ensure inert gas flows to the drill teeth.

3. Apparatus as claimed in claim 2, in which the closure is a temporary or sacrificial seal or patch.

4. Apparatus as claimed in claim 3, in which the temporary seal or patch is replaceable after each drilling operation.

5. Apparatus as claimed in at least claim 1, wherein the inert gas is stored in pressurised gas bottles, which form the inert gas reservoir or supply means, and the bottles are located on the drilling rig.

6. Apparatus as claimed in any of claims 1 to 4, in which the inert gas reservoir is connected by flexible pipework to a hollow drive/swivel head which is capable of the acceptance and transfer of gasses or liquids.

7. Apparatus as claimed in claim 6 in which the drive/swivel head provides the mechanism for turning the drilling tool.

8. Apparatus as claimed in any of claims 1 to 7, in which the drilling head is connected to the barrel auger by means of hollow stem rods thus providing a conduit for the delivery of the inert gas from the gas storage cylinder to the cutting tool or shoe on the bottom of the barrel auger.

9. Apparatus as claimed in any of claims I to 8, in which the barrel auger has a "window" which in an orifice in the side of the barrel which prevents the barrel becoming pressurised as waster is forced into it during drilling.

10. Apparatus as claimed in claim 9, in which the window is sealed, temporarily, using a sacrificial patch prior to drilling operations commencing.

11. Apparatus as claimed in claim 10, in which the sacrificial patch is placed over the window to effect a temporary seal on the barrel auger such that any inert gas delivered to the barrel via the hollow stem rods and drilling head can only be released from the base of the barrel auger at the drilling shoe.

12. A method of barrel auger drilling especially suitable for drilling landfill sites, comprises using hollow drill or stem rods communicating with their interior spaces with interior spaces of the barrel auger and supplying inert gas down the drill rods to the barrel auger during drilling.

13. A method as claimed in claim 12, further including providing a temporary closure in/over the window or wall aperture of the barrel and removed to discharge waster from the barrel.

14. A method as claimed in claims 12 or 13, in which inert gas is added to the rods and the barrel using the regulation valve on the gas cylinders.

15. A method as claimed in any of claims 12 to 14, in which when inert gas is detected at the drilling shoe, then the drilling method is commenced and the pressure of the inert gas within the barrel is above expected 35Ombar "under pressure" level of the landfill site, during active gas abstraction, the inert gas displaces the gasses in the immediate area of the drilling shoe.

16. A method as claimed in any of claims 12 to 15, in which drilling operations continue with additional hollow rods being added to enable the barrel auger to drill the borehole to the required depth.

17. A method as claimed in any of claims 12 to 16, in which the supply of inert gas is temporarily suspended during rod addition.

18. A method as claimed in any of claims 12 to 17, in which when the barrel auger is full of waste, the barrel auger is returned to the surface by the incremental removal or rods.

19. A method as claimed in claim 18, in which, if necessary, the temporary patch is removed prior to waste extraction from the barrel.

20. A method as claimed in claim 19, in which on completion of waste extraction from the barrel, a further temporary patch is applied to the barrel aperture or window and the inert gas supply reactivated, prior to introducing the barrel auger back into the borehole.

21. Drilling apparatus substantially as herein described with reference to the accompanying drawings.

IENDMEN [S TO TIlE CLAIMS HAVE BEEN FILED AS FOLLOWS

CLAIMS

1. A landfill barrel auger/drill drilling apparatus including hollow drill or stem rods or a hollow drilling string carrying a barrel auger/drill at the lower end, with the interior space of the barrel auger being in communication with the interior of the drill rods, an inert gas reservoir or supply means connected to the upper end of the drill rods and operable to supply inert gas down the hollow interior of the drill rods to the interior space of the auger barrel, and in which an aperture or "window" provided in the side of the auger barrel has a removable closure or seal applied thereto to ensure inert gas flows to drill teeth on the lower end when drilling commences.

2. Apparatus as claimed in claim 1, in which the closure is a temporary or sacrificial seal or patch.

3. Apparatus as claimed in claim 2, in which the seal or patch is replaceable after each drilling operation.

4. Apparatus as claimed in any of claims I to 3, wherein the inert gas is stored in pressurised gas bottles, which form the inert gas reservoir or supply means.

5. Apparatus as claimed in any of claims I to 4, in which the inert gas reservoir is connected by flexible pipework to a hollow drive/swivel head which is capable of the acceptance and transfer of gasses or liquids.

6. Apparatus as claimed in claim 5 in which the drive/swivel head provides the mechanism for turning the drill stem.

7. Apparatus as claimed in any of claims I to 6, in which the drilling head is connected to the barrel auger by means of hollow stem rods thus providing a conduit for the delivery of the inert gas from the gas storage cylinder to the cutting tool or shoe on the bottom of the barrel auger.

8. Apparatus as claimed in any of claims I to 7, in which the "window" in the barrel drill/auger is an orifice in the upper region of the side of the barrel and one which prevents the barrel becoming pressurised as waste is forced into it during drilling.

9. Apparatus as claimed in claim 8, in which the window is sealed, temporarily, using the closure in the form of a sacrificial patch, prior to drilling operations commencing.

10. Apparatus as claimed in claim 9, in which the sacrificial patch is placed over the window to effect a temporary seal on the barrel auger such that any inert gas delivered to the barrel via the hollow stem rods and drilling head can only be released from the base of the barrel auger at the drilling shoe when drilling commences.

11. A method of barrel auger drilling especially suitable for drilling landfill sites, comprises using hollow drill or stem rods communicating with their interior spaces with interior spaces of the barrel drill/auger and supplying inert gas down the drill rods to the barrel drill/auger during drilling, and further including providing a temporary closure in/over a window or wall aperture of the barrel and which, when drilling commences, ensures inert gas flows to the teeth at the lower end and which may be removed to enable discharge of waste from the barrel.

12. A method as claimed in claim 11, in which inert gas is added to the rods and the barrel using a regulation valve on a gas cylinder.

13. A method as claimed in any of claims 11 to 12, in which when inert gas is detected at the drill, then the drilling method is commenced and the
2.

pressure of the inert gas within the barrel is above expected 35Ombar "under pressure" level of the landfill site, during active gas abstraction, the inert gas displaces the gasses in the immediate area of the drill.

14. A method as claimed in any of claims 11 to 13, in which drilling operations continue with additional hollow rods being added to enable the barrel auger to drill the borehole to the required depth.

15. A method as claimed in any of claims 11 to 13, in which the supply of inert gas is temporarily suspended during rod addition.

16. A method as claimed in any of claims 11 to 15, in which when the barrel auger is full of waste, the barrel auger is returned to the surface by the incremental removal or rods.

17. A method as claimed in claim 16, in which, if necessary, a temporary closure is removed prior to waste extraction from the barrel.

18. A method as claimed in claim 17, in which on completion of waste extraction from the barrel, a further temporary closure is applied to the barrel aperture or window and the inert gas supply reactivated, prior to introducing the barrel auger back into the borehole.

19. A method as claimed in any of claims 11 to 18, in which the sacrificed patch is sacrificed by each drilling operation and replaced prior to a further drilling operation.

20. A landfill barrel auger/drill including drill teeth at the lower end, with the interior space of the barrel auger being communicatable with the interior of drill rods to be connected thereon and for supply of an inert gas from a reservoir or supply means connected to the upper end of the drill rods and operable to supply inert gas down the hollow interior of the drill rods to the l3 interior space of the auger barrel, and in which there is an aperture or "window" in an upper region of the side of the auger barrel, and further comprising a removable closure or seal applied or appliable to such aperture or window to ensure inert gas flows to the drill teeth on the lower end when drilling commences and with continued drilling prevent pressurization of the inert gas.

21. Apparatus as claimed in claim 20, in which the closure is a temporary or sacrificial seal or patch.

22. Apparatus as claimed in claim 21, in which the seal or patch is replaceable after each drilling operation.

23. Drilling apparatus or a landfill barrel auger/drill substantially as herein described with reference to the accompanying drawing. I'-'-