Patents
Summary of Patents Obtained/Applied for by Dragon Drilling Limited
1. Improvements to Drilling Shoe
UK Patent Application No. 0523467.9
Date Applied for 18/11/2005
Patent Number 2426988
Granted 20th May 2007
Brief Description of Problem
When drilling through waste it is essential that the drilling tool is capable of cutting through a diverse range of materials for depths in excess of 60m. Items which can present problems to drilling operations included reinforced concrete and metallic objects (including engine blocks). The failure to achieve the required drilling depth can result in borehole abandonment or the installation of an inferior structure.
On sites where drilling is undertaken for replacement leachate chimneys a target pad of concrete has often been installed during cell preparation work. It is essential that drilling activities hit the target pad to ensure effective leachate management. The abandonment of drilling operations due to an inability to reach the target pad can result in drilling activities being undertaken without a target pad which requires extreme caution during drilling to prevent compromise of containment engineering.
Description of Patent
The patent is concerned with modification to the drilling shoe to improve the cutting ability and durability of the shoe.
The teeth on the drilling shoe are staggered in an alternate arrangement on the inside and outside edge of the shoe. Each tooth, therefore, only partially follows the preceding tooth but follows directly the tooth in front of the preceding tooth. The teeth cut a wider incision through the waste and the surrounding collar of the shoe acts as a reamer to reduce drag on the barrel as it is rotated. The invention, therefore, has the benefits of being able to cut through material that would be difficult with a conventional shoe. This results in less fuel being used, reduced torque at the drill head and deeper wells to be drilled. The abandonment of wells is reduced if not eliminated.
2. Use of Binding Agent to Improve Recovery
UK Patent Application No. 0606117.0
Date Applied for 29/03/2006
Patent Number 2431177
Granted 13th August 2008
Brief Description of Problem
When drilling through saturated waste it is often found that recovery of material is poor as the waste and leachate cannot be retained within the barrel during retraction. Historically the waste/leachate has been removed using a baler or the material is forced out under pressure from an air lift system. The use of an air delivery system into a landfill provides oxygen into a methane rich environment and is an unacceptable risk under the Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR).
Failure to remove the waste/leachate will prevent the installation of a satisfactory well casing and the borehole will be incapable of being used for effective leachate management.
Description of Patent
Conventional drilling practices are undertaken until satisfactory recovery is not achieved
i.e. the waste and leachate have formed a homogeneous material that is lost from the barrel when it is removed and brought to the surface.
Steel casing is inserted into the borehole and extends approximately 1m above ground level to the base where drilling has been abandoned. The steel casing is equipped with a sacrificial shoe and extended collar as described in UK patent No. 2426988, above.
A binding agent (bentonite, powdered glass, active polymer, individually or in combination, the type will depend on the waste characteristics) is added to the base of the steel casing. A Flight auger is then used to blend the binding agent with the leachate/waste until a viscous, homogeneous waste mass is created. Due to the viscous properties of the material the polymer/waste will adhere to the fins of the Flight auger and the waste/polymer will be removed when the Flight auger is retracted to the surface.
When the polymer has been removed the steel casing is advanced into the waste/leachate by rotation with the sacrificial shoe cutting through the waste in the same way as the barrel auger. The waste/leachate is then conditioned with the binding agent and removed with the Flight auger. The process is repeated until the required depth is achieved.
3. Improvement to Bentonite Seal Used for Boreholes
UK Patent Application No. 0604249.3
Date Applied for 03/03/2006
Patent Number 2433215
Granted 15th June 2007
Brief Description of Problem
On completion of drilling activities well casing is installed to facilitate the movement of gas and or leachate into the borehole. At depth the annulus between the well casing and the borehole is filled with stone or gravel. At the surface a seal is required to prevent odours escaping and also the ingress of water or oxygen. Bentonite is the material used for effecting a seal which range from 2m deep to several m deep. The bentonite is in the form of an anhydrous powder or pellets. It is added to the borehole and then hydrated by adding water. This process is not conducive to a quality standard for the seal.
Description of Patent
Water is added to a mixing vessel of approximate capacity of 200litres. The mixer has a graduated scale to 
ensure the correct amount of water is added. A specified amount of bentonite powder is then added to the mixer which is equipped with two rotating paddles to ensure a homogenous mixture. The paddles are operated from the hydraulic system of an excavator and the mixing vessel is attached to the "quick hitch" connector on the arm of the machine. As the bentonite is thixotrophic the mixture is continuously agitated until the bentonite is added to the annulus of the casing and borehole using a pouring spout.
4. Method for Collecting and Treating Gasses Released from a Borehole
UK Patent Application No. 0524600.4 Date Applied for 14/09/2006
Brief Description of Problem
During drilling activities landfill gas will be released into the vicinity of the drilling rig and workforce if the landfill gas is under pressure. The rate of release will be variable and dependent on the gas pressure within the site, atmospheric pressure and whether atmospheric pressure is rising or falling. In addition to the risk of forming a potentially explosive atmosphere in the vicinity of the rig which should be subject to a risk assessment under DSEAR, there is also the risk to operatives of being subjected to poisonous, flammable or potentially asphyxiant gasses. In addition to DSEAR a risk assessment is required under COSHH.
Description of Patent
A local exhaust ventilation system (LEV) is installed on the rig to remove gasses released from the borehole and transferring them to a point which can be safely released to atmosphere. The LEV system comprises a flexible manifold which partially encircles the borehole being drilled. The manifold has inlet ports which intercepts gasses released from the borehole and dilutes it with ambient air at a ratio of approximately 20:1. This ensures that the gas concentration within the LEV system is less than the lower explosive limit for methane.
The intercepted gasses and ambient air pass through a condensate trap before entering a hydraulically driven gas booster located on the side of the rig or a self contained LEV unit adjacent to the rig. After passing through the gas booster the methane concentration can be reduced further by a valve arrangement which passes the gasses through a venturi mixer which adds a further 200% of ambient air to the extracted gas/air mixture.
The Gasses can then be released through a vent stack which is located some 3m above ground to the rear of the rig. Carbon filtration of the off-gasses can be incorporated if odour is required to be controlled.
5. Delivery of an Inert Gas into a Borehole During Drilling
UK Patent Application No. 0608995.7
Date Applied for 10/05/2006
Patent Number 2437961
Granted 25th June 2008
Brief Description of Problem
Patent 4 dealt with sites which have a positive gas pressure which can result in the release of landfill gas during drilling activities. On sites where active gas abstraction is already employed there is the possibility that oxygen can be drawn into the borehole being drilled. The introduction of oxygen into a confined area, with a fuel source such as methane and possible sources of ignition, due to impact events with the drilling equipment requires a risk assessment under DSEAR.
Description of Patent
In order to eliminate the risk it is necessary to remove one of the items on the "fire triangle," namely the fuel, ignition source or oxygen. As it is impossible to prevent methane being present or the use of metallic drilling tools the only solution is to eliminate oxygen.
An inert gas, usually nitrogen, is delivered from storage bottles on the rig to the hollow drive swivel head. From there it passes through the hollow drill rods to the barrel auger. In order for the inert gas to be delivered to the shoe on the barrel auger the "window" on the barrel auger is temporarily sealed using a sacrificial patch. When the barrel auger is completely below ground level the sacrificial patch is worn away and the inert gas is delivered to the borehole through the window. The delivery of the inert gas is above atmospheric pressure ensuring that oxygen is excluded from the borehole.
Water Boreholes North Wales
Ground Source Heating North Wales
Landfill Drilling North Wales
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