GB2358015A - Treatment of oil-based drilling mud cuttings - Google Patents

Abstract

A method of treating oil-based drilling mud cuttings comprises the bioremediation of the cuttings in at least one container. A further method of treating the cuttings includes connecting the cuttings accommodated in at least one container to a stream of warm air heated by landfill gas. Both methods may comprise the bioremediation of cuttings in a plurality of containers which may be connectable to a stream of air warmed by heat generated from landfill gas. Pipes may also be provided to allow passage of the warm air through the cuttings. Typically, the methods take place at a landfill site. A use of landfill generated heat in the bioremediation of oil-based drilling mud cuttings is also disclosed.

Description

1 2358015 1 1 -Treatment of Drilling Mud', 2 3 The continued success of

oil winning operations in 4 the North Sea depends upon successful exploration techniques. The search for new oil reserves and the

6 development of existing fields often involves the

7 sinking of numerous exploratory boreholes. Drilling 8 muds aid in the drilling process by carrying arisings 9 to the surface and cooling and lubricating the drill equipment. Drilling muds can be either water or oil 11 based. Water Based Muds (WBM,s) are used in 12 technically simple drilling situations. Oil Based 13 Muds (OBM's) offer safety and technical advantages to 14 oil producers. The use of OBM's avoid the difficulties often encountered when using WBM to 16 drill through water sensitive structures such as 17 clays and shales. OBM also allows high pressure 18 drilling where permeability varies down the 19 stratigraphic column and is more effective as a 2 1 lubricant than WBM therefore reducing incidents where 2 the drill pipe becomes stuck in the strata. 3 4 The term Oil Based Mud relates to those muds which 5 are mineral oil based. Latterly synthetic oil has 6 been used rather than mineral oil because it was 7 originally thought they offered significant 8 environmental advantage. Those muds containing 9 synthetic oils are known as Synthetic Based Muds 10 (SBM's). 11 12 The mix of material displaced during drilling using 13 OBM or SBM is known as Oil Based Drilling Mud 14 Cuttings (OBDMC's). A number of techniques are used is to separate muds from these cuttings after drilling. 16 However, the properties of OBM and SBM ensure that 17 complete separation is impossible and cuttings retain 18 a diminished but significant amount of oil. These 19 oil-based cuttings form a considerable waste stream. 20 21 Before 1993 OBDW's were disposed of to the seabed 22 where they formed cutting piles. An estimated 1.5 23 million tonnes of material lie in cutting piles on 24 the bed of the North Sea and the uplift and treatment 25 of this material is now being seriously considered. 26 27 The marine discharge of mineral oil OBDMC was phased 28 out in the period 1993-1997. The discharge of SBM's 29 is to be phased out shortly as it has been realised 30 that synthetic oil does not readily degrade in the 31 marine environment.

3 1 Since OBM and SBM are essentially regarded as having 2 the same environmental impacts by the oil industry 3 for the purposes of this report they shall both be 4 refereed to as OBM except where otherwise specified.

Similarly the term OBDMC will mean those cuttings 6 based on either mineral oil or synthetic oil.

7 The oil industry has made the following commitments 8 with respect to the issue of OBDMC:

9 a) Quantities of OBDMC should be minimised by the 11 use of Water Based Muds (WBM) where possible.

12 13 b) The marine discharge of all cuttings with an oil 14 content exceeding 1% will be reduced to zero by is December 31, 2000.

16 17 c) Where possible cuttings should be disposed of 18 by injection into redundant wells.

19 d) Shore based treatment of cuttings is acceptable 21 providing these methods are acceptable in terms 22 of environmental impact. Such methods should be 23 sustainable and ideally enable the re-use of 24 treated material in some way.

26 e) Disposal of cuttings to landfill is 27 environmentally undesirable and, where possible, 28 should be avoided.

29 In order to establish the opinion of the oil industry 31 to the proposal a questionnaire was distributed to 4 1 members of UKOOA (UK offshore operators Association) 2 during summer 1999. The findings of this market 3 research clearly indicated a requirement for a 4 treatment method for OBDMCs that was economic and met the objectives of environmental best practice in 6 terms of reuse, recycling, sustainability and 7 environmental, impact of treatment method.

8 9 Currently OBDMC's are treated in the following ways:

11 a) Thermal Distillation: Oil operators presently 12 use a thermal distillation treatment process. It 13 is understood that 3 treatment plants are 14 currently in operation located in Aberdeen and is Peterhead in Scotland and Lowestoft in England.

16 The plants are capable of treating up to 10 000 17 15 000 tonnes of cuttings each per annum ie a 18 total of 30 - 45,000 tonnes per annum.

19 Cuttings are shipped to shore and heat-treated.

21 The oil component of the cuttings is driven off 22 and subsequently distilled and recovered. This 23 oil is then either used as fuel in the process 24 of heating or, if possible, re-used further as OBM. The resulting solid material was 26 originally intended for use in civil engineering 27 projects, for example road construction. Some 28 limited re-use of cuttings has taken place.

29 However, at the time of writing large-scale re use in civil engineering projects has not 1 occurred and, following stockpiling, the main 2 re-use is as landfill engineering material.

3 At present thermal distillation is the only 4 commercial treatment method available to the oil industry. However treatment in this way does 6 not achieve all the objectives of the oil 7 industry as described above and is expensive.

8 b) Re-injection: In some situations it is possible 9 to re-inject cuttings into redundant wells.

However the number of wells, which are suitable 11 for re-injection, is limited and it is estimated 12 that a maximum of 20% of cuttings can be 13 disposed of in this way at present.

14 Currently the main focus of the oil producing 16 industry is on the issue of cuttings piles lying on 17 the bed of the North Sea which are the product of 18 three decades of oil exploration and production.

19 A UKOOA Drill Cuttings Initiative has formed a Joint 21 Industries Project to investigate current research 22 programmes focusing on the various aspects of these 23 piles. Seventeen sub-committees have been formed, 24 each focusing on a separate aspect. One committee is responsible for a review of onshore treatment 26 technologies including bioremediation. During the 27 early part of the year 2000 all parties in the Joint 28 Industries Project will meet to discuss their 29 findings and a report will be issued. This will give a detailed account of the level of research that has 31 been undertaken.

6 1 It is understood that the following technologies have 2 been or are currently being researched:

3 4 a) Treatment by solvent extraction.

b) Treatment using supercritical fluid technology.

6 c) Treatment by biocleaning.

7 d) Treatment by use of novel surfactants (micro 8 emulsification).

9 The quantities of OBDM's which will be produced in 11 the medium term future is difficult to predict since 12 exploration activity is strongly dependent on market 13 forces, in particular the price of oil. Expansion of 14 exploration activity within the Atlantic frontier is could also lead to increasing quantities of OBDM's 16 being produced. The oil industry anticipates a 17 reduction in these quantities largely due to the 18 increased use of WBM's. However, the application of 19 WBM is limited. In addition increasing the use of re-injection as a disposal method will ensure a 21 further reduction in cuttings, which require 22 treatment. However, significant quantities of 23 OBDM's, comparable with current production tonnage, 24 will be produced annually for the foreseeable future, the majority of which will require treatment.

26 27 Research into the treatment of material derived from 28 sea bed cuttings piles is receiving a lot of 29 attention at present and the production of the Joint Industries Project Report in early 2000 will seek to 31 clarify the issues involved in cuttings treatment in 7 1 general. If treatment of these cutting piles is to 2 take place it is possible that an onshore method 3 could be chosen. This would probably result in an 4 increase in the market for cuttings treatment in the 5 coming years and a corresponding increase in research 6 into treatment technologies. 7 8 Trends in commercial scale treatment methods 9 available to oil producers are difficult to 10 anticipate. The long-term success of this method of 11 treatment will depend largely on the ability to 12 produce a re-useable product from cuttings and the 13 absence of alternative treatment technologies. The 14 presence of a more economic environmentally is advantageous technology could attract the attention 16 of those companies who produce significant quantities 17 of cuttings. The findings of market research suggest 18 that the oil industry would accept and use an 19 alternative technology providing that it fulfilled 20 their criteria. 21 22 It is an aim of the present invention to provide a 23 suitable cutting treatment process. 24 25 Several factors have ensured that the oil industry 26 has taken a lead in responsible consideration of the 27 issue of OBDMC treatment. As a result the need for 28 cutting treatment research is significant. 29 30 European statutory regulations applying to the 31 offshore oil industry commonly originate from the 8 1 findings of OSPAR, the Oslo and Paris Conventions, a 2 meeting of European Union Environment Ministers. 3 OSPAR govern all aspects of marine pollution in the 4 North East Atlantic Region. 5 6 Regulation OSPAR 92/2 states that cuttings containing 7 mineral oil based OBM should not be discharged to the 8 marine environment if the mineral oil content exceeds 9 1%. 10 11 This regulation applied to exploration wells in 1993 12 and development and production wells in 1997. In the 13 UK these requirements were inserted into the 14 Prevention of Oil Pollution Act 1971.

is 16 Since it is impossible for oil content of cuttings to 17 be reduced below 1% during on-rig separation this 18 legislation ensures that treatment is necessary for 19 the majority of OBDW's.

21 Due to the definition of oil in the Prevention of oil 22 Pollution Act 1971 synthetic oil OBM's do not fall 23 within regulation under this legislation. However, 24 since it has become apparent that synthetic oils do not degrade readily in the marine environment the oil 26 industry has decided to voluntarily impose the 1% 27 discharge standard to OBDMC1s which contain synthetic 28 oils and this will become practice from the end of 29 year 2000. The expansion of this standard to synthetic oil OBDMC's also pre-empts the 31 implementation of the IPPC (Integrated Pollution 9 1 Prevention and Control) regulations which will bring 2 into force new legislation relating to the management 3 of oily wastes in the year 2000. 4 5 The regulations and standards described herein ensure 6 that any OBDMC currently produced require either well 7 re-injection or subjection to a treatment technology. 8 Environmental policy of the oil industry relating to 9 OBDM's is strongly influenced by both statutory 10 instruments and the broad principles of environmental 11 best practice. 12 13 oil producers are keen to minimise the use of OBM's, 14 and hence the production of OBDM's, by using WBM's is wherever possible. Where the production of OBDMIs 16 is necessary the treatment and disposal should have 17 minimum environmental impact. Re-injection disposal 18 of cuttings is considered desirable as this avoids 19 the environmental impacts and risks associated with 20 shipment to shore and treatment. 21 22 Rates of cutting production exceed the capacity of 23 existing wells suitable for re-injection fivefold and 24 therefore shore-based methods of treatment are 25 required. The merits of any treatment method is 26 measured by the oil industry in terms of a 27 combination its associated economic and environmental 28 characteristics. These include treatment cost, 29 sustainability and re-use of the treated material and 30 environmental impact of the treatment process.

1 Thermal distillation methods of treatment do allow 2 limited recovery of the oil component of OBDMC and 3 some re-use of the solid component of treated 4 material. However the level of re-use and 5 sustainability is limited and the process is energy 6 intensive. Therefore it is considered that the 7 potential for the development of alternative 8 technologies does exist. 9 10 Currently the principal commercial treatment 11 available is thermal distillation. However, this 12 process is expensive, involving a process cost in the 13 region of ú180 per tonne at the treatment plant i.e. 14 not including transport and other extra costs. is 16 The oil industry considers that the important factors 17 in choice of treatment method should be cost, 18 environmental impact and sustainability. Cost is 19 regarded as a deciding factor where all other 20 considerations are equal and is important in the 21 development of alternative treatment technologies. 22 23 Research is being undertaken into the feasibility of 24 uplift and treatment of historic cuttings existing in 25 piles present on the seabed. This research could 26 ultimately result in the onshore treatment of this 27 material and the expansion of the market for cutting 28 treatment. 29 30 Bioremediation is treatment of hydrocarbon31 contaminated substances using biological processes in 11 1 order to degrade that contamination and is usually 2 associated with the treatment of contaminated soils. 3 The end products of effective bioremediation, such as 4 water and carbon dioxide, are non-toxic and harmless 5 to the environment. For this reason most methods 6 involve the excavation of contaminated material and 7 the introduction of an aerobic environment which is 8 achieved by the implementation of an engineered 9 remediation system. 10 11 Most hydrocarbon- contaminated soils and other 12 substances, including OBDMC's, contain large 13 populations of the microorganisms, but are not 14 usually in an environment that favours rapid 15 biodegradation of those contaminants. Microbial 16 activity can be inhibited by adverse environmental 17 conditions, such as inappropriate pH, temperature, 18 lack of mineral nutrients, and lack of oxygen. 19 Methods of bioremediation seek to encourage 20 favourable conditions for biodegradation of 21 pollution. 22 23 According to one aspect of the present invention 24 there is provided a method of treatment of OBDMC's 25 including the application of bioremediation to 26 cuttings held in containers. 27 28 In another aspect of the invention cuttings are 29 connected to a stream of warm air heated by landfill 30 gas to aid a treatment process. 31

12 1 Most preferably these aspects of the invention are 2 combined to provide a method of treatment of OBDMCs 3 wherein bioremediation of cutting takes place in 4 containers which are connectable to a stream of warm air which are capable of being heated, peferably by 6 landfill gas generated heat, to aid the remediation 7 process.

8 9 Preferably a system of pipes allows the passage of warm air through the system.

11 12 Preferably the method includes an initial step of 13 bioaugmentation of bacteria and/or nutrient addition.

14 Preferably the method takes place on or at a landfill 16 site.

17 18 The viability of bioremediation as a treatment for 19 OBDM's in several key areas meets the objectives of confirming that the methodology achieves the aims of 21 the oil industry. The method of the present invention 22 tests various specific technological parameters which 23 affect the performance of the system.

24 The following factors of the technology can be 26 assessed using the method of the invention:

27 28 a) Commercial scale potential.

29 b) Environmental impact and sustainability.

c) The potential for after-use of treated material.

13 1 d) Technical feasibility of the technology in terms 2 of engineering, biological systems and 3 logistics.

4 e) Economic potential.

6 Several parameters control the level of hydrocarbon 7 biodegradation, which is achieved in any 8 bioremediation system. The main parameters are:

9 Degree of mixing with organic based materials.

11 Hydrocarbon contaminated material usually requires 12 mixing with other materials for a number of reasons:

13 14 a) To encourage improved physical structure to is allow drainage and passage of oxygen.

16 17 b) To improve the range and quantity of micro 18 organisms.

19 c) To make the material more handlable for the 21 treatment method adopted.

22 23 d) To act as a buffer for possible deleterious 24 properties of the contaminated material e.g. pH.

26 Typical additives would include top-soil and shredded 27 wood.

28 29 Diversity of micro-organism species.

A wide variety of micro-organisms are capable of 31 hydrocarbon oxidation. Some hydrocarbon-contaminated 1 materials allow the free development of cultures of 2 many different species of micro-organism which are 3 capable of this biodegradation. Other materials may 4 inhibit microbial growth. The additives present in 5 OBDW's, for example metals, corrosion inhibitors and 6 biocides have the potential to limit diversity of 7 these species and the extent of their populations. 8 Appropriate bacterial cultures can be developed and 9 grown in the laboratory. 10 11 Temperature of the bioremediation system. 12 Most hydrocarbon degrading species flourish in warm 13 conditions, usually between 25'C and 30 OC. Colder 14 temperatures, such as those common throughout the UK 15 in the winter months, can limit microbial metabolism 16 within a bioremediation system. This can result in a 17 loss of performance during these months. 18 19 Supply of oxygen to the bioremediation system. 20 Aerobic bacteria are most efficient in degrading 21 hydrocarbon substances. For this reason oxygen 22 supply must not be limiting within a bioremediation. 23 24 Concentration of inorganic nutrients. 25 A C:N:P:K ratio (carbon/ nitrogen /phosphorus /po tas s ium 26 ratio) of 100:10:1:1 is required to sustain 27 microbial growth and multiplication. Bacteria within 28 a bioremediation system degrade hydrocarbon 29 substances by consuming them. However some 30 hydrocarbon contaminated materials can support only 31 small numbers of bacteria.The addition of extra 1 nutrients can amend the C:N:P:K ratio, boost 2 bacterial population and increase the level of 3 biodegradation.

4 Preferably the present invention establishes the 6 optimum conditions for the bioremediation of OBDMC by 7 testing the effects of the parameters set out above.

8 Specifically this will involve:

9 a) Selection of a suitable material for mixing with 11 OBDMC's and undertaking of a laboratory based 12 treatability study to find the mixing ratio 13 which optimises the efficient handling of the 14 material whilst maximising biodegradation of the hydrocarbon component.

16 17 b) Assessment of micro-organism diversity and 18 population within the bioremediation system and 19 laboratory and experimentation to identify and develop microorganism cultures which maximise 21 rates of hydrocarbon degradation in the field.

22 23 c) Introduction of an inorganic nutrient supply to

24 the bioremediation system on the field scale following the undertaking of a laboratory based 26 treatability study. A C:N:P:K ratio of 27 100:10:1:1 will be sought in the field so that

28 bacterial degradation of the hydrocarbon 29 component of OBDM's is optimised.

1 d) Introduction of a heat source to the

2 bioremediation system on the field scale and

3 assessment of the benefit of its effect.

4 e) Introduction of an engineered oxygen supply to

6 the bioremediation system on the field scale and

7 assessment of the benefit of its effect. It is 8 intended that a supply of heat and oxygen be 9 combined by providing a source of warm air to the system. The air will be heated by passing 11 over flared landfill gas.

12 13 In addition to those objectives listed above there 14 are two other technical objectives of the proposed is pilot project:

16 17 f) Design and development of an engineered 18 bioremediation system that allows the effective 19 treatment of OBWC's on the field scale.

21 g) Assessment of the environmental impact and 22 sustainability of bioremediation as a method of 23 treatment for OBDMC.

24 The objectives listed above will be achieved by 26 undertaking the proposed project in a phased manner.

27 This will enable the development, refinement and 28 evolution of the bioremediation system through 29 laboratory and field experimentation.

Laboratory scale treatability studies determine the 31 optimal hydrocarbon degradation rate by manipulation 17 1 of the variables described. An experimental approach 2 on the field scale will complement the treatability 3 study and test the validity of these findings on the 4 large scale. During these phases of experimentation 5 the effect of variation of each of these attributes 6 will be determined and conclusions drawn about their 7 relative contribution to hydrocarbon degradation. 8 9 Once the process has been completed so that the 10 process of biodegradation is optimised the findings 11 of the project will be reported upon. Conclusions 12 will be made regarding the specific technical 13 objectives listed above and also the broader project 14 objectives listed previously. 15 16 Example 17 A pilot project in Tarbothill Landfill Site in 18 Aberdeen is an active landfill site, operated by 19 Shank Waste Solutions, which receives a variety of 20 waste streams from both local and national s.ources. 21 22 The project involves the engineering of six large 23 RoRo containers (Roll on, Roll off containers used in 24 the transport of wastes with a capacity of 25 approximately 35 cubic metres). These containers 26 will be connected by piping to a source of warm air 27 derived from a landfill gas flare stack. Slotted 28 pipes will be installed within the containers so that 29 the warm air can be distributed within them during 30 the field experimental stage of the project. An 31 engineered heat exchange system will enable the

18 1 production of sufficient quantities of hot air from 2 the flare stack. A schematic diagram of the proposed 3 heating system is shown on Figure 1.

4 During the field scale trials described below the

6 maximum amount of base oil will be removed from the 7 OBDMC before mixing to the optimum consistency.

8 Appropriate methods of achieving this separation will 9 be investigated. An industrial scale centrifuge may be required for this purpose.

11 12 The various phases of the Project are set out in 13 Figure 2 and are described in more detail below.

14 Phase 1 Treatability Study 1 16 This phase will take place in the laboratories of 17 Napier University. OBDM's are produced as sludge 18 like material and are unfit for direct treatment by 19 bioremediation. Therefore cuttings treated during the pilot project will require initial mixing. An 21 initial treatability study will be undertaken and 22 will seek to:

23 24 a) Determine the optimum consistency and level of mixing with topsoil and wood chippings so that a 26 suitable consistency for hydrocarbon breakdown 27 is reached. This will involve systematic mixing 28 on the laboratory scale. When a structure is 29 attained which has reasonable permeability and porosity and potential for bacterial growth the 31 pilot project will proceed.

19 1 2 b) Assess the effect of bioaugmentation and 3 nutrient addition on rates of hydrocarbon 4 biodegradation.

6 Phase 2 Field Trials 1

7 Based on the findings of Phase 1 field scale

8 experimentation will be carried out to establish 9 whether bioaugmentation (the addition of laboratory grown bacterial cultures to the system) and nutrient 11 addition enhances the degradation rate of hydrocarbon 12 in OBDM's. Augmenting three of the containers, 13 adding nutrients to two and leaving the remaining one 14 untreated will achieve this. All other factors, including heating with landfill gas, will be kept 16 equal so that any differences in performance are due 17 to bioaugmentation and nutrient addition alone.

18 19 Phase 3 Treatability Study 2 A second treatability study phase of the project will 21 explore the use of a variety of alternative materials 22 as a mixing media for OBDMIs. This will seek to 23 establish alternative, more sustainable, mixing media 24 than topsoil. These substances might include compost or sand although their exact nature will be decided 26 during the course of the project. A mix will be 27 developed which maximises the rate of biodegradation 28 on the laboratory scale.

29 31 1 Phase 2 Field Trials 2 2 A second phase of field scale experimentation will 3 seek to establish whether the mix developed during 4 the phase 3 treatability study is effective in the 5 biodegradation of hydrocarbons in OBDMC on the field 6 scale. 7 8 Throughout the experimental stages of the project the 9 system will undergo chemical and biological analysis 10 to determine the effectiveness of the system in terms 11 of the extent of biodegradation of the hydrocarbon 12 component of the material treated in the system. In 13 addition the system will be monitored for various 14 other parameters related in particular to 15 environmental impact. This will include monitoring 16 for respiratory gases produced from the microbial 17 degradation process, volatile hydrocarbons that may 18 be driven off particularly by the warming of the 19 cuttings and the release of bio-aerosols. 20 21 This level of testing, which constitutes a 22 considerable proportion of the overall cost, is 23 considered to be important to the findings of the 24 project. The project is essentially designed to prove 25 the viability of the technology on a field scale and 26 it's potential for commercial exploitation. However 27 in order to establish the latter it is considered to 28 be important to establish how the technology works 29 thereby allowing the controllable parameters such as 30 proportion of cuttings in the mix, temperature, 31 moisture content, nutrient content and level of

21 1 microbial activity to be varied. These will dictate 2 the ultimate costs of the treatment method and 3 determine the commercial viability of the process. In 4 addition it essential to establish what adverse 5 environmental impact the technology has, if any, to 6 convince the oil industry that it satisfies their 7 criteria. 8 9 In order to produce sufficient quantities of organism 10 rich solutions for the augmentation of the process it 11 is proposed to install simple plant on site. 12 Mobile mixing plant (concrete mixer) for initial 13 mixing of cuttings soil and wood chips is anticipated 14 to be required for 1-2 weeks at the beginning of each 15 of the three phases. in addition this equipment will 16 be necessary if mixing of batches is required at 17 other times. 18 19 It is proposed to use wood chips in the mix. It is 20 proposed to process these on site from woods 21 stockpiled from incoming wastes. The project will 22 hire a shredder for this purpose. 23 24 After processing it is anticipated that the final 25 product will be screened. The project will hire a 26 screening plant for this purpose. 27 28 In order to maintain optimum moisture contents it 29 will be necessary to add water at various times. The 30 project will hire small a small pump for this 31 purpose.

1 Handling of the liquid sludge may well be critical 2 aspect of the trial. The project will hire 3 specialised sludge pumping plant and evaluate it in 4 comparison to other handling methods.

6 It is proposed to investigate the potential for the 7 removal of oil from the sludges. Specialist 8 centrifuge equipment will be used for this purpose.

9 It is anticipated that the undertaking of this project will assist in the development of a 11 commercial treatment method for three related waste 12 streams i.e.

13 14 a) Large scale commercial treatment of OBDM's is currently being produced in North Sea oil 16 winning operations 17 18 b) Large scale commercial treatment of historic 19 OBDMC previously disposed of at sea and forming piles on the seabed around installations.

21 Current proposals for these include for the 22 removal and treatment on-shore. 23 24 c) Large-scale commercial treatment of exhausted OBM's. on-rig

separation techniques allow the 26 recovery and re-use of OBM's. However, after 27 several cycles of re-use the OBM's eventually 28 lose the characteristics. which aid the drilling 29 process and become exhausted.

23

Claims (8)

1 CLAIMS

2 3 1 A method of treatment of OBDMCs wherein the 4 method includes the application of bioremediation to OWM cuttings held in at least 6 one containers.

7 8

2. A method of treatment of OBDMCs wherein the 9 method includes the connection of OWM cuttings in at least one container to a stream of warm 11 air heated by landfill gas to and a treatment 12 process.

13 14

3. A method as claimed in claim 1 or claim 2 is wherein bioremediation of cuttings takes place 16 in containers which are connectable to a stream 17 of warm air and capable of being heated by 18 landfill gas generated heat. to aid the 19 remediation process.

21

4. A method as claimed in any of the preceding 22 claims wherein pipes allow the passage of warm 23 air through cuttings.

24

5. A method as claimed in any of the preceding 26 claims wherein the method includes an initial 27 step of bioaugmentation of bacteria and/or 28 nutrient addition.

29 24 1

6. A method as claimed in any of the preceding 2 claims wherein the method takes place on or at 3 landfill site.

4

7. Apparatus for use in a method as claimed in any 6 of the preceding claims.

7 8

8. Use of landfill generated heat in bioremediation 9 of OBDMCs.