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Disclaimer I am not an expert in UCG Talk uses public sources with added interpretation/opinion by author Contains more detail than can be covered here.

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Presentation on theme: "Disclaimer I am not an expert in UCG Talk uses public sources with added interpretation/opinion by author Contains more detail than can be covered here."— Presentation transcript:


2 Disclaimer I am not an expert in UCG Talk uses public sources with added interpretation/opinion by author Contains more detail than can be covered here May be useful later A lot of “ Average ” numbers used in calculations Results only indicative at best Use with extreme caution Listener beware Be critical

3 Introduction to UCG Some generalities

4 What is Underground Coal Gasification UCG Burn coal insitu and recover a low btu gas at surface link air injection hole and gas recovery hole Burn can move towards air injection hole (counter current circulation ) or in same direction as air towards gas recovery hole (co current circulation) Courtesy ErgoExergy Coal seam

5 Putting UCG in perspective Coal gasification and liquefaction at surface are commercial processes around the world Over 30% of petroleum used in South Africa is produced from coal by SASOL UCG involves similar reactions but in an environment that is harder to test and control Coal

6 Surface and Underground Coal Gasification produces a low btu gas of varying composition depending on conditions

7 Gas from UCG A very Unconventional Gas UCG Gas is multi gas composition has low btu contains moderate CO 2 content Approximate comparisons Example from Hanna USA

8 A brief History of UCG Much of the early research was Behind the Iron Curtain Russia (Former Soviet Union = FSU ) Various methods developed in the FSU

9 History of UCG Initial Development Began Behind the Iron Curtain  With vast coal reserves and in 1930’s limited natural gas reserves; FSU aggressively investigated opportunities for UCG  A lot of detailed science and experience stayed behind the Iron Curtain till 1970’s  FSU developed a number of techniques and gasified different ranks of coal in different geological environments but generally low rank coal at shallow depth  Important to develop a pathway from air injection hole though burn zone to gas recovery hole. Initially FSU tunneled to connect injection and gas recovery holes later they used directional drilling along seam  FSU used forward and counter current directions for injected air flow ie burn progresses in same direction as injected air or progresses towards injected air  Trials in FSU in steep dipping seams using co current combustion (Juschno-Abinsk) were moderately successful.

10 Main Locations of Russian (FSU) UCG

11 Summary of Russian (FSU) Data from main locations Another version compare later

12 Early FSU Methods for UCG in Dipping Seams  Initial linkage injection hole to gas removal hole was a tunnel  Injection and gas removal holes drilled down dip in coal seam  Burn zone moves up dip with coke and rubble collapsing down dip into cavity  Roles of holes periodically reversed to ensure even burn along linkage Bulldoze alluvium to seal fractures limit gas leak Kreinin and Revva (1966) Cavity development in steep dipping seams is similar to fixed bed surface gasification (Lurgi gasifier) with air injected at the bottom and fresh coal fed by gravity at top.

13 FSU Method for UCG in Steep Dipping Seams Initial injection holes vertical Later holes drilled below coal seams Gas recovery holes drilled in seams Vertical water recovery holes drilled into cooled rubble zone An overview of Soviet effort in underground gasification of coal Gregg et al 1976

14 FSU Design for UCG in Steep Dipping Seams Kreinin and Revva (1966)

15 FSU UCG Steep Dipping Seams Developed early version of horizontal drilling to connect injection and gas recovery holes Second stage air injection holes drilled in footwall clear of subsidence Kreinin and Revva (1966)

16 FSU also developed UCG in Horizontal Seams Generally at shallow depth using vertical holes 800’C Coal seam Pyrolysis products Water influx ’Ç Overburden Pyrolysis products Gas losses Rubble Gas recovery hole 150’C Injection air

17 FSU Vertical Drill Pattern for horizontal seams Plan views of developing geometry by stage Air injection holeGas recovery hole Stage 1 Form linkage along line of vertical holes counter current burn Stage 2 Complete linkage using counter current flow Stage 3 start parallel line of holes link to first row of holes using co current flow Burn progression Gas flow

18 FSU Vertical Drill Pattern into Horizontal Seam Plan view of air injection and gas recovery holes as development progresses Gregg et al 1976 An Overview of Soviet Effort in Underground gasification of Coal

19 Recent Development in UCG geometry

20 Width height ratio about 6/1 therefore seam thickness controls amount of resource around each hole Gas moves in same direction as injected air through previous burn zone to recovery hole Recent Important Development in UCG Geometry CRIP (Controlled Retractable Injection Points) Makes use of modern horizontal drilling techniques applied to horizontal seams Coal Seam Must drill along base of seam

21 Development of the CRIP Method (Controlled Retractable Injection Points) Centralia Washington (Toni 1) 1983 Hanna Wyoming (Rocky Mountain RM1) 1987  Tests showed that CRIP process is capable of producing consistently high quality gas from single injection hole for extended time.  CRIP in horizontal injection hole, has advantage over vertical injection holes. Maintains air low in seam for optimal resource recovery.  Provides a method for re-ignition of coal at different locations when gas quality declines as maturing reactor begins to interact with overburden.  CRIP in sub-bituminous and lower rank coals has reached a level where remaining technical uncertainties and risk to commercial development are reduced.  RM1 CRIP module operated for 93 days and gasified over 10,000 tonnes of coal, Gas average dry product heating value of 253 kJ/mol (287 Btu/scf=2554 Kcal/m^3).

22 CRIP adapted by British Gas ( Knife edge CRIP)  Gas production horozontal holes up to 500 metres along seam drilled parallel to horizontal oxygen+steam injection holes  Injection started with a vertical hole  Injection holes completed with slotted liner + ignition source which is pulled back along hole.  Gas flows thru coal from injection hole to production hole  Prior to ignition it is possible to hydro frac the injection hole ??  Orientation of injection and gas recovery holes drilled to take advantage of cleat geometry ??

23 Development of UCG Ergo Exergy, εUCG technology  Company adapted and patented FSU methodology, but not much published on εUCG process and Ignition and Injection procedures.  May be using vertical holes  Don’t know differences between FSU UCG, εUCG and CRIP  Don’t know methods used in εUCG to establish reliable connections between injection and production wells.  Don’t know how εUCG compares with CRIP in terms of reproducibility, reliability, cost

24 UCG Activity Around the World

25 UCG Activity around the World in

26 UCG Activity around the World Interest in UCG spread around world following increase in oil and gas prices A lot of expertise is still in FSU Friedmann Burton Upadhye Lawrence Livermore National Laboratory 2007 For CO 2 storage

27 “Best Practices in Underground Coal Gasification”, E.Burton, J.Friedman, R. Upadhye, Lawrence Livermore Nat. Lab., DOE Contract No. W-7405-Eng-48 Evolution of Test Site Experience Progression Trying deeper seams Trying thinner seams Minimum thickness Trying deeper and thinner

28 United States More than 30 experiments between 1972 and 1989 Introduced Continuous Retraction Injection Point (CRIP) process. Pilots conducted at Hanna Wyoming Hoe Creek Wyoming Centralia Washington UCG Activity around the World Extracts from from Potential for Underground Coal Gasification in Indiana Phase I Report to CCTR Evgeny Shafirovich, Maria Mastalerz, John Rupp and Arvind Varma1Purdue University, September 16, 2008 and other sources

29 Friedmann Burton Upadhye Lawrence Livermore National Laboratory 2007 US UCG Projects Hanna

30 Experience from the Hanna UCG Project Wyoming 1973 One of the earliest tests outside FSU

31 Data from the Hanna Project Air injection rate drives gas production Air injection red Gas production black 900 Kcal/m^ Kcal/m^3

32 Canada Ergo Exergy Technologies Inc (Montreal) is providing UCG technology to several customers in different countries They use εUCGTM technology, apparently based on FSU UCG technology; may include recent approaches developed in FSU Laurus Energy is developing commercial projects, based on εUCGTM technology, in Canada with projects in Alberta and Nova Scotia. UCG gas from coal deposits in vicinity of two coal- fired power plants in Nova Scotia, can be co-fired with imported coal and petcoke to reduce SOx emissions and provide large fuel cost savings. A gas-fired power plant in Alberta may switch to UCG gas produced from deep adjacent coal resources. This could significantly reduce electricity production costs. Total capacity fueled by UCG in above projects is planned to exceed 1,000 MWe. Laurus is planning several other industrial UCG plants in Canada to produce chemicals and liquid fuels Synergia Polygen Ltd UCG (ISCG) pilot. Pilot targets Manville coals Swan Hills area 7 seams in section with target seam 4 to 5.2 metres thick.

33 Synergia Polygen Swan Hills Laurus Energy Km Location of UCG projects in Western Canada

34 Australia Linc Energy Ltd UCG trial Chinchilla, Queensland using Ergo Exergy’s technology Project ( ) demonstrated feasibility to control UCG process Gasified coal at 130 metres depth seam thickness 10 metres Gasified 35,000 tons of coal, with no environmental issues. 80 million Nm3 of gas produced at MJ/m3 ( BTU/sft) Maximum gasification rate 80,000 Nm3/hr or 675 tons coal/day Gas production over 30 months high quality and consistency of gas 95% recovery of coal resource; 75% of total energy recovery ; 9 injection / production vertical wells; 19 monitoring wells; average depth of 140 m; Since 2006 Linc Energy Ltd co-operate with Skochinsky Institute of Mining Moscow; acquired a 60% controlling interest in Yerostigaz, which owns the UCG site in Angren (Uzbekistan) Cougar Energy Ltd plans pilot burn for a 400MW combined cycle power project Carbon Energy PL plans 100-day trial to show commercial feasibility of the CRIP UCG process Chinchilla probably air dried analysis of sub bituminous coal

35 Linc Linc Energy Limited Presentation 2006 Level 7, 10 Eagle Street BRISBANE, QLD 4000 Ph: (07) Location Chinchilla Project

36 India India has fourth-largest coal reserves in world UCG will be used to tap those India coal reserves that are difficult to extract by conventional technologies. Oil and Natural Gas Corporation Ltd. (ONGC) and Gas Authority of India Ltd. (GAIL) plan pilot projects using recommendations of experts from Skochinsky Institute of Mining in Moscow and Ergo Exergy (Khadse et al., 2007). Scheduled production is 2009 UCG Lignite coal for electric power. It is also reported that AE Coal Technologies India Pvt. Limited, a company belonging to the ABHIJEET GROUP of India, is implementing UCG Projects in India Western Europe A number of UCG tests have been carried out A significant difference of these tests is depth of seams ( m) In , UCG project was conducted by Spain, UK and Belgium at “El Tremedal” (Spain) In 2004, DTI (UK) identified UCG as one of the potential future technologies for development of UK's large coal reserves New Zealand Solid Energy New Zealand Ltd, company founded on mining coal in difficult conditions plans to use Ergo Exergy’s εUCGTM technology for low cost access to un-minable coal Japan University of Tokyo and coal companies are conducting technical and economic studies of UCG on a small scale are planning a trial soon

37 South Africa Eskom, A coal-fired utility, is investigating UCG at its Majuba 4,100 MW power plant Ergo Exergy provides technology to build and operate a UCG pilot which was ignited in 2007 Project will be expanded in a staged manner, based on success of each preceding phase Project currently generates ~3,000 m^3/hr of flared gas. Volumes will increase to 70,000 m^3/hr early next year and be piped to power station before eventually rising to 250,000 m3/hr Some 3.5 million m^3/hr will be supplied to power station at full production that is anticipated around 2012 Eskom is moving ahead with the next phase UCG project. Declining coal reserves is one of the biggest problems facing Eskom, as it struggles to overcome a power shortages since January. Eskom plans to pipe greater volumes of gas to Majuba power station to help it become more coal efficient. Coal from nearby mines supplies the Majuba Power Station but transportation costs are high because of bad roads. UCG utilizes unmineable coal resources. Eskom estimates there are an additional 45 billion tons of coal suitable for UCG in the country, excluding coalfields in KwaZulu-Natal province. Eskom produces about 95% of South Africa's electricity and is spending billions of dollars to expand generating capacity to meet demand from country's growing economy.

38 Eskom Power Plants Majuba plant

39 China China has largest UCG program Since late 1980s, 16 UCG trials previous or current Chinese UCG trials utilize abandoned coal mines Vertical boreholes drilled into abandoned galleries to act as injection and production wells Commercialization Xin Wencoal mining group has six reactors with syngas used for cooking and heating A project in Shanxi Province uses UCG gas for production of ammonia and hydrogen HebeiXin’ao Group is constructing a liquid fuel production facility fed by UCG ($112 million); 100,000 ton/yr of methanol and generate 32.4 million kWh/yr Researchers investigated the two-stage UCG process proposed by Kreinin (1990) for production of hydrogen, where a system of alternating air and steam injection is used. Experiments, conducted in Woniushan Mine, Xuzhou, Jiangsu Province, prove feasibility to use UCG for large-scale hydrogen production (Yang et al., 2008).

40 Rick Wan, Ph.D XinAo Group ( P. R. UCG in China

41 Long Tunnel 、 Large section two Stages Rick Wan, Ph.D XinAo Group ( P. R. China System

42 Gasification Reactions and Implications for Gas Composition

43 Gasification Reactions and Implications for Gas Composition Gas composition depends on reactions initiated by introduction of Air or Oxygen and availability of Hydrogen ( in part from coal mainly from formation water)  As coal burns it provides energy to produce combustible gases CO, H and CH 4  As gas is extracted back through burn cavity different reactions take place based on temperature amount of water infiltration oxidizing or reducing conditions  Actual thickness of burn zone is thin ( <0.5 metres) because of low conductivity of coal  Rate of advance controlled by rate of injection of Air or Oxygen to drive process  1 cubic metre of gas requires about 0.4 Kg of coal or 1 tonne coal produces 2500 m^3 gas

44 Gasification Reactions and Implications for Gas Composition Changes in composition transverse to burn direction Equilibrium Calculation for Coal Gasification (From Stephens, 1980). Provides surface area for gasification reactions An Overview of Soviet Effort in Underground Clasification of Coal Gregg et al (1976)

45 Combustion Zone 2/ Combustion Zone Oxidation zone exothermic Temperature rising Coal consumed C+O 2  CO 2 C+1/2 O 2  CO 2CO+O 2  2 CO 2 CH 4 +O 2  CO 2 +2H 2 O Gasification Zone 3/ Gasification Zone Reduction zone Endothermic Temperature falling until reactions stop no more coal consumed C+CO 2  2 CO H 2 O+C  CO+H 2 Reduction Zone 4/ Reduction Zone Gas transport zone Lower temperature Shift conversion reaction reduces heat value of gas CO+H 2 O  CO 2 +H 2 methanation C+2 H 2  CH 4 General Gasification Zones in Burn Cavity along burn direction Initiation of cavity using counter current flow De-volatilization zone 1/ De-volatilization zone Adapted from

46 De-volatilization zone Methane evolved from coal is consumed CH 4 +O 2  CO 2 +2H 2 O -891 kJ/mol Reaction provides heat in advance of main burn front UCG Relationship of Reactions to Location in Burn Zone Un-affected coal De-volatilization zone

47 Combustion zone Burning at coal face provides heat Oxidation C+O 2  CO Kj/mole Partial Oxidation C+1/2 O 2  CO -123 Kj/mole Main volume of heat generation zone is surprisingly thin CO 2 produced to provide energy to make combustible gases UCG Relationship of Reactions to Location in Burn Zone Combustion zone

48 Gasification zone As Oxygen is used reduction of CO 2 occurs Boudouard Reaction C+CO 2  2 CO Kj/mole also reversal 2 CO+O 2  2 CO 2 Heat is used up to generate a gas rich in CO The Boudouard Reaction is sensitive to chemistry of ash rubble forming in burn cavity Gasification zone UCG Relationship of Reactions to Location in Burn Zone

49 Reduction zone Water shift reaction steam enters burn zone H 2 O+C  CO+H Kj/mole Shift conversion reaction CO+H 2 O  H 2 + CO Kj/mole Hydrogenating gasification C+2 H 2  CH 4 –87.5 Kj/mole methanation CO+3H 2  CH 4 + H 2 O -206 Kj/mole Reactions use heat Temperature falling Reactions use water entering cavity to convert CO to H resulting in a lower heat value gas Reduction Zone UCG Relationship of Reactions to Location in Burn Zone

50 Produced Gas Composition Implications on Processes

51 Air injection Oxygen+Steam (?) injection Summary of Gas Composition for World Projects N ?

52 Gasification at Gas Composition using Air or Oxygen Injection Increasing CO 2 production

53 Implications of Counter Current and Co Current Burn Geometries Co Current (forward) Geometries  Co Current more oxygen in channel  Best for continuing gas production  In the CRIP method channel A to B is a slotted liner in a hole An Overview of Soviet Effort in Underground Clasification of Coal Gregg et al (11976)

54 Implications of Counter Current and Co Current Burn Geometries Counter Current (reverse )  Counter Current Develops small channel with constant diameter  Is less susceptible to plugging caused by coal swelling or plugging by liquids.  Ideal for forming high permeable channels in coal during initial burn but results in poor use or resource for continued burn Implications for gas composition (??) In Co Current method product gas stays hotter moves over char rubble zone maybe more reverse shift reaction CO+H 2 O  H 2 + CO 2 In Counter Current method gas cooler may pick up CH 4 form coal may be more CO rich

55 Gas Composition some Basic Controls using Mass Balancing Some analyses of product gas illustrate basic mass balances of gasification process Note results are illustrative a number of hidden assumptions

56 Gas composition some Basic Controls Carbon  Amount of carbon in produced gas indicates amount of coal consumed per cubic metre of gas recovered = Amount A  Based on heat value of coal (HVB coal with 45% FC; 22 Mj/Kg; 6% H arb) and heat value of gas (6 Mj/Kg) it is possible to calculate minimum amount of coal required = amount B  It is then possible to calculate a thermal efficiency for coal to gas conversion = B/A

57 Gas composition some Basic Controls Oxygen  Pressure of injected air less than hydrostatic pressure to limit gas loss control water inflow  Therefore seam depth influences injection pressure P 1  Amount of oxygen in product gas indicates amount of air being injected per m^ 3 product gas (assuming air not oxygen)  Rate of air injection controlled by P 1 (=seam depth) Permeability Distance between injection and recovery holes and P 2 (Pressure maintained in recovery hole)  Gas recovery rate controlled by P 2 Low P 2 provides high rate but risk high water inflow  Rate of air injected controls rate of burn but must match burn cavity volume

58 Gas Composition some Basic Controls Hydrogen Amount of H in product gas indicates how much water other than that in coal is required to make gas ( ie inflow or injected) Hydrogen in coal is present as  H in ultimate analysis (dry basis) (decreases with increasing rank 6% - 1%)  H in water in Equilibrium Moisture (decreases with increasing rank 4% - 0.1%)  H in water Surface Moisture(variable 0% - 2%) All these Coal sources of hydrogen tend to decrease as rank increases but total amount of H is never sufficient to provide all H in product gas Excess is expressed as m^3/tonne coal gasified) Need infiltration or steam injection of about 1 m^3 water per tonne coal gasified

59 Gas Composition some Basic Controls Hydrogen The uneasy balance  Gasification requires more H (water) than is available in coal Amount increases with rank  High injection pressure may increase subsidence into burn cavity causing increase gas loss (possibly higher heat value) Therefore inject at below hydrostatic pressure  Increase water inflow will degrade heat value of gas especially if seam < 2 metres thick  Using water from surrounding rock draws down hydraulic head  Inflow brine brings alkalies into chemical reactions Mj/m^3 Seam thickness metres Excess water Decrease heat value Thinner seam greater heat loss

60 Gas Composition some Basic Controls Hydrogen The uneasy balance  excess water increases CO2 content of gas and decreases H 2, CO and CH 4 contents  Decrease in seam thickness causes decrease in H 2, CO and CH 4 contents at constant water inflow An Overview of Soviet Effort in Underground Classification of Coal Gregg et al (1976)

61 Temperature Kelvin Vapour Water Inflow Implications As excess water enters cavity it is heated from insitu to burn cavity temperature (40C to 800C ?) Water is converted to high density vapour. There is some expansion which produces extra pressure in burn cavity This may increase permeability connection to surrounding rocks and increase gas loss Martin Chaplin October, 2008

62 Water Contamination Concentrations of benzene, total phenols, total PAH, at Chinchilla, Hoe Creek and Carbon City. Condensate water and oil, second and third sets, show high levels of these compounds are produced, but groundwater levels below background (red line) (Blinderman and Jones, 2002). Based on experience in FSU and Australia Important to keep injection pressure just below hydrostatic pressure This ensures some water inflow which keeps burn chamber hot and oil compounds in vapour phase also forms a steam jacket around burn cavity acts as a dynamic seal Chinchilla

63 Coal and Ash Influence on UCG

64 Rank Influences on Gasification Reactions  During pyrolysis volatiles and moisture are lost from coal causing shrinkage of over 40% for low rank coals 35% to 40% for bituminous coals and 5% to 10% for anthracites, High volatile+moisture content = less residue char volume to gasify and increased burn cavity volume.  UCG works best on low rank, non-caking coals (lignite sub-bituminous) (Burton et al., 2006) These coals tend to shrink upon heating, enhancing permeability and connectivity between injection and production wells.  low rank coals have high reactivity and high moisture and volatile contents.  UCG works on some bituminous coals however they tend to swell (plasticize) (Stephens, et al., 1985) which may affect permeability required for injected gases.  Tests on bituminous coals at Lisichansk, Russia, and Princetown, USA.  In FSU, one test using semi-anthracite (Thulin), which was not a success.  Gasification of higher rank coals will require more water injection higher combustion temperatures. Sources File pdf Best Practices in Underground Coal Gasification Burton Friedmann Upadhye Lawrence Livermore National Laboratory

65 Considerations Based on Rank and Coal Quality Water content Low rank coals require less extra water or steam injection Plasticity Bituminous coals swell and get sticky during heating can block gas movement ( anthracites do not swell but will not shrink much) Amount of tars Can condense in pipes decrease permeability in coal enter ground water Cleating Controls natural permeability of seam aids/inhibits gas water movement Reactivity Decreases as with rank increases Shrinkage Less volatiles+moisture as rank increases less shrinkage shrinkage

66 Influence of Ash Amount and Composition on Gasification Ash content from 0% to 40% does not appear to impact heat value of gas  Acts as a heat sink stabilizes gasification reactions  Ash composition effects temperature at which ash softens and melts effects cavity wall  Need a slagging ash lower temperature melting less dry ash in recovered gas seal cavity walls  Need a fouling ash high melting temperature Ash collects in burn cavity with char and helps support burn cavity  In detail ash chemistry probably effects gasification reactions

67 Effect of Rock Chemistry on Burn Cavity Wall Conditions Ash chemistry controls temperature at which ash softens and eventually melts Ash that softens at lower temperature (high propensity to slag) will release less ash into gas and fuse/seal cavity walls better Controls on slagging melting temp decreases If Base/Acid ratio higher If Iron/Calcium ratio higher If Silica/Alumina ratio higher If Na+Ka content higher If Total S content higher Vaninetti and Busch 1982

68 Effect of Rock Chemistry on Gasification Reactions The Boudouard reaction C+CO 2  2 CO Kj/mole Is strongly influenced by presence of alkali elements in coal ash or in roof or floor rocks There are many studies on coke making for steel industry that document relationship between coke reactivity and alkali elements in coke Coke reactivity index Percent K in coke Price and Gransden 1987 It has also been suggested that the impurities in lower rank coals improve the kinetics of gasification by acting as catalysts for the burn process. Best Practices in Underground Coal Gasification Burton Friedmann Upadhye Lawrence Livermore National Laboratory Coke strength after reaction (CSR) and Coke reactivity Index (CRI) Tests Coke is reacted in an atmosphere of CO 2 at 1100Ç If K% changes 0 to 0.1% there is a 15.8% increase in CO% and decrease in CO 2 % in off gas This helps convert excess CO 2 and increase heat value of gas

69 Heat flow per second =conductivity* (temp difference)/( distance) Temperature increase = heat/specific heat/mass Rock Properties Importance of Conductivity and Specific Heat of coal and adjacent rocks  During gasification it is important that heat not escape  Low conductivity of coal helps insulate burn cavity  Collapse of roof may aid gas loss and convective heat loss  If cavity contacts roof rock then there is increase heat loss and change in gas composition  Conductive heat loss is sufficient to significantly increase temperature of adjacent seams and initiate temperature driven methane desorption

70 Production and Resource Considerations

71 Production Considerations  Must establish high permeability linkage from injection to recovery hole  Production parameters; such as Air Injection Pressure and Rate, Gas Recovery Pressure, Gas Flow Rate, Water Content in gas, Gas Composition, Heat Value; are all inter connected  Coal consumption calculated from gas volume/day and carbon content of gas  Air injection (m^3/hr) controls Gas production (m^3/hr) and coal consumption  Inject air or oxygen at below hydrostatic pressure Some water inflow Minimum gas loss  Air injection rate must match surface area available for burning and oxygen Consumption needs cavity with reactive char  Ash content Moderate ash may be beneficial provides mechanical and thermal stability to burn chamber Promote reactions  At greater depth counter current burn may be difficult depending on linkage method  Deeper seams probably need oxygen injection not air (no 80% N to compress)  Huff and Puff method alternating steam and air or O. produces higher heat value for gas  Steep Dipping seams may cave into burn zone making for better resource utilization  Keep temperature in channel and recovery hole above 150Ç to stop condensation and plugging

72 Resource Considerations UCG recovers about 55% of energy in coal CBM recovers 1% to 3% CRIP type gasification method Must drill injection hole along footwall Burn chamber width/height ratio about 6 to 1 with 70% utilization of coal within rectangle If thermal efficiencies 55% This gives resource utilization of about 40% If horizontal hole =1000 metres in 4 metre thick seam about 0.1 million tonnes coal gasified At 4 mmcf/d (113 m^3/d) this gives ten year life for drill hole infrastructure Need to expand cavity transverse to burn direction Paired horizontal hole method by British Gas increases resource per hole

73 Resource Considerations Inclined seam method can recover more gas per drill hole based on length of linkage Potential to gasify larger tonnage of coal geometry similar to long wall mining

74 UCG Synergies and Problems

75 UCG Synergies with CBM  CBM production prior to UCG can dewater seam while recovering CH 4 May limit problems from water inflow during UCG  CBM horizontal holes adapted for CRIP after CBM extraction  Heating of surrounding seams may stimulate CH 4 desorption without pressure decrease  Could be UCG of a seam and CBM recovery of adjacent seams.  Advances in hydraulic fracturing in horizontal CBM and shale gas holes may have application in preparing injection holes for UCG and improving linkage in CRIP British Gas method of UCG

76 The CO 2 Problem UCG produces more CO 2 per unit of heat than coal Needs to be paired with carbon capture sequestration (CCS) Sequestration Options are  Adsorbed on coal  Free gas in burn cavity  Super critical fluid in burn cavity  Other or combination Using average coal 55% C and 0.35 Kg coal (ash free) required to make 1m^3 gas 1 m^3 of burn cavity responsible for over 2000 m^3 of gas production at stp Equivalent volume of CO 2 at surface is about 750 m^3 stp

77 The CO 2 Problem Adsorb CO 2 on Coal Adjacent to Burn Cavity Coking of coal decreases adsorption ability As documented by decrease adsorption ability of inert coal macerals compared to vitrinite macerals Coal available for CO 2 adsorption per m^3 of cavity limited Adsorption ability low Very unlikely to be able to adsorb 750 m^3 CO 2 per 1 m^3 burn cavity Free Gas in Burn Cavity above 800 metres The 750 m^3 CO2 will occupy about 10 m^3 at 800 metres Sequestering free gas not possible

78 The CO 2 Problem Super Critical Fluid in burn cavity Plot shows changes in SG of CO 2 above critical point Red line is tract for geothermal gradient  1 m^3 cavity responsible for 750 m^3 CO 2 gas with mass of 1470 kg (CO 2 )  Density of CO 2 fluid at 1500 metres is 710 kg/m^3  Volume required to sequester 1.8 Kg CO 2 over 2 m^3 but only 1m^3 space available

79 The CO 2 Problem Other or Combination  There may be potential for mineral sequestration of CO 2 by forming carbonates with oxides in ash left after burning coal  Hydrated oxides of Ca Mg and Fe may form carbonates when CO 2 is introduced into burn cavity. However some of the CO 2 sequestered was originally present in the ash as carbonates ( no net benefit)  It may be possible to pre treat cooled burn cavity to improve seal prior to CO 2 injection

80 UCG Applications in BC Where ever UCG is suggested there must be considerable preparatory studies to convince agencies that environmental impacts in terms of Ground Water Contamination - GHG Emissions - Ground Subsidence Are acceptable  Low rank coals large scale UCG for electrical generation - Hat Creek has options for UCG in steeply dipping beds similar to early FSU projects  High-volatile bituminous coals deep CRIP UCG - Gething seams in northern part of Peace River Coalfield are deep and flat dipping similar to present projects in Alberta  Low rank coals local small scale UCG for electrical generation - Tuya River, Coal Creek shallow flat dipping similar to Chinchilla  High-volatile bituminous coals shallow CRIP UCG - Telkwa flat dipping shallow

81 Summary

82 Summary Facts UCG can make use of coal resources that might otherwise not be used UCG can recover over 50% of heat value in coal and up to 70% of coal targeted by drilling It is possible to sustain and control UCG Apply to seams thicker than 2 metres Apply to low rank coals (high-volatile bituminous Rmax 0.5% to 0.8%) non swelling Use co current flow for continued production Inject Air or Oxygen at or below hydrostatic pressure control gas loss and water inflow For deeper UCG use oxygen rather than air to minimize compression costs also gas low N content can be transported (remove CO 2 ) use as syn gas It may be necessary to extract water from burn cavity during and after burn for treatment In flow water ensures contaminants removed as steam during cavity cleaning

83 Summary Opinion Up Beat ☻ Gas that comes to surface is generally lower in particulates, Hg, SO 2, and tars than Syngas generated by coal gasification at surface ☻ New UCG production methods (CRIP CRIP knife edge) combined with horizontal holes drilled along seam footwall provide better control and access to coal resource ☻ Inject Oxygen to decrease Nitrogen content in produced gas and compression costs ☻ Make use of heat of recovered gas (pre heat injected air?) ☻ Consider ash chemistry to influence Boudouard Reaction to minimize production of CO 2 ☻ Deep UCG less risk of aquifer contamination problems ☻ Burn cavity may be available for sequestration of super critical CO 2 fluid ☻ Gas may contain valuable bi products

84 Summary Opinion Down Beat UCG gas is low heat value must be used close to source UCG gas high CO 2 content Produces more CO 2 per unit of heat than burning coal In future UCG must be paired with CCS ? A number of pilots had problems controlling water influx and water contamination by organic compounds (Benzene) Roof subsidence into burn cavity can initiate gas loss and excess water inflow Recovered gas may contain H 2 S Condensates in recovered gas can plug pipes Temperature in gas production pipes can damage cement bond and pipe steel

85 Observation Unconventional Gas Really is Gas with increased Problems Costs Risks When and Where To Go to CBM Shale Gas UCG gas Your Challenge ?? Tight Gas ??

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