Coal Gas Technologies - New Initiatives

1. Coal Gas Technologies - New Initiatives Ajay K. Singh Central Institute of Mining and Fuel Research (Erstwhile Central Mining Research Institute) DHANBAD – 826001 ajayabha@yahoo.com Manuguru, SCCL 4 July 2007

2. Methane in Coal Organic debris Peat Gas Water Pressure COAL HEAT TIME

3. AnthraciteBituminousLignitePeat

4. Mechanism of retention • Unconventional Reservoir. • In conventional natural gas reservoirs, gas is in free state at high pressure. • Unlike natural gas reservoirs, most of the gases are adsorbed on the coal surface in CBM reservoir. • In CBM reservoir only a small percentage is present in free state in the macro-pores.

5. Adsorption of gases Two types of adsorption are believed to occur between the gaseous and the solid phases. These two types of adsorption are: 1. Physical Adsorption 2. Chemical or Chemisorption

6. Physical Adsorption • Involves intermolecular forces (Van der Waals forces) between the gas (methane) molecules and the solid (coal) molecules.

7. Chemisorption • Chemisorption usually involves sharing or transfer of electrons.

8. Transport of Methane in Coal • Three Stage process > Desorption from coal surface. > Diffusion through micropores. > Flow in macropores.

9. Cover Roof 4.2m 2m Floor NOT TO SCALE Safety Hazard in u/g Mines

10. Opencast Mines O.B.DUMP

11. Greenhouse Effect Some solar radiation is reflected by the earth to the atmosphere SUN Some of the infra-red radiation is absorbed and re-emitted by the greenhouse gases Solar radiation passes through clear atmosphere ATMOSPHERE Infra-red radiation is emitted from the earth’s surface Most solar radiation is absorbed by the earth’s surface and warms it EARTH

12. Key GHGs

13. Short-lived Air Pollutants

14. CARBON DIOXIDE (63.5%) CO 2 Others HALOGENATED GASES (11.5%) N O N O 2 CH 4 NITROUS OXIDE (4.5%) METHANE (20.5%) Contributions to Global Warming Energy from fossil fuels contribute to about 50% of the enhanced greenhouse effect

15. Measures to reduce greenhouse emissions • Direct Reductions through: • Energy efficiency improvements • Demand and supply side • Fuel switching • Replacing fossil fuels with renewable energy • Nuclear power?? • CO2 Capture and Storage • Indirect measures (Kyoto instruments) • Emissions trading • Joint Implementation actions • Clean Development Mechanism

16. Unminable Coal Seams 30 Gt CO2 Able to store <2 Years of 2030Emissions Depleted Oil & Gas Fields 930 Gt CO2 Able to Store 50 Years of 2030Emissions Deep Saline Aquifers 400-10 000 Gt CO2 Able to store 20 - 530 Years of 2030 Emissions Global CO2 geological storage capacity Note: Economical CO2 Storage potential at a storage cost of 20 US $ per tonne of CO2

17. CCS Demonstration Projects Snøhvit Sleipner In-Salah Weyburn Images Courtesy of BP, Statoil Chevron and PTRC

20. Typical CBM Well in Production Gas Water

21. What about Enhanced Gas Recovery ?!?

22. CH4 CO2 Affinity of CO2 Adsorption for Coal

23. What if we use CO2 for pressure maintenance? CO2 Methane

24. Using CO2 for pressure maintenance can also reduce CO2 emissions (sequestration). Methane Production CO2 Injection

25. Utilisation of VAM

27. Underground Coal Gasification

29. What is Gasification? • Gasification is a general term for various processes that converts fuels such as coal and heavy oil, into synthesis gas (Syngas) by reacting them with steam and oxygen at elevated temperatures. • Gasification is NOT combustion. • Syngas is primarily made up of H2 and CO.

30. Gasification (Contd..) • Partial Combustion C + O2 = 2CO exothermic • Combustion C + O2 = CO2 exothermic C + CO2 = 2CO endothermic • Water-Gas C + H2O = CO + H2 endothermic • Hydrogasification C + 2H2 = CH4 exothermic • Shift CO + H2O = CO2 + H2 exothermic • Reformation CO + 3H2 = CH4+ H2O exothermic

31. UCG - Concept Two boreholes are drilled into the coal seam

32. UCG - Concept Coal is ignited, combustion is maintained by injecting air or oxygen and steam

33. UCG - Concept The resulting gases are brought to surface by the second bore hole

34. Input of UCG • Oxygen (or Air or Enriched Air) • Steam

35. Gas Composition Typical composition of UCG Dry Syn Gas Calorific Value 2600 Kcal / sm3 Calorific Value 4000 Kcal / sm3 With no CO2 capture With CO2 capture After Blinderman et al. (2002)

36. Pre-requisites of UCG (1/5) UCG is a high risk project. It is advantageous and rather mandatory to investigate various strategic aspects on pilot scale before going for commercial level projects. • Surface features including geography and topography of the UCG block. • Site geology such as faults, fractures, intrusions, dykes, boundary strata composition. Their orientation and extension etc. • Availability of virgin coal seams in the block.

37. Pre-requisites of UCG (2/5) • Geotechnical data of coal seams and enclosing strata comprising depth, thickness, lithology, uniformity, dip, coal seam geometry and composition and cleat orientation. • Perophysical data such as porosity, permeability, water and gas saturation and pore pressure etc of coal seam and surrounding strata. • Data on hydrological subsurface characteristics such as aquifer identification, water table, transmissivity, ground water flow rate and direction.

38. Pre-requisites of UCG (3/5) • Physico-mechanical properties of coal seams and enclosing strata such as bulk density, uniaxial compressive strength, triaxial strength properties, Young's modulus and Poissons's ratio etc. • Chemical analysis of coal including proximate and ultimate analysis, calorific value and maceral analysis. • Special well completion design, high temperature resistant cement, temperature and corrosion resistant downhole casings, flow line and well head assembly with well bore cooling and sustaining high pressure provisions.

39. Pre-requisites of UCG (4/5) • Identification of an economical and feasible linking technique suitable for the target seam. • Understanding chemical kinetics of the prevalent coal seam conditions and perception of ideal composition of reactants such as air/oxygen and steam. • Cavity growth and subsidence prediction using UCG process models or simulators. • Environmental impact assessment of UCG processes such as treatment and disposal of produced chemicals, gases and water.

40. Pre-requisites of UCG (5/5) • Availability of drilling and other equipment, compressed air and surface installations. • Economic considerations in respect of UCG process as a whole for its commercialisation.

41. Technical criterion for UCG Keeping in view the pre-requisites, the technical criteria for successful UCG operation can be grouped in the following three categories: • Coal characterisation. • Geological aspects. • Operational parameters.

42. Coal Characterisation • Shrinking coal, which do not swell on heating are preferred. • Caking coals expend on heating and therefore not suited for UCG. • Coals with good permeability and well developed cleat systems are better for transport of oxidants. • Drying and Devolatilization of coal further increase the permeability. • Reactive coals are better choice. • Optimum amount of ash in coal reduces the void volume and minimizes oxygen bypassing. It withholds a considerable portion of sulphur. • VM percentage, hydrocarbons and some aromatic compounds are liberated. This carbonization behaviour is very important for prediction of the yield.

43. 1 m3 of water per ton of gas produced 2 3 4 Geological Aspects • Seam Thickness and water inflow • Roof failure (Sagging or fragmentation). Roof failure is desirable in the sense that the void space in the gasifier gets reduced which offers sufficient resistance to oxygen bypassing. It is damaging for the possibility of increase of water influx and gas leakage.

44. Operational Parameters • Optimum pressure maintenance is crucial for UCG operation. While low pressure process lowers risk of gas leakage and simultaneously minimizes the possibilities of ground water adulteration, it may also result in higher rates of water influx into the gasifier. • Sweep efficiency which is the coal contacted or reacted over a large area of operation may vary from as low as 10% to a higher value of 90%. A maximum sweep efficiency ultimately results in a minimum operational cost. Sweep efficiency has been found to be a direct function of the well spacing by the Soviets. Sweep efficiency dropped from 83% to 63% with an increase in well spacing from 25m to 40m. Experiments with enriched air resulted in higher sweep efficiencies in comparison to those with air.

45. Different Drilling Technologies Vertical wells Horizontal, multilateral wells

46. UCG and Directional Drilling

47. Impact • Supplementing gas resources for energy. • Dependence on national resources instead of imported oil/gas. • Clean source of energy. • May attract Carbon Credit. • Feedstock for fertilizers and other chemicals.

48. UCG - Potential UN MINEABLE COAL RESOURCES : 210.14 Billion tons UN MINEABLE LIGNITE RESOURCES : 32.76 Billion tons TOTAL UNMINEABLE RESOURCES : 242.90 Billion tons PERCENTAGE OF COAL AMENABLE TO UCG : 30 % COAL RESERVES AMENABLE TO UCG : 72.87 Billion tons UCG GAS (considering 2700 m3/ton) : 196.749 Trillion m3 NATURAL GAS EQUIVALENT : 19.67 Trillion m3 CALORIFIC VALUE OF PRODUCED GAS : 3- 5 MJ/m3 CALORIFIC VALUE OF NATURAL GAS = 38 MJ/m3

49. Demonstrated Expertise & Strength • Expertise in: • Drilling • In-Situ Combustion • 3-D Seismic • Geological Mapping • Capability of Handling High Pressures CONSULTANTS, LABORATORY BACK-UP • UCG Expertise from Skochinsky Institute of Mining • IIT, Bombay; IICT, Hyderabad; CIMFR, Dhanbad.

50. Experience in: • Ignition , Tracking Combustion Front • More than 50 air injectors • Compression & Injection of Oxygen/ Air/ Steam: • Air injection @ 2 million m3/day is already going on in Balol & Santhal field • Similar facilities may be required for UCG • Flue gas utilisation: • Flue gases producing from heavy oil areas are comparable with the UCG gases