Enhanced Coalbed Methane Recovery and CO 2 Sequestration in Coal: An Overview of Current Research at Imperial College

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1 Enhanced Coalbed Methane Recovery and CO 2 Sequestration in Coal: An Overview of Current Research at Imperial College Sevket Durucan and J Quan Shi Royal School of Mines Imperial College, London First International Forum on Geologic Sequestration of CO2 in Deep, Unmineable Coalseams Coal-Seq I March 22, Houston, Texas ENVIRONMENTAL AND MINING ENGINEERING RESEARCH GROUP em

2 Enhanced Coalbed Methane Recovery/CO 2 Storage - R&D PRIORITIES Rock and Fluid Characteristics PVT behaviour of CO 2 and other gas mixtures Matrix swelling/shrinkage effects on permeability and flow Stress, pore pressure and wellbore effects Relative permeability behaviour Diffusion characteristics of gas mixtures Binary gas sorption behaviour Hydrochemistry Modelling tools - upscaling from matrix/cleat to reservoir scale Injection Well spacing Horizontal vs vertical wells improved injectivity? Techniques to improve permeability Storage Capacity and Longevity Type and integrity of caprock Depth? Criteria on mineable/unmineable seams Timescale? Leakage (1-1%? 1 years?)

3 Coalbed Methane Research at Imperial College Coal Seam Reservoir Characterisation Dynamic Stress-Permeability Modelling Laboratory Investigations Coalbed Methane Flow and Geotechnical Models Openhole Cavity Model CBM Simulator Horizontal CBM Well Model Abandoned Mines Gas Production Primary Recovery through Reservoir Depletion Enhanced Recovery and CO 2 Sequestration S. Durucan, RITE CO 2 Workshop, Kyoto 21

4 An Investigation into the Effects of Matrix Swelling on Coal Permeability for ECBM And CO 2 Sequestration Assessment Development of Advanced Reservoir Characterisation and Simulation Tools for Improved Coalbed Methane Recovery (ICBM) ICSTM-BP-TUD-IFP-DSK-WA Laboratory investigations into potential matrix swelling mechanisms Characterisation of sorption and diffusion behaviour of CH 4 -CO 2 mixtures in coal Relative permeability and capillary pressure characterisation of the cleat-matrix structure in coal Stress-permeability-stimulation characterisation of coals for the flow of CH 4 -CO 2 mixtures Geostatistical and fractal characterisation and upscaling of natural fractures Development of a two-phase, multicomponent simulator Optimisation of enhanced methane recovery and CH 4 -CO 2 storage S. Durucan, RITE CO 2 Workshop, Kyoto 21

5 Saar Coalfield: Coal Mines, Power Stations, Gas Network

6 Coalfields and Sample Collection UK coalfields including: -South Wales - North Derbyshire - Central Scotland German coalfields including: - the Saar - Ensdorf Colliery - Warndt/Luisenthal Colliery French coalfields including: - Lorrainne Basin - Nord Pas de Calais - Ales Basin

7 Cleat characterisation Slabs: -Face Cleat -Butt Cleat -Cleat Angle IMAGE ANALYSIS Cuttings: - Micro-cleat size Cleat angle Discrete cleat angle and size distribution -Cleat Angle Source: TUD, 21, ICBM

8 Stress-permeability-stimulation characterisation for the flow of CH4-CO2 mixtures Intact coal Stress Permeability Relationship for Coal Permeability (md).6 1st loading (pre-failure).5 1st unloading (post-failure).4 2nd loading (post-failure) 2nd unloading (post-failure) effective confinement (MPa) Effective confinement: 5 MPa.5 # 6: fractured 2.4 stress permeability Permeability (md) Deviatoric stres ( MPa) Mean axial strain (millistrain) Post-failure

9 Stress - Permeability Relationships for Coal.6.5 Durucan Puri et al Somerton Permeability (md) P(r e,t) Finite Element Mesh for Well Inflow Finite Difference Mesh for Macro-Flow P(r,t) w Effective Stress (psi) Intact coal Post-failure Permeability (k), 1-15 m Three Yard Great Row Cannel Row Confining Stress (MPa) 1

10 Stress-permeability-welbore characterisation for the flow of CH4-CO2 mixtures - Hollow Cylinder Testing Radial 2 Permeability, md Strain, millistrain 8 Permeability, md Bore Strain Permeability OH-6-HC OH-5-HC OH-12-HC Radial Mean Effective Stress, MPa Mean Effective Stress, MPa Cavity Well breakout

11 Matrix Shrinkage and Swelling Effect of Gas Sorption 1 Microstrain Methane Helium CO Pressure, psi Source: Seidle and Huitt, 1995

12 Pore Pressure Permeability Behaviour of Coalbed Reservoirs (Primary CH 4 Production) Change in effective horizonta stress (psi) 1-1 p = 175 psi -2 p = 1154 psi Reservoir pressure (psi) Permeability rebound as a function of initial reservoir porosity and pressure Effective horizontal stress as a function of initial reservoir pressure 1. p = 1154 psi k/k 1. p = 175 psi Reservoir pressure (psi)

13 Pore Pressure Permeability Behaviour of Coalbed Reservoirs (Primary CH 4 Production) k/k stress effect only history matched permeability response curve IC model (METSIM) Reservoir pressure (psi) San Juan, Valencia Canyon Wells Data Source: Mavor and Vaughn, 1997 k/k San Juan Fairway Well B#1 Data Source: Palmer and Mansoori, 1996 The reservoir permeability shows a strong rebound with reservoir pressure reduction VC 29-4 VC 32-4 VC 32-1 well test IC model (METSIM) Mavor and Vaughn (VC 32-1) p/p

14 Pore Pressure Porosity/Permeability Behaviour of Coalbed Reservoirs (Gas Desorption) % CO 2 k/k % CH 4 +1% CO Reservoir pressure (psi) Re-adsorption of CO 2 in coal could potentially have an impact on coal porosity/permeability, thus reducing CO 2 injectivity.

15 Relative permeability and capillary pressure characterisation of the cleat-matrix structure Watson Head UK - opencast coal Critical Saturation (S gcrit ) Range = Absolute Permeability Range = 1-2 md Porosity Range = % Relative Permeability Gas.2.1 Water Gas Saturation

16 CO 2 Injection Experiments: Methane and Water Production Conditions during the experiments 52 bar, low temperature autoclave for large samples Coal samples: original and prepared Results on CO 2 -injection and CH 4 / H 2 O- production Source: TUD, 21, ICBM

17 CH 4 -CO 2 Simulator Development Pore-Diffusion Model Large Core CO 2 Injection Tests: Model Predictions vs Laboratory Data 1 9 CH4 concentration (%) concentration outflow rate Outflow rate (% of injection rate) Normalised injected volume 3

18 CARBON DIOXIDE SEQUESTRATION TECHNOLOGY NETWORK (CO2NET) 29 Partners in 9 European Countries Facilitate European Research Collaboration, Map European Centres of Excellence, Access and Define R&D Strategy, Facilitate Exploitation and Dissemination of Results, Provide Information to Assist Policy Making, Develop Training Material and Educational Activities Assess best Practice Increase Public Awareness ENERGY, ENVIRONMENT and SUSTAINABLE DEVELOPMENT

19 CO2NET MEMBER PROJECTS R&D GESTCO European survey of geological sinks ICBM - ECBM NASCENT Natural Analogues AZEP Gas seperation NGCAS Geological storage and risk assessment GRACE Capture and cost reduction Demonstration SACS Saline Aquifers RECOPOL - ECBM WEYBURN - EOR