INJEÇÃO DE CO 2 PARA PRODUÇÃO ACRESCIDA DE METANO DE CARVÃO EM CAMADA CO 2 INJECTION FOR ENHANCED COALBED METHANE (ECBM) C.F. Rodrigues 1 & M.J. Lemos de Sousa 3 1 FP-ENAS, University of Fernando Pessoa, Praça de 9 de Abril, 349, 4249-004 Porto. Portugal. E-mail: cfrodrig@gmail.com 3 FP-ENAS, University of Fernando Pessoa, Praça de 9 de Abril, 349, 4249-004 Porto. Portugal and Academia das Ciências de Lisboa, Rua da Academia das Ciências, 19, 1249-122 Lisboa. Portugal. E-mail: lemosdesousa@gmail.com Workshop: Tecnologias CCUS Universidade de São Paulo, 16 Novembro 2017
WHY CO 2 -ECBM?
SECURE COMPETITIVE SUSTAINABLE ENERGY CLIMATE STRATEGY
REAL ENERGY DEMAND NON-RENEWABLE ENERGIES CCS Technologies ED 2009/31/EC Geological Storage of CO 2 Clean Coal Technologies Zero Emissions Technologies Coal to Liquids ED 2003/87/EC ED 2004/101/EC
CCS TECHNOLOGIES CAPTURE TRANSPORT STORAGE (Lemos de Sousa and Rodrigues, 2011)
Deep saline aquifers Depleted Oil and Gas reservoirs Coal seams Shale Gas RESERVOIR CHARACTERIZATION
ALL THE RESERVOIRS HAVE THE SAME PERFORMANCE IN STORAGE CIRCULATION No
RESERVOIRS PERFORMANCE DEPENDS DIRECTLY ON TWO COMPONENTS 1- Static component 2- Dynamic component Geological Model Fluid flow Model
CONCEPTS NEED TO BE UNDERSTOOD?
Absorbed state Free state Fluids are HOMOGENEOUSLY DISPERSED on the porous structure, depending on their concentrations Fluids Grains 4 µ Scale
Laminar Flow Darcy Law Fluid circulates into a specific direction depending on the PRESSURE GRADIENT and on FLUID VISCOSITY. u = - k m dp dz u = flow rate (cm/s) K = permeability (md or D) µ = fluid viscosity P = pressure (atm) Z = distance (cm)
Absorbed state Free state Adsorbed state Fluids are HETEROGENEOUSLY DISPERSED on the porous structure.
Organic Fragment Pores Fluid Fluid molecules grabbed to the pore walls. 6 µ Scale Due to the high affinity to the organic structure.
Laminar Flow Darcy Law Diffusional Flow Fluid flow depends on the PRESSURE GRADIENT OF THE DIFFERENT COMPONENTS PRESENT ON THE FLUID MIXTURE and THEIR INTERACTIONS WITH the ORGANIC STRUCTURE, as well as, on the ORGANIC MATTER SHRINKING AND SWELLING EFFECTS.
CONVENTIONAL RESERVOIRS VS UNCONVENTIONAL RESERVOIRS
Pores < dimensions Pores > dimensions Larger pores implies higher storage capacity. Fluid Grains Scale: 4 µ
Pores < dimensions Pores > dimensions Organic Fragments Smaller pores implies higher storage capacity. Scale: 6 µ Fluid Pores
STORAGE CAPACITY Conventional Reservoirs Unconventional Reservoirs (organic-rich rock) Larger pores implies higher storage capacity Smaller pores implies higher storage capacity Smaller pores implies higher internal surface areas, and consequently higher storage capacities.
CO 2 -ECBM HOW IT WORKS?
CBM PRODUCTION HISTORY Dewatering (drilling of a well) induces the hydrostatic pressure reduction and consequently accelerates the desorption process. Dewatering and reservoir pressure depletion is a simple but relatively inefficient process, recovering less than 50% of the gas in place. Dewatering stage Stable production stage Decline stage (Rodrigues, 2002) CBM wells initially primarily produce water; then gas production eventually increases, while water production declines. Production TIME (Rice et al. 1993)
FACTORS INFLUENCING CO 2 STORAGE AND ENHANCED GAS RECOVERY IN COAL SEAMS ECBM and storage of CO 2 in coal seams processes involve: 1. CAPTURING CO 2 from a flue gas stream 2. COMPRESSING CO 2 for transport to an injection site 3. INJECTION of CO 2 into the coal to enhance methane recovery and/or store CO 2. CBM and ECBM PRODUCTION POTENTIAL DEPENDS ON : Fracture permeability Development history Gas migration Coal maturation Coal distribution Geologic structure Well completion options Hydrostatic pressure Produced water management VARY FROM BASIN TO BASIN
CO 2 INJECTION ECBM RECOVERY: HOW IT WORKS? To reduce the hydrostatic pressure, usually by dewatering the formation and/or to reduce the partial pressure of the methane by injecting CO 2 and then the methane on the surface gets displaced by the CO 2 Fracture (CLEAT) system one of the main controlling factor LOW PERMEABILITY IS A FACT, SO Many wells at relatively close spacing must be drilled to achieve economic gas production Hydraulic fracturing are, normally, used to assist recovery
COAL IS A SAFETY AND A PERMANENT OPTION FOR CO 2 STORAGE? CO 2 is stored in coal following two process: sorption and diffusion. In coal seams, ADSORPTION TRAPPING is the MAIN SEQUESTRATION METHOD. The adsorption process causes the CO 2 to bond to the coal structure, which will allow to CO 2 TO BE PHYSICALLY AND PERMANENTLY TRAPPED on the coal, provided sufficient pressure is maintained. CO2 can safely remain stored in coal for GEOLOGICALLY SIGNIFICANT TIME PERIODS
PREDICTION OF CO 2 SEQUESTRATION CAPACITY EQUATION TO ESTIMATE ORIGINAL GAS IN PLACE CO2 STORAGE CAPACITY IN (OGIP) VOLUMETRIC COAL SEAM(S) COMPUTATION Defined by Simplifying CO2 STORAGE CAPACITY = CO2 density, kg/m3 x Coal seam(s) thickness, m x Coal bulk density, kg/m3 capacity, m3/kg x Prospective area, m2 x Gas sorption This equation is applicable for 100% gas saturation in coal matrix and adsorption process as the main and the only storage mechanism in coal seams.
COAL PROPERTIES AT A RESERVOIR SCALE?
GAS STORAGE IN A COAL SEAM IT IS MAINLY CONTROLLED BY PHYSICAL MECHANISMS COAL IS A MICROPOROUS RESERVOIR Micropores Mesopores Macropores It means Gas in coal is mainly stored in the adsorbed state on the INTERNAL SURFACE AREA of the coal microporous structure. It means To store a volume of gas much higher than its pore volume capacity.
METHODOLOGY SORPTION ISOTHERMS Was used to establish the adsorbed volume kinetic equilibrium V V g P V L P L g = V P P P L - Gas volume (m 3 /ton) - Equilibrium pressure (MPa) - Langmuir Volume (m 3 /ton) - Langmuir Pressure (MPa) L Requires precise and continuous monitoring of changes in pressure and gas concentration in both cells, during the whole sorption D = br 3.3851 V s i V i 1 D - Diffusion coefficient (cm 2 /sec) b - Slope (first linear part of the data curve) r s - Spherical particle radius (cm) V i - Gas content at the end of step I (cm 3 /ton) V i-1 - Gas content at the end of step I-1 (cm 3 /ton) 2 DETAILED STUDY OF THE CLEAT SYSTEM
PARAMETERS CAPABLE TO INFLUENCE SORPTION BEHAVIOR PRESSURE TEMPERATURE GAS COMPOSITION MOISTURE PETROGRAPHIC CHARACTERISTICS Mean Random Vitrinite Reflectance Vitrinite content Liptinite content Inertinite content Mineral Matter content
Gas Volume (cm3/g) PRESSURE EFFECT 7 6 5 4 3 2 G1 G1 psi 200 400 600 800 G2 P1 P1 P2 240 200 160 120 80 1 40 0 0 1 2 3 4 5 6 Pressure (MPa)
Gas Volume (cm3/g) TEMPERATURE EFFECT 14 12 10 8 psi 250 500 750 1000 T = 22ºC T T = 30ºC = 30ºC 15% 480 400 320 6 240 4 160 2 80 0 0 2 4 6 8 Pressure (MPa)
Gas Volume (cm3/g) MOISTURE EFFECT 7 6 5 4 psi 200 400 600 800 240 200 160 3 2 1 0 Moisture 3.0% Moisture 5.7% Moisture 11.5% (MHC = 4.3%) 120 80 40 0 1 2 3 4 5 6 Pressure (MPa)
Gas Volume (cm3/g) MINERAL MATTER EFFECT 5 psi 250 500 750 1000 170 4 136 3 MM = 7% 61% 102 2 68 1 MM = 44% 34 0 0 2 4 6 8 Pressure (MPa)
Gas Volume (cm3/g) scf/ton RANK EFFECT 7 6 5 4 psi 250 500 750 1000 Rr = 1.93% Rr = 0.91% 28% 240 200 160 3 63% 120 2 Rr = 0.43% 80 1 40 0 0 2 4 6 8 Pressure (MPa)
Gas Volume (cm3/g) PETROGRAPHIC COMPOSITION EFFECT 7 6 5 psi 200 400 600 800 V=83%; L=6%; I=11% 240 200 4 3 V=72%; L=6%; I=22% 160 120 2 80 1 40 0 0 1 2 3 4 5 6 Pressure (MPa)
Gas Volume (cm3/g) GAS COMPOSITION EFFECT 16 14 psi 200 400 600 800 CO 2 500 12 400 10 8 CH 4 + CO 2 + N 2 300 6 CH 4 200 4 2 N 2 100 0 0 1 2 3 4 5 6 Pressure (MPa)
COMPRESSIBILITY FACTOR
ACCURACY VALUES FOR THE COMPRESSIBILITY FACTOR 220 200 180 160 140 120 100 80 60 40 CH 4 Accuracy 0.0001 0.001 0.01 0.1 0 200 400 600 800 1000 Pressure (psi) 60 50 40 30 20 10 N 2 Accuracy 0.0001 0.001 0.01 0.1 0 200 400 600 800 P ressure (psi) 450 400 CO 2 300 250 CH 4 + CO 2 + N 2 350 300 250 200 150 Accuracy 0 200 400 600 800 P ressure (psi) 0.0001 0.001 0.01 0.1 200 150 100 50 Accuracy 0.0001 0.001 0.01 0.1 0 200 400 600 800 1000 P ressure (psi)
Gas content (scf/ton) GAS SORPTION ISOTHERMS FROM LIGNITE TO ANTHRACITE 450 400 350 300 250 200 150 100 50 0 0 100 200 300 400 500 600 700 800 900 Pressure (psi) H E F G (Rr=3.07%) (Rr=2.10%) (Rr=5.31%) (Rr=0.72%) D (Rr=0.62%) (Rr=0.55%) C (Rr=0.31%)B A (Rr=0.17%)
DETAILED STUDY OF THE CLEAT SYSTEM (a) cleat characteristics in plan view; (b) cleat hierarchies in cross- section view (Laubach et al 1998)
COAL CLEAT CHARACTERISTICS CLEAT DIRECTIONS RELATIVE TO A REFERENCE CLEAT FREQUENCY CLEAT HEIGHT CLEAT LENGTH CLEAT SPACING CLEAT APERTURE NUMBER OF CLEATS FILLED BY MINERALS NUMBER OF CLEAT INTERSECTIONS (CONNECTIVITY INDEX)
Frequency (%) STATISTICAL ANALYSES FROM GEOREFERENTIATED DATA Plane W-E (W dip direction) 100 80 60 40 20 0 10 20 30 40 50 60 70 80 dip (degree) Cleat frequency (decrease order) Cleat lines measured in N-S plane (N dip direction) Cleat lines measured in W-E plane (E dip direction) 1 88º 0º 88º 90º 2 89º 0º 87º 90º 3 87º 0º 85º 90º 4 85º 0º 86º 90º 5 86º 0º 84º 90º 6 80º 0º 89º 90º 7 3º 0º; 83º 0º and 84º 0º 83º 90º 8 2º 0º 3º 90º 9 5º 0º 82º 90º 10 82º 0º 7º 90º and 5º 90º Dip direction interval 120º - 150º N Cleat frequency 1 N Mean Orientation = 87/037 Mean Resultant dir'n = 87-037 Mean Resultant length = 1,00 (Variance = 0,00) Calculated. girdle: 8/145 Calculated beta axis: 82-325 Mean Direction = 89-045 Mean Resultant dir'n = 89/045 Mean Resultant length = 1,00 (Variance = 0,00) Calculated. girdle: 89/045 Plane: N 135º, 89ºE Mean Plane: N 127º, 87ºE
Frequency (%) CONNECTIVITY FREQUENCY Class designation Dip interval Class 0 0º Class 1 > 0º and 30º Class 2 > 30º and 60º Class 3 > 60º and 90º Class 4 90 Connectivity frequency (Example) 50% 40% 30% 20% 10% 0% 0-1 0-2 0-3 0-4 1-2 1-3 1-4 2-3 2-4 3-4 Classes
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