Implications of carbon dioxide sorption kinetics of low rank coal (original) (raw)
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International Journal of Greenhouse Gas Control, 2011
Permeability is one of the most important parameters for CO 2 injection in coal to enhance coalbed methane recovery. Laboratory characterization of coal permeability provides useful information for in situ permeability behavior of coal seams when adsorbing gases such as CO 2 are injected. In this study, a series of experiments have been conducted for coal samples using both non-adsorbing and adsorbing gases at various confining stresses and pore pressures. Our observations have showed that even under controlled stress conditions, coal permeability decreases with respect to pore pressure during the injection of adsorbing gases. In order to find out the causes of permeability decrease for adsorbing gases, a nonadsorbing gas (helium) is used to determine the effective stress coefficient. In these experiments using helium, the impact of gas sorption can be neglected and any permeability reduction is considered as due to the variation in the effective stress, which is controlled by the effective stress coefficient. The results show that the effective stress coefficient is pore pressure dependent and less than unity for the coal samples studied. The permeability reduction from helium experiments is then used to calibrate the subsequent flow-through experiments using adsorbing gases, CH 4 and CO 2 . Through this calibration, the sole effect of sorption-induced strain on permeability change is obtained for these adsorbing gas flow-through experiments. In this paper, experimental results and analyses are reported including how the impact of effective stress coefficient is separated from that of the sorption-induced strain on the evolution of coal permeability. (Z. Pan). methane recovered as an energy source, while providing the additional benefit of reducing greenhouse gas emissions by storing the CO 2 underground .
Improvements in Measuring Sorption-Induced Strain and Permeability in Coal
All Days, 2008
Total worldwide CBM in-place reserves estimates are between 3500 Tcf and 9500 Tcf. Unminable coal beds have been recommended as good CO2 sequestration sites as the world prepares to sequester large amounts of greenhouse gases. In the U.S., these coal seams have the capacity to adsorb and sequester roughly 50 years of CO2 emissions from all the U.S. coal-fired power plants at today's output rates. The amount and type of gas adsorbed in coal has a strong impact on the permeability of the coal seam. An improved mixed gas adsorption isotherm model based on the extended-Langmuir theory is discussed and is applied to mixed gas sorption-induced strain based on pure gas strain data and a parameter accounting for gas-gas interactions that is independent of the coal substrate. Advantages and disadvantages of using freestanding versus constrained samples for sorption-induced strain measurements are also discussed. A permeability equation used to model laboratory was found to be very accura...
Modeling Laboratory Permeability in Coal Using Sorption-Induced-Strain Data
SPE Reservoir Evaluation & Engineering, 2007
Summary Sorption-induced strain and permeability were measured as a function of pore pressure using subbituminous coal from the Powder River basin of Wyoming, USA, and high-volatile bituminous coal from the Uinta-Piceance basin of Utah, USA. We found that for these coal samples, cleat compressibility was not constant, but variable. Calculated variable cleat-compressibility constants were found to correlate well with previously published data for other coals. Sorption-induced matrix strain (shrinkage/swelling) was measured on unconstrained samples for different gases: carbon dioxide (CO2), methane (CH4), and nitrogen (N2). During permeability tests, sorption-induced matrix shrinkage was demonstrated clearly by higher-permeability values at lower pore pressures while holding overburden pressure constant; this effect was more pronounced when gases with higher adsorption isotherms such as CO2 were used. Measured permeability data were modeled using three different permeability models th...
Sorption behavior of coal for implication in coal bed methane an overview
International journal of mining science and technology, 2017
CBM has been recognized as a significant natural gas resource for a long time. Recently, CO 2 sequestration in coalbeds for ECBM has been attracting growing attention because of greater concerns about the effects of greenhouse gases and the emerging commercial significance of CBM. Reservoir-simulation technology, as a useful tool of reservoir development, has the capability to provide us with an economic means to solve complex reservoir-engineering problems with efficiency. The pore structure of coal is highly heterogeneous, and the heterogeneity of the pores depends on the coal type and rank.
Study on CO 2 Sorption Capacity of Coal – An Experimental Approach
In the present situation of global warming, the percentage of í µí° ¶í µí± 2 in atmospheric air is increasing very rapidly, which will create major problem for the future generation. Storage of í µí° ¶í µí± 2 is gaining widespread interest as a potential method of controlling greenhouse gas emissions as suggested by Intergovernmental Panel on Climate Change (IPCC). This study includes methane desorption mechanism from coal bed, and suggests that the desorbed methane can be used as a pure fuel for many purposes. It is generally acknowledged that coal beds are an important rock medium with regard to their capacity to act as a reservoir for í µí° ¶í µí± 2 gas. In this paper, í µí° ¶í µí± 2 sorption capacity of coal under different temperatures has been investigated by experimental approach and also explains the effect of cracks on coal surface in its sorption capacity. As temperature and pressure increases, with the depth of seam from surface level, the mathematical relation derived from this experiment will be helpful in determination of total amount of í µí° ¶í µí± 2 that can be stored in a coal seam at various reservoir temperature. The results will be helpful to use enhanced production of methane as additional benefit and also to use coal seam as a permanent sink for anthropogenic í µí° ¶í µí± 2 emission.
CO2 adsorption the numerical simulations and the controlling factors to low rank coal
IOP Conference Series: Earth and Environmental Science, 2018
Carbon Capture Sequestration (CCS) in unmineable coal seams questionably gives benefits for the commercial success through potential release of additional methane during the injection of CO2 adsorbs into the coal seams, the process known as enhanced coalbed methane (ECBM) recovery. However, a significant concern lies in the loss of injectivity due to reduction in permeability by coal matrix swelling occurences with CO2 adsorption although this effect can be partially be offset with 'huff and puff' scheme of cyclic CO2 injection followed by extraction of the released methane. The paper discusses the results of a numerical simulation study carried out with GEM compositional reservoir simulator to evaluate the effects of uncertainties in various reservoir parameters on the overall volume of CO2 storage and additional methane recovery of low rank coalfield. A 12-15m thick seam at shallow depth, 50-75 m was considered for fluid flow simulation study. While some information on the reservoir setting was obtained through literature and personal communication with the CBM operators, the rest of the information was derived through laboratory studies. The reservoir parameters considered for the study are injection pressure, adsorption capacity, cleat permeability and porosity, and initial gas saturation. A 100-acre drainage area with 5-spot vertical well pattern was considered with one central injector and four producers on four corners of the study area. The maximum allowable injection pressure was estimated to be 7500 kPa at the reservoir setting. The injection pressure was varied from 1000 kPa to 7500 kPa in the simulation .A number of adsorption isotherms were established in the laboratory. The variations in the adsorption parameters observed through the isotherms were considered as uncertainty in the storage capacities. Significant variations were observed due to the variation in adsorption isotherms both for CO2 storage and additional methane recovery. Fracture permeability was varied from 3 md to 200 md, which is the range of permeability observed in the coalfield is around 100-200 mD. The results of simulation indicate a strong influence of porosity on the CO2 storage and ECBM recovery. Fluid flow simulation study shows that variation in sorption time has no significant effect for a low permeability situation while some marginal effect in high permeability situation. Cleat porosity was varied from 1 % to 10 %. Within this range of porosities, enhanced methane recovery varied from 1 % to 10 % relative to the primary recovery but the volume of stored CO2 did not vary significantly. Lastly, the pore pressure, adsorption and gas saturation of CO2 sequestered volume and additional methane recovery were found to increase substantially.
2016
Enhanced coal bed methane recovery (ECBM) is considered as a promising way to produce methane from coal beds while storing carbon dioxide (CO2). The adsorption of CO2 on coal surfaces is known to render softening and swelling of coals, however, to what extent it will affect to permeability and P-wave velocity is still poorly understood. This study investigated the effect of swelling of coal induced by CO2 adsorption on permeability and P-wave velocity. It appeared that CO2 adsorption caused decreases in permeability and an increase in P-wave velocity. This study presents valuable laboratory test results of transport and geophysical properties and the obtained results provide a direct evidence of swelling effect caused by CO2 adsorption on coals.
Acta Geophysica, 2008
The aim of this study was to assess whether acoustic emission (AE) could carry information on preferential sorption/desorption of CH 4 or CO 2 in coal. AE and expansion/contraction of two nearly identical cylindrical coal samples were continuously monitored during displacement sorption experiments. One sample was subjected to presorption of CH 4 , followed by sorption of CH 4 /CO 2 mixture. With the other one, presorption of CO 2 preceded sorption of the mixture. The results obtained are the following: first, AE and stain kinetics show that the affinity of the coal tested is higher for CO 2 than for CH 4 ; second, methane is preferentially desorbed after presorption of CH 4-sorption of mixture of CH 4 and CO 2 ; third, during displacement sorption, kinetics of AE and sample swelling/shrinkage bring out the importance of presorption and the sorbate used. It matters whether the coal is first exposed to CH 4 or to CO 2. The present study has demonstrated that injection of CO 2 into the coal previously exposed to CH 4 causes considerable swelling of the coal. On desorption after CH 4 /CO 2 exchange sorption, initial shrinkage is followed by swelling of the coal. These results could have implications for the sequestration of CO 2 in coal seams and CH 4 recovery from coalbeds (ECBM). Swelling/shrinkage of the coal matrix should be included in models used to predict coal permeability and gas flow rates. They also show that the AE technique can give more insights into coal matrix-gas interactions.
Methane and Carbon Dioxide Sorption and Transport Rates in Coal at In-situ Conditions
Energy Procedia, 2009
Geologic sequestration of carbon dioxide is an option for the mitigation of industrial emissions. However, considerable effort remains to shift this technology from its current status as potential solution to a safe, effective and trusted foundation to the global energy system. Characterization of gas movement and sorption capacity of coal at in-situ conditions is required. Using the volumetric method, measurements of CH 4 and CO 2 sorption and diffusion in coal have been made on powder and non-powder confined coal. Results obtained, emphasized that the sorption capacity and the kinetics of gas in coal are both influenced by the stress state of the sample. The application of 6.9 MPa confining stress contributed to about 30% and 80% of sorption capacity reduction for CO 2 and CH 4 respectively. The sorption and diffusion of CO 2 in confined coal follow two distinct rates described with diffusion coefficients of 2.3 x 10-6 m 2 /s and 9.4 x 10-12 m 2 /s respectively. In contrast, the flow of methane is characterized by a continuous process with a diffusion coefficient of 3.8 x 10-7 m 2 /s. These observations confirms the complex interaction of CO 2 with the coal structure and stressed that CH 4 and CO 2 sorption and transport in coal should be characterized differently, specifically when dealing with non-powder confined samples. Consequently, the use of information collected on pulverized coal samples for the simulation and prediction of long term underground sequestration and enhanced coalbed methane is not justified.
All Days, 2003
Coalbed methane now accounts for a significant fraction of domestic natural gas production. Injection of carbon dioxide into coal seams is a promising technology for reducing anthropogenic greenhouse gas emissions and increasing ultimate production of coalbed methane. Reservoir simulations are an inexpensive method for designing field projects and predicting optimal tradeoffs between maximum sequestration and maximum methane production. Optimum project design and operation are expected to depend on the anisotropy of the permeability along the face-cleat and buttcleat directions, the spacing between cleats, and the sorption isotherms for methane and carbon dioxide. In this work PSU-COALCOMP, a dual-porosity coalbed methane simulator, is used to model primary and secondary production of methane from coal, for a variety of coal properties and operational parameters. It is assumed that the face and butt cleats are perpendicular to each other, with horizontal wells parallel to one type of cleat and perpendicular to the other. The well pattern consists of four horizontal production wells that form a rectangle, with four shorter horizontal wells centered within the rectangle. In the limiting case of no permeability anisotropy, the central wells form a "plus" sign within the square of production wells. All wells are operated as producers of methane and water until a specified reservoir pressure is reached, after which the central wells are operated as injectors for CO 2. Production of methane continues until the CO 2 concentration in the produced gas is too high. The simulation results predict the optimum lengths of the injection wells along the face-and butt-cleat directions, and how these optimum lengths depend on the permeabilities in the two directions. If the cleat spacing is sufficiently small and diffusion of the gas through the pores to the cleats is sufficiently rapid, instantaneous sorption may be assumed. Otherwise, the field performance depends on the characteristic time for transport to the cleats. The pressures at which the injection wells are operated also affect the amounts of CO 2 sequestered, through the pressure and volume constants of the sorption isotherms.