CO2-induced Swelling Research Articles

Swelling damage characteristics induced by CO2 adsorption in shale: Experimental and modeling approaches

Carbon dioxide (CO2) geological sequestration represents a critical technology in mitigating climate change. Shale reservoirs demonstrate a pronounced affinity for CO2, resulting in adsorption-induced swelling that significantly impacts permeability, mechanical strength, injection efficiency, and sequestration safety. For this, we tried to explore the key factors driving the swelling of shale upon CO2 injection and its subsequent impact on reservoir properties. Utilizing a self-developed high-temperature-pressure gas adsorption apparatus, we measured strain in Jurassic shale at 308 K under constant hydrostatic pressure with helium (He) at 1300 psi (1 psi = 6.895 kPa) and CO2 at 850 psi. Next, we investigated the influence of CO2 concentration on swelling protentional while maintaining constant pressure, uncovering the anisotropic deformation in relation to pressure. It shows that CO2 adsorption induces significant swelling in shale, following a Langmuir-type pressure relationship. Deformation is more pronounced perpendicular than that parallel to the bedding plane. At low pressure, vertical swelling is 2.28 times greater than the horizontal; while at high pressure, the vertical compression is 31.26 times greater than the horizontal. It seems that the anisotropic swelling enhances permeability predictions during CO2 injection. Mixed gases under constant compression can prompt gas desorption, stress redistribution, and alterations in pore structure, amplifying He compression effect. The strain induced after replacing CO2 with He exceeds that from pure He injection. The asynchronous response of CO2-induced swelling and mechanical compression can precipitate crack propagation and fracturing. Overall, anisotropic swelling from CO2 adsorption changes pore structure and permeability, affecting fluid flow and storage. Considering CO2 concentration and anisotropic characteristics in reservoir modeling is essential for optimizing injection strategies and enhancing reservoir efficiency.

CO2/CH4 mixed-gas separation in PIM-1 at high pressures: Bridging atomistic simulations with process modeling

Polymeric membranes with intrinsic microporosity have been at the center of attention for gas separation applications since the introduction of PIM-1. This study utilizes atomistic simulations to model and to understand the pure- and mixed-gas transport properties of PIM-1 for the CO2/CH4 gas pair. Monte Carlo and molecular dynamics methods were combined in the estimation of sorption and diffusion of CO2 and CH4 in PIM-1. Simulated sorption and permeability data compared very well with experimental reports. Mixed-gas adsorption simulations proved the existence of competitive adsorption, favoring CO2, hence resulting in an increase in solubility selectivities. However, in mixed-gas environment CH4 permeabilities increased significantly compared to pure gas conditions, overall decreasing perm-selectivities of the polymer. Plasticization of the polymer around 25 bar CO2 partial fugacity was apparent both in pure- and mixed-gas conditions. Simulations at different gas feed compositions proved the dependence of competitive sorption and CO2-induced swelling in partial feed gas fugacities. Simulation results were combined to obtain a macroscopic permeability model that relates the multicomponent permeability to the permeate pressure and composition. Accurate estimations of permeabilities by the model were achieved allowing future implementation of the model in process simulation tools.

Enhanced molecular selectivity and plasticization resistance in ring-opened Tröger's base polymer membranes

As a new class of membrane materials, Tröger's base (TB) polymers suffer from CO2-induced plasticization, which leads to a loss in their gas separation selectivity. To address this challenge, we describe a new approach for enhancing their plasticization resistance by ring-opening a TB polymer to establish hydrogen bonds between polymer chains. The ring-opened membranes, called TB-OR, exhibit H2/CO2 and H2/CH4 selectivities of 5.1 and 186.7, respectively. High-pressure CO2 feed measurements reveal that the TB-OR membranes possess better plasticization resistance than untreated TB polymers. The increased plasticization resistance is likely due to hydrogen bonds formed between –N-H groups and N atoms in TB-OR polymers, which reduce the polymer chain mobility and CO2-induced swelling of polymers. The design principles open a new route for making molecularly-selective membranes with significantly enhanced CO2 plasticization resistance that are potentially useful for CO2 separation and hydrogen purification.

CO2/CH4 separation characteristics of poly(RTIL)-RTIL-zeolite mixed-matrix membranes evaluated under binary feeds up to 40 bar and 50°C

Three-component mixed-matrix membranes composed of a polymerized room-temperature ionic liquid (poly(RTIL)), a room-temperature ionic liquid (RTIL), and a zeolite were synthesized and evaluated for CO2/CH4 permeability under binary gas feeds, and operating pressures and temperatures of up to 40 bar and 50 °C, respectively. A CO2/CH4 selectivity of 43 with a CO2 permeability of 202 barrers was achieved by a MMM containing 30 wt % SAPO-34 at 40 bar and 17 °C with an equimolar CO2/CH4 feed. The differences in selectivity and permeability between membranes containing 30 wt% SAPO-34 vs. SSZ-13 suggest that CO2-induced swelling of the poly(RTIL) + RTIL matrix may lead to delamination of the matrix from the zeolite particle surface. This effect may detrimentally affect zeolites with a weaker surface charge. For membranes containing 30 wt % SAPO-34, at 17 °C, both CO2 permeability and CO2/CH4 selectivity increase when the feed composition increases from 25 mol % to 50 mol % CO2, likely due to competitive sorption. At 50 °C, the highest recorded selectivity was 26, which can be attributed to selectivity losses from decreased CO2 adsorption onto the zeolites and thermally induced poly(RTIL) + RTIL matrix swelling by CO2.

Swelling of Shales by Supercritical Carbon Dioxide and Its Relationship to Sorption.

Shale gas is a promising energy source offering additional energy security over concerns of fossil fuel depletion. Injecting CO2 into depleted shale gas reservoirs might provide a feasible solution for CO2 storage and enhanced gas recovery. However, shale strain caused by the CO2 injection as well as CO2 sequestration in the reservoir needs to be considered during shale gas production. For this purpose, this paper examines the adsorption capacities, CO2-induced swelling, and He-induced strain of shales at 0–16 MPa and 35–75 °C. The maximum excess adsorption at different temperatures correlated with the bulk phase density: as the CO2 temperature increased, the maximum excess adsorption density decreased. The density of the adsorbed phase, obtained using the Dubinin–Radushkevich model, was used to fit the excess adsorption data. At low pressure, the CO2-induced strain on shale was caused by the gas adsorption, whereas at high pressure, it was caused by gas pressure. The absolute adsorption linearly correlated with the adsorption-induced strain.

Simultaneous measurement of CO2 sorption and swelling of phosphate-based ionic liquid

The development of alternative CO2 capture solvents such as ionic liquids (ILs) and nanoparticle organic hybrid materials (NOHMs) have provided interesting options for CO2 capture. In this study, CO2 interactions with 1,3-dimethylimidazolium dimethylphosphate ([MMIM]DMP), 1-ethyl-3-methylimidazolium dimethylphosphate ([EMIM]DMP) and 1-ethyl-3-methylimidazolium diethylphosphate ([EMIM]DEP) that contain inorganic ester groups based on phosphate, were investigated using ATR FT-IR spectroscopy. CO2-induced swelling, CO2 diffusivity and CO2 capture capacity were simultaneously measured to identify CO2 capture mechanisms, kinetics and diffusion behaviors as a function of the alkyl chain length of the cation. Henry's law constants of CO2 were found to be in the range of 4–11 MPa, which is in agreement with those reported in other studies.

Swelling of shale in supercritical carbon dioxide

Shale gas is an unconventional but promising natural resource. One means of producing this gas is by injecting CO2 into shale formations, and this technique has received widespread attention of late. This method not only allows the possibility of storing CO2 in shale formations but also enhances the gas recovery process. The swelling of the shale matrix caused by CO2 adsorption has important consequence with regard to the production of shale gas and the sequestration of CO2 in shale formations. In this study, an apparatus was designed and used to measure CO2-induced swelling in shale samples at temperatures between 308 and 348 K and pressures up to 15 MPa. The results show that CO2-induced swelling occurs in shale samples. With increasing CO2 pressure, the swelling of shale samples initially increases and then lessens. With increasing CO2 temperature, the maximum swelling of the shale gradually decreases. The strain induced in the shale during this process in response to a constant CO2 pressure can be divided into three regions: transient shrinkage, slow swelling and stable strain. The results of calculations employing a simplified local-density model were in agreement with the experimental data obtained from CO2-induced swelling in shale. All experimental samples exhibited anisotropic strains in response to CO2 injection, with the strains always being less in the direction parallel to the bedding plane.

Sub- and super-critical carbon dioxide flow behavior in naturally fractured black coal: An experimental study

A proper understanding of super-critical carbon dioxide (CO2) flow behavior in coal is essential, as CO2 normally exists in its super-critical state in deep coal seams and studies are lacking. The main objective of this study is to distinguish the permeability behavior of coal for sub-critical and super-critical CO2 flows. Therefore, a series of triaxial experiments was conducted on naturally fractured black coal specimens. Permeability tests were carried out for 15, 20 and 25MPa confinements at 33.5°C temperature. Three test scenarios were conducted to investigate, (1) variation of the permeability behavior of coal with CO2 phase condition, (2) the swelling effect on sub- and super-critical CO2 permeability patterns, and (3) the potential of nitrogen (N2) to reverse CO2-induced swelling. According to the test results, the permeability of super-critical CO2 is significantly lower than sub-critical CO2 due to the higher viscosity and swelling associated with super-critical CO2. Moreover, at super-critical state there is a higher decline of CO2 permeability with increasing injecting pressure due to the higher increments in the associated viscosity and swelling. Although CO2 adsorption-induced swelling causes permeability of both CO2 and N2 to be reduced at low injection pressures the poro-elastic effect becomes more dominant and may cause CO2 permeability to increase for higher injecting pressures, because CO2 flow behavior may transfer from super-critical to sub-critical after the swelling due to the decline of downstream pressure development. Moreover, N2 has the potential to reverse some swelling effects due to CO2 adsorption, and this recovery rate is higher at lower injecting pressures and higher confining pressures.

Swelling of moist coal in carbon dioxide and methane

Abstract Determining the feasibility of injecting CO2 into coal seams for enhanced coalbed methane (ECBM) recovery as well as providing long-term carbon sequestration is an active area of research. It is now well known that coal swells in the presence of water and gases, which in turn may affect its in-seam permeability. If the swelling of the coal matrix by each component can be quantified, it may be possible to make better predictions about the suitability of particular seams for ECBM and carbon sequestration. Despite numerous studies where coal swelling has been measured in gases or water, there is relatively little information relating to how swelling of coals by gases is affected by water. In this paper we report on the gas-induced swelling behaviour of four moist Australian coals. Blocks of coal, nominally 30 × 9 × 9 mm, were cut parallel and perpendicular to the bedding plane from larger lumps. Samples were moisture-equilibrated at 97% relative humidity before being exposed to CO2 or CH4 at pressures up to 16 MPa and a temperature of 55 °C. Swelling of each sample was measured directly using digital cameras to monitor the change in length of the block as a function of pressure. Results show that swelling was greater in CO2 than CH4, with lower rank coals swelling more than high rank material. The presence of moisture significantly reduced the amount of additional swelling by the gas compared to dry coals; however, the degree to which the swelling of the coals was affected by moisture depended on the rank of the coal. It was also found that, proportionally, CH4-induced swelling was more affected by the presence of moisture than CO2-induced swelling. Although moist coals swelled less in CO2 or CH4 than dry coals, if the swelling due to moisture is included, the total swelling is more than that induced by the corresponding gas in the dry coal.

Adsorption and strain: The CO 2-induced swelling of coal

Enhanced coal bed methane recovery (ECBM) consists in injecting carbon dioxide in coal bed methane reservoirs in order to facilitate the recovery of the methane. The injected carbon dioxide gets adsorbed at the surface of the coal pores, which causes the coal to swell. This swelling in confined conditions leads to a closure of the coal reservoir cleat system, which hinders further injection. In this work we provide a comprehensive framework to calculate the macroscopic strains induced by adsorption in a porous medium from the molecular level. Using a thermodynamic approach we extend the realm of poromechanics to surface energy and surface stress. We then focus on how the surface stress is modified by adsorption and on how to estimate adsorption behavior with molecular simulations. The developed framework is here applied to the specific case of the swelling of CO 2-injected coal, although it is relevant to any problem in which adsorption in a porous medium causes strains.

Visual Representation of Carbon Dioxide Adsorption in a Low-Volatile Bituminous Coal Molecular Model

Carbon dioxide can be sequestered in unmineable coal seams to aid in mitigating global climate change, while concurrently CH4 can be desorbed from the coal seam and used as a domestic energy source. In this work, a previously constructed molecular representation was used to simulate several processes that occur during sequestration, such as sorption capacities of CO2 and CH4, CO2-induced swelling, contraction because of CH4 and water loss, and the pore-blocking role of moisture. This is carried out by calculating the energy minima of the molecular model with different amounts of CO2, CH4, and H2O. The model used is large (>22 000 atoms) and contains a molecular-weight distribution, so that it has the flexibility to be used by other researchers and for other purposes in the future. In the low-level molecular modeling presented here, it was anticipated that CO2 would be adsorbed more readily than CH4, that swelling would be anisotropic, greater perpendicular to the bedding plane because of the rank of this ...

Long-Term CO2 Sorption on Upper Freeport Coal Powder and Lumps

Powder and lumps of the Argonne Premium Upper Freeport coal were compared in a 9-month-long CO2 sorption−desorption study. On the basis of the slope analysis, CO2 induced the lumps swelling by 7%. The powder swelled by 8% and then rapidly shrank by 3% on desorption. This was verified by a “single point” injection of helium and the pressure-and-density technique, which was sufficiently sensitive. Low-pressure Langmuir-fit parameters suggest that the microporous textures of the powder and lumps are similar. The samples demonstrated greatly increased sticking coefficients and a slightly larger number of the “sorption ready” sites, after the CO2-induced swelling and structural rearrangement resulted in variable degrees of the matrix shrinkage. No permanent changes in the void volume and dry mass were detected after complete desorption. The observed hysteresis in sorption−desorption behavior of both samples upon the approach to the CO2 density fluctuation ridge is interpreted as a contribution of condensation and coalescence of CO2 clusters in mesopores. The differences between the two samples in the magnitude of the enhanced capillary condensation, with or without dissolution, demonstrate the importance of changes in mesoporous texture caused by grinding of coal lumps into powder.

Effects of Matrix Shrinkage and Swelling on the Economics of Enhanced-Coalbed-Methane Production and CO2 Sequestration in Coal

Summary Increases in carbon dioxide (CO2) levels in the atmosphere and their contributions to global climate change are a major concern. CO2 sequestration in unmineable coals may be a very attractive option, for economic as well as environmental reasons, if a combination of enhanced-coalbed-methane (ECBM) production and tax incentives becomes sufficiently favorable compared to the costs of capture, transport, and injection of CO2. Darcy flow through cleats is an important transport mechanism in coal. Cleat compression and permeability changes caused by gas sorption/desorption, changes of effective stress, and matrix swelling and shrinkage introduce a high level of complexity into the feasibility of a coal sequestration project. The economic effects of CO2-induced swelling on permeabilities and injectivities has received little (if any) detailed attention. CO2 and methane (CH4) have different swelling effects on coal. In this work, the Palmer-Mansoori model for coal shrinkage and permeability increases during primary methane production was rewritten to also account for coal swelling caused by CO2 sorption. The generalized model was added to a compositional, dual-porosity coalbed-methane reservoir simulator for primary (CBM) and ECBM production. A standard five-spot of vertical wells and representative coal properties for Appalachian coals was used (Rogers 1994). Simulations and sensitivity analyses were performed with the modified simulator for nine different parameters, including coal seam and operational parameters and economic criteria. The coal properties and operating parameters that were varied included Young's modulus, Poisson's ratio, cleat porosity, and injection pressure. The economic variables included CH4 price, CO2 cost, CO2 credit, water disposal cost, and interest rate. Net-present-value (NPV) analyses of the simulation results included profits resulting from CH4 production and potential incentives for sequestered CO2. This work shows that for some coal seams, the combination of compressibility, cleat porosity, and shrinkage/swelling of the coal may have a significant impact on project economics.

Chemical cross-linking modification of 6FDA-2,6-DAT hollow fiber membranes for natural gas separation

A simple and practical chemical cross-linking method has been demonstrated to make 6FDA-2,6-DAT asymmetric hollow fibers more resistant to plasticization by immersing them into a p-xylenediamine or m-xylenediamine/methanol solution for a short period of time at ambient temperature. FTIR spectra confirm that chemical cross-linking reactions take place between xylenediamine and imide groups of 6FDA-2,6-DAT and form amide groups. The effects of cross-linking modifications on gas separation performance and the resistance to plasticization characteristics are examined by using both pure and CO 2/CH 4 mixed gas tests. Permeances of all gases tested decrease with an increase in the degree of cross-linking, while CO 2/CH 4 permselectivity varies in a narrow range. 6FDA-2,6-DAT hollow fibers show favorable resistance to plasticization once the cross-linking reaches a certain degree. XRD spectra indicate almost no changes on the average intersegmental distance of polymer chains after cross-linking modifications, strongly indicating the cross-linking modifications likely protect nodule integrity from CO 2-induced swelling and restrict polymer chain vibration for diffusion jumps. In addition, we found that m-xylenediamine has a similar cross-linking effectiveness as p-xylenediamine on 6FDA-2,6-DAT hollow fibers, both yield hollow fiber membranes with comparable CO 2/CH 4 selectivity and permeance.

97/03742 State of the fire, ignition and explosion of gases during active and passive fire extinguishing

Determining the feasibility of injecting CO2 into coal seams for enhanced coalbed methane (ECBM) recovery as well as providing long-term carbon sequestration is an active area of research. It is now well known that coal swells in the presence of water and gases, which in turn may affect its in-seam permeability. If the swelling of the coal matrix by each component can be quantified, it may be possible to make better predictions about the suitability of particular seams for ECBM and carbon sequestration. Despite numerous studies where coal swelling has been measured in gases or water, there is relatively little information relating to how swelling of coals by gases is affected by water.In this paper we report on the gas-induced swelling behaviour of four moist Australian coals. Blocks of coal, nominally 30 × 9 × 9 mm, were cut parallel and perpendicular to the bedding plane from larger lumps. Samples were moisture-equilibrated at 97% relative humidity before being exposed to CO2 or CH4 at pressures up to 16 MPa and a temperature of 55 °C. Swelling of each sample was measured directly using digital cameras to monitor the change in length of the block as a function of pressure.Results show that swelling was greater in CO2 than CH4, with lower rank coals swelling more than high rank material. The presence of moisture significantly reduced the amount of additional swelling by the gas compared to dry coals; however, the degree to which the swelling of the coals was affected by moisture depended on the rank of the coal. It was also found that, proportionally, CH4-induced swelling was more affected by the presence of moisture than CO2-induced swelling. Although moist coals swelled less in CO2 or CH4 than dry coals, if the swelling due to moisture is included, the total swelling is more than that induced by the corresponding gas in the dry coal.

CO 2 surface area of coals: The 25-year paradox

Coals are highly porous materials with most of their surface area enclosed in pores of molecular dimensions. Even though coal porosity plays a key role in practically all aspects of its utilization, we still do not know with any certainty the magnitude of coal surface area and its pore size distribution. Surface areas of coals measured by the conventional BETN 2 method are very low, primarily because of the activated diffusion phenomenon. In order to overcome this drawback, the use of CO 2 adsorption for measuring surface areas of coals was proposed about 25 years ago. In the 1970's and 1980's, there was a growing realization that CO 2 over-estimates the surface area because it induces swelling in coals. The present status of our understanding of CO 2-induced swelling in coals and its implications towards surface area and nature of porosity in coal are discussed. While CO 2 gives higher surface area, at CO 2 pressures <1 atm and for short “equilibrium” time the contribution of swelling to total surface area is small. Because of the uncertainties in the values of CO 2-measured monolayer capacity and the cross-sectional area of an adsorbed molecule in pores of molecular dimensions, surface areas of coals are meaningless and, therefore, should not be reported.