Geosequestration Research Articles

Adsorption Mechanism of CO2/CH4 in Kaolinite Clay: Insight from Molecular Simulation

Understanding the adsorption mechanism of CO2/CH4 in kaolinite clay is essential for the carbon dioxide geological sequestration and enhanced gas recovery in shale reservoirs. In the present work, grand canonical Monte Carlo simulations were employed to investigate the mechanism of competitive adsorption of CO2/CH4 in kaolinite clay. The effects of pore size (1–6 nm), pressure (0.1–30 MPa), temperature (298–378 K), and moisture content (0–0.122 g/cm3) on the adsorption behaviors of pure CH4 and CO2/CH4 mixture were explored in-depth. Specifically, two adsorption layers, i.e., strong and weak adsorption layers, in kaolinite slitlike micropore under high pressure condition have been observed. It was found that pore size and pressure have great effects on the gas adsorption mechanism in kaolinite. The two adsorption mechanisms including monolayer adsorption and micropore filling under high pressure or small pore size conditions were discussed. In addition, simulation results showed that CO2 has much stronger...

A screening framework study to evaluate CO2storage performance in single and stacked caprock–reservoir systems of the Northern Appalachian Basin

AbstractIn the context of geologic carbon dioxide (CO2) sequestration, the storage effectiveness of a caprock–reservoir system is a function of the properties of both the caprock and reservoir – namely, the ability of the caprock to prevent upward leakage of CO2(caprock sealing capability), the mechanical response of the reservoir and caprock (by evaluatingin situstress changes), and the extent and degree to which CO2can be trapped over long periods of time. In this work, all three parameters were considered to evaluate the storage effectiveness of the Cambrian–Ordovician sequence of the Northern Appalachian Basin. We constructed a series of hydro‐mechanical models to investigate interactions between CO2flow and geomechanical processes and to evaluate the three aspects of storage performance. Models were built to evaluate two scenarios: (1) single reservoirs with a single overlying caprock, and (2) systems comprising multiple reservoirs and multiple intermediate caprock units in addition to the primary (uppermost) caprock unit. The overall conclusion of the work is that focusing only on one aspect of storage effectiveness might not necessarily warrant long‐term CO2storage. Results of the sensitivity analysis for the single caprock–reservoir system show that each storage effectiveness metric has its own control parameters. A comparison among three stacked caprock–reservoir systems in different parts of the study area shows that each location in the study area could be appropriate for one of the storage effectiveness metrics. Therefore, we conclude that the screening process to select the best site for CO2sequestration should be based on an evaluation of all three metrics. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd.

CH4 and CO2 adsorption-induced deformation of carbon slit pores with implications for CO2 sequestration and enhanced CH4 recovery

Geological sequestration of carbon dioxide (CO2) into coal seams and shale gas reservoirs have the benefits of CO2 storage as well as enhanced gas recovery. However, the coal or shale swelling during CO2 enhanced methane (CH4) production significantly reduces the gas injection and production rate. In this work, the CH4 and CO2 adsorption-induced deformation of carbon slit pores as representative of coal and shale nanopores was studied using grand canonical Monte Carlo simulation. We focused on the strain difference by comparing the CO2 and CH4 adsorption-induced deformation of pores with various widths. The effect of each pore width on the bulk swelling was analyzed under different pressures and temperatures. The results showed that the strain difference between CO2 and CH4 at different conditions oscillates with a damped amplitude as the pore width increases, which can be positive or negative indicating pore swelling or contraction when CH4 is displaced by CO2. The maximum swelling occurs among the pores inaccessible to CH4 but accessible to CO2 molecules and the contracting pores contribute negatively to the bulk swelling. Furthermore, this study provided fundamental adsorption induced strain of each pore width for predicting the bulk deformation during CO2 enhanced CH4 production when the coal or shale pore size distribution is known.

Salinity effect on micro-scale contact angles using a 2D micromodel for geological carbon dioxide sequestration

One of the most effective methods of mitigating carbon dioxide emission is geological sequestration, in which an enormous amount of CO2 captured from the main sources of CO2 is injected into deep underground layers for long-term storage. The most capacious of these storage sites are saline aquifers. The capacity and safety of these storage sites are governed by capillary force. Among the parameters influencing capillary pressure, the wettability of rock, which is quantified by the contact angle, has the highest uncertainty. Measuring the contact angle in real conditions inside the pores of a rock is ideal, but technical issues force researchers to measure the contact angle of a bubble of CO2 or a water/brine droplet on a flat surface, which cannot model the real fluid configuration inside the pores. In our experimental study, we used a transparent glass 2D micromodel with randomly patterned channels in order to inject CO2 and brine with different salinities, then measured the contact angle of the water-CO2 interface on glass channel wall surfaces. Our pore-scale dynamic contact angle results showed that by increasing the pressure from 1 to 8 MPa (equivalent to increasing the depth from 100 to 800 m, respectfully), the receding and advancing contact angles increased for all brines with different salinities (0.1, 1, and 3 molarity of NaCl). For example, the receding contact angle increased from ∼60° to ∼90° with the increased pressure for brine with 1M salinity. A higher contact angle, which indicates lower capillary pressure, increases the risk of the leakage through ground layers and the migration of CO2 back to the surface. Moreover, increased salinity results in an increased contact angle for a specific pressure, which must be considered for the safety of any storage site. Also, contact angle hysteresis, which is an important parameter for immobilizing CO2 bubbles inside of the rock pores, increases with pressure and decreases with salinity.

Seismic monitoring of CO2 Geosequestration: CO2CRC Otway project case study

The CO2CRC Otway Project is Australia?s first demonstration of the deep geological storage of carbon dioxide. Its test site is located in Victoria, onshore. Within the bound of the first phase of the Otway project ~61000 tonnes of CO2/CH4 mixture were injected into depleted gas reservoir located at a depth of 2 km. Second phase of the project is dedicated to injection of small amount (up to 10 000 tonnes) of CO2-rich gas to saline aquifer at depth of ~1.3 km. Time-lapse seismic is a powerful tool for imaging of changes in the subsurface such as migration of CO2 within reservoir and assurance monitoring of possible leakage to other formations. However imaging of gas-into-gas injection (phase I) or injection of very small amounts (phase II) using land seismic are complicated problems. To meet these challenges a comprehensive seismic program is developed and being implemented. It includes surface and borehole time-lapse seismic surveys. First 3D survey was acquired in year 2000 to find gas fields in the area, two more surveys were shot in 2008 (pre-injection baseline) and 2009 (first monitor, ~31 000 tonnes of gas were injected to the date of survey), next survey is scheduled at January, 2010. A number or repeated 2D surveys were acquired over last several years to optimize 3D seismic acquisition technique and investigate repeatability of land seismic data.

Rapid gas transport in the near-surface of the earth

Conventional models of gas transport in the earth centres on diffusion, convection and advection. Anecdotal and experimental evidence suggests that sometimes gas transport can be orders of magnitude faster. A model of microbubble transport with vertical velocities of the order of 1 - 1000 m/day, dependant on microfracture size, provides a mechanism for these observations. Because the force acting on a microbubble is buoyancy, the flow will be vertical with little dispersion. This presentation will review this theory and some of the tests conducted to confirm such rapid vertical velocities. Fast gas transport also has applications. For example, radon (222Rn, t½ = 3.8 days) is often used for locating uranium but can only work with rapid movement of a carrier gas. Radon has also been used for fault location. Measurement of radon gas flux on the surface has also been used to locate in-situ fires in coal seams in the Hunter Valley, fires which are located at 300 ? 450m depth. Whether the radon is from the source (burning coal) or picked up by the flowing gas (CO2), the surface measurements of radon show an anomaly located vertically over the fires and which may then be used to locate such events. The occurrence of rapid gas movement gives cause for concern over geosequestration of CO2 as zones of high flux must be mapped and avoided.

Critical review of applications of iron and steel slags for carbon sequestration and environmental remediation

One of the major concerns faced by the iron and steel industry, other than the abundant emission of carbon dioxide into the atmosphere, is the huge quantity of slag that is generated during the manufacturing of iron and steel. A comprehensive understanding of the iron and steel slag properties has diverted them away from stockpiling or landfilling to useful engineering applications. The similarity of these slags to natural minerals used in geologic carbon dioxide sequestration has made them sustainable alternative for industrial-scale carbon capture and storage. Further, they possess properties that are conducive for remediation of soil and groundwater contaminated with heavy metals and other toxic chemicals. This paper reviews the iron and steel slag characteristics suitable for engineering applications, describes several engineering application examples, and discusses challenges and opportunities to develop practical applications using iron and steel slags. This paper also discusses the on-going research which explores the use of steel slag along with the biochar-amended soil to develop a biogeochemical landfill cover to sequester fugitive gas emissions such as CH4, CO2 and H2S from MSW landfills and attain zero-emissions landfill.

Hydromechanical modelling of CO2 sequestration using a component-based multiphysics code

Geologic carbon dioxide sequestration (GCS) is a complex process with coupled multiphysics mechanisms, including non-linear solid deformations and fluid flow. When applying a finite-element method to solve such a complex problem, implementing and solving non-linear partial differential equations with sophisticated material models pose great challenges. In this work, a generic component-based multiphysics analysis code – Albany – is introduced for the modelling and analysis of GCS problems. The component-based approach allows the application code development effort to focus on writing physics models. A notable feature of Albany is the powerful automatic differentiation utilities that can be used to calculate automatically system Jacobians and consistent tangents. Two numerical problems, namely, wellbore injection and carbon dioxide transport in a confined underground channel, are developed to demonstrate the performance of the Albany analysis framework. The results are verified against and matched well with those from Comsol – a robust commercial multiphysics finite-element package. The numerical results are also thoroughly analysed to gain insights into distribution profiles and temporal evolutions of pore pressure and displacement fields during a GCS process.

A new model to conduct hydraulic fracture design in coalbed methane reservoirs by incorporating stress variations

Coalbed reservoirs are considered as suitable media for injection operations, especially for geological sequestration of carbon dioxide (CO2). This type of reservoirs might be stimulated to enhance the efficiency of injection as the permeability of these formations is usually low (0.1–10 mD). The hydraulic fracturing technology is one of the effective methods to attain a greater injectivity. To design an efficient hydraulic fracture, it is vital to systematically investigate important changes (e.g., pressure and stresses) occurring over the injection process on the fracturing performance. An increase in the reservoir pressure is an inevitable occuerrence during the fracturing operation. In situ stresses will also vary due to the fluid injection. As a consequence, the permeability of coalbed will be altered during the reservoir life. In this research study, a novel model for the hydraulic fracture design is introduced to consider the changes in the reservoir permeability during the injection process. A Direct Boundary Element Method (DBEM), which is a fundamental concept in the Unified Fracture Design (UFD), is employed to determine the fracture injectivity. In this study, the pressure change is estimated based on the injectivity. The variations of in situ stresses are determined using a model, which uses the Boundary Element Method (BEM) and theory of inclusions. Permeability is then updated based on the new values of stresses and the design dimensions of the fracture for the new time steps. Therefore, the model presents a suitable design of hydraulic fracture by considering the reservoir pressure changes during the injection. The proposed method is implemented on Latrobe Valley brown coal. The results suggest that the reservoir life is an important parameter to optimize the hydraulic fracturing design. Fractures with the same width and different penetrations yield very different efficiencies during the injection. The highest amount of cumulative injection can be achieved after 10 years using a fracture, which seems to be not optimum at the initiation stage of the injection process. This study proposes that it is necessary to take into account the stress changes in the design of a hydraulic fracture system in a coalbed to attain the effective injection operation regardless of high penetrations.

Effect of CO2 on P- and S-wave velocities at seismic and ultrasonic frequencies

Time-lapse seismic is a widely used technology for monitoring the geological sequestration of carbon dioxide (CO2), consisting of mapping its movement in the subsurface and of demonstrating that the CO2 is safely stored in the reservoir (Xue and Ohsumi, 2004). In this work, the effect of CO2 on P- and S-wave velocities was investigated. Laboratory measurements were performed with Castlegate sandstone both at seismic frequencies (1–155 Hz), and at ultrasonic frequency (around 500 kHz). Different CO2 saturations between 2% and 10% were obtained by controlled depressurization of CO2-saturated water with which the sandstone sample had been saturated with. At seismic frequencies, the results of the experiments revealed that P-wave velocity is strongly reduced in the presence of free gas CO2 in the pore space, whereas at ultrasonic frequency, the P-wave velocity changed only slightly. Therefore, the presence of free CO2 gas increased significantly the P-wave dispersion between seismic and ultrasonic frequencies. The S-wave velocity, on the other hand, was hardly affected by the pore fluid at seismic frequencies. At seismic frequencies, P- and S-wave velocities were consistent with the Biot–Gassmann model. The P-wave velocity dispersion and corresponding attenuation were simulated by applying the Cole–Cole model. The transition frequency was found around 200 kHz.

Using mercury injection pressure analyses to estimate sealing capacity of the Tuscaloosa marine shale in Mississippi, USA: Implications for carbon dioxide sequestration

This work used mercury injection capillary pressure (MICP) analyses of the Tuscaloosa Group in Mississippi, including the Tuscaloosa marine shale (TMS), to assess their efficacy and sealing capacity for geologic carbon dioxide (CO2) sequestration. Tuscaloosa Group porosity and permeability from MICP were evaluated to calculate CO2 column height retention. TMS and Lower Tuscaloosa shale samples have, respectively, Swanson permeability values less than 0.003 md and 0.00245 md; porosity from 3.86% to 9.86% and 1.34% to 7.96%; median pore throat sizes from 0.00342 to 0.0111 μm and 0.00311 to 0.017 μm; and pore radii from 0.0130 to 0.152 μm and 0.0132 to 0.149 μm. Mercury entry pressures for the TMS and Lower Tuscaloosa range from 4.9 to 57.1 MPa and 5.0 to 56.3 MPa, respectively. Calculated CO2 column heights that the TMS sample set can retain in the reservoir range from 23 to 255 m when the TMS is near 100% water saturation. Potential top seal leakage is more likely to be influenced by the numerous well penetrations through the confining system of the TMS rather than capillary failure. Results of this study demonstrate desirable sealing capacity of the TMS for geologic CO2 sequestration in reservoir sandstones of the Lower Tuscaloosa and could provide an analogue to other potential CO2 sequestration top seals.

Analysis of Coal Swelling Deformation Caused by Carbon Dioxide Adsorption Based on X-Ray Computed Tomography

The geologic sequestration of carbon dioxide by coal beds leads to the swelling deformation of coal. In order to investigate the swelling deformation characteristics at the microscopic scale, X-ray computed tomography (CT) scanning technology was used. X-ray CT scanning technology detects the internal structure, deformation, and porosity of coal at different gas pressures. Results show that swelling deformation is nonuniform, which is caused by the heterogeneity of the coal structure. Through quantitative measurement of the distance between fractures and pseudocolor processing of CT images, we observed that fractures gradually close with the increase of adsorption pressure. As adsorption pressure increases, the porosity of coal decreases, and the density of coal increases.

A Simple Analytical Model for Estimating the Dissolution-Driven Instability in a Porous Medium

This article deals with the stability problem that arises in the modeling of the geological sequestration of carbon dioxide. It provides a more detailed description of the alternative approach to tackling the stability problem put forth by Vo and Hadji (Physics of Fluids, 2017, 29, 127101) and Wanstall and Hadji (Journal of Engineering Mathematics, 2018, 108, 53–71), and it extends two-dimensional analysis to the three-dimensional case. This new approach, which is based on a step-function base profile, is contrasted with the usual time-evolving base state. While both provide only estimates for the instability threshold values, the step-function base profile approach has one great advantage in the sense that the problem at hand can be viewed as a stationary Rayleigh–Bénard problem, the model of which is physically sound and the stability of which is not only well-defined but can be analyzed by a variety of existing analytical methods using only paper and pencil.

Geologic CO2 sequestration monitoring design: A machine learning and uncertainty quantification based approach

Monitoring is a crucial aspect of geologic carbon dioxide (CO2) sequestration risk management. Effective monitoring is critical to ensure CO2 is safely and permanently stored throughout the life-cycle of a geologic CO2 sequestration project. Effective monitoring involves deciding: (i) where is the optimal location to place the monitoring well(s), and (ii) what type of data (pressure, temperature, CO2 saturation, etc.) should be measured taking into consideration the uncertainties at geologic sequestration sites. We have developed a filtering-based data assimilation procedure to design effective monitoring approaches. To reduce the computational cost of the filtering-based data assimilation process, a machine-learning algorithm: Multivariate Adaptive Regression Splines is used to derive computationally efficient reduced order models from results of full-physics numerical simulations of CO2 injection in saline aquifer and subsequent multi-phase fluid flow. We use example scenarios of CO2 leakage through legacy wellbore and demonstrate a monitoring strategy can be selected with the aim of reducing uncertainty in metrics related to CO2 leakage. We demonstrate the proposed framework with two synthetic examples: a simple validation case and a more complicated case including multiple monitoring wells. The examples demonstrate that the proposed approach can be effective in developing monitoring approaches that take into consideration uncertainties.

Evaluation of the Foamability Potential of a Novel Biosurfactant Using the Solution to Advective-Diffusive Transport Model in Porous Media With a Linear Adsorption Trend

While geological sequestration of anthropogenic carbon dioxide is a technically and economically viable option for reducing emissions to the level required to avoid the predicted 2 degrees Celsius increase of atmospheric temperature by the end of this century, efficient sequestration planning is vital for the achievement of this goal.The petroleum industry has used conventional surfactants in enhance oil recovery projects aimed at prolonging the life span of a field, thereby increasing ultimate reserves. Notable among these is the use of surfactants for injected gas relative mobility control. Therefore, the potential for carbon dioxide mobility control in saline aquifers using surfactant alternating gas injection is huge, given the rich experience that can be tapped from the petroleum industry practice.Considering the expected surfactant loses in surfactant-enhanced geological sequestration similar to that encountered in the petroleum industry, this paper has used the analytical solution to advective diffusive equation that exists in the literature with a linear adsorption model where, adsorption has been used to predict trends in minimum pressure drop required for foam generation. The greatest utility of this work lies in the fact that the analytical solution is related a linear adsorption model related to a novel surfactant found from biological and hydrocarbon sources of geologic origin. This paper, therefore, extends the work of linear adsorption models for this novel surfactant aimed at exploring improved oil recovery potentials; in addition to exploring its potential for efficient geological carbon storage in saline aquifers.

Modeling flow in porous media with double porosity/permeability: A stabilized mixed formulation, error analysis, and numerical solutions

The flow of incompressible fluids through porous media plays a crucial role in many technological applications such as enhanced oil recovery and geological carbon-dioxide sequestration. The flow within numerous natural and synthetic porous materials that contain multiple scales of pores cannot be adequately described by the classical Darcy equations. It is for this reason that mathematical models for fluid flow in media with multiple scales of pores have been proposed in the literature. However, these models are analytically intractable for realistic problems. In this paper, a stabilized mixed four-field finite element formulation is presented to study the flow of an incompressible fluid in porous media exhibiting double porosity/permeability. The stabilization terms and the stabilization parameters are derived in a mathematically consistent manner, and the computationally convenient equal-order interpolation of all the field variables is shown to be stable. A systematic error analysis is performed on the resulting stabilized weak formulation. Representative problems, patch tests and numerical convergence analyses are performed to illustrate the performance and convergence behavior of the proposed mixed formulation in the discrete setting. The accuracy of numerical solutions is assessed using the mathematical properties satisfied by the solutions of this double porosity/permeability model. Moreover, it is shown that the proposed framework can perform well under transient conditions and that it can capture well-known instabilities such as viscous fingering.

Transient analysis of advancing contact angle measurements on polished rock surfaces

Abstract Contact angle measurements for gas-liquid-rock systems are important for modeling multi-phase flow and transport in the subsurface. These data are needed in applications such as the extraction of oil and gas resources, geologic sequestration of carbon dioxide, contaminant fate and transport, and aquifer recharge through the vadose zone. Contact angles are frequently measured with the sessile drop method. Previous research has largely ignored the dynamic behavior of sessile droplets on geologic materials. This study investigates the dynamic behavior of sessile water droplets on prepared rock surfaces in the presence of air. Droplet diameter and advancing contact angle were determined at 0.5 s intervals for ∼ 90 s on flat polished disks of Burlington limestone, Crossville sandstone, Mancos shale, Sierra White granite, Vermilion Bay granite, and Westerly granite using a Kruss DSA 30 Drop Shape Analyzer. The droplet diameter and advancing contact angle data sets were nonlinearly regressed against time using two different two-parameter models. The median coefficients of determination for the fits were 0.85 and 0.96, respectively. The resulting parameter estimates were used to compute the apparent equilibrium contact angle, θe, for each disk following droplet diameter stabilization. Estimates of θe ranged from 37.2° for Mancos shale to 75.6° for Burlington limestone. Analysis of variance indicated statistically significant differences in θe between the rock types at the 95% confidence level. The variability of θe on the polished rock surfaces, as quantified by the coefficient of variation (CV) for θe, varied between ∼ 3 and ∼ 9%; there were no significant differences in CV between the rock types. Neutron radiography indicated changes droplet morphology over time were due to the spontaneous imbibition of water into the rock matrix. The transient analysis employed in this study permits a more meaningful estimate of the equilibrium contact angle for rocks than taking the initial value or averaging over time as is frequently done.

The influence of different diffusion pattern to the sub- and super-critical fluid flow in brown coal

Sub- and super-critical CO2 flowing in nanoscale pores are recently becoming of great interest due to that it is closely related to many engineering applications, such as geological burial and sequestration of carbon dioxide, Enhanced Coal Bed Methane recovery ( ECBM), super-critical CO2 fracturing and so on. Gas flow in nanopores cannot be described simply by the Darcy equation. Different diffusion pattern such as Fick diffusion, Knudsen diffusion, transitional diffusion and slip flow at the solid matrix separate the seepage behaviour from Darcy-type flow. According to the principle of different diffusion pattern, the flow of sub- and super-critical CO2 in brown coal was simulated by numerical method, and the results were compared with the experimental results to explore the contribution of different diffusion pattern and swelling effect in sub- and super-critical CO2 flow in nanoscale pores.

VS2DRTI: Simulating Heat and Reactive Solute Transport in Variably Saturated Porous Media.

Variably saturated groundwater flow, heat transport, and solute transport are important processes in environmental phenomena, such as the natural evolution of water chemistry of aquifers and streams, the storage of radioactive waste in a geologic repository, the contamination of water resources from acid-rock drainage, and the geologic sequestration of carbon dioxide. Up to now, our ability to simulate these processes simultaneously with fully coupled reactive transport models has been limited to complex and often difficult-to-use models. To address the need for a simple and easy-to-use model, the VS2DRTI software package has been developed for simulating water flow, heat transport, and reactive solute transport through variably saturated porous media. The underlying numerical model, VS2DRT, was created by coupling the flow and transport capabilities of the VS2DT and VS2DH models with the equilibrium and kinetic reaction capabilities of PhreeqcRM. Flow capabilities include two-dimensional, constant-density, variably saturated flow; transport capabilities include both heat and multicomponent solute transport; and the reaction capabilities are a complete implementation of geochemical reactions of PHREEQC. The graphical user interface includes a preprocessor for building simulations and a postprocessor for visual display of simulation results. To demonstrate the simulation of multiple processes, the model is applied to a hypothetical example of injection of heated waste water to an aquifer with temperature-dependent cation exchange. VS2DRTI is freely available public domain software.

Clean Coal Technologies – a chance for Poland’s energy security. Decision-making using AHP with Benefits, Opportunities, Costs and Risk Analysis

AbstractThe comprehensive use of available domestic energy resources, mainly coal and lignite, is the basis for the development of Poland’s economy and energy security due to the country’s large resource base. The implementation of clean coal technologies (CCT) is a necessary condition for maintaining coal’s leading position in Poland. Coal gasification technologies are seen as potentially attractive for the Polish economy, both for the chemical sector as well as for the mining sector. Working on the commercial implementation of coal gasification technologies, which ensures the effective substitution of scarce hydrocarbon fuels, will be a challenge to Polish industrial policy and support for CCT. This paper presents an analysis of coal gasification technologies using the decision support procedures, BOCR and SWOT analyses. These procedures helped determine the ranking of technologies and the types of development strategies plausible for the analysed technological variants. Taking into consideration the conditions of the Polish economy, the highest-ranking technologies included those aimed towards the production of methanol with the geological sequestration of carbon dioxide (CCS). In the case of underground coal gasification, it was found that the technology is not yet ready for implementation on a commercial scale and investment is subject to very high risk.