Measurements of non-wetting phase trapping applied to carbon dioxide storage

We measure the trapped non-wetting phase saturation as a function of the initial saturation in sand packs. The application of the work is for CO₂ storage in aquifers where capillary trapping is a rapid and effective mechanism to render injected CO₂ immobile. The CO₂ is injected into the formation followed by chase brine injection, or natural groundwater flow, which displaces and traps CO₂ on the pore scale as a residual immobile phase. Current models to predict the amount of trapping are based on experiments in consolidated media, while CO₂ may be stored in relatively shallow, poorly consolidated systems. We use analogue fluids at ambient conditions. The trapped saturation initially rises linearly with initial saturation to a value of approximately 0.13 for oil/water systems and 0.14 for gas/water systems. There then follows a region where the residual saturation is constant with further increases in initial saturation. This behaviour is not predicted by the traditional literature trapping models, but is physically consistent with unconsolidated media where most of the larger pores can easily be invaded at relatively low saturation and there is, overall, relatively little trapping. A good match to our experimental data was achieved with the trapping model proposed by Aissaoui.     

Non-isothermal flow of carbon dioxide in injection wells during geological storage

During sequestration, carbon dioxide within injection wells is likely to be in a dense state and therefore its weight within the wellbore will play an important role in determining the bottomhole pressure and thus the injection rate. However, the density could vary significantly along the well in response to the variation in pressure and temperature. A numerical procedure is formulated in this paper to evaluate the flow of carbon dioxide and its mixtures in non-isothermal wells. This procedure solves the coupled heat, mass and momentum equations with the various fluid and thermodynamic properties, including the saturation pressure, of the gas mixture calculated using a real gas equation of state. This treatment is particularly useful when dealing with gas mixtures where experimental data on mixture properties are not available and these must be predicted. To test the developed procedure two wellbore flow problems from the literature, involving geothermal gradients and wellbore phase transitions are considered; production of 97% carbon dioxide and injection of superheated steam. While these are not typical carbon dioxide injection problems they provide field observations of wellbore flow processes which encompass the mechanisms of interest for carbon dioxide injection, such as phase transition, temperature and density variations with depth. These two examples show that the developed procedure can offer accurate predictions. In a third application the role of wellbore hydraulics during a hypothetical carbon dioxide injection application is considered. The results obtained illustrate the potential complexity of carbon dioxide wellbore hydraulics for sequestration applications and the significant role it can play in determining the well bottomhole pressure and thus injection rate.     

Evaluation of carbon dioxide storage potential for the Bohai Basin,north-east China

The storage potential of selected sites within the Bohai Basin was assessed for the COACH project. The Gangdong oilfield is considered to have a small potential storage capacity (23 Mt) and to be possibly suitable for an enhanced oil recovery or small-scale storage pilot rather than large-scale storage. The Shengli oilfield province is considered to have a great potential storage capacity (472 Mt in eight selected fields), however, these fields, like those of the Gangdong oilfield province, are compartmentalised by faulting and stratigraphy and likely to be quite challenging for injection. Unmineable coal seams in the Kailuan mining area were also considered for storage, the estimated capacity is 504 Gt adsorbed onto the coal and 38,100 Mt void storage capacity. However, the coals have low porosity and permeability, so they would be expected to have poor injectivity. This is also an active mining area and so any storage site would have to be chosen carefully to avoid affecting future energy resources. The Huimin sub-basin within the Jiyang Depression was identified for consideration as an aquifer storage site; the Guantao Formation has good porosity and permeability in this region, and the regional-level storage capacity of these areas was estimated to be 0.7 Gt. The aquifers in the Huimin sub-basin appear promising for storage, however, less data are available than for the oilfields and the sealing formations are not directly proven to trap buoyant fluids, though in adjacent oilfield in the Shengli oilfield province, the Minghuazhen Formation forms a regional seal for the Guantao Formation.     

Lessons learned from natural and industrial analogues for storage of carbon dioxide

The deployment of CCS (carbon capture and storage) at industrial scale implies the development of effective monitoring tools. Noble gases are tracers usually proposed to track CO₂. This methodology, combined with the geochemistry of carbon isotopes, has been tested on available analogues.At first, gases from natural analogues were sampled in the Colorado Plateau and in the French carbogaseous provinces, in both well-confined and leaking-sites. Second, we performed a 2-years tracing experience on an underground natural gas storage, sampling gas each month during injection and withdrawal periods.In natural analogues, the geochemical fingerprints are dependent on the containment criterion and on the geological context, giving tools to detect a leakage of deep-CO₂ toward surface. This study also provides information on the origin of CO₂, as well as residence time of fluids within the crust and clues on the physico-chemical processes occurring during the geological story.The study on the industrial analogue demonstrates the feasibility of using noble gases as tracers of CO₂. Withdrawn gases follow geochemical trends coherent with mixing processes between injected gas end-members. Physico-chemical processes revealed by the tracing occur at transient state.These two complementary studies proved the interest of geochemical monitoring to survey the CO₂ behaviour, and gave information on its use.     

Intermediate storage of carbon dioxide in geological formations: A technical perspective

Enhanced oil recovery (EOR) through CO₂ flooding has been practiced on a commercial basis for the last 35 years and continues today at several sites, currently injecting in total over 30 million tons of CO₂ annually. This practice is currently exclusively for economic gain, but can potentially contribute to the reduction of emissions of greenhouse gases provided it is implemented on a large scale. Optimal operations in distributing CO₂ to CO₂-EOR or enhanced gas recovery (EGR) projects (referred to here collectively as CO₂-EHR) on a large scale and long time span imply that intermediate storage of CO₂ in geological formations may be a key component. Intermediate storage is defined as the storage of CO₂ in geological media for a limited time span such that the CO₂ can be sufficiently reproduced for later use in CO₂-EHR. This paper investigates the technical aspects, key individual parameters and possibilities of intermediate storage of CO₂ in geological formations aiming at large scale implementation of carbon dioxide capture and storage (CCS) for deep emission reduction. The main parameters are thus the depth of injection and density, CO₂ flow and transport processes, storage mechanisms, reservoir heterogeneity, the presence of impurities, the type of the reservoirs and the duration of intermediate storage. Structural traps with no flow of formation water combined with proper injection planning such as gas-phase injection favour intermediate storage in deep saline aquifers. In depleted oil and gas fields, high permeability, homogeneous reservoirs with structural traps (e.g. anticlinal structures) are good candidates for intermediate CO₂ storage. Intuitively, depleted natural gas reservoirs can be potential candidates for intermediate storage of carbon dioxide due to similarity in storage characteristics.     

Life cycle assessment of carbon dioxide capture and storage from lignite power plants

In this article, we present a life cycle assessment (LCA) of CO₂ capture and storage (CCS) for several lignite power plant technologies. The LCA includes post-combustion, pre-combustion and oxyfuel capture processes as well as subsequent pipeline transport and storage of the separated CO₂ in a depleted gas field.The results show an increase in cumulative energy demand and a substantial decrease in greenhouse gas (GHG) emissions for all CO₂ capture approaches in comparison with power plants without CCS, assuming negligible leakage within the time horizon under consideration. Leakage will, however, not be zero. Due to the energy penalty, CCS leads to additional production of CO₂. However, the CO₂ emissions occur at a much lower rate and are significantly delayed, thus leading to different, and most likely smaller, impacts compared to the no-sequestration case. In addition, a certain share of the CO₂ will be captured permanently due to chemical reactions and physical trapping.For other environmental impact categories, the results depend strongly on the chosen technology and the details of the process. The post-combustion approach, which is closest to commercial application, leads to sharp increases in many categories of impacts, with the impacts in only one category, acidification, reduced. In comparison with a conventional power plant, the pre-combustion approach results in decreased impact in all categories. This is mainly due to the different power generation process (IGCC) which is coupled with the pre-combustion technology.In the case of the oxyfuel approach, the outcome of the LCA depends highly on two uncertain parameters: the energy demand for air separation and the feasibility of co-capture of pollutants other than CO₂. If co-capture were possible, oxyfuel could lead to a near-zero emission power plant.     

Certification framework based on effective trapping for geologic carbon sequestration

We have developed a certification framework (CF) for certifying the safety and effectiveness of geologic carbon sequestration (GCS) sites. Safety and effectiveness are achieved if CO₂ and displaced brine have no significant impact on humans, other living things, resources, or the environment. In the CF, we relate effective trapping to CO₂ leakage risk which takes into account both the impact and probability of leakage. We achieve simplicity in the CF by using (1) wells and faults as the potential leakage pathways, (2) compartments to represent environmental resources that may be impacted by leakage, (3) CO₂ fluxes and concentrations in the compartments as proxies for impact to vulnerable entities, (4) broad ranges of storage formation properties to generate a catalog of simulated plume movements, and (5) probabilities of intersection of the CO₂ plume with the conduits and compartments. We demonstrate the approach on a hypothetical GCS site in a Texas Gulf Coast saline formation. Through its generality and flexibility, the CF can contribute to the assessment of risk of CO₂ and brine leakage as part of the certification process for licensing and permitting of GCS sites around the world regardless of the specific regulations in place in any given country.     

Training carbon management engineers: Removing a major hurdle for geologic CO2 storage by increasing educational capacity

Implementing geologic storage of CO₂ at a material scale (ca. 1 Gt C/year) will require an industry comparable in size to the current oil and gas industry and a workforce trained in subsurface engineering. Since the same technologies that apply to hydrocarbon production apply to the subsurface storage of CO₂, petroleum engineering (PE) graduates will be valuable candidates to work in the carbon storage industry. We expect however that the demand for PEs from the oil and gas industry will increase, and that already strained educational capacity will not be sufficient to supply both industries. Thus we advocate building new targeted educational infrastructure. We present a model curriculum based on an existing accredited multidisciplinary degree program. This program combines the fundamentals of petroleum engineering with the subsurface architecture emphasis of geology and the environmental perspective of hydrogeology. We indicate key elements of this program that could be integrated with other, more traditional undergraduate engineering majors that also deal with the subsurface.     

Value of information analysis for adequate monitoring of carbon dioxide storage in geological reservoirs under uncertainty

As monitoring is essential for the proper management of geological storage of carbon dioxide (CO₂), the ability to value information from monitoring is indispensable to adequately design a monitoring program. It is necessary to judge whether the expected improvement in management is worth the cost of monitoring. The value of information (VOI) is closely related to the possible increase in expected utility gained by gathering the information, the concept of which can be applied to such judgement. Although VOI analysis has been extensively studied in the context of decision analysis, its application to the management of carbon dioxide capture and storage (CCS) operations is rare. This paper introduces and discusses the methodology of VOI analyses in the context of monitoring CO₂ storage. A motivating problem with discrete probabilities is used to illustrate the concept of VOI. It is demonstrated that information is not always of value; for information to be worthwhile, monitoring under uncertainty must satisfy certain conditions. This concept is then extended to continuous probability distributions. The effects of prior uncertainty and information reliability on the VOI are examined. It is shown that an excessive improvement in information accuracy yields little value and that the optimal level of reliability can be inferred. VOI analyses provide quantitative insights into the value of information-gathering activities and therefore can be an objective means to adequately design and impartially justify a monitoring program.     

Moving from misinformation derived from public attitude surveys on carbon dioxide capture and storage towards realistic stakeholder involvement

Stakeholder involvement (SI) can include many activities, from providing information on a website to one-on-one conversations with people confronting an issue in their community. For carbon dioxide capture and storage (CCS), there are now quite a few surveys of public attitudes towards CCS that are being used to inform the design of SI efforts. These surveys, focused on the nascent commercial deployment of CCS technologies, have demonstrated that the general public has little knowledge about CCS—yet the surveys go on to collect what are known as “pseudo opinions” or “non-attitudes” of respondents who know little or nothing about CCS. Beyond establishing the lack of knowledge about CCS, the results of these surveys should not be relied upon by the larger CCS community and public and private decision makers to inform the critical task of implementing and executing SI activities. The paper discusses the issues involved in providing information as part of the survey, maintaining that such information is never unbiased and thus tends to produce pseudo opinions that reflect the pollster's or researcher's bias. Other content and methodological issues are discussed, leading to the conclusion that most of the survey results should be used neither as a gauge of public attitudes nor as an indication of public acceptance. Then the framing of SI in CCS is examined, including the assumptions that clear stakeholder acceptance is a realistic goal and that the public has a decisive say in choosing the energy technologies of the present and the future. Finally, a broader suite of SI activities is recommended as more suited to realistic and contextual goals.     

CO2 transportation for carbon capture and storage: Sublimation of carbon dioxide from a dry ice bank

Climate change is being caused by greenhouse gases such as carbon dioxide (CO₂). Carbon capture and storage (CCS) is of interest to the scientific community as one way of achieving significant global reductions of atmospheric CO₂ emissions in the medium term. CO₂ would be captured from large stationary sources such as power plants and transported via pipelines under high pressure conditions to underground storage. If a downward leakage from a surface transportation system module occurs, the CO₂ would undergo a large temperature reduction and form a bank of “dry ice” on the ground surface; the sublimation of the gas from this bank represents an area source term for subsequent atmospheric dispersion, with an emission rate dependent on the energy balance at the bank surface. Gaseous CO₂ is denser than air and tends to remain close to the surface; it is an asphyxiant, a cerebral vasodilator and at high concentrations causes rapid circulatory insufficiency leading to coma and death. Hence a subliming bank of dry ice represents safety hazard. A model is presented for evaluating the energy balance and sublimation rate at the surface of a solid frozen CO₂ bank under different environmental conditions. The results suggest that subliming gas behaves as a proper dense gas (i.e. it remains close to the ground surface) only for low ambient wind speeds.     

Actuarial risk assessment of expected fatalities attributable to carbon capture and storage in 2050

This study estimates the human cost of failures in the CCS industry in 2050, using the actuarial approach. The range of expected fatalities is assessed integrating all steps of the CCS chain: additional coal production, coal transportation, carbon capture, transport, injection and storage, based on empirical evidence from technical or social analogues. The main finding is that a few hundred fatalities per year should be expected if the technology is used to avoid emitting 3.67 GtCO₂ year⁻¹ in 2050 at baseload coal power plants. The large majority of fatalities are attributable to mining and delivering more coal. These risks compare to today's industrial hazards: technical, knowable and occupational dangers for which there are socially acceptable non-zero risk levels. Some contemporary European societies tolerate about one fatality per thousand years around industrial installations. If storage sites perform like that, then expected fatalities per year due to leakage should have a minor contribution in the total expected fatalities per year: less than one. But to statistically validate such a safety level, reliability theory and the technology roadmap suggest that CO₂ storage demonstration projects over the next 20 years have to cause exactly zero fatality.     

A preliminary cost and engineering estimate for desalinating produced formation water associated with carbon dioxide capture and storage

The risk associated with storage of carbon dioxide in the subsurface can be reduced by removal of a comparable volume of existing brines (e.g. Buscheck et al., 2011). In order to avoid high costs for disposal, the brines should be processed into useful forms such as fresh and low-hardness water. We have carried out a cost analysis of treatment of typical subsurface saline waters found in sedimentary basins, compared with conventional seawater desalination. We have also accounted for some cost savings by utilization of potential well-head pressures at brine production wells, which may be present in some fields due to CO₂ injection, to drive desalination using reverse osmosis. Predicted desalination costs for brines having salinities equal to seawater are about half the cost of conventional seawater desalination when we assume the energy can be obtained from excess pressure at the well head. These costs range from 32 to 40¢ per m³ permeate produced. Without well-head energy recovery, the costs are from 60 to 80¢ per m³ permeate. These costs do not include the cost of any brine production or brine reinjection wells, or pipelines to the well field, or other site-dependent factors.     

A statistical analysis of the carbon dioxide capture process

Post combustion carbon dioxide (CO₂) capture is one of the most commonly adopted technologies for reducing industrial CO₂ emissions, which is now an important goal given the widespread concern over global warming. Research on amine-based CO₂ capture has mainly focused on improving effectiveness and efficiency of the CO₂ capture process. Our research work focuses on studying the relationships among the significant parameters influencing CO₂ production because an enhanced understanding of the intricate relationships among the parameters involved in the process is critical for improving efficiency of the CO₂ capture process. This paper presents a statistical study that explores the relationships among parameters involved in the amine-based post combustion CO₂ capture process at the International Centre for CO₂ Capture (ITC) located in Regina, Saskatchewan of Canada. A multiple regression technique has been applied for analysis of data collected at the CO₂ capture pilot plant at ITC. The parameters have been carefully selected to avoid issues of multicollinearity, and four mathematical models among the key parameters identified have been developed. The models have been tested, and accuracy of the models is found to be satisfactory. The models developed in this study describe part of the CO₂ capture process and can help to predict performance of the CO₂ capture process at ITC under different conditions. Some results from a preliminary validation process will also be presented.     

The value of post-combustion carbon dioxide capture and storage technologies in a world with uncertain greenhouse gas emissions constraints

By analyzing how the largest CO₂ emitting electricity-generating region in the United States, the East Central Area Reliability Coordination Agreement (ECAR), responds to hypothetical constraints on greenhouse gas emissions, the authors demonstrate that there is an enduring role for post-combustion CO₂ capture technologies. The utilization of pulverized coal generation with carbon dioxide capture and storage (PC + CCS) technologies is particularly significant in a world where there is uncertainty about the future evolution of climate policy and in particular uncertainty about the rate at which the climate policy will become more stringent. The paper's analysis shows that within this one large, heavily coal-dominated electricity-generating region, as much as 20–40 GW of PC + CCS could be operating before the middle of this century. Depending upon the state of PC + CCS technology development and the evolution of future climate policy, the analysis shows that these CCS systems could be mated to either pre-existing PC units or PC units that are currently under construction, announced and planned units, as well as PC units that could continue to be built for a number of decades even in the face of a climate policy. In nearly all the cases analyzed here, these PC + CCS generation units are in addition to a much larger deployment of CCS-enabled coal-fueled integrated gasification combined cycle (IGCC) power plants. The analysis presented here shows that the combined deployment of PC + CCS and IGCC + CCS units within this one region of the U.S. could result in the potential capture and storage of between 3.2 and 4.9 Gt of CO₂ before the middle of this century in the region's deep geologic storage formations.     

How organizational motives and communications affect public trust in organizations: The case of carbon dioxide capture and storage

Preventing climate change is among the greatest environmental challenges facing the world today. Recently developed carbon dioxide capture and storage (CCS) technology is an important strategy to mitigate climate change. Public trust in organizations involved in CCS technology is important for successful implementation of this technology. This work adresses how inferred organizational motives and organizational communications affect public trust in these organizations. Study 1 (N = 264) showed that Dutch citizens generally have less trust in the industrial organizations than in the environmental NGOs involved in CCS. As predicted, inferred organizational motives (organization-serving motives versus public-serving motives) accounted for this difference. In Study 2 (N = 78) and Study 3 (N = 51) we used experimental designs. Both experiments showed that organizations that communicated arguments incongruent with inferred organizational motives instigated less trust than organizations that communicated arguments congruent with inferred organizational motives. Study 3 additionally showed that communicating an incongruent and a congruent argument together diminished the negative effects of the incongruent argument. In both Study 2 and Study 3 the effect of congruency on trust was mediated by perceived honesty of the organizations.     

3D geomechanical modelling for CO2 geologic storage in the Dogger carbonates of the Paris Basin

CO₂ injection into a depleted hydrocarbon field or aquifer may give rise to a variety of coupled physical and chemical processes. During CO₂ injection, the increase in pore pressure can induce reservoir expansion. As a result the in situ stress field may change in and around the reservoir. The geomechanical behaviour induced by oil production followed by CO₂ injections into an oil field reservoir in the Paris Basin has been numerically modelled. This paper deals with an evaluation of the induced deformations and in situ stress changes, and their potential effects on faults, using a 3D geomechanical model. The geomechanical analysis of the reservoir–caprock system was carried out as a feasibility study using pressure information in a “one way” coupling, where pressures issued from reservoir simulations were integrated as input for a geomechanical model. The results show that under specific assumptions the mechanical effects of CO₂ injection do not affect the mechanical stability of the reservoir–caprock system. The ground vertical movement at the surface ranges from ?2 mm during oil production to +2.5 mm during CO₂ injection. Furthermore, the changes in in situ stresses predicted under specific assumptions by geomechanical modelling are not significant enough to jeopardize the mechanical stability of the reservoir and caprock. The stress changes issued from the 3D geomechanical modelling are also combined with a Mohr–Coulomb analysis to determine the fault slip tendency. By integrating the stress changes issued from the geomechanical modelling into the fault stability analysis, the critical pore pressure for fault reactivation is higher than calculated for the fault stability analysis considering constant horizontal stresses.     

Adsorption of carbon dioxide using impregnated activated carbon promoted by Zinc

The effect of impregnation of activated carbon with Cr₂O and Fe₂O₃ and promotion by Zn²⁺ on its adsorptive properties of carbon dioxide was studied using a volumetric adsorption apparatus at ambient temperature and low pressures. Slurry and solution impregnation methods were used to compare CO₂ capture capacity of the impregnated activated carbon promoted by Zinc. The obtained adsorption isotherms showed that amount of CO₂ adsorbed on the samples impregnated by Cr₂O was increased about 20% in compare to raw activated carbon. The results also showed that Fe₂O₃ was not an effective impregnating species for activated carbon modification. Moreover slurry impregnation method showed higher CO₂ adsorption capacity in comparison with solution impregnation method. Samples prepared by co-impregnation of two metal species showed more adsorption capacity than samples impregnated by just one metal species individually. Washing the impregnated samples by metal oxide resulted in 15% increase in CO₂ adsorption capacities of activated carbons which can be attributed to the metal oxides removal covering the adsorption surface. Decreasing impregnation temperature from 95 to 25 °C in solution method showed a significant increase in CO₂ adsorption capacity. Sips equation was found a suitable model fitting to the adsorption data in the range studied.     

The impact of electric passenger transport technology under an economy-wide climate policy in the United States: Carbon dioxide emissions,coal use,and carbon dioxide capture and storage

Plug-in hybrid electric vehicles (PHEVs) have the potential to be an economic means of reducing direct (or tailpipe) carbon dioxide (CO₂) emissions from the transportation sector. However, without a climate policy that places a limit on CO₂ emissions from the electric generation sector, the net impact of widespread deployment of PHEVs on overall U.S. CO₂ emissions is not as clear. A comprehensive analysis must consider jointly the transportation and electricity sectors, along with feedbacks to the rest of the energy system. In this paper, we use the Pacific Northwest National Laboratory's MiniCAM model to perform an integrated economic analysis of the penetration of PHEVs and the resulting impact on total U.S. CO₂ emissions. In MiniCAM, the deployment of PHEVs (or any technology) is determined based on its relative economics compared to all other methods of providing fuels and energy carriers to serve passenger transportation demands. Under the assumptions used in this analysis where PHEVs obtain 50–60% of the market for passenger automobiles and light-duty trucks, the ability to deploy PHEVs under the two climate policies modelled here results in over 400 million tons (MT) CO₂ per year of additional cost-effective emissions reductions from the U.S. economy by 2050. In addition to investments in nuclear and renewables, one of the key technology options for mitigating emissions in the electric sector is CO₂ capture and storage (CCS). The additional demand for geologic CO₂ storage created by the introduction of the PHEVs is relatively modest: approximately equal to the cumulative geologic CO₂ storage demanded by two to three large 1000 megawatt (MW) coal-fired power plants using CCS over a 50-year period. The introduction of PHEVs into the U.S. transportation sector, coupled with climate policies such as those examined here, could also reduce U.S. demand for oil by 20–30% by 2050 compared to today's levels.