Abstract

Sequestrating CO2 in deep saline aquifers is maybe the most effective option to mitigate CO2 emission. The storage capacity of CO2 is the key factor for site selection before a project is carried out. Most of the existing methods are for assessment of CO2 sequestered by stratigraphic and structural trapping, as well as residual trapping and solubility trapping. In this study, we used a new method that considers CO2 consumption through geochemical reactions with minerals of reservoir rocks, mainly sandstones. Contribution of storage capacity from carbonate mineral mainly refers to calcite is excluded. That is because lifetime of calcite (the whole time from reaction starting to calcite running out) is very short contrast with geological time-scale or it is a temporary trapping. The geochemical reactions between CO2 and feldspar minerals with thousand-year lifetime are regarded as the permanent methods for trapping CO2. CO2 consumptions by K-feldspar, albite, and anorthite are assessed with volume method based on corresponding geochemical reactions. Storage efficiency factor is also considered as one of the most important parameters in the reaction formula and it depends on specific surface area of minerals contacting with formation water and kinetics of precipitation and dissolution of minerals. We assessed the CO2 storage capacity of mineral trapping in Baokang sedimentary system, south Songliao Basin through the detailed analysis of geological data in this area. The calculated results show the total CO2 storage capacity of mineral trapping of the study area is 457.5–5114.5 Mt and the corresponding storage efficiency factor is 1%. The CO2 consumed by albite makes up more than 60% of the total storage capacity and it is about 30% for anorthite.

Abstract

Two-dimensional glass model experiments are used to investigate the residual trapping mechanism of CO2 stored in saline aquifers. For this purpose, two proxy fluids are chosen to simulate the CO2-brine behavior under reservoir conditions. The first set of experiments is carried out by flooding n-heptane in a mixture of glycerol and water inside a glass bead porous media. Fluids and porous materials are designed so that the dimensionless groups are in the range of real storage sites. Another set of proxy fluid consists of dodecane and a different mixture of glycerol and water, representing the second wettability condition for the system. The size of the glass beads chosen was fine (70–110 μm) in order to investigate residual trapping phenomena. For each set, after complete drainage process, an imbibition process is performed and in each time step, images are taken from the phenomena. The images are processed using a red, green, blue (RGB) color concept using a Matlab code that was developed for this study. By using this process, it is possible to measure the residual trapping of CO2 proxy fluid for each test and to determine the saturation profile in the model. Tests are carried out at various imbibition and drainage rates to study the effect of the rate on the results. Fine-scale numerical simulation models are constructed for comparison with experimental results. Good agreement is obtained between the simulation results and the image processing estimations, as well as the readings from the material balances during the experiments. This study could provide a framework for modeling different reservoir conditions for residual trapping mechanism and the impact of different parameters in future studies.

Abstract

The large amount of CO 2 that can be mitigated by geologic storage had gained interest during the last 15 years. Acceptance of CCS under CDM is still under discussion(IEA, 2008) however there are several pilot or field scale projects and monitoring surveys that are underway which will make the technology better known and resolve the risks involved. This study involves assessment of possible geologic sites for CO 2 storage and calculation of CO 2 emissions from thermal power plants with capacities "500 MWe, cement factories, steel industry, sugar factories and refineries in Turkey. In emission calculations IPCC methodology is used. Coupling of sources and sinks resulted in a decision to use the emissions from a cement factory which is about 130 km from the selected oil field, Caylarbasi. The cement factory does not have capture facilities yet, but during modelling it was assumed that CO 2 is available at the factory site. According to the results of the model study, during the project life of 20 years, enhanced oil recovery effect of CO 2 lasts 8 years and 2 million barrels of oil will be produced and the remaining 12 years are modelled as CO 2 storage phase which shows 220 million Sm 3 of CO 2 can be stored.The transportation phase was designed with two alternatives, pipeline transport and transport by tankers. Economic evaluation at 100$/barrel of oil value, it will be possible to produce for 6 years. For the following years during CO 2 storage, incentives are necessary to cover operating costs so that project will continue for 20 years. Since the initial investment is already made, only the operational costs must be financed. Natural CO 2 field in Dodan is another possibility for geologic storage, the field has already produced 7 billion Sm 3 of CO 2 for the BatiRaman EOR project. Total capacity is about 10 billion Sm 3 . Other possible storage sites are deep saline aquifers, which were encountered in Thrace region, Central Anatolia and South Eastern Turkey and salt caverns of the soda mines. The experience of the Turkish oil industry for use of CO 2 in EOR application in BatiRaman field will be utilized if and when such an application is required.

Abstract

In this study, we identify and characterize known and new environmental consequences associated with CO 2 capture from power plants, transport by pipeline and storage in geological formations. We have reviewed (analogous) environmental impact assessment procedures and scientific literature on carbon capture and storage (CCS) options. Analogues include the construction of new power plants, transport of natural gas by pipelines, underground natural gas storage (UGS), natural gas production and enhanced oil recovery (EOR) projects. It is investigated whether crucial knowledge on environmental impacts is lacking that may postpone the implementation of CCS projects. This review shows that the capture of CO 2 from power plants results in a change in the environmental profile of the power plant. This change encompasses both increase and reduction of key atmospheric emissions, being: NO x , SO 2 , NH 3 , particulate matter, Hg, HF and HCl. The largest trade-offs are found for the emission of NO x and NH 3 when equipping power plants with post-combustion capture. Synergy is expected for SO 2 emissions, which are low for all power plants with CO 2 capture. An increase in water consumption ranging between 32% and 93% and an increase in waste and by-product creation with tens of kilotonnes annually is expected for a large-scale power plant (1 GW e ), but exact flows and composition are uncertain. The cross-media effects of CO 2 capture are found to be uncertain and to a large extent not quantified. For the assessment of the safety of CO 2 transport by pipeline at high pressure an important knowledge gap is the absence of validated release and dispersion models for CO 2 releases. We also highlight factors that result in some (not major) uncertainties when estimating the failure rates for CO 2 pipelines. Furthermore, uniform CO 2 exposure thresholds, detailed dose–response models and specific CO 2 pipeline regulation are absent. Most gaps in environmental information regarding the CCS chain are identified and characterized for the risk assessment of the underground, non-engineered, part of the storage activity. This uncertainty is considered to be larger for aquifers than for hydrocarbon reservoirs. Failure rates are found to be heavily based on expert opinions and the dose–response models for ecosystems or target species are not yet developed. Integration and validation of various sub-models describing fate and transport of CO 2 in various compartments of the geosphere is at an infant stage. In conclusion, it is not possible to execute a quantitative risk assessment for the non-engineered part of the storage activity with high confidence.