Role of Impurities on CO2 Injection: Experimental and Numerical Simulations of Thermodynamic Properties of Water-salt-gas Mixtures (CO2 + Co-injected Gases) Under Geological Storage Conditions

International audienceRole of impurities on CO 2 injection: experimental and numerical simulations of thermodynamic properties of water-salt-gas mixtures (CO 2 + co-injected gases) under geological storage conditions Abstract Regarding the hydrocarbon source and CO 2 capture processes, fuel gas from boilers may be accompanied by so-called "annex gases" which could be co-injected in a geological storage. These gases, such as SOx, NOx, or oxygen for instance, are likely to interact with reservoir fluids and rocks and well materials (casing and cement) and could potentially affect the safety of the storage. However, there are currently only few data on the behaviour of such gas mixtures, as well as on their chemical reactivity, especially in the presence of water. One reason for this lack comes from the difficulty in handling because of their dangerousness and their chemical reactivity. Therefore, the purpose of the Gaz Annexes was to develop new experimental and analytical protocols in order to acquire new thermodynamic data on these annex gases, in fine for predicting the behaviour of a geological storage of CO 2 + co-injected gases in the short, medium and long terms. This paper presents Gaz Annexes concerning acquisition of PVT experimental and pseudo-experimental data to adjust and validate thermodynamic models for water / gas / salts mixtures as well as the possible influence of SO 2 and NO on the geological storage of CO 2. The Gaz Annexes s new insights for the establishment of recommendations concerning acceptable content of annex gases

Experimental and numerical simulation of thermodynamic properties of water-salt-gas mixtures (CO2 + co-contaminant) under geological storage conditions

In the context of the reduction of greenhouse gas emissions, capture processes of CO2 constitute the main problem to solve. Indeed this step has the most important cost of all the treatment chain: capture/transport/sequestration. As a function of the industrial sources (energy production, iron industry, concrete production, etc.) and capture process, the composition of the gaseous mixture should vary considerably in nature and concentration. The degree of purity of captured CO2 is thus a key factor for transportation, injection and sequestration. In addition to CO2 and water, more or less important quantities of other gases (O2, N2, SOx, NOx, H2, CO, Ar...) would be admixed in different proportions. These gases are taken into account in industrial processes of capture but they remain poorly studied for the development of geological storage technologies. Furthermore, co-injected gases could mix with pre-existing natural gases (CH4, gas condensates, H2S) in depleted hydrocarbon reservoirs. Gas mixing could induce mineral dissolution – precipitation reactions and/or modifications of pressure - temperature properties of the system. The impact of such co-injected and/or residual gases on the mineral assemblages from reservoir, cap-rock and well-bore completion has to be understood under geological storage conditions at high pressures, high temperatures, and high salinity. In this context, a project called "Gaz Annexes" supported by the french national agency for research (ANR) was conducted since 2006 with some of the major actors working on the CCS in France, i.e. Nancy University and ENSIC, BRGM, IFP, Ecole des Mines de Paris and Total. The goal of the project “Gaz Annexes” is to acquire new data to characterize phase equilibria of geological systems including co-injected gases such as SOx, NOx, N2, Ar in order to improve our understanding of the reactivity of such systems. Hence, new thermodynamic data relevant for CO2 injection-storage conditions were measured and fitted to extract the lacking Equation Of State (EOS) parameters. The project is divided in five phases: i) Qualitative and quantitative compilation of co-injected gases generated as a function of industrial and capture processes. The goal is to determine which are the reactive gases and which quantity could be injected, ii) Acquisition of new experimental data on water/gas/salt systems by performing lab experiments and in situ measurements. Data are collected using two main analytical methods: chromatography and Raman spectroscopy, iii) Thermodynamic characterization of equilibrium between the different fluid phases (gas mixtures and saline waters), iv) Integration of the relevant new data into hydro-geochemical codes in order to better predict the behaviour of CO2 and co-injected gases into saline aquifers or oil reservoirs, v) Validation and application of developed geochemical codes on experimental data obtained on rock/water/gas systems with laboratory experiments carried out under geological conditions of storage. The chemical behaviour of co-injected (i.e., SOx, NOx, ...) gases if of prime interest if considering that such gases could generate very high acidity of the native brines and could accelerate the water – rock interactions. This could lead to an important impact on the petrophysical properties (porosity, permeability, etc.) of the whole reservoir. The region close to well bore of CO2 injection could be also drastically affected causing possible difficulties for the injectivity process. The obtained results will be presented for discussion at the GHG10 congress

Treatment of primary varicose veins by endovenous obliteration with the VNUS closure system: Results of a prospective multicentre study

Background. Radio frequency obliteration of the saphenous veins has been introduced as a less invasive alternative to traditional surgery for varicose veins. Objective. To report the efficacy of obliteration and clinical outcomes following endovenous obliteration of the saphenous vein with limited follow-up to 3 years. Materials and methods. Radiofreq uency obliteration (Closure® system, VNUS Medical Technologies, San Jose, CA) was performed in 330 limbs of 294 patients in a prospective worldwide multicentre study with 31 participating sites. Follow-up duplex ultrasound and clinical examinations were performed at annual intervals. The main outcome measures were the completeness of occlusion of the treated vein segment, presence of reflux and presence of signs and symptoms of venous disease. Results. Before treatment 3.9% of limbs were categorised as CEAP clinical class zero or one. This improved to 82.9% at 1 year, 83.1% at 2 years and 86.8% at 3 years following treatment. Varicose vein free rates were 1 year: 90.1%, 2 years: 87.2%, 3 years: 88.2%. Duplex ultrasound demonstrated a reflux-free rate of about 88% over 3 years. Total occlusion (TO) of veins was 1 year: 81%, 2 years: 80.4% and 3 years: 75%. Partial occlusion (PO, 5 cm open segment) was 1 year: 12.7%, 2 years: 12.2% and 3 years: 7.4%. Partial occlusion did not result in any differences in the symptom severity score, the number of symptom free limbs, or the varicose vein absence rates at any follow-up time point when compared to the total occlusion group. The varicose vein absence rates were significantly lower in the IO group comparing to the TO and PO groups. Conclusions. Radiofrequency saphenous vein obliteration improves the symptoms of varicose veins. The reflux-free rates in the treated veins remain constant over a 3 year follow-up period. There is no difference in clinical outcomes between the TO and the PO limbs, suggesting clinical effectiveness of the PO category. Greater than a 5 cm open segment in treated veins poses a risk of recurrence. © 2004 Elsevier Ltd. All rights reserved