Experimental investigation of wellbore integrity and CO2–brine flow along the casing–cement microannulus

Wellbore integrity is one of the key performance criteria in the geological storage of CO₂. It is significant in any proposed storage site but may be critical to the suitability of depleted oil and gas reservoirs that may have 10’s to 1000’s of abandoned wells. Much previous work has focused on Portland cement which is the primary material used to seal wellbore systems. This work has emphasized the potential dissolution of Portland cement. However, an increasing number of field studies (e.g., Carey et al., 2007), experimental studies (e.g., Kutchko et al., 2006) and theoretical considerations indicate that the most significant leakage mechanism is likely to be flow of CO₂ along the casing–cement microannulus, cement–cement fractures, or the cement–caprock interface.In this study, we investigate the casing–cement microannulus through core-flood experiments. The experiments were conducted on a synthetic wellbore system consisting of a 5-cm diameter sample of cement that was cured with an embedded rectangular length of steel casing that had grooves to accommodate fluid flow. The experiments were conducted at 40 $°$ C and 14 MPa pore pressure for 394 h. During the experiment, 6.2 l of a 50:50 mixture of supercritical CO₂ and 30,000 ppm NaCl-rich brine flowed through 10-cm of limestone before flowing through the 6-cm length cement–casing wellbore system. Approximately 59,000 pore volumes of fluid moved through the casing–cement grooves. Scanning electron microscopy revealed that the CO₂–brine mixture impacted both the casing and the cement. The Portland cement was carbonated to depths of 50–250 $\mu$m by a diffusion-dominated process. There was very little evidence for mass loss or erosion of the Portland cement. By contrast, the steel casing reacted to form abundant precipitates of mixed calcium and iron carbonate that lined the channels and in one case almost completely filled a channel. The depth of steel corroded was estimated at 25– $30\mu$m and was similar in value to results obtained with a simplified corrosion model.The experimental results were applied to field observations of carbonated wellbore cement by Carey et al. (2007) and Crow et al. (2009) to show that carbonation of the field samples was not accompanied by significant CO₂–brine flow at the casing–cement interface. The sensitivity of standard-grade steel casing to corrosion suggests that relatively straight-forward wireline logging of external casing corrosion could be used as a useful indicator of flow behind casing. These experiments also reinforce other studies that indicate rates of Portland cement deterioration are slow, even in the high-flux CO₂–brine experiments reported here.     

Occurrence and fate of the human pharmaceutical metabolite ritalinic acid in the aquatic system

To investigate the occurrence and fate of ritalinic acid - the main human metabolite of the psychostimulant drug methylphenidate - in the aquatic environment, a HPLC-electrospray-MS/MS method for the quantification of ritalinic acid in wastewater, surface water and bank filtrate was developed. Carbamazepine known as very stable in the aquatic environment was analyzed as anthropogenic marker in parallel. Furthermore, the removal of ritalinic acid was studied in a sewage treatment plant using an activated sludge system during a field study and in lab-scale plants. In good agreement between lab-scale and field studies a low removal rate of 13% and 23%, respectively, was determined. As a consequence, the concentration of ritalinic acid in the wastewater effluents were in the range of <50-170 ngL(-1) which corresponds to a mean specific load per capita of 17.7 μgd(-1). Ritalinic acid has further been detected in German rivers at concentrations of 4-23 ngL(-1) and in bank filtrate samples in 100-850 m distance from the river up to 5 ngL(-1) demonstrating the widespread occurrence of this stable metabolite in the aquatic environment. A comparison to available sales data shows that a significant amount of methylphenidate applied can be found in waters as ritalinic acid.     

Exposure patterns of UV filters, fragrances, parabens, phthalates, organochlor pesticides, PBDEs, and PCBs in human milk: correlation of UV filters with use of cosmetics

In order to assess potential risks of exposure to environmental chemicals, more information on concomitant exposure to different chemicals is needed. We present data on chemicals in human milk of a cohort study (2004, 2005, 2006) of 54 mother/child pairs, where for the first time, cosmetic UV filters, synthetic musks, parabens and phthalate metabolites were analyzed in the same sample along with persistent organochlor pollutants (POPs), i.e., organochlor pesticides and metabolites, polybrominated diphenylethers and polychlorinated biphenyls (PCBs). The two groups of chemicals exhibited different exposure patterns. Six out of seven PCB congeners and a majority of pesticides were present in all milk samples, with significant correlations between certain PCB congener and pesticide levels, whereas the cosmetic-derived compounds, UV filters, parabens and synthetic musks, exhibited a more variable exposure pattern with inter-individual differences. UV filters were present in 85.2% of milk samples, in the range of PCB levels. Comparison with a questionnaire revealed a significant correlation between use of products containing UV filters and their presence in milk for two frequently used and detected UV filters, 4-methylbenzylidene camphor and octocrylene, and for the whole group of UV filters. Concentrations of PCBs and organochlor pesticides were within ranges seen in Western and Southern European countries. For several POPs, mean and/or maximum daily intake calculated from individual concentrations was above recent US EPA reference dose values. Our data emphasize the need for analyses of complex mixtures to obtain more information on inter-individual and temporal variability of human exposure to different types of chemicals.     

Thorough analysis of polyhalogenated compounds in ray liver samples off the coast of Rio de Janeiro, Brazil

Introduction  

Five liver samples of two different ray species (Gymnura altavela and Zapteryx brevirostris) off the coast of Rio de Janeiro, Brazil, were analyzed for their pollution with anthropogenic and naturally occurring organohalogen compounds.     

Disaster risk reduction capacity assessment for precarious settlements in Guatemala City

This study presents findings of an institutional capacity analysis of urban disaster risk reduction for informal settlements in the Guatemala Metropolitan Region. It uses a resource access perspective of vulnerability, actor-network theory, and qualitative data collection. The analysis reveals that there is interest in disaster risk reduction for the informal settlements; however, there is little in the way of direct financial or oversight relationships between informal settlement residents and all other actors. Respondents observed that informal settlements would probably remain inhabited; thus, there is a need for disaster risk reduction within these settlements. Disaster risk reduction capacity for informal settlements exists and can be further leveraged, as long as steps are taken to ensure appropriate access to and control of resources and oversight. Further, the nascent institutional arrangements should be strengthened through increased communication and coordination between actors, a decentralization of oversight and financial relationships, and mediation of identified resource conflicts.     

Spatio-temporal distribution of organic and inorganic pollutants from Lake Geneva (Switzerland) reveals strong interacting effects of sewage treatment plant and eutrophication on microbial abundance

Variation with depth and time of organic matter (carbon, nitrogen, phosphorus), inorganic pollutant (mercury), as well as bacterial abundance and activity, were investigated for the first time in sediment profiles of different parts of Lake Geneva (Switzerland) over the last decades. The highest organic contents (about 32%), mercury concentration (27 mg kg⁻¹), bacterial abundance (in order of 9 × 10⁹ cell g⁻¹ dry sediment), and bacterial activity (1299 Relative Light Units (RLU)) were found in the highly polluted sediments contaminated by the waste water treatment plant (WWTP) discharge, which deposited during the period of cultural eutrophication. Such data, which contrast with the other sampled sites from deeper and more remote parts of the lake, prove that the organic matter and nutrients released from the municipal WWTP have considerable effects on bacterial abundance and activities in freshwater sediments. In fact, the relatively unpolluted deepwater sites and the coastal polluted site show large synchronous increases in bacterial densities linked to the anoxic conditions in the 1970s (lake eutrophication caused by external nutrient input) that subsequently increased the nutrient loading fluxes. These results show that the microbial activities response to natural or human-induced changing limnological conditions (e.g., nutrient supply, oxygen availability, redox conditions) constitutes a threat to the security of water resources, which in turn poses concerns for the world’s freshwater resources in the context of global warming and the degradation of water quality (oxygen depletion in the bottom water due to reduced deep waters mixing). Moreover, the accumulation of inorganic pollutants such as high mercury (methyl-mercury) concentration may represent a significant source of toxicity for sediment dwelling organisms.     

Bromination of 2-methoxydiphenyl ether to an average of tetrabrominated 2-methoxydiphenyl ethers

Brominated 2-phenoxyanisoles (2-methoxydiphenyl ethers, 2-MeO-BDEs) are a class of halogenated natural products, produced by algae and sponges. Especially two tetrabrominated isomers, i.e. 2′-MeO-BDE 68 (BC-2) and 6-MeO-BDE 47 (BC-3), have also been frequently determined in environmental and food samples. In addition, 2-MeO-BDEs are under discussion as metabolites of polybrominated diphenyl ethers (PBDEs). In this study, we synthesized the backbone 2-methoxydiphenyl ether and brominated it to an average degree of four bromine substituents. The reaction mixture only contained one major product (∼90%) along with three further MeO-BDEs and ∼5% hydroxylated BDEs. In all likelihood, the HO-BDEs were formed in a side reaction by cleavage of the methoxy group. The major MeO-BDE was identified as 6′-methoxy-2,3′,4,4′-tetrabromodiphenyl ether (6′-MeO-BDE-66). The HO-BDEs were separated by KOH/n-hexane partitioning, and the resulting 2-MeO-BDEs were fractionated by means of high-speed counter-current chromatography (HSCCC). Due to the excellent enrichment facilities of HSCCC, some 15 MeO-BDEs, mainly present at traces only, could be detected in 26 fractions, and eight of them could be characterized by nuclear magnetic resonance spectroscopy (NMR). Only two of the compounds - 2′-MeO-BDE 68 and 6-MeO-BDE 123 - had been characterized as natural products while the prominent halogenated natural product 6-MeO-BDE 47 was not detected at all in the reaction product. The “non-natural” 2-MeO-BDEs may be useful internal standards in trace analysis.     

Performance of firefighters' protective clothing after heat exposure.

Heat and mechanical protection properties of 6 fabric combinations commonly used in firefighters' protective clothing were assessed before and after different heat treatment. It was shown that after heat exposure, the values obtained were generally lower than in the original state. The mechanical properties of the materials were more affected by heat than by heat protective properties. In 2 cases, degradation started before a visible change in the material could be observed, which might be potentially dangerous for the end user who will not realize the alteration of the material.     

Mercury reduction studies to facilitate the thermal decontamination of phosphor powder residues from spent fluorescent lamps

This work investigates the thermal release of mercury from phosphor powder of spent fluorescent lamps. The treatment conditions and the ability of various reducing agents (primarily sodium borohydride) to lower the overall heating temperature required to improve the release of Hg have been evaluated. Hg species in samples were monitored in a thermal desorption atomic absorption spectrometer system, and total mercury was analyzed in a cold vapor atomic absorption spectrometer. Sodium borohydride was the best reducing agent among the ones studied. However, citric acid presented a high capacity to weaken mercury bonds with the matrix. When the sample was crushed with sodium borohydride for 40min in a mass ratio of 10:1 (sample:reducing agent) and submitted to thermal treatment at 300 degrees C for 2h, the concentration of mercury in a phosphor powder sample with 103mgkg(-1) of mercury reached 6.6mgkg(-1).     

Headwater Influences on Downstream Water Quality

We investigated the influence of riparian and whole watershed land use as a function of stream size on surface water chemistry and assessed regional variation in these relationships. Sixty-eight watersheds in four level III U.S. EPA ecoregions in eastern Kansas were selected as study sites. Riparian land cover and watershed land use were quantified for the entire watershed, and by Strahler order. Multiple regression analyses using riparian land cover classifications as independent variables explained among-site variation in water chemistry parameters, particularly total nitrogen (41%), nitrate (61%), and total phosphorus (63%) concentrations. Whole watershed land use explained slightly less variance, but riparian and whole watershed land use were so tightly correlated that it was difficult to separate their effects. Water chemistry parameters sampled in downstream reaches were most closely correlated with riparian land cover adjacent to the smallest (first-order) streams of watersheds or land use in the entire watershed, with riparian zones immediately upstream of sampling sites offering less explanatory power as stream size increased. Interestingly, headwater effects were evident even at times when these small streams were unlikely to be flowing. Relationships were similar among ecoregions, indicating that land use characteristics were most responsible for water quality variation among watersheds. These findings suggest that nonpoint pollution control strategies should consider the influence of small upland streams and protection of downstream riparian zones alone is not sufficient to protect water quality.