The chemistry and saturation states of subsurface fluids during the in situ mineralisation of CO2 and H2S at the CarbFix site in SW-Iceland

In situ carbonation of basaltic rocks could provide a long-term carbon storage solution, which is essential for the success and public acceptance of carbon storage. To demonstrate the viability of this carbon storage solution, 175 tonnes (t) of pure CO2 and 73 tonnes (t) of a 75% CO2-24% H2S-1% H2-gas mixture were sequentially injected into basaltic rocks at the CarbFix site at Hellisheidi, SW-Iceland from January to August 2012. This paper reports the chemistry and saturation states with respect to potential secondary minerals of sub-surface fluids sampled prior to, during, and after the injections. All gases were dissolved in water during their injection into permeable basalts located at 500–800 m depth with temperatures ranging from 20 to 50 °C. A pH decrease and dissolved inorganic carbon (DIC) increase was observed in the first monitoring well, HN-04, about two weeks after each injection began. At storage reservoir target depth, this diverted monitoring well is located ∼125 m downstream from the injection well. A significant increase in H2S concentration, however, was not observed after the second injection. Sampled fluids from the HN-04 well show a rapid increase in Ca, Mg, and Fe concentration during the injections with a gradual decline in the following months. Calculations indicate that the sampled fluids are saturated with respect to siderite about four weeks after the injections began, and these fluids attained calcite saturation about three months after each injection. Pyrite is supersaturated prior to and during the mixed gas injection and in the following months. In July 2013, the HN-04 fluid sampling pump broke down due to calcite precipitation, verifying the carbonation of the injected CO2. Mass balance calculations, based on the recovery of non-reactive tracers co-injected into the subsurface together with the acid-gases, confirm that more than 95% of the CO2 injected into the subsurface was mineralised within a year, and essentially all of the injected H2S was mineralised within four months of its injection. These results demonstrate the viability of the in situ mineralisation of these gases in basaltic rocks as a long-term and safe storage solution for CO2 and H2S

Geotechnical site investigation Casuarina Police Station

It is proposed to upgrade the existing police facilities on Lot 4802 Dripstone Rd, Casuarina by the demolition of the existing building and the construction new facilities. The new building will comprise a single storey reinforced masonry structure built on a slab on grade with strip footings. There will be a two storey high section surrounding the entrance to the building. The scope of this site investigation was to determine the subsurface conditions, provide a site classification in accordance with AS2870-1996 and locate and map underground services on the site. - IntroductionMade available by the Northern Territory Library via the Publications (Legal Deposit) Act 2004 (NT).Introduction -- Preliminaries -- Results and discussion -- Conclusion -- References -- Important information on interpretation, use and liability of this report -- Appendix 1-4

THE USE OF LIDAR TO FACILITATE DESIGN AND CONSTRUCTION OF PIPELINES

ABSTRACT Within the last decade, airborne lidar (Light Detection And Ranging) equipment has evolved to the point where it can provide accurate ground surface elevations on a dense grid (often 1m by 1m) along pipeline corridors, at a cost that is a fraction of the cost for a comparable ground based topographic survey. This paper explains how lidar is used to acquire topographic data and how the data are converted to digital terrain models referenced to geodetic benchmarks. The accuracy and density of topographic data acquired by lidar surveys can be used to greatly facilitate pipeline design and reduce pipeline construction costs. The major benefits include

Compositional data analysis as a robust tool to delineate hydrochemical facies within and between gas-bearing aquifers

Isometric log ratios of proportions of major ions, derived from intuitive sequential binary partitions, are used to characterize hydrochemical variability within and between coal seam gas (CSG) and surrounding aquifers in a number of sedimentary basins in the USA and Australia. These isometric log ratios are the coordinates corresponding to an orthonormal basis in the sample space (the simplex). The characteristic proportions of ions, as described by linear models of isometric log ratios, can be used for a mathematical-descriptive classification of water types. This is a more informative and robust method of describing water types than simply classifying a water type based on the dominant ions. The approach allows (a) compositional distinctions between very similar water types to be made and (b) large data sets with a high degree of variability to be rapidly assessed with respect to particular relationships/compositions that are of interest. A major advantage of these techniques is that major and minor ion components can be comprehensively assessed and subtle processes-which may be masked by conventional techniques such as Stiff diagrams, Piper plots, and classic ion ratios-can be highlighted. Results show that while all CSG groundwaters are dominated by Na, HCO3, and Cl ions, the proportions of other ions indicate they can evolve via different means and the particular proportions of ions within total or subcompositions can be unique to particular basins. Using isometric log ratios, subtle differences in the behavior of Na, K, and Cl between CSG water types and very similar Na-HCO3 water types in adjacent aquifers are also described. A complementary pair of isometric log ratios, derived from a geochemically-intuitive sequential binary partition that is designed to reflect compositional variability within and between CSG groundwater, is proposed. These isometric log ratios can be used to model a hydrochemical pathway associated with methanogenesis and/or to delineate groundwater associated with high gas concentrations