Some of the most promising potential applications of nanotechnology to hydraulic fracturing of coal seam gas (CSG) are reviewed with a focus on Australian CSG wells. Three propitious applications were identified: (1) Nanoparticle enhanced viscoelastic surfactants (VES) fracturing fluids to prevent fluid loss by up to 30%, made possible by the formation of pseudo-filter cakes and reducing the viscosity of the VES fluids. Besides, there is no requirement of clay control additives or biocides. (2) Nano-proppants to extend fracture networks and reduce proppant embedment by introducing them prior to the emplacement of larger proppants. Fly Ash nanoparticles can be particularly effective because of their high sphericity and mechanical strength. (3) Nanoparticle-coated proppants, to mitigate the migration of particle fines by restricting them close to their source by adsorption, with MgO being the most effective. The use of nanotechnology in hydraulic fracturing applications is currently hindered due to a discordant regulatory environment compounded by the cost of the nanoparticles themselves, as well as, a lack of field data to validate the technology under real downhole conditions. Although the necessary field tests are unlikely to be conducted for as long as abundant natural gas is available, exploratory studies could pave the way for future applications. Graphical abstract

The decay rates of building stones and, the processes leading to their deterioration is governed by intrinsic properties such as texture, mineralogy, porosity and pore size distribution, along with other extrinsic factors related to the climate and anthropogenic activities. For urban cities such as London, the influence of extrinsic factors like temperature and rainfall, as well as the concentrations of air pollutants, such as sulphur and nitrogen oxides, along with the emissions of carbonaceous aerosols, can be particularly significant. While considering the long-term preservation of building stones used in various heritage sites in the city, it is imperative to consider how the stone could be affected by the changing air pollutant concentrations, superimposed on the effects of climate change in the region, including rising average annual temperature and precipitation with a hotter, drier summer and, warmer, wetter winter months. This paper deals with the intrinsic rock properties of the common building stones of London, including limestone, marble, granite, sandstone, slate, flint as well as bricks, building on known characteristics including strength and durability that determine how and where they are placed in a building structure. The study reviews how these stones decay due to different processes such as salt weathering in sandstone, microcracking of quartz with kaolinisation of K-feldspar and biotite in granite and dissolution of calcite and dolomite, followed by precipitation of sulphate minerals in the carbonate rocks of limestone and marble. In the urban environment of London, with progressive build up in the concentration of atmospheric nitrogen oxides leading to an increasingly acidic environment and, with predicted climate change, the diverse stone-built heritage will be affected. For example, there can be enhanced carbonate dissolution in limestone with increased annual precipitation. Due to the prolonged wetter winter, any sandstone building stone will also undergo greater damage with a deeper wetting front. On the other hand, due to predicted wetter and warmer winter months, microcracking of any plagioclase in a granite is unlikely, thereby reducing the access of fluid and air pollutants to the Ca-rich core of the zoned crystals limiting the process of sericitisation. Management of the building stones in London should include routine expert visual inspection for signs of deterioration, along with mineralogical and compositional analyses and assessment of any recession rate.

Drill core shale samples are critical for palaeoenvironmental studies and potential hydrocarbon reservoirs. They need to be preserved carefully to maximise their retention of reservoir condition properties. However, they are susceptible to alteration due to cooling and depressurisation during retrieval to the surface, resulting in volume expansion and formation of desiccation and micro fractures. This leads to inconsistent measurements of different critical attributes, such as porosity and permeability. Best practices for core handling start during retrieval while extracting from the barrel, followed by correct procedures for transportation and storage. Appropriate preservation measures should be adopted depending on the objectives of the scientific investigation and core coherency, with respect to consolidation and weathering. It is particularly desirable to maintain a constant temperature of 1 to 4 °C and a consistent relative humidity of >75% to minimise any micro fracturing and internal moisture movement in the core. While core re-sampling, it should be ensured that there is no further core compaction, especially while using a hand corer.

Stability and mobility of organic matter in shale is significant from the perspective of carbon cycle. Shale can only be an effective sink provided that the organic carbon present is stable and immobile so that it is not released easily during low temperature geological processes such as burial diagenesis. To examine this, three Jurassic shale samples of known mineralogy and total organic carbon content, with continental source of organic matter, belonging to the Haynesville-Bossier Formation were combusted by incremental heating from temperature of 200 to 1400°C. The samples were analysed for their carbon and nitrogen release profiles, bulk δ13C composition and C/N atomic ratio, based on which, at least four organic carbon components are identified associated with different minerals such as clay, carbonate and silicate. They have different stability depending on their host sites and occurrences relative to the mineral phases and consequently, released at different temperature during combustion. The components identified are denoted as, C1 (organic carbon occurring as free accumulates at the edge or mouth of pore spaces), C-2 (associated with clay minerals, adsorbed or as organomineral nanocomposites; with carbonate minerals, biomineralised and/or occluded) C3-1 (occurring with silicate minerals, biomineralised and/or occluded and C3-2 (graphitized carbon). They show an increasing stability and decreasing mobility from C1 to C3-2. Based on the stability of the different OC components, shale is clearly an efficient sink for the long term C cycle as, except for C1 which forms a very small fraction of the total and is released at temperature ~ 200°C, OC can be efficiently locked in shale surviving conditions of burial diagenesis. C3-2 can be even efficiently retained as a refractory phase under shallow mantle conditions if subducted. It is evident that the association and interaction of the organic matter with the different minerals play an important role in its retention in the shale.

Nitrogen in the mantle exists in various speciation depending on oxidation conditions. Based on thermodynamic calculations, it predominantly occurs as N2 under relatively oxidized conditions and as NH4+ when conditions are reducing (Mikhail and Sverjensky, 2014). The speciation has an effect on its compatibility behaviour, being more soluble in melts when in reduced form, while the reverse is true for fluids (Mysen, 2019).  Carbonatites are very important to constrain the nitrogen composition of the mantle with important implications for the subduction history of the Earth. Carbonatites entrain components from different reservoirs including the deep Earth near the core-mantle boundary and, temporally encompass a wide range in age (Dauphas and Marty., 1999; Basu and Murty, 2015).  Studies from some young carbonatites in India from Sung Valley (107 Ma) and Ambadongar (65 Ma) indicate that the nitrogen is present as more than one component in the source, unhomogenised and hence identifiable, that can be related to their occurrence in more than one chemical form (Basu and Murty, 2015).The emergence of efficient and long-lived plate tectonics is thought to be as early as Late Archean, based on nitrogen isotopic composition of placer diamonds from Witwatersand from the Kapvaal craton (Smart et al., 2016). While this may represent a global occurrence, we have undertaken a more robust study with carbonatites ranging in age from 2500 to 770 Myrs, with the goal of identification of the initiation of subduction in a global scale and investigation of any change in the nitrogen stored in the mantle with time. The carbonatites studied are from Khambamettu (2.5 Ga), Hogenakal (2.4 Ga), and Sevattur (770 Ma), located in the southern part of India. Calcites and apatites separated from the host rocks were analysed by vacuum crushing. The apatites were also analysed by stepwise pyrolysis to release and decouple different components at different temperatures. In the carbonates, the nitrogen contents vary from 140 to 1507 ppb with accompanying δ15N ranging from 4.7±0.4 to 11.7±1.3 ‰. The nitrogen in the apatites from Hogenakal and Khambamettu show depleted signatures with δ15N as low as ~ -22 ‰, accompanied by low nitrogen content of ~ 60 to 140 ppb. The apatite from the younger Sevattur complex is comparable to the carbonates in terms of both concentration and isotopic composition. This can be related to increase in nitrogen input via subduction with time during Earth’s history since the Proterozoic, transported to the deep mantle, consequently overprinting any primordial signatures inherited from precursor building material such as the echondrites.ReferencesBasu, S. and Murty, S.V.S. Journal of Asian Earth Sciences 107: 53-61 (2015). https://doi.org/10.1016/j.jseaes.2015.03.044Dauphas, N. and Marty, B. Science 286(5449): 2488-2490 (1999). https://doi.org/10.1126/science.286.5449.2488Mikhail, S. and Sverjensky, D.A. Nature Geoscience 7(11): 816-819 (2014). https://doi.org/10.1038/ngeo2271Mysen, B. Prog Earth Planet Sci 6, 38 (2019). https://doi.org/10.1186/s40645-019-0286-xSmart, K.A., Tappe, S., Stern, R.A., Webb, S.J. and Ashwal, L.D.  Nature Geoscience 9(3): 255-259 (2016). https://doi.org/ 10.1038/NGEO2628

Geoscience is being increasingly embedded in collaborative research related to the management of natural resources and the environment, alongside engineering and social sciences.  Masters students exercise rigorous choices in selecting their study courses that enhance employability, considering carefully the kind of learning experience they are likely to have. The interdisciplinary M.Sc. programme ‘Global Management of Natural Resources’ (in Chemical Engineering, University College London, UK) has generated a lot of interest since its initiation in 2016. The geoscience module ‘Geology for Global Managers and Engineers’ (GGME), is a part of the above taught programme, studied by students from diverse academic background considered in four sets, namely, set 1 (geologists), set 2 (chemists, environmentalists, ecologist) set 3 (engineers) and set 4 (others, without science background such as economics and finances).Traditional assessment methods for geology include written examination papers, field trip reports and essays and, practical based on hand specimen and microscopic studies. But, the role of assessment is no longer solely associated with awarding a grade but, should enhance inclusion and serve as effective teaching tools (Hounsell et al., 2005; Kaur et al., 2017). This can be better achieved by applying diverse assessment methods taking into account the different skill sets of the students, ensuring fairness and consistency with consideration of increased workload for both lecturers and students (Brown, 2012). Here we studied the effectiveness of multiple assessment for the taught GGME module including a combination of software based coursework, fieldtrip activities and hands on specimen studies, spread over the term, followed by an end of term multiple-choice questions’ based sit-in examination.Our study indicates that prior academic background did affect students’ scores in the assessments. The students from set 4 had the lowest average score, although ~ 15 % attained higher marks comparable to set 1, attributable to a combination of factors including the set multiple assessments. The students performed better in course works involving smaller learning components where there was more time for reflection. But, they scored lower when the course works were set too early or late during the term. Assessing the same learning outcome by more than one method with provided feedback worked as effective, continuous learning activities with a reduced attainment gap in the final examination between the students from sets 1 and 4, for components already covered in the course works. Noteworthy that although the students were from diverse ethnic background, there was no attainment gap attributable to their ethnicity. A combination of assessment methods with both individual and group work components proved to be effective in closing any attainment gaps between diverse groups of students.ReferencesBrown, S. (2012). AISHE-J 4(2), 85.1–85.12.Hounsell, D., Entwistle, N., Anderson, C., Bromage, A., Day, K.,  Hounsell, J., Land, R., Litjens, J., McCune, V., Meyer, E., Reimann, N. and Xu, R. (2005). Final Report to the Economic and Social Research Council, on TLRP Project L139251099.Kaur, A., Noman, M. and Nordin, H.  (2017). 42(5), 756-771.