Igneous sills and dykes that intrude pervasively into prospective sedimentary basins are a common occurrence in volcanic rifted margins, impacting the petroleum system and causing geological and technical drilling challenges during hydrocarbon exploration. The Faroe-Shetland Basin (FSB), NE Atlantic Margin, has been the focus of exploration for over 45 years, with many wells penetrating igneous intrusions. Utilising 29 FSB wells with 251 intrusions and 3D seismic data, this study presents new insights into the impacts that igneous intrusions have on hydrocarbon exploration. Examination of cores reveals that there can be up to 35% additional igneous rock in individual wells compared to estimates using seismic or petrophysical data alone, leading to potential underestimation of the igneous component in a basin. Furthermore, analysis of petrophysical data shows that within the FSB there are evolved intrusions such as diorite and rhyolite in addition to the commonly encountered basaltic intrusions. These evolved intrusions are difficult to recognise in seismic and petrophysical data and have historically been misidentified on seismic as exploration targets. Drilling data acquired through intrusions provide valuable insight into the problems exploration wells can encounter, often unexpectedly, many of which can be detrimental to safe drilling practice and result in prolonged nonproductive time.
Fractures are ubiquitous in crystalline rocks and control the strength and geophysical and fluid transport characteristics of the Earth's upper crust. A quantitative description of fracture attributes may constrain models of fracture formation and evolution. In this study, fracture attributes collected from one-dimensional samples across exposures of typical crystalline rocks show comparable variability in fracture size and spacing to sedimentary rocks. Vein thickness and fracture aperture data show predominately power-law distributions. Vein and fracture spacing data are best described by exponential distributions with negative slopes and appear to vary with composition in intrusive rocks. The fracture systems exhibit a range of anti-clustered to clustered patterns, and densities are an order of magnitude higher for joints compared to veins. Fracture clustering data can be used in conjunction with the spatial distributions to provide information on the controlling processes of fracture spacing. We suggest that exponential spacing distribution is produced as a sampling effect for both periodic-spaced and clustered fracture sets. In the examples given here, thermal stress-related joint patterns are distinguishable from tectonic-related fractures in plutonic rocks and fracture density and clustering is increased towards a major reactivated basement fault.
Rift-related magmatism resulting in widespread igneous intrusions has been documented in various basins, including the Faroe Shetland Basin (UK), Voring and Møre Basins (Norway) and along the NW Shelf of Australia. Seismic mapping, combined with field work, has resulted in greater understanding of subsurface intrusive plumbing systems, but knowledge of emplacement style and the mechanisms by which intrusions propagate is limited. The interpretation of a 3D seismic dataset from the Exmouth sub-basin, NW Shelf Australia, has identified numerous igneous intrusions where a close relationship between intrusions and normal faults is observed. These faults influence intrusion morphology but also form pathways by which intrusions have propagated up through the basin stratigraphy. The steep nature of the faults has resulted in the intrusions exploiting them and thus manifesting as fault-concordant, inclined dykes, whereas in the deeper parts of the basin, intrusions that have not propagated up faults typically have saucer-shaped sill morphologies. This transition in the morphology of intrusions related to fault interaction also highlights how dykes observed in outcrop may link with sills in the subsurface. Our interpretation of the seismic data also reveal subsurface examples of bifurcating intrusions with numerous splays, which have previously only been studied in outcrop.
In situ overpressures in sedimentary basins are commonly attributed to disequilibrium compaction or fluid expansion mechanisms, although overpressures in shallow sedimentary sequences may also develop by vertical transfer of pressure from deeper basin levels, for example, via faults. Mafic sill complexes are common features of sedimentary basins at rifted continental margins, often comprising networks of interconnected sills and dikes that facilitate the transfer of magma over considerable vertical distances to shallow basinal depths. Here, we document evidence for deep sills (depths >5 km [>16,000 ft]) hosting permeable, open fracture systems that may have allowed transmission of overpressure from ultradeep basinal (>7 km [>23,000 ft]) levels in the Faroe-Shetland Basin, northeast Atlantic margin. Most notably, well 214/28-1 encountered overpressured, thin (<8 m [<26 ft]), and fractured gas-charged intrusions, which resulted in temporary loss of well control. Although the overpressure could reflect local gas generation related to thermal maturation of Cretaceous shales into which the sills were emplaced, this would require the overpressures to have been sustained for unfeasibly long timescales (>58 m.y.). We instead suggest that transgressive, interconnected sill complexes, such as those penetrated by well 214/28-1, may represent a previously unrecognized mechanism of transferring overpressures (and indeed hydrocarbons) laterally and vertically from deep to shallow levels in sedimentary basins and that they represent a potentially underrecognized hazard to both scientific and petroleum drilling in the vicinity of subsurface igneous complexes.
VT-1161 is a novel tetrazole antifungal agent with high specificity for fungal CYP51 (compared to human CYP enzymes) which has been proven to have fewer adverse effects and drug–drug interaction profiles due to fewer off-target inhibitors. In this study, we evaluated the anti-biofilm potential of VT-1161 against mono- and dual-species biofilms of Candida albicans, Klebsiella pneumoniae and Staphylococcus aureus. VT-1161 inhibited planktonic growth of all three strains, with an MIC value of 2 µg mL−1 for C. albicans and 0.5 µg mL−1 for K. pneumoniae and S. aureus, and killed 99.9% of the microbial populations, indicating a cytocidal action. Additionally, VT-1161 showed an excellent anti-biofilm action, since it inhibited mono-microbial biofilms by 80% at 0.5 µg mL−1, and dual-species biofilms of C. albicans/K. pneumoniae and C. albicans/S. aureus by 90% at the same concentration. Additionally, the eradication of mature biofilms after 24 h of VT-1161 exposure was excellent, reaching 90% at 2 μg mL−1 for both mono- and dual-species biofilms. In such mixed biofilms, the use of VT-1161 was revealed to be an alternative treatment because it was able to reduce the number of cells of each species during both inhibition and eradication. Since long-term therapy is necessary for most fungal biofilm infections due to their recurrence and obstinacy, VT-1161 showed low cytotoxicity against normal human cell lines and also against the invertebrate model Caenorhabditis elegans. Considering the excellent anti-biofilm potential and its GRAS (generally recognized as safe) status, VT-1161 may find use in the prevention or therapeutic treatment of mono- or poly-microbial biofilms.
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