The effect of heterogeneity in sedimentary properties on fluid flow behaviour at the pore-scale

Sandstone reservoir rocks are important for numerous applications, such as oil and gas recovery, CO2 storage and groundwater aquifers, and understanding how reservoir rock properties influence the dynamics of fluids and gases within reservoir rocks is essential yet difficult to predict. Heterogeneity complicates the identification of viable areas of recovery, potential areas of migration and groundwater catchment planning. To improve accuracy in reservoir flow models further analysis of the impact of heterogeneous reservoir rock properties on fluid transport is required. Pore network analysis is key in understanding fundamental concepts of fluid flow behaviour as pore network geometry is a dominant control on the effectiveness of fluid transport within a reservoir and is strongly associated with porosity and permeability. Despite this, there has been limited research into how heterogeneous rock properties influence fluid flow behaviour at the pore scale and analysis is commonly focused on samples which have homogeneous grain size and mineralogy. Heterogeneity in sandstone reservoir rocks can be categorised into three main types; 1) sedimentary, 2) structural, and 3) diagenetic. This thesis focuses on sedimentary heterogeneities, which are influenced by the environmental conditions at the time of sediment deposition, and the main aim of this thesis is to quantify the effect of heterogeneity in grain size and mineralogy on pore network geometry (pore diameter, porosity), fluid flow behaviour and mineral dissolution in the pore network. Ten synthetic, glass bead pack samples were designed based on naturally occurring sedimentary heterogeneities identified in cores from the Triassic Sherwood Sandstone and the Permian Rotliegend Group and used in pore-scale permeability experiments which validate the results from 3D visual analysis and simulations conducted in the Avizo Fire software and CFD simulations conducted in the ANSYS Fluent software. The experimental methodology for the pore-scale permeability experiments was designed and developed to enable reliable and accurate measurements of flow rate and pressure difference over a 3D customised bead pack sample. In order to achieve this, two degassing techniques were employed to fully purge trapped bubbles of air which occurred in the system/sample. The experiments produce reliable and repeatable data which are in agreement with results from the literature and permeability calculated using the Kozeny-Carman model, Avizo Fire simulations and ANSYS Fluent CFD simulations. The results from the experiments and simulations confirm the widely held view that bead size and heterogeneity in bead size influences the pore network geometry, fluid flow behaviour and permeability of a sample. In samples with homogeneous bead size, increasing bead size (54.5%) corresponds to larger mean pore diameter size (35.2%), a larger range in mean pore diameter size, less uniform distribution in pore diameter size, and greater porosity (0.74-3.47%). Less uniformity in pore diameter size increases tortuosity (2.65%) and facilitates high velocity preferential pathways which increases permeability (52.2-98.5% across all homogeneous samples and techniques). The effect of bead size heterogeneity is determined by the arrangement of the bead size (e.g. smaller beads changing to larger beads) and the mean pore diameter size and range of mean pore diameter size is lower (7.7%) and the distribution of pore diameter size is more uniform when smaller beads transition to larger beads. This is due to the reduction in pore space due to a poorer degree of sorting and increased packing density as smaller beads are able to invade the pore space between the larger beads. Greater uniformity in pore diameter size results in more consistent fluid flow (multiple, well distributed, smaller, low velocity flow pathways) and higher permeability (0.60-55.9% across all techniques) when fluid flow passes a transition from smaller beads to larger beads. The onset of non-Darcy flow was analysed in the samples with differing homogeneous bead size and heterogeneous bead size and the results suggest that the critical Reynold's number (the Reynold's number which corresponds with the onset of non-Darcy flow) is determined by pore size and greater pore size corresponds to a larger critical Reynold's number due to larger pores being more able to facilitate high velocity flow. In the samples with heterogeneous bead size different factors influence the critical Reynold's number and the critical Reynold's number decreases with decreasing tortuosity when fluid flow passes a transition from smaller beads to larger beads and the critical Reynold's number decreases due to increasing heterogeneity and decreasing permeability when flow flow crosses a transition from larger beads to smaller beads. The beta factor was also calculated and increases with decreasing bead size and the results from the samples with homogeneous bead size suggest that beta factor increases with decreasing permeability. The results from samples which present mineralogical heterogeneity show that the addition of kaolinite and dolomite reduces the mean pore diameter size (56.8-68.0%), the range of mean pore diameter size and the porosity (2.2-3.8%). Kaolinite results in a greater reduction in mean pore diameter size (68.0%) and increases the range of mean pore diameter size and this is due to the size and distribution of kaolinite which is more randomly distributed throughout the sample due to its greater range in particle size (0-63um). The impact of kaolinite is reduced when it occurs with dolomite as dolomite content restricts the distribution of kaolinite and this is due to the shape and size of the dolomite grains. Angular grains of dolomite occupy pore cavities and wedge alongside beads which is more destructive to porosity and limits accumulations of kaolinite to fewer pores. Increased variation in pore diameter size is related to increased tortuosity and longer fluid flow pathways which increases access to reactive minerals and increases dissolution. Kaolinite content is most destructive to permeability (73.4-88.0%), in comparison to dolomite content, as it increases heterogeneity in pore diameter size and reduces pore space the most. The impact of kaolinite on permeability is less severe when kaolinite occurs with dolomite as dolomite limits the random distribution of kaolinite throughout the pore network which limits heterogeneity. The permeability of the samples which contain dolomite was reduced after acidic flow despite evidence of mineral dissolution and this is interpreted to occur as a result of small particles becoming detached during dissolution and becoming lodged in pores and pore throats. Heterogeneity in bead size and mineralogy decreases the mean pore diameter size (31.6-65.4%) and porosity (3.7-5.7%), increases the range in mean pore diameter (20.3-26.0%) and reduces permeability (75.7%), in comparison to the bead pack samples which present mineralogical heterogeneity. The bead pack sample which presents heterogeneity in bead size and mineralogy displays comparable pore diameter, porosity and permeability results to the crushed rock sample which indicates that bead pack samples can present realistic pore network geometries. Dolomite dissolution increases (1.4-2.4%) when bead size is heterogeneous and permeability is reduced (76.6%) after acidic flow and the reduction in permeability is greater (44.1%) when heterogeneous bead size and mineralogy occur in a sample together and this is due to local variations in permeability which in turn can result in local fluctuations in reaction rates and mineral dissolution. Local fluctuations in reaction rates and dissolution may enhance the variations in permeability after acidic flow or create a series of permeability contrasts where regions of higher permeability enable a higher rate of reactions and dissolution and the regions of low permeability are less able to facilitate fluid and particle transport meaning that the pore space becomes clogged more easily which reduces permeability further

A role for phospholipase A in auxin-regulated gene expression

AbstractAuxin increases phospholipase A2 activity within 2min (Paul, R., Holk, A. and Scherer, G.F.E. (1998) Fatty acids and lysophospholipids as potential second messengers in auxin action. Rapid activation of phospholipase A2 activity by auxin in suspension-cultured parsley and soybean cells. Plant J. 16, 601–611) and the phospholipase A inhibitors, ETYA and HELSS, inhibit elongation growth of etiolated Arabidopsis hypoctyls (Holk, A., Rietz, S., Zahn, M., Quader, H. and Scherer, G.F.E. (2002) Molecular identification of cytosolic, patatin-related phospholipases A from Arabidopsis with potential functions in plant signal transduction. Plant Physiol. 130, 90–101). To identify the mode of action, rapid auxin-regulated gene expression was tested for sensitivity to these PLA2 inhibitors using seedlings expressing β-glucuronidase (GUS) under the control of the synthetic auxin-responsive promoter DR5. ETYA and HELSS inhibited the auxin-induced increases in GUS activity, the steady-state level of the corresponding GUS mRNA and the mRNAs encoded by four other auxin-induced genes, IAA1, IAA5, IAA19 and ARF19. Factors that bind to the auxin response elements of the DR5 promoter and thereby regulate gene expression are regulated by a set of proteins such as Aux/IAA1 whose abundances are, in part, under control of E3 ubiquitin ligase SCF complexes. To investigate this mechanism further, the effect of ETYA on Aux/IAA1 degradation rate was examined using seedlings expressing Aux/IAA1:luciferase fusion proteins. In the presence of cycloheximide and excluding synthesis of IAA1:luciferase, ETYA had no apparent effect on degradation rates of IAA1, either with or without exogenous auxin. Therefore, the E3 ubiquitin ligase SCFTIR1 complex is an unlikely direct target of the PLA inhibitor. When cycloheximide was omitted, however, the inhibitors ETYA and HELSS blocked a sustained auxin-induced decrease in its steady-state level, indicating an unknown target capable to regulate Aux/IAA protein levels and, hence, transcription

Decreased Haemodynamic Response and Decoupling of Cortical Gamma Band Activity and Tissue Oxygen Perfusion after Striatal Interleukin-1 Injection.

Background: Neurovascular coupling describes the mechanism by which the energy and oxygen demand arising from neuronal activity is met by an increase in regional blood flow; known as the haemodynamic response. Interleukin 1 (IL-1) is a pro-inflammatory cytokine and an important mediator of neuronal injury, though mechanisms through which IL-1 exerts its effects in the brain are not fully understood. In this study we set out to investigate if increased cerebral levels of IL-1 have a negative effect on neurovascular coupling in the cortex in response to sensory stimulation. Methods: We used two approaches to measure the neuronal activity and haemodynamic changes in the anaesthetised rat barrel somatosensory cortex in response to mechanical whisker stimulation, before and for 6 h after intrastriatal injection of interleukin-1β or vehicle. First, we used two dimensional optical imaging spectroscopy (2D-OIS) to measure the size of the functional haemodynamic response, indicated by changes of oxyhaemoglobin (HbO2) and total haemoglobin (HbT) concentration. In the same animals immunostaining of immunoglobulin G and SJC-positive extravasated neutrophils was used to confirm the pro-inflammatory effects of IL-1β. Second, to examine the functional coupling between neuronal activity and the haemodynamic response, we used a ‘Clark-style’ electrode combined with a single sharp electrode to simultaneously record local tissue oxygenation (pO2) in layer IV/V of the stimulated barrel cortex and multi-unit activity (MUA) together with local field potentials (LFPs) respectively. Results: 2D-OIS data revealed that the size of the haemodynamic response to mechanical whisker stimulation declined over the 6 h following IL-1β injection whereas the vehicle group remained stable, significant differences being seen after 5 h. Moreover, the size of the transient increases of neuronal LFP activity in response to whisker stimulation decreased after IL-1β injection, significant changes compared to vehicle being seen for gamma-band activity after 1 h and beta-bandactivity after 3 h. The amplitude of the functional pO2 response similarly decreased after 3 h post IL-1β injection, whereas IL-1β had no significant effect on the peak of whisker-stimulation-induced MUA. The stimulation-evoked increases in gamma power and pO2 correlated significantly throughout the 6 h in the vehicle group, but such a correlation was not observed in the IL-1β-injected group. Conclusions: We conclude that intrastriatal IL-1β decouples cortical neuronal activity from its haemodynamic response. This finding may have implications for neurological conditions where IL-1β plays a part, especially those involving reductions in cerebral blood flow (such as stroke)

Anomaly Mediation, Fayet-Iliopoulos D-terms and the Renormalisation Group

We address renormalisation group evolution issues that arise in the Anomaly Mediated Supersymmetry Breaking scenario when the tachyonic slepton problem is resolved by Fayet-Iliopoulos term contributions. We present typical sparticle spectra both for the original formulation of this idea and an alternative using Fayet-Iliopoulos terms for a U(1) compatible with a straightforward GUT embedding.Comment: 20 pages, 2 figure

Expression of tumor necrosis factor [alpha] converting enzyme in endocrine cancers

Tumor necrosis factor [alpha] converting enzyme (TACE) mediates shedding of human epidermal growth factor receptor-4 (HER4). Recent data suggest that released HER4 intracellular domain (4ICD) induces apoptosis in breast cancer. TACE expression, as measured by immunohistochemical analysis, was observed in 183 of 383 breast carcinomas, 39 of 217 ovarian carcinomas, and 16 of 24 and 17 of 24 hormone-sensitive and hormone-insensitive prostate carcinomas, respectively. HER4 expression was detected in breast carcinomas by using 2 antibodies recognizing an extracellular or intracellular epitope. TACE expression was predominantly seen in tumors with high levels of 4ICD and membranous HER4. Apoptotic activity was measured by the terminal deoxynucleotidyl transferase-mediated nick-end labeling (TUNEL) assay and cleaved caspase-3 staining in breast carcinomas. There was no significant association between cleaved caspase-3 or TUNEL positivity and 4ICD, whereas TUNEL positivity was seen predominantly in tumors with high levels of internalized HER4. The data presented herein show TACE expression in endocrine cancers and further support a role for TACE in breast cancer apoptosis

Assisted Tachyonic Inflation

The model of inflation with a single tachyon field generates larger anisotropy and has difficulties in describing the formation of the Universe . In this paper we consider a model with multi tachyon fields and study the assisted inflationary solution. Our results show that this model satisfies the observation.Comment: 5 pages, no figures, a revised version and reference adde

Reconstructing the Antarctic ice-sheet shape at the Last Glacial Maximum using ice-core data

The Antarctic ice sheet (AIS) is the Earth’s largest store of frozen water; understanding how it changed in the past allows us to improve projections of how it, and sea levels, may change. Here, we use previous AIS reconstructions, water isotope ratios from ice cores, and simulator predictions of the relationship between the ice-sheet shape and isotope ratios to create a model of the AIS at the Last Glacial Maximum. We develop a prior distribution that captures expert opinion about the AIS, generate a designed ensemble of potential shapes, run these through the climate model HadCM3, and train a Gaussian process emulator of the link between ice-sheet shape and isotope ratios. To make the analysis computationally tractable, we develop a preferential principal component method that allows us to reduce the dimension of the problem in a way that accounts for the differing importance we place in reconstructions, allowing us to create a basis that reflects prior uncertainty. We use Markov chain Monte Carlo to sample from the posterior distribution, finding shapes for which HadCM3 predicts isotope ratios closely matching observations from ice cores. The posterior distribution allows us to quantify the uncertainty in the reconstructed shape, a feature missing in other analyses

Psychological processes in adapting to dementia: illness representations among the IDEAL cohort

YesHow people understand and adapt to living with dementia may influence well-being. Leventhal’s Common Sense Model (CSM) of Self-Regulation provides a theoretical basis for exploring this process. We used cross-sectional and longitudinal data from 1,109 people with mild-to-moderate dementia in the Improving the experience of Dementia and Enhancing Active Life (IDEAL) cohort. We elicited dementia representations (DRs) using the Representations and Adjustment to Dementia Index (RADIX), a validated measure based on the CSM, identified groups sharing distinct DR profiles, and explored predictors of group membership and associations with well-being, and whether problem-focused coping played a mediating role in these associations. We identified four DR classes: people who see the condition as a disease and adopt a diagnostic label; people who see the condition as a disease but refer to symptoms rather than a diagnostic label; those who see the condition as part of aging; and those who are unsure how to make sense of the condition. A fifth group did not acknowledge any difficulties. “Disease” representations were associated with better cognition and younger age, while “aging” and “no problem” representations were associated with better mood and well-being. The association with well-being remained stable over 24 months. There was limited partial support for a mediating role of problem-focused coping. Variations in DRs may reflect individual differences in the psychological processes involved in adjusting to dementia. DRs provide a framework for personalizing and tailoring both communications about dementia and interventions aimed at supporting people in coping with dementia. There is a need to debate what constitutes a positive DR and how its development might be encouraged

Linear response function around a localized impurity in a superconductor

Imaging the effects of an impurity like Zn in high-Tc superconductors [Nature 61 (2000) 746] has rekindled interest in defect problems in the superconducting phase. This has prompted us here to re-examine the early work of March and Murray [Phys. Rev. 120 (1960) 830] on the linear response function in an initially translationally invariant Fermi gas. In particular, we present corresponding results for a superconductor at zero temperature, both in the s- and in the d-wave case, and mention their direct physical relevance in the case when the impurity potential is highly localized