Measurements of zeta potential for improved understanding of controlled salinity waterflooding

Improved oil recovery (IOR) processes increase the efficiency of oil extraction from subsurface reservoirs. Controlled salinity waterflooding (CSW) is an IOR process where brine of a specific ionic composition is injected into a reservoir. However, CSW does not always yield IOR and the underlying mechanism(s) responsible remain unclear. It is generally accepted that successful CSW is associated with a shift to a more water-wet state. The wetting state is thought to be controlled by the zeta potential, a measure of the electrical potential, at the mineral and oil interfaces. This thesis explores how modifying the brine composition changes the zeta potential of these interfaces and impacts wettability in sandstones and carbonates. This is primarily done by streaming potential measurements (SPM) of natural, intact rock cores at conditions relevant to CSW. Results are discussed with specific focus on their application to CSW. Under fully water saturated conditions, the zeta potential of carbonates becomes more negative with reduction of the divalent cations Ca2+ and Mg2+. Sandstones exhibit more complex behaviour; however, the bulk clay content appears to be an important control. Following wettability alteration with crude oil, the zeta potential of carbonate samples became more positive or negative with increasing oil-wetness. The direction of change is interpreted to represent the polarity of the oil-brine zeta potential. During CSW, if the injection brine yields a mineral-brine zeta potential polarity that is the same as the oil-brine zeta potential, then IOR is observed. Determining the polarity of the oil-brine zeta potential appears critical in controlling CSW but directly measuring this under relevant conditions is challenging using conventional methods. A theoretical pore network model was developed which allows for prediction of the oil-brine zeta potential under such conditions. The model predicts that this was positive in most of the carbonate experiments. However, previous literature data from conventional methods suggest positive values are rare. Therefore, a new method to directly measure the oil-brine zeta potential was also developed. Strongly oil-wet substrates were prepared using natural porous media and coated with crude oil. The zeta potential of these substrates reflects the oil-brine zeta potential. These results show Ca2+ is a key control, however, most of the data were negative, conflicting with prior results. There is an apparent difference between the zeta potential of the ‘pristine’ oil-brine interface and that of the ‘in-situ’ oil-brine interface present in the subsurface; the latter of which appears critical in controlling CSW. Understanding the in-situ oil-brine zeta potential contributes to better design and optimisation of CSW processes to maximise oil recovery.Open Acces

WSES guidelines for management of Clostridium difficile infection in surgical patients

In the last two decades there have been dramatic changes in the epidemiology of Clostridium difficile infection (CDI), with increases in incidence and severity of disease in many countries worldwide. The incidence of CDI has also increased in surgical patients. Optimization of management of C difficile, has therefore become increasingly urgent. An international multidisciplinary panel of experts prepared evidenced-based World Society of Emergency Surgery (WSES) guidelines for management of CDI in surgical patients.Peer reviewe

Mapping the human genetic architecture of COVID-19

The genetic make-up of an individual contributes to the susceptibility and response to viral infection. Although environmental, clinical and social factors have a role in the chance of exposure to SARS-CoV-2 and the severity of COVID-191,2, host genetics may also be important. Identifying host-specific genetic factors may reveal biological mechanisms of therapeutic relevance and clarify causal relationships of modifiable environmental risk factors for SARS-CoV-2 infection and outcomes. We formed a global network of researchers to investigate the role of human genetics in SARS-CoV-2 infection and COVID-19 severity. Here we describe the results of three genome-wide association meta-analyses that consist of up to 49,562 patients with COVID-19 from 46 studies across 19 countries. We report 13 genome-wide significant loci that are associated with SARS-CoV-2 infection or severe manifestations of COVID-19. Several of these loci correspond to previously documented associations to lung or autoimmune and inflammatory diseases3–7. They also represent potentially actionable mechanisms in response to infection. Mendelian randomization analyses support a causal role for smoking and body-mass index for severe COVID-19 although not for type II diabetes. The identification of novel host genetic factors associated with COVID-19 was made possible by the community of human genetics researchers coming together to prioritize the sharing of data, results, resources and analytical frameworks. This working model of international collaboration underscores what is possible for future genetic discoveries in emerging pandemics, or indeed for any complex human disease

Mapping the human genetic architecture of COVID-19

The genetic make-up of an individual contributes to the susceptibility and response to viral infection. Although environmental, clinical and social factors have a role in the chance of exposure to SARS-CoV-2 and the severity of COVID-191,2, host genetics may also be important. Identifying host-specific genetic factors may reveal biological mechanisms of therapeutic relevance and clarify causal relationships of modifiable environmental risk factors for SARS-CoV-2 infection and outcomes. We formed a global network of researchers to investigate the role of human genetics in SARS-CoV-2 infection and COVID-19 severity. Here we describe the results of three genome-wide association meta-analyses that consist of up to 49,562 patients with COVID-19 from 46 studies across 19 countries. We report 13 genome-wide significant loci that are associated with SARS-CoV-2 infection or severe manifestations of COVID-19. Several of these loci correspond to previously documented associations to lung or autoimmune and inflammatory diseases3,4,5,6,7. They also represent potentially actionable mechanisms in response to infection. Mendelian randomization analyses support a causal role for smoking and body-mass index for severe COVID-19 although not for type II diabetes. The identification of novel host genetic factors associated with COVID-19 was made possible by the community of human genetics researchers coming together to prioritize the sharing of data, results, resources and analytical frameworks. This working model of international collaboration underscores what is possible for future genetic discoveries in emerging pandemics, or indeed for any complex human disease