Coupling a Geomechanical Reservoir and Fracturing Simulator with a Wellbore Model for Horizontal Injection Wells

Reservoir cooling during waterflooding or waste-water injection can significantly alter the reservoir stress field by thermo-poro-elastic effects. Colloidal particles in the injected water decrease the matrix permeability and buildup the injection pressure. Fractures may initiate and propagate from injectors. These fractures are of great concern for both environmental reasons and strong influence on reservoir sweep and oil recovery. This paper introduces methods to fully couple reservoir simulation with wellbore flow models in fractured injection wells. A method to fully couple reservoir-fracture-wellbore models was developed. Fluid flow, solid mechanics, energy balance, fracture propagation, and particle filtration are modelled in the reservoir, fracture and wellbore domains. Effective stress in the reservoir domain is altered by thermo-poro-elastic effects during cold water injection. Fracture initiation and propagation induced by thermal and filtration effects is modelled in the fracture domain. Particle filtration on the borehole and fracture surfaces is modelled by matrix permeability reduction and filter cake build-up. Leakoff through the borehole and fracture surface is balanced dynamically. The coupled nonlinear system of equations is solved implicitly using Newton-Raphson method. We validate our model with existing analytical solutions for simple cases. We show how the poro-elasticity effect, thermo-elasticity effect, water quality, and wellbore open/cased conditions influence well injectivity, induced fracture propagation and flow distribution. Simulation results show that water quality and thermal effects control fluid leak-off and fracture growth. While it is difficult to predict the exact location of fracture initiation due to reservoir heterogeneity, we proposed a reasonable method to handle fracture initiation without predefined fracture location in the water injection applications. In open-hole completions, this may lead to "thief" fractures propagating deep into the reservoir. Thermal stress changes in the injection zone are shown to be significant because of the combined effect of forced convection, heat conduction and poroelasticity. The accurate predictions of thermal stress in different reservoir layers allow us to study fracture height growth and containment numerically for the first time. We show that controlling the temperature and the injection water quality is also found to be an effective way to ensure fracture containment.

Comparison of Bacterial Filtration Efficiency vs. Particle Filtration Efficiency to Assess the Performance of Non-Medical Face Masks in the Emergency Context of COVID-19 Pandemic

As a result of the current COVID-19 pandemic, the use of facemasks has become commonplace. The performance of medical facemasks is assessed using Bacterial Filtration Efficiency (BFE) tests. However, as BFE tests, require specific expertise and equipment and are time-consuming, the performance of non-medical facemasks is assessed with non-biological Particle Filtration Efficiency (PFE) tests which are comparatively easier to implement. It is necessary to better understand the possible correlations between BFE and PFE to be able to compare the performances of the different types of masks (medical vs. non-medical). In this study BFE results obtained in accordance with the standard EN 14683 are compared to the results of PFE from a reference test protocol defined by AFNOR SPEC S76-001 with the aim to determine if BFE could be predicted from PFE. Our results showed a correlation between PFE and BFE. It was also observed that PFE values were higher than BFE and this was attributed to the difference in particle size distribution considered for efficiency calculation. In order to properly compare these test protocols for a better deduction, it would be interesting to compare the filtration efficiency for a similar granulometric range.

Novel 3D printable powered air purifying respirator for emergency use during PPE shortage of the COVID-19 pandemic: a study protocol and device safety analysis

ObjectivesTo design a low-cost 3D printable powered air-purifying respirator (PAPR) that meets National Institute for Occupational Safety and Health (NIOSH) standard for flow rate and Occupational Safety and Health Administration (OSHA) standard for particle filtration for loose-fitting PAPRs and that can be made with a 3D printer and widely available materials.DesignDetailed description of components, assembly instructions and testing of a novel PAPR design in an academic laboratory following respective protocols. The assembled PAPR must meet NIOSH standards of flow rate, 170 L/min; OSHA fit factor for particle filtration, ≥250 and maintain positive pressure during regular and deep breathing.Main outcome measuresThe PAPR design was run through a series of tests: air flow (L/min), particle filtration (quantitative and qualitative) and positive pressure measured inside the helmet (mm Hg).ResultsFlow rate was 443.32 L/min (NIOSH standard: minimum 170 L/min) and overall fit factor for particle filtration was 1362 (OSHA pass level: ≥500), n=1. The device passed qualitative particle filtration, n=2, and measured peak pressure of 6mm Hg (>0 mm Hg indicates positive pressure) in the helmet, n=1.ConclusionsThe Hygieia PAPR is a low-cost, easily accessible, just-in-time 3D printable PAPR design that meets minimum NIOSH and OSHA standards for flow-rate and particle filtration for loose-fitting PAPR devices to be made and used when industry-made designs are unavailable.