Virtual Materials Group (Canada)

Paclitaxel is a highly successful anti-neoplastic cancer drug. The first clinically successful paclitaxl-delivery method is a mixture with cremophor EL and ethanol, here termed the taxol micelle. Until now, molecular dynamics analysis has not been presented to quantify the structural and conformation properties of these drug molecules when interacting with each other to create this nonstandard micelle. Here we apply systematic molecular simulation and statistical analysis of paclitaxel and cremophor EL conformations based on all atom and coarse-grained approaches. The cremophor EL in the taxol micelle showed a clustering network in a 3D landscape where paclitaxel can be loaded at much higher than standard concentration with no aggregation. Paclitaxel particles within the cremophor EL cavities showed some oscillatory behaviour due to a repeated adsorption/desorption with the surrounding network. Paclitaxel conformations at the lowest energy state can be described when the side-chain phenyl rings are closer relative to the immobile core. Cremophor EL molecules reached the highest energy state when wings were fully spread and at the lowest energy state when wings were fully closed. The spiral shapes were observed to be the dominant species in the cremophor EL population. We then established reliable statistical correlations between molecular conformations and the energy states. Our reliable all atom and coarse-grained modelling approach can also be applied for effective drug design analysis using different drug delivery systems.

Abstract Seismic imaging in the Tarim Basin, China, presents significant challenges due to complex near-surface conditions, including desert environments, foothills, and loess mountains. These challenges are comparable to those found in regions such as the Arabian Peninsula, North Africa, the Andes Mountains, and other complex terrains worldwide. Recent advancements in seismic imaging aimed at overcoming these obstacles include: (1) advanced constrained near-surface tomography, which has significantly enhanced the robustness of near-surface velocity-depth model estimation, leading to improved resolution of deep reservoir images; (2) a recent ultra-long-offset (greater than 15 km) experiment in the foreland basin of the Tarim Oilfield, demonstrating that more accurate and deeper near-surface velocity models can be generated on land using turning-ray tomography; (3) finite-frequency wavepath tomography, which has been proven through field data examples to be a robust alternative to traditional full-waveform inversion for land seismic data; and (4) integrated tomography, which combines diving waves and reflected seismic data to develop a comprehensive velocity model from shallow to deep sections for anisotropic prestack depth migration from topography. These technologies, developed for and applied to the Tarim Basin, can be applied, with modifications, to other land basins around the world.

Formation damage in drilling comes from drilling fluid invasion due to high differential pressure between a wellbore and the formation. This mechanism happens with fracture fluid invasion of multi-fractured horizontal wells in tight formations. Some multi-fractured wells show production rates and cumulative productions far lower than expected. Those damaged wells may sustain further impact such as well shutting due to unexpected events such as the COVID-19 outbreak and then experience a further reduction in cumulative production. This paper focuses on the root causes of formation damage of fractured wells and provides possible solutions to improve production. A simulation study was conducted using Computer Modelling Group software to simulate formation damage due to fracture fluid invasion and well shut-in. Simulation results revealed that the decrease in cumulative hydrocarbon production due to leak-off and shut-in of the simulated well could range from 20 to 41%, depending on different conditions. The results showed that the main causes are high critical water saturation of tight formations, low drawdown, and low residual proppant permeability under formation closure stress. The sensitivity analysis suggests two feasible solutions to mitigate formation damage: optimizing drawdown during production and optimized proppant pack permeability of the hydraulic fracturing process. Optimizing pressure drawdown is effective in fixing leak-off damage, but it does not mitigate shut-in damage. Formation damage due to shut-in should be prevented in advance by using an appropriate proppant permeability. These key findings enhance productivity and improve the economics of tight gas and shale oil formations.

Gas injection is one of the established methods in enhanced oil recovery. Nevertheless, poor sweep efficiency and viscous instabilities result in early gas breakthrough. Lowering injected gas mobility through foaming is a potential solution to solve the forenamed challenges. Although foaming of the injected gas has been proposed in various stages of oil production, comparatively few studies are carried out about foam injection modeling in the presence of oil. In this study, we aimed to numerically investigate the immiscible foam propagation in a thick, heterogeneous, water-flooded sandstone reservoir with a primary goal to control the surge of the produced gas–oil ratio (GOR) and also the possible incremental oil production by foam. To this end, the implicit-texture local-equilibrium foam model was used to address that how a stable foam front could affect fluid saturation and their mobility in the presence of waterflood residual oil. We treated the reservoir model by considering a pair of horizontal injection/production well through the upper and lower parts of the reservoir to mimic the foam-assisted gravity drainage scheme. Foam generation was considered through alternating (SAG) and simultaneous injection of gas and surfactant solution, and its performance was compared with continuous gas injection and water alternating gas injection. Results showed that gas-phase mobility was reduced in the presence of foam, leading to delaying of gas breakthrough and thereby improvement of gas sweep efficiency. The latter caused a significant reduction in produced gas–oil ratio, enhanced the control of the front movement, and resulted in better oil sweeping. In comparison to the SAG method, occurrence of fingering phenomena in foam co-injection was less likely. In addition, foam front in co-injection method exhibited relatively slower movement compared to the SAG method. Also, with ignoring the prescribed pressure constraint in injection well, the stability and uniformity of the generated foam front decreased, leading to more occurrences of fingering and thus reduction in oil recovery.

Spinning up a highly complex, coupled Earth system model (ESM) is a time consuming and computationally demanding exercise. For models with interactive ice sheet components, this becomes a major challenge, as ice sheets are sensitive to bidirectional feedback processes and equilibrate over glacial timescales of up to many millennia. This work describes and demonstrates a computationally tractable, iterative procedure for spinning up a contemporary, highly complex ESM that includes an interactive ice sheet component. The procedure alternates between a computationally expensive coupled configuration and a computationally cheaper configuration where the atmospheric component is replaced by a data model. By periodically regenerating atmospheric forcing consistent with the coupled system, the data atmosphere remains adequately constrained to ensure that the broader model state evolves realistically. The applicability of the method is demonstrated by spinning up the preindustrial climate in the Community Earth System Model Version 2 (CESM2), coupled to the Community Ice Sheet Model Version 2 (CISM2) over Greenland. The equilibrium climate state is similar to the control climate from a coupled simulation with a prescribed Greenland ice sheet, indicating that the iterative procedure is consistent with a traditional spin‐up approach without interactive ice sheets. These results suggest that the iterative method presented here provides a faster and computationally cheaper method for spinning up a highly complex ESM, with or without interactive ice sheet components. The method described here has been used to develop the climate/ice sheet initial conditions for transient, ice sheet‐enabled simulations with CESM2‐CISM2 in the Coupled Model Intercomparison Project Phase 6 (CMIP6).

According to practice engagement theory, everyday workplace tasks offer an opportunity for skill development among youth and young adults, yet prior research highlights the prevalence of routine and low-skill work within entry-level jobs. Utilizing data from the Programme for the International Assessment of Adult Competencies (PIAAC), the following study demonstrates how workplace reading, writing, and numeracy-based activities differ among youth aged 16 to 34 in Canada. Latent class analysis provides a typology of skill-based activities at work and generates insight into how socio-demographic, employment, and educational factors are associated with each group. The findings highlight that youth employment cannot be uniformly characterized as low-skill. Rather, there are unique low and high skill youth employment groups with differing characteristics.

Abstract Multiphase flow mechanistic models are macroscopic conservation equations (mass and momentum) supported by several empirical closure relations. There are several empirical corelationsavailable for each closure relationship. The success of mechanistic models largely depends on the employed closure relationships. Although, ideally, the closure relationships are desired to be applicable for all operating conditions and fluids;however, in reality, it is difficult to find such universal closures due to empiricism involved in the development of the closureships. Until the development of universal closure relationships, another viable approach is to find different set of closure relationships for identifiably different flow conditions such as low liquid loading flow or high viscosity liquids. In this study, we present a procedure to test the performance of multiple closure relationships against available databases. As an initial application of the procedure, we have tested different combination of closure relationships in the Unified Model (Zhang et al., 2003) and identified the combinations of closures that produce the best model performance for low liquid loading conditions using the field data set consisting of the nineteen field measurements from Frigg to St. Fergus gas and condensates export line. The results of the 37,620 simulations were analyzed. The results showed that the original set of closure relationships used in Zhang et al. (2003) was not optimal for this particular set of data. Instead, a different set of closure relationships is proposed to improve the model's performance for these specific field cases. Total absolute average pressure drop deviation was reduced form 11% to 10%. Total absolute average liquid content deviation was reduced from 66% to 1%. Using the proposed procedure, with the availability of additional large-scale field data, the set of closure relationships can be further refined, and even the elusive goal of finding universal closure laws would be possible.

This paper introduces a new fast algorithm for the 8-point discrete cosine transform (DCT) based on the summation-by-parts formula. The proposed method converts the DCT matrix into an alternative transformation matrix that can be decomposed into sparse matrices of low multiplicative complexity. The method is capable of scaled and exact DCT computation and its associated fast algorithm achieves the theoretical minimal multiplicative complexity for the 8-point DCT. Depending on the nature of the input signal simplifications can be introduced and the overall complexity of the proposed algorithm can be further reduced. Several types of input signal are analyzed: arbitrary, null mean, accumulated, and null mean/accumulated signal. The proposed tool has potential application in harmonic detection, image enhancement, and feature extraction, where input signal DC level is discarded and/or the signal is required to be integrated.