Efficient blending in large crude oil storage tanks is essential for product quality control, pipeline transfer, and custody measurement. However, reliable prediction of blending time remains difficult when geometric enlargement, jet driven recirculation, and composition dependent property differences interact simultaneously. In this study, the coupled effects of blending ratio, jet flow rate, and tank scale on swirl jet blending were systematically investigated, and a physics based framework for predicting blending time under geometric enlargement was developed using convective scaling and Gaussian process regression based residual correction. Transient computational fluid dynamics simulations were performed using an Eulerian-Eulerian framework coupled with the shear stress transport turbulence model, and blending performance was evaluated using the coefficient of variation criterion. The results show that blending time decreases with increasing blending ratio and jet flow rate, but increases markedly with tank diameter. Increasing the blending ratio from 10% to 40% reduced the blending time by nearly 60%, whereas geometric enlargement increased the blending time at low blending ratio by more than 60%. Flow field analysis further indicates that blending efficiency is more closely associated with circulation coverage and connectivity than with the average turbulence magnitude alone. The physics based model achieved a coefficient of determination of 0.93, while the hybrid model improved it to 0.96 and also provided a predictive interval. The prediction for the additional enlarged case remained within this interval, indicating that the framework retains applicability under moderate geometric extrapolation. Overall, this study provides a practical and physically interpretable method for blending time prediction and scale up assessment in enlarged swirl jet storage tanks.
Fractures in the subsurface, spanning scales from microscopic cracks to macroscopic faults, significantly influence the mechanical, hydraulic, and seismic properties of rock systems. Understanding and modeling the influences of multiscale fractures on the seismic wave dispersion and attenuation plays a critical role in advancing geophysical exploration, enhancing reservoir characterization, and improving the predictive capabilities for energy resource management and geohazard assessment. However, existing theoretical models often address the wave dispersion and attenuation for the single-scale fractures, lacking a unified framework to integrate multiscale and multi-physical processes. We develop a unified theoretical model that comprehensively characterizes seismic wave dispersion and attenuation in multiscale fractured rocks. The model integrates mechanisms such as microscale squirt flow, mesoscopic fluid flow between fractures and background pores, fluid flow between intersecting fractures, and scattering attenuation, while accounting for fracture lengths spanning five orders of magnitude (from 10-4 to 101 m), as well as their orientation, filling materials, and distribution patterns. Multiscale fractured rocks exhibit pronounced scale-dependent elastic properties, characterized by decreasing velocity and increasing attenuation with increasing scale. Mesoscopic fluid flow between fractures and background pores, as well as fluid flow between intersecting fractures, is the dominant mechanisms of seismic wave attenuation in earthquake and exploration seismic frequency bands, while scattering attenuation plays a critical role under gas-saturated conditions. In fractal distributions, these effects become particularly significant at seismic scales, whereas in log-Gaussian distributions, the most notable changes occur at the logging scale. The developed modeling framework has the potential to improve the understanding and predictive capabilities of fracture-dominated systems and enhance the interpretation of multiscale fractures using cross-scale geophysical data.
Drillstring vibrations are a critical concern in horizontal well drilling, often leading to premature component failure, well trajectory deviation, severe bit and stabilizer wear, and reduced rates of penetration. However, the underlying mechanisms governing these induced vibrations remain insufficiently understood. To address this issue, a novel experimental platform capable of simulating horizontal well geometries was developed to investigate the coupled dynamic behavior of drillstrings. Influencing factors, including rotational speed, feed rate, weight-on-bit (WOB), and formation lithology, were systematically examined. Dynamic responses were measured using force, torque, and triaxial acceleration sensors. To improve the accuracy of vibration characterization, the measured acceleration signals were transformed from sensor coordinates to a fixed geographic coordinate system based on Euler rotation theorem, thereby accounting for gravity and sensor installation eccentricity. Results demonstrate that increasing rotational speed excites nonlinear coupled vibrations and significantly amplifies both axial and lateral vibrations with distinct frequency-doubling characteristics. An increase in feed rate mainly intensifies lateral vibration, while simultaneously improving overall drilling stability by reducing fluctuations in WOB and torque. Increasing surface WOB suppresses axial bit bounce but aggravates lateral and torsional instability due to intensified drillstring buckling. Higher formation strength alters stick–slip behavior, resulting in a more stable rock-breaking process while slightly increasing axial vibration amplitudes. These findings provide new insight into the vibration mechanisms of drillstrings in constrained wellbores and offer a useful basis for drilling parameters optimization and vibration mitigation in horizontal drilling operations.
The incompressible flows in a circular pipe with sudden expansion are numerically investigated in the laminar regime for both the Newtonian fluid and the non-Newtonian Herschel-Bulkley (HB) fluid, with the emphases on the difference caused by different rheological models. The Reynolds number, which is defined by the mean inlet velocity, inlet diameter, and viscosity of Newtonian model, ranges from 50 to 500. For uniform axial flow, steady and axisymmetric annular recirculation region develops after the expansion with the length increasing linearly with Reynolds number. The HB flow generates shorter recirculation region than the Newtonian flow. When a swirling flow is introduced at inlet, the axisymmetric flow breaks into helical flow with multiple vortices when the strength of swirling is large enough. The transition happens at weaker swirling for the Newtonian fluid than the HB fluid. The helical flow experiences the subcritical transition to a bubble shape structure when a azimuthally asymmetric mode with large enough amplitude is added to the inlet swirling flow for both fluid models. For all cases, the total pressure drop between the inlet and outlet is larger for the HB flow than the Newtonian flow under the same conditions.
We synthesized a homologous series of alkyl amidines with chain lengths from C4 to C18 and systematically investigated their physicochemical properties, CO2 responsiveness and applications. Key findings demonstrate a dual dependence of properties on the alkyl chain length and CO2-induced protonation. Both unprotonated and protonated surfactants show an inverted volcano-shaped relationship between surface tension and chain length, with optimal surface activity at intermediate lengths (C8-C14), whereas oil-water interfacial tension shows minimal dependence on either chain length or CO2-induced protonation. Interestingly, these alkyl amidines exhibit distinct chain-length-dependent and CO2-switchable emulsification-demulsification behaviors. The unprotonated short-chain surfactants (C4-C10) form O/W emulsions but cause demulsification upon protonation, whereas the unprotonated long-chain surfactants (C12-C18) cannot emulsify but their protonated forms can stabilize O/W emulsions. The resultant emulsions stabilized by unprotonated short chains show a negatively charged interface due to hydrogen bond-induced water deprotonation by the amidine group, thereby generating the interfacial OH- ions. In contrast, emulsions stabilized by protonated long-chain amidines possess a positively charged interface via CO2-induced cationization. Importantly, the unique chain length dependence and CO2 responsiveness were successfully leveraged for diverse applications, including clay stabilization, crude oil washing, and CO2-enhanced foam fire suppression.
