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Concerning low-permeability reservoirs with hard-to-recover (HTR) hydrocarbon reserves, we comprehensively analyzed the influence of nonlinear reservoir processes on well flow rate–drawdown pressure relationship.
We identified new nonlinear relationships between the flow rate of low-permeability reservoirs and reservoir drawdown (indicator curves). The nonlinearity of the indicator curves is due to the combined effects of nonlinear filtration, technogenic reservoir change, and the dependence of formation damage parameters on drawdown. The applied approach allowed us to find out qualitatively new regularities in the relationship between flow rate and drawdown in low-permeability reservoirs. A well productivity analysis revealed hysteresis in the indicator curves and a shift in critical drawdown values when considering both formation damage and filtration nonlinearity. It was established that the combined effects of nonlinear filtration and damage effects lead to an additional flow rate reduction of 25–40% compared to separately considering each of these effects. The obtained results are of practical significance for optimizing the development of low-permeability reservoirs with HTR reserves and for predicting their productivity.

The paper presents results of investigation of a natural Ib-IaA diamond containing Y-defects from Yubileinaya kimberlite pipe. Analysis of spatial distribution of A and C defects and intensity of IR absorption at Raman frequency (1332 сm^-1) reveals anticorrelation between these defects. Transmission electron microscopy of a zone with abundant Y-defects shows presence of dislocations in various configurations and numerous clusters of point defects generated by non-conservative dislocation movement. Extended defects with shape resembling thin (1-3 nm) rhombic plates with the largest dimension up to 5-20 nm. Analysis of contrast of these defects shows that they represent nanosised voids (vacancy clusters). It is suggested that the defects were formed by annihilation of dislocation dipoles with subsequent growth by consumption of vacancies produced by non-conservative motion of dislocations. Upon excitation by 787 nm laser, in region 800-900 nm of photoluminescence spectra numerous narrow lines are observed, their intensity and position show irregular temporal variations. Such behavior (blinking) was earlier note for hydrogenated nanodiamonds. It is suggested that unusual behavior of the luminescence lines may be explained by recombination processes on internal walls of the voids.

This paper investigates a line-drive waterflood pattern with two injection wells, between which a hydraulic fracture spontaneously propagates. Using a simplified model implemented in the RN-KIM hydrodynamic simulator, we consider a scenario where propped fractures from the two injectors connect to form a single dominant spontaneous hydraulic fracture. We model the propagation of a spontaneous fracture between two wells with existing propped fractures and analyze how the difference in wellhead injection pressures affects the injection rate in each well. The results demonstrate that an injection pressure difference between adjacent wells can cause a severalfold decrease in the injection rate or even a complete well shut-in. This occurs when the well with the higher bottomhole pressure “dominates” the flow within the high-conductivity fracture. Furthermore, we analyze the impact of the operating conditions of adjacent injectors and the geomechanical properties of the reservoir on the injection rate.

We analyze unsteady characteristics of the flow resulting from the interaction between a longitudinal vortex-generated by jet injection from a wall-and a turbulent boundary layer. Velocity fields are measured using particle image velocimetry. Our data analysis includes the assessment of turbulence anisotropy and characteristic length scales of turbulent structures, as well as proper orthogonal decomposition. The results reveal mutual interaction between the turbulent boundary layer and the longitudinal vortex, which depends on the vortex intensity. It is demonstrated that the jet vortex generator significantly alters not only the mean flow but also the unsteady characteristics of the turbulent boundary layer.

This paper presents a numerical investigation of the stress-strain state in a non-spherical shell subjected to pulsed loading. We examine the influence of the height-to-radius ratio of elliptical heads on the maximum stress values within explosion chamber shells. The dependence of the stress-strain state at the shell pole on the head height is also analyzed. It is demonstrated that employing elliptical heads with an optimal height-to-radius ratio mitigates stress concentration.

We derive a particular solution for a macroscopic model of a two-velocity, two-temperature mixture of gas and suspended particles. The solution to the system of partial differential equations takes the form of a monochromatic sound wave. The mixture is modeled within the interpenetrating continuum approach, incorporating relaxation terms that account for momentum and thermal energy exchange between the carrier and dispersed phases. The particular solution is constructed via the Fourier method and can serve as a verification test for numerical models of gas-particle flows. For arbitrary velocity and thermal relaxation times, the solution is obtained by numerically calculating the complex roots of a sixth-degree polynomial dispersion relation. In the case of infinitely small relaxation times (a state of relaxation equilibrium pertinent to modeling ultra-dispersed mixtures), the reference solution reduces to a traveling wave propagating at the effective speed of sound in the gas-dust medium. We demonstrate the sensitivity of this effective sound speed to the parameters governing the heat transfer processes. The code used to generate the particular solution for arbitrary input parameters is publicly available.

We investigate the electrophoresis of a dielectric particle possessing a hydrophobic surface and high surface conductivity through a combination of numerical simulations and analytical methods. Our results show that, under a moderate electric field and high surface charge density, the particle velocity increases, with the contribution from surface conductivity significantly exceeding that of the slip length. An analytical expression for the electrophoretic mobility of a hydrophobic particle is derived. This formula consists of three terms: (1) the linear term from the classical Helmholtz-Smoluchowski relation; (2) a term accounting for the hydrophobic surface effect; (3) a term representing the contribution of surface conductivity induced by the high surface charge density. Results are presented for both small and large slip lengths, corresponding to micro- and nanoparticles, respectively. A comparison between the numerical and analytical solutions demonstrates excellent agreement between the two approaches.

We present an experimental investigation of the transport of water-dissolved rhodamine B fluorescent dye within a porous medium subjected to oscillatory flow. The porous medium consists of a rectangular cell packed with cylinders oriented perpendicular to the cell plane. The applied measurement technique enables simultaneous determination of the rhodamine B mass transfer rate and acquisition of both the instantaneous and time-averaged secondary flow velocity fields in the inter-cylinder space. The results demonstrate that the effective diffusion coefficient attributable to secondary flow scales linearly with the Peclet number, which is defined using the characteristic velocity of the secondary flow. At low dimensionless oscillation frequencies, a universal relationship is observed between the effective diffusion coefficient and the Peclet number. At moderate dimensionless oscillation frequencies, however, the proportionality constant between these parameters increases with rising oscillation frequency.

We investigate the effects of the Reynolds number, static pressure, and flow temperature on the evolution of vortex structures in the turbulent wake of a circular Teflon cylinder. Velocity fields are measured using particle image velocimetry (PIV) in a hydrodynamic facility for Reynolds numbers in a range of 1.75 · 105 ÷ 2.84 · 105. The hydraulic drag coefficient of the cylinder, together with time-averaged wake characteristics, indicates an earlier onset of the drag crisis, similar to that observed for rough, non-hydrophobic surfaces. It is shown that a reduction in the freestream pressure leads to both an increase in the wake size and the hydraulic drag. Furthermore, an increase in the flow temperature leads to a decrease of the hydraulic drag of the cylinder, despite larger wake dimensions. This reduction is attributed to a possible decrease in Reynolds stresses on the cylinder surface and the associated frictional drag component.

We experimentally investigate the perforation of wire mesh screens by an aluminum projectile over a range of impact angles. The study focuses on the fragmentation mechanism driven by the penetration of mesh wires into the projectile material. A series of hypervelocity impact tests on thin mesh screens reveal the following: as shockwave-induced fragmentation diminishes and the impact angle increases, the projectile undergoes fragmentation primarily via the wire penetration mechanism. We assess the performance of a mesh screen as a protective layer at various impact angles, comparing its effectiveness to that of a solid bumper shield. Additionally, the ballistic characteristics of the resulting fragment cloud are determined.