Perforation Parameters Research Articles

The influences of perforating phase and bedding planes on the fracture deflection in laminated shale

The perforating phase leads to complex and diverse hydraulic fracture propagation behaviors in laminated shale formations. In this paper, a 2D high-speed imaging scheme which can capture the interaction between perforating phase and natural shale bedding planes was proposed. The phase field method was used to simulate the same conditions as in the experiment for verification and hydraulic fracture propagation mechanism under the competition of perforating phase and bedding planes was discussed. The results indicate that the bedding planes appear to be no influence on fracture propagation while the perforating phase is perpendicular to the bedding planes, and the fracture propagates along the perforating phase without deflection. When the perforating phase algins with the bedding planes, the fracture initiation pressure reserves the lowest value, and no deflection occurs during fracture propagation. When the perforating phase is the angle 45°, 60° and 75° of bedding planes, the bedding planes begin to play a key role on the fracture deflection. The maximum deflection degree is reached at the perforating phase of 75°. Numerical simulation provides evidence that the existence of shale bedding planes is not exactly equivalent to anisotropy for fracture propagation and the difference of mechanical properties between different shale layers is the fundamental reason for fracture deflection. The findings help to understand the intrinsic characteristics of shale and provide a theoretical basis for the optimization design of field perforation parameters.

Multi-objective optimization of geometrical parameters of laterally perforated on silt fin by gray relation analysis based on Taguchi method

In this paper, slit fin with lateral perforations are presented and the optimal parameters of the perforation on the silt fin are determined. The effects of the three design parameters of perforation length H, perforation height P and tilt angle θ on the j and f-factor are analyzed using gray relation analysis (GRA) base on the Taguchi method (TM). Numerical simulations were performed for different combinations of the three geometric parameters for 16 cases. Based on the Taguchi method (single-objective optimization) analysis, out of the three perforation parameters, the perforation length H exhibited the most pronounced impact on the j-factor, boasting a substantial contribution ratio of 33.1 %. The contribution ratios of the perforation length H, height P, and tilt angle θ influencing the f-factor were determined to be 31.1 %, 46.2 %, and 18.4 %, respectively. The optimal combination of parameters for perforation on the slit fins was obtained by Gray relation analysis (multi-objective optimization) with values of H = 1/3, P = 1 mm and θ = 90°, representing the highest j-factor and the lowest f-factor of the parameter configuration, in contrast to the remaining parameter combinations, the SNR values for its j and f-factor stand at −49.14 and 35.1, respectively while the JF-factor also outperformed those of the other 16 groups of cases. Finally, the results obtained by Taguchi method and GRA are analyzed in conjunction with flow behavior.

Mechanism of slow-wave generation and tuning in a perforation-modulated sonic black hole structure

A sonic black hole (SBH) in a retarding duct can be used to manipulate sound waves and achieve sound absorption. The SBH incorporates two indispensable physical processes: wave speed reduction and energy dissipation. In this study, a perforation-modulated SBH (PMSBH) retarding structure is proposed, in which the two physical phenomena can be balanced to enhance the black hole effects by modulating the perforation parameters. To fully investigate the mechanism of slow-wave generation and the effect of perforation parameters, an analytic model is established based on the Wentzel–Kramers–Brillouin (WKB) solutions to the linear acoustic wave equation. By examining the analytical solutions and comparing them with the numerical results obtained from transient finite element simulations, the effect of several important parameters on reducing the sound speed and enhancing sound absorption performance is revealed, offering a set of criteria and physical insights for modulating the parameters to design an optimal slow-sound absorber. Finally, an experiment is conducted to confirm the theoretical studies and demonstrate the performance of PMSBH. This study brings forward the concept of tunable design to improve the performance of SBH structures, which can benefit the design of sound wave manipulation and noise control devices.

Vibration response of viscoelastic nanobeams including cutouts under moving load

This manuscript presents a mathematical model and numerical solution to predict vibration responses of nonlocal strain gradient (NLS) perforated viscoelastic nanobeam under dynamic moving loads. The microstructure and size length scales are considered in the frame of NLS theory. The viscoelastic damping of the structure is considered by linear Kelvin Voigt viscoelastic model. Timoshenko and Euler Bernoulli beam theories are developed to consider both thin and thick structure response. The moving load is portrayed by point load and harmonic type. The dynamic equations of motion incorporating viscoelasticity and size dependency effects is derived by using Hamilton principle. A differential quadrature method (DQM) with Chebyshev–Gauss–Lobatto formula is used to discretize the space domain and solve the model numerically. The obtained results are validated and compared with available literature. Numerical studies are conducted to show the influence of the material viscosity parameter, perforation parameters, shear deformation effect, nonlocal strain gradient, moving load velocity, and beams slenderness ratio on the dynamic behavior of viscoelastic perforated nanobeams under moving load. The material viscosity parameter can effectively control the magnitude and stability of the magnification factor profiles. Higher filling ratios result in larger values of the dynamic magnification factor, whereas larger numbers of hole rows lead to smaller values. The proposed procedure is supportive in the analysis and design of perforated viscoelastic NEMS structures under moving load.

Influential mechanism of perforation parameters in geothermal fixed-plane perforation recovery

The fixed-plane perforation technology, which is derived from oil and gas production, offers remarkable advantages in inducing fracturing and increasing fracture volume, but its theoretical foundation incompatible with the practical application of hot dry rock (HDR). In this study, a coupled thermal–hydraulic–mechanical model is developed to reveal the influence of perforation parameters on fracturing results in an environment of HDR. The stress, temperature distribution and damage volume of the rock at different numerical levels of the perforation parameters are compared to characterize the mechanism of the effect of perforation parameters on the fracturing results. Under the experimental conditions, the results of the control experiments show that the EGS system achieves a high techno-economic performance when the injection angle is about 45°, the injection density is about 5 clusters/m, and the injection depth is about 2.0 m. The analysis of orthogonal results not only reveals the time-varying sensitivity of rock cracking to perforating parameters, but also reveals that the in-plane perforation spacing is crucial to the effect of perforating parameters on fracturing. The analysis of variance also indicates that the degree of influence of perforation parameters on fracture varies over time. The area of the perforation wall defines the fracturing efficiency in the early stage of fracturing; the volume of fluid-rock interaction space, determined by in-plane perforation spacing, controls the fracturing efficiency in the later stage of fracturing. The results of the orthogonal analysis considering the interactions demonstrate that the interactions between the perforation parameters have a negligible effect on the fracturing results compared to the perforation parameters. This research can be utilized to optimize perforation parameters for fixed-plane fracturing.

Employing perforated copper foam to improve the thermal performance of latent thermal energy storage units

The performance of latent thermal energy storage units (LTESU) is limited by the low thermal conductivity of phase change materials (PCM). Copper foam can enhance PCM's heat conduction, but its structure inhibits the internal natural convection. Based on this, the perforated copper foam was proposed to enhance the natural convection of PCM. The contrast experiment built three LTESUs (Namely, the LTESU only with the copper tube (LTESU-CT), the LTESU with full copper foam (LTESU-FCF) and the LTESU with perforated copper foam (LTESU-PCF). The melting and solidifying state, temperature distribution, and thermal efficiency were compared in three LTESUs during thermal charging and discharging processes. Results showed using copper foam could enhance the thermal performance of LTESU obviously and the perforated copper foam could generate the convective heat exchange, which had a time-average Nusselt number 34.1 % higher in LTESU-PCF than that in LTESU-FCF. Due to the reduced heat transfer area, LTESU-PCF had the lower thermal efficiency than LTESU-FCF, but its thermal storage capacity and release capacity were 6.4 % and 1.4 % higher than that in LTESU-FCF, respectively. It was confirmed that employing perforated copper foam could s enhance the natural convection and heat transfer of PCM significantly, but the perforation parameter still needs to be further explored to achieve higher thermal performance.

Research on Productivity Prediction Model of Three-Dimensional Directional Wells in Different Reservoirs

Productivity prediction of perforation completion is key for well optimizing completion methods and reservoir engineering research. Productivity prediction models using an additional pressure drop to represent skin factor are limited. In this study, a steady-state productivity prediction model coupled with reservoir seepage and fluid flow in the wellbore was developed. The impact of different perforation parameters on well production was studied. Considering perforation depth, perforation density, perforation diameter, phase angle, depth of contaminated zone, and pollution degree of the contaminated zone, a semi-analytical skin calculation model under different reservoir conditions and completion methods with the least-squares method combining the consideration of perforation depth, perforation density, perforation diameter, phase angle, depth of contaminated zone, and pollution degree of the contaminated zone was developed. Perforation parameters were optimized. A 3D directional well unsteady productivity prediction model was established using the finite-volume method considering the influence of conventional perforation completion parameters, gravel packing perforation completion parameters, natural fractures, reservoir heterogeneity, reservoir scale, skin factor, fluid gravity, fluid compressibility, and rock compressibility. A new method for optimizing perforation parameters and characterizing skin factors was developed, providing a theoretical basis and simulation means for deeper understanding of the development law of directional wells.

Control of Azimuthal Combustion Instability Through the Injector Mounting Surface of Annular Combustors

A three-dimensional combustion instability model is presented to study the effects of the wall impedance distributions of annular combustors on thermoacoustic unstable modes, consequently seeking an effective passive methodology to suppress azimuthal combustion instability. The eigenfunction is obtained by use of Green’s function in an enclosed space, whereas the scattered disturbances at flames, the perforated screen where the injectors are installed, and the side perforated liner are characterized by the monopoles, respectively. Results show that compared to the side perforated liner with the restriction of radial size, the impedances over the injector mounting surface provide more acoustic energy dissipation to suppress the azimuthal combustion instabilities. Two patterns of impedance distribution, uniform and radial nonuniform, over the injector mounting surface are then investigated through the parametric variations and associated acoustic energy analysis. A stable combustion system can be realized in combination with homogeny or difference between the spatial impedance distributions and associated optimum perforated parameters, such as perforation ratio, Mach number of the mean bias flow, and aperture radius. It allows mitigating possible design limitations with the appropriate parameter combinations. The present investigation thereby offers an alternative model and methodology for suppression of azimuthal combustion instabilities in gas turbines.

Numerical Study on Simultaneous Propagation of Multiple Fractures: A Method to Design Nonuniform Perforation and In-Stage Diversion

Summary The uneven propagation of multifractures is a key factor restricting production growth due to stress shadow and heterogeneity. To date, limited-entry fracturing techniques, nonuniform perforation, and in-stage diversion have been commonly used to promote even multifracture growth. In this study, a fully coupled multiple pseudo-3D (P3D) fracture simulator has been developed to examine the competitive propagation of multifractures during multicluster fracturing in a horizontal well. The present model considers stress interaction among multiple fractures, perforation erosion, fluid distribution among clusters, and in-stage diversion. The results of the model are validated against the reference data. Using the model, a series of numerical simulations are performed to investigate multifracture propagation with nonuniform perforation and in-stage diversion fracturing. We estimate the value of stress interaction for different fractures and time based on the approximate solution of Perkins-Kern-Nordgren (PKN) fracture in the viscosity-dominated regime and improve the dimensionless parameter that characterizes the competition between stress interaction and perforation friction. The fluid distributes evenly when the dimensionless parameter is less than unity (perforation friction is larger than stress interference). Based on this dimensionless parameter, a method to design nonuniform perforation and in-stage diversion is proposed. Results show that in the case of homogeneous in-stage stress, the perforation parameters should be selected under the condition that the dimensionless parameter is less than unity. In the case of heterogeneous in-stage stress and based on the perforation parameters selected under homogeneous stress conditions, the perforation holes in the high-stress cluster should be increased, making the reduction of perforation friction equal to the value of the in-stage stress heterogeneity. The stress heterogeneity can be balanced by decreasing the perforation friction of the high-stress clusters. In this way, nonuniform perforation under heterogeneous in-stage stress conditions can be designed quantitatively without numerical simulation. For in-stage diversion treatment, a method to design the number of ball sealers is proposed based on the results of nonuniform perforation, and only several or even zero groups of simulation are necessary to find the optimal number of ball sealers. A series of numerical simulations shows that the proposed design method is reliable and achieves a satisfactory result in an actual field case. The results can be helpful for nonuniform perforation and in-stage diversion design for multicluster fracturing in a horizontal well.

Performance simulation and perforated parameters optimize for perforated wells with compaction zone and drilling damage in tight gas reservoirs

It is essential to understand how to improve the production of perforated well in tight reservoirs. In this paper, based on the experiment of experiment evaluation of perforation tunnel and perforation compaction zone, the drilling mud invasion zone and stress sensitivity, a new productivity numerical model is established considering the damaged zone being drilling, and the compaction zone being penetrated and the sensitivity in tight gas reservoirs. Considering perforation interaction, drill damage and seepage interference, the production rate under different parameters of perforation, compaction zone, damaged zone is discussed to yield the highest productivity. The numerical results show that it exists an optimal hole density in specific formation and when the perforated hole penetrates the invasion zone, increasing the depth of the perforation hole by the same amount would not result in a significant increase in gas production. The invasion and compaction zone permeability have little effect on the cumulative gas production, but an inflexion point still existed. Further, according to the principle of orthogonal experimental design, forty-one groups of orthogonal experimental calculations are designed and conducted. By analyzing the experimental results, the perforation density, hole diameter, invasion thickness, compaction zone thickness, invasion permeability, compaction zone permeability and stress sensitivity on productivity of perforated well is in descending order. The work presented in this paper can offer a technological basis and theoretical foundation for optimizing perforation parameters in specific tight gas reservoirs.

On Bending of Piezoelectrically Layered Perforated Nanobeams Embedded in an Elastic Foundation with Flexoelectricity

Analysis of the electromechanical-size-dependent bending of piezoelectric composite structural components with flexoelectricity has been considered by many researchers because of the developments of nanotechnology and the applicability of piezoelectric composite nanobeam structures in Micro/Nano-Electro-Mechanical Systems (MEMS/NEMS). Therefore, the work investigates the size-dependent electromechanical bending of piezoelectrically layered perforated nanobeams resting on elastic foundations including the flexoelectric effect. Within the framework of the modified nonlocal strain gradient elasticity theory, both the microstructure and nonlocality effects are captured. The governing equilibrium equations including piezoelectric and flexoelectric effects are derived using Hamilton’s principle. Closed forms for the non-classical electromechanical bending profiles are derived. The accuracy of the proposed methodology is verified by comparing the obtained results with the available corresponding results in the literature within a 0.3% maximum deviation. Parametric studies are conducted to explore effects of perforation parameters, elastic foundation parameters, geometric dimensions, nonclassical parameters, flexoelectric parameters, as well as the piezoelectric parameters on the bending behavior of piezoelectrically layered perforated nanobeams. The obtained results demonstrate that incorporation of the nondimensional elastic foundation parameters, Kp = 2 and Kw = 20, results in a reduction in the relative percentage reduction in the maximum nondimensional mechanical transverse deflection due to increasing the perforation filling ratio from 0.2 to 1 from 199.86% to 91.83% for a point load and 89.39% for a uniformly distributed load. On the other hand, with Kp = 5 and Kw = 50, the relative percentage difference of the electromechanical bending deflection due to increasing the piezoelectric coefficient, e311, reaches about 8.7% for a point load and 8.5% for a uniformly distributed load at a beam aspect ratio of 50. Thus, the electromechanical as well as mechanical behaviors could be improved by controlling these parameters. The proposed methodology and the obtained results are supportive in many industrial and engineering applications, i.e., MEMS/NEMS.

Ultimate strength of hyper-ellipse flanged-perforated plates under uniaxial compression loading

Abstract In order to address the impact of the perforated parameters on the mechanical properties of the plate, the ultimate strength of hyper-ellipse flanged-perforated plates under uniaxial compression stress is numerically investigated in this article. The four edges of the flanged-perforated plate are only supported in the out-of-plane direction while the plate is exposed to uniaxial compressive loads. The impact of the cutout size, flange height, cutout position, rotation angle, and cutout form on the ultimate bearing capacity of the perforated plate with varied thicknesses is investigated and compared through a series of elasto-plastic buckling analyses using the ANSYS software. The structure’s stress and deformation analysis is then used to explain the results of the ultimate strength test. The flange efficiently raises the maximum bearing strength of the structure with cutouts. For the limit strength of thick plate, the cutout size, elliptical shape, cutout rotation angle, and cutout position have considerably more of an impact than they do on the maximum bearing capacity of thin plate. The findings can assist the structural layout of this sort of perforated plate, and the right cutout parameters should be chosen in accordance with the various performance specifications.

АНАЛИЗ УСТОЙЧИВОСТИ ПРИ СДВИГЕ СТАЛЬНЫХ БАЛОК-СТЕНОК С КРУГЛЫМИ ВЫРЕЗАМИ

In spite of half century experience of application of perforated beams the local bucking of their webposts is not finally researched till now. In manuals there is no relations for their critical loads corresponding to buckling of web-posts under shear. In the study the numerical analysis by the finite element method is performed for evaluating the local stability of simply supported cellular beam-webs with circular openings. Variant of loading of beam with concentrated force was considered, which assure constant value of shear force along the length of beam. Obtained empirical relation allow take into account not only parameters of perforation but influence also of bending moment on the shear buckling of web-posts. Analysis by FEM also confirmed permitted accuracy of analytical approach to evaluation of stability of web-posts.

New method for predicting perforation parameters of a concrete slab target to a penetrating projectile

The present paper investigates the perforation of a projectile through a concrete slab and proposes a new approach for assessing the perforation parameters, including the projectile residual velocity, and the slab perforation and ballistic limits. The new approach is rather simple and easy to implement and provides a fast solution. A new parameter denoted the “pseudo-residual velocity (VP)” is defined and is theoretically calculated. For a given slab thickness H0, the magnitude of VP(H0) is always smaller than the corresponding true residual velocity. The developed approach reduces the determination of the perforation parameters to a sequence of pseudo-perforation problems that are quickly solved using the modified (hybrid) DISCS method, which had been developed for penetration analysis into thick targets, using the constitutive equations of the slab concrete material. In contrary to many other simplified models, the proposed approach is based on a theoretical model and engineering insight and does not require any empirical constants, or calibrations prior to the analysis. Numerous examples compare the proposed approach predictions to test results, covering different types of concrete, slab thicknesses and projectile impact velocities. In all comparisons, very good predictions of the proposed approach are demonstrated.

Numerical Analysis of Residual Strength in the Perforated Casing of Ultra Deep Wells

A three-dimensional model for the numerical simulation of casing-cement behavior is used to investigate residual strength in the perforated casing of ultra deep wells. The influence of the hole diameter, hole density and phase angle on the residual strength of the casing under non-uniform stress and fracturing conditions is revealed through the consideration of different perforation parameters. It is shown that the residual strength of the casing increases with the hole diameter and periodically changes with the hole density; the phase angle is the main factor that affects the residual strength of the perforated casing, and the perforation should be avoided in the direction of the minimum principal stress to reduce stress concentration at the perforation hole. Moreover, as shown by a companion orthogonal experiment, the descending order of influence of the different influential parameters is: phase angle, hole diameter, hole density and the thickness of casing.

A new investigation on optimization of perforation key parameters based on physical experiment and numerical simulation

Casing is inevitably damaged during perforation operation, and the perforation parameters will have a significant impact on the degree of casing damage, which will directly affect the stability of casing structure in the process of hydraulic fracturing. A three-dimensional numerical model, which was composed of perforating charge, casing–cement sheath, and formation and consistent with the engineering practice, was established, considering the dynamic characteristics of materials in the process of explosion impact. The numerical simulation results were verified by physical model tests and showed that the stress superposition between adjacent perforations increases the damage degree of casing. Perforation density and phase angle directly affect the range of stress superposition area, with the increase of perforation density or decrease of phase angle, the damage area and damage coefficient of casing are increasing. Based on the results of numerical simulation, an innovative perforation parameter optimization method considering casing yield strength was proposed, which could effectively reduce the stress superposition area between adjacent perforations and keep casing damage within a reasonable range. Finally, perforation parameter optimization based on real wells was carried out, and analysis results showed that the casing stress was lower than the yield strength after parameter optimization, which could ensure the stability of the casing. The research results can provide an important reference for the optimization of perforation design and field operation.

Evolution of Near-Well Damage Caused by Fluid Injection through Perforations in Wellbores in Low-Permeability Reservoirs: A Case Study in a Shale Oil Reservoir

Abstract During the development of shale oil resources, fluid injection is usually involved in the process of hydraulic fracturing. Fluid injection through perforations causes near-well damage, which is closely related to the subsequent initiation and propagation of hydraulic fractures. This study is focused on the characterization of the temporal and spatial evolving patterns for near-well damage induced by fluid injection through perforations in the early stage of hydraulic fracturing. A coupled hydromechanical model is introduced in a case study in a shale oil reservoir in northwestern China. The model considers porous media flow during fluid injection. It also considers elasticity in the rock skeleton before the damage. Once the damage is initiated, a damage factor is employed to quantify the magnitude of injection-induced damage. Results show that damage evolution is highly sensitive to perforation number and injection rate in each individual perforation. Damage propagation is more favorable in the direction of the initial maximum horizontal principal stress. The propagation of damage is drastic at the beginning of fluid injection, while the damage front travels relatively slow afterward. This study provides insights into the near-well damage evolution before main fractures are initiated and can be used as a reference for the optimization of perforation parameters in the hydraulic fracturing design in this shale oil field.

Design of microperforated nanofibrous membrane coated nonwoven structure for acoustic applications

In this paper, a promising acoustic structure for noise reduction was prepared, in which microperforated nanofibrous resonant membrane together with nonwovens were used. The role of microperforated nanofibrous film, the effect of perforation parameters, cavity and the assembly sequence of the composite fibrous structure on sound absorption performance has been studied. This structure effectively combined the porous sound absorbing, micro-perforated absorbing and membrane resonance mechanisms, which can improve the sound absorbing performance without weight and thickness penalty offering a competitive advantage in noise reduction. In addition, the composite materials exhibited favorable performance in a wide-frequency regime under the condition of appropriate assembly sequence and perforation parameters.

Dynamic Analysis of a Piezoelectrically Layered Perforated Nonlocal Strain Gradient Nanobeam with Flexoelectricity

This study presents a mathematical size-dependent model capable of investigating the dynamic behavior of a sandwich perforated nanobeam incorporating the flexoelectricity effect. The nonlocal strain gradient elasticity theory is developed for both continuum mechanics and flexoelectricity. Closed forms of the equivalent perforated geometrical variables are developed. The Hamiltonian principle is exploited to derive the governing equation of motion of the sandwich beam including the flexoelectric effect. Closed forms for the eigen values are derived for different boundary conditions. The accuracy of the developed model is verified by comparing the obtained results with the available published results. Parametric studies are conducted to explore the effects of the perforation parameters, geometric dimensions, nonclassical parameters, flexoelectric parameters, as well as the piezoelectric parameters on the vibration behavior of a piezoelectric perforated sandwich nanobeam. The obtained results demonstrate that both the flexoelectric and piezoelectric parameters increased the vibration frequency of the nanobeam. The nonlocal parameter reduced the natural vibration frequency due to a decrease in the stiffness of the structures. However, the strain gradient parameter increased the stiffness of the structures and hence increased the natural vibration frequency. The natural vibration frequency based on the NSGT can be increased or decreased, depending on the ration of the value of the nonlocal parameter to the strain gradient parameter. This model can be employed in the analysis and design of NEMS, nanosensors, and nanoactuators.

Optimization of Non-Uniform Perforation Parameters for Multi-Cluster Fracturing

Stress shadowing affects the simultaneous propagation of fractures from multiple perforation clusters. Employing uniform perforation parameters for all clusters cause the unbalanced growth of fractures, which arouses the demand of optimizing non-uniform perforation parameters. An optimization workflow combining a fracture propagation model and the particle swarm optimization method (PSO) is proposed for multi-cluster fracturing in this study. The fracture model considers the coupling of rock deformation and fluid flow along the wellbore and fractures, and it is solved by using the Newton iteration method. The optimization is performed by taking the variance of multiple fracture lengths as fitness value function in the frame of the PSO method. Numerical results show that using the same spacings and perforation parameters for all clusters is detrimental to the balanced growth of multiple fractures. The variance of fracture lengths drops greatly through optimization of cluster spacings and perforation number/diameter. Properly increasing the spacing and perforation number/diameter for the middle clusters promotes the balanced growth of multiple fractures. This study provides an efficient optimization workflow for multi-cluster fracturing treatment in horizontal wells.