Partially Penetrated Research Articles

Effect of Microchemistry Elements in Relation of Laser Welding Parameters on the Morphology 304 Stainless Steel Welds Using Response Surface Methodology

Small differences in the contents of surface active elements can change flow direction and thus heat transfer, even for different batches of a given alloy. This study aims to determine the effects of sulfur on weld bead morphology in the laser process. The paper presents the results related to the weld bead shape of two thin AISI 304 industrial stainless steel casts. One cast contains 80 ppm (0.008%) of sulfur, considered as a high sulfur content, and the other one contains 30 ppm (0.003%) sulfur, which can be considered low sulfur. The welds were executed using a CO2 laser. The effects of laser power (3.75, 3.67, 6 kW), welding speed (1.25, 2.40, 2.45, 3.6 m/min), focus point position (2, 7, 12 mm), and shield gas (Helium, mixed 40% helium + 60% argon and mixed 70% helium + 30% argon) with a flow rate of 10 L/min on the depth of the weld (D) and the aspect ratio (R = D/W) were investigated using RSM (response surface methodology). The experimental results show that the transfer of energy from the laser beam to the workpiece can be total in cases where the selected welding parameters prevent plasma formation. For the 304 HS cast, the focus point is the major factor in determining the depth of penetration, and its contribution is up to 52.35%. However, for 304 LS, the interaction between shield gas and focus point seems to play an important role, and the contribution of their interaction raises to 28% in relation to the laser depth of the weld. Moreover, the study shows that sulfur plays a surface-active role only in the case of partial penetration beads, so that a 56% partially penetrated weld supports the hypothesis of its surface-active role in the formation of the weld pool. However, a penetration of only 36% confirms the effects of a sulfur surface-active when the bead is fully penetrated.

Quantifying the partial penetration skin factor for evaluating the completion efficiency of vertical oil wells

An oil well's productivity is generally considered the standard measure of the well's performance. However, productivity depends on several factors, including fluid characteristics, formation damage, the reservoir's formation, and the kind of completion the well undergoes. How a partial completion can affect a well's performance will be investigated in detail in this study, as nearly every vertical well is only partially completed as a result of gas cap or water coning issues. Partially penetrated wells typically experience a larger pressure drop of fluid flow caused by restricted regions, thus increasing the skin factor. A major challenge for engineers when developing completion designs or optimizing skin factor variables is devising and testing suitable partial penetration skin and comparing completion options. Several researchers have studied and calculated a partial penetration skin factor, but some of their results tend to be inaccurate and cause excessive errors. The present work proposes experimental work and a numerical simulation model for accurate estimation of the pseudo-skin factor for partially penetrated wells. The work developed a simple correlation for predicting the partial penetration skin factor for perforated vertical wells. The work also compared the results from available models that are widely accepted by the industry as a basis for gauging the accuracy of the new correlation in estimating the skin factor. Compared to other approaches, the novel correlation performs well by providing estimates for the partial penetration skin factor that are relatively close to those obtained by the tested models. This work's main contribution is the presentation of a novel correlation that simplifies the estimation of the partial penetration skin factor in partially completed vertical wells.

Semi-analytical solutions for transient flow to a partially penetrated well with variable discharge in a general three-layer aquifer system

A general semi-analytical model for transient flow in a three-layered aquifer system with a partial penetration well having a variable discharge of pumping is developed with the consideration of the interface flow on the adjacent layers. This general three-layer system includes the conventional aquitard-aquifer-aquitard system as a subset and does not require that the permeability contrasts of different layers must be greater than a few orders of magnitude and does not ignore any flow components (either vertical or horizontal) in any layer. The pumping well of infinitesimal radius is screened at any portion of the middle layer. Three widely used types of top and bottom boundary conditions are assigned prescribed head (Case 1), zero flux (Case 2), or prescribed head at top and zero flux at bottom (Case 3). Laplace domain solutions for dimensionless drawdown are obtained using Hankel transformation, and associated time-domain solutions are evaluated numerically. The newly obtained solutions include some available solutions for two- or single-layer aquifer systems as subsets. The drawdowns for individual layers caused by a well with an exponentially decreased discharge are explored as an example of illustration. The results indicate that the pumped layer drawdown close to the partially penetrated well is mainly influenced by the variable pumping rate. The late-time drawdown for all layers is remarkably affected by the chosen types of top and bottom boundary conditions, and the drawdown for Case 3 is greater than that for Case 1 and smaller than that for Case 2. Additionally, the effect of the pumped layer anisotropy on drawdowns in the three-layer system is significant, and the anisotropy of the unpumped layers significantly affects the drawdown in the whole aquifer system without large contrast of hydraulic conductivity between the unpumped layers and the pumped layer. The drawdowns in all three layers are greatly affected by the location and length of well screen, and a larger drawdown can be seen at the position that is closer to the middle point of the screen of the partially penetrating pumping well.

Karakterizacija zavarenih spojeva sa delimičnom penetracijom na konstrukcionom čeliku S355N

Existing standards require welded joints with full penetration. It is considered that welded joints with complete penetration minimize the stress concentration in the root passage. However, there are numerous situations in the industry, in which the load-bearing capacity of the welded joint with partial penetration is satisfactory. If the tests of partially penetrated welds show satisfactory load capacity, the benefits compared to fully penetrated welds are reflected in lower costs, ie less time is required to prepare the joint, less additional material is needed, ie shorter time is required to make the welded joint. The paper presents the testing of butt welded joints of structural steel S355N, with partial penetration, achieved by the MAG welding in the overhead position (PD) in the protection of the gas mixture. The samples were welded with different welding parameters and with different joint preparation, and the tests were performed by non destructive methods (visual inspection, testing with penetrants and magnetic particles) and destructive methods - tension and bending tests, Vickers hardness testing.

Study on Short-Circuiting GMAW Pool Behavior and Microstructure of the Weld with Different Waveform Control Methods

In order to study internal relation among the behavior of the weld pool, the microstructure of weld bead and the waveform of short-circuiting gas metal arc welding (S-GMAW), a high speed photograph-images analysis system was formed to extract characteristics of weld pool behavior. Three representative waveform control methods were used to provide partly and fully penetrated weld pools and beads. It was found that the behavior of the weld pool was related to the instantaneous power density of the liquid bridge at the break-up time. Weld pool oscillation was triggered by the explosion of the liquid bridge, the natural oscillation frequencies were derived by the continuous wavelet transform. The change of weld pool state caused the transition of oscillation mode, and it led to different nature oscillation frequencies between partial and full penetration. Slags flow pattern could be an indication of the weld pool flow. Compared with the scattered slags on fully penetrated weld pool, slag particles accumulated on partially penetrated weld pools. The oscillating promoted the convection of the welding pool and resulted in larger melting width and depth, the grain size, and the content of pro-eutectoid ferrite in the weld microstructure of S235JR increased, the content of acicular ferrite decreased.

Benefits of very high feed rates for laser beam welding of AlMgSi aluminum alloys

The present paper shows that laser beam welding of AA6016 aluminum sheets without filler wire but at high feed rates in the order of several tens of m/min is beneficial with respect to depth fluctuation, pores, and centerline cracks. Welds in the overlap configuration with a laser power of 16 kW (cw) at feed rates of 30 m/min and above were investigated. A comparably large laser beam diameter of 630 μm enabled welding at more than 50 m/min without humping. Full penetration and partial penetration welds were accomplished with depths of 2.4 and 2.0 mm, respectively, without pore formation. The partially penetrated welds show negligible local depth fluctuations in the range of only a few μm. Full penetration welds were performed at edge distances of 4, 5, and 6 mm without occurrence of centerline cracks. This constitutes a significant reduction of the critical zone for the formation of centerline cracks at the close edge position compared to conventional laser beam welding parameters.

Semi-analytical solution to pumping test data with barrier, wellbore storage, and partial penetration effects

There exist some difficulties in determining aquifer parameters based on pumping test data within a partially penetrated retaining walls using traditional Cooper-Jacob method. Many other site-specific factors, such as the effect of partially penetrating well and the large diameter of the wells, cannot easily be accommodated in theoretical well formulae. The semi-log drawdown-time curves affected by the effects of barrier, wellbore storage, and partial penetration well can be characterised by four distinct stages of drawdown: i) Stage I, drawdown is unaffected by the barrier, ii) Stage II, drawdown is significantly influenced by the barrier, iii) Stage III, the drawdown-time curve runs parallel to that deduced from greenfield conditions, and iv) Stage IV, the drawdown becomes a constant value. To handle the four distinct stages of drawdown, a semi-analytical method using the slope of the late-time drawdown asymptote of Stage III for determining the transmissivity is proposed. The horizontal intercept, resulting from an extension of the late-time drawdown asymptote from Stage II, is used for determining the storage coefficient. Pumping test data from a case history are analysed using the proposed semi-analytical method, and the results obtained are compared with those deduced from the numerical simulation. The comparison between the analytical results and those obtained from the numerical simulation appeared satisfactory.

Magnetic invisibility of the magnetically coated type-II superconductor in partially penetrated state

The magnetic behavior of a cylindrical paramagnet/superconductor heterostructure has been studied by numerical simulations. Relying on the variational statement of the critical state model, our results show that magnetic invisibility is compatible with the partial penetration regime in the superconductor. This result accomplishes previous analytic studies that proved a possible perfect undetectability for the full penetration of magnetic flux. For a given geometry, invisibility may be realized only at a certain magnitude of the applied field. Such value decreases with increasing permeability of the magnetic sheath and eventually collapses to zero. This establishes a condition for obtaining realizable invisibility that extends previous expectations relying either on the full penetration ansatz or on perfect diamagnetism.

Laparoscopic Removal of a Migrated Intrauterine Contraceptive Device With Bladder Penetration

This letter reports on a case in which a migrated intrauterine device (IUD) partially penetrated the bladder resulting in formation of a bladder stone and a peritoneal adhesion which was completely removed simply by gentle traction via laparoscopy. The authors state that this case shows that when trying to remove a migrated IUD with partial bladder penetration especially when most of the IUD is located in the peritoneal cavity laparoscopy is preferable to laparotomy.

In-process monitoring and feedback control for stable production of full-penetration weld in continuous wave fibre laser welding

Laser micro-welding has been applied for device sealing in electronics and automobile industries. Welding of corners in goods and products is a problem owing to easier formation of a weld with burn-through, shallow penetration or a non-bonded part when a drastic change in the welding speed or laser power occurs. This research was therefore undertaken with the objective of obtaining a fundamental knowledge of in-process monitoring and feedback control for the stable production of a full-penetration weld with a constant bead width on the bottom surface irrespective of the changes in the laser power and the welding speed. Variation in weld penetration geometry was investigated by rapid deceleration and acceleration in the welding speed during lap welding of pure titanium thin sheets with a continuous wave (CW) single-mode fibre laser beam. The rapid deceleration in the welding speed led to a considerable change in the full-penetration weld geometry or a partially penetrated weld (if the power was accordingly reduced), resulting in the difficulty in the stable production of a full-penetration weld bead. The heat radiation intensity measured from the laser-irradiated area was useful as an in-process monitoring signal for detecting the molten pool size on the laser-irradiated surface. However, the utilization of monitoring of heat radiation was difficult for predicting the weld bead width on the bottom surface due to the formation of partial penetration or the change in the penetration shape. The laser power was controlled at a 4 ms interval according to the heat radiation signal in order to adjust the weld bead width on the laser-irradiated surface to the target weld penetration geometry affected by thermal storage. Consequently, the feedback-controlled laser power produced a stable full-penetration weld with the designed bead width on the bottom surface irrespective of the rapid deceleration of the welding speed and the corresponding decrease in laser power. Furthermore, the developed feedback control algorithm was effective in rapid acceleration of the welding speed. From these results, it was confirmed that the consideration of the feedback control algorithm including a thermophysical property such as thermal storage was essential for the suppression of the effect due to rapid deceleration and acceleration of the welding speed and the laser power in lap seam micro-welding with a CW fibre laser.

A Theoretical and Numerical Investigation of the Pseudoskin Factor

Abstract Partial completion of wells to inhibit gas and/or water coning in producing wells has been a common practice in the petroleum. industry for many years. This procedure, however, causes an additional pressure drop or pseudoskin that reduces the well productivity. In formations that are producing with partial completion, the precise quantification of this additional pressure drop is of paramount importance for completely identifying the existence. of formation damage. Many authors have proposed mathematical solutions that can be used to estimate the pseudoskin factor caused by restricted entry. In this work, a comprehensive investigation of the available models listed in the literature used for the estimation of pseudoskin due to restricted entry was performed. Selected models were implemented in a methodology and computer program. Then, a sensitivity analysis focusing on producing wells was carried out. The effect of the height of the producing interval, height rom the. middle portion of the producing interval to the bottom of the reservoir, reservoir thickness, horizontal and vertical permeabilities and wellbore radius were investigated. Furthermore, the extension of the methodology for the determination of mechanical skin in injectivity and fall-off tests executed in injector wells is described. At the end of this paper, an example highlights the range of applicability and potential benefits of the proposed methodology. Introduction It is very frequent that wells are completed over only a fraction of their productive zone in order to delay water and/or gas coning. A well completed in this manner is referred to as a partially penetrated or restricted-entry well. Two questions of practical importance in this scenario are:what is the productivity loss caused by the partial penetration; and,should the well be stimulated? The answer to these questions requires an estimation of the pseudoskin factor caused by the partial penetration and an estimation of the mechanical (real) skin caused by formation damage or stimulation. In this work, a comprehensive investigation of the available models listed in the literature used for the estimation of pseudoskin due to restricted entry was performed. A methodology and computer code was established that, if given the relative position of the perforated interval with respect to the producing zone and the values of vertical and horizontal permeability, the pseudoskin (dimensionless pressure drop) due to the restricted entry can be computed. Five selected formulas were studied, including Streltsova-Adams(1), Kuchuk and Kirwan(2), Papatzacos(3), Yeh and Reynolds(4) and Odeh(5). The assumptions, simplifications and range of validity associated with each formula are presented. All the pseudoskin formulas used in this work assume the single phase of a fluid with small compressibility and constant viscosity. The reservoir is considered homogeneous and isotropic, with constant thickness and infinite extension. The reservoir top and base are considered impermeable. The gravitational effects are considered negligible. Considering all these assumptions, the total skin obtained from a well test interpretation is given by: Equation 1 Available in Full Paper

Observations of improved confinement in field reversed configurations sustained by antisymmetric rotating magnetic fields

Rotating magnetic fields (RMF) have been employed to both form and sustain currents in field reversed configurations (FRC). A major concern about this method has been the fear of opening up magnetic field lines with even small ratios of vacuum RMF Bω to external confinement field Be. A recently proposed innovation was to use an antisymmetric arrangement of RMF, but vacuum calculations with full RMF penetration showed that very low values of Bω∕Be would still be required to provide field-line closure. Recent comparisons of symmetric and antisymmetric RMF drive on the translation, confinement, and sustainment (TCS) facility [A. L. Hoffman, H. Y. Guo, J. T. Slough et al., Fusion Sci. Technol. 41, 92 (2002)] have shown strong improvements in the basic confinement properties of the FRCs when using antisymmetric drive, even with ratios of Bω∕Be as high as 0.3. This is due to normal standard operation with only partial penetration of the RMF beyond the FRC separatrix. The uniform transverse RMF in vacuum is shielded by the conducting plasma, resulting in a mostly azimuthal field near the FRC separatrix with a very small radial component. Simple numerical calculations using analytical solutions for the partially penetrated antisymmetric RMF, superimposed on Grad–Shafranov solutions for the poloidal FRC fields, show good field-line closure for the TCS experimental conditions. The antisymmetric arrangement also leads to more efficient current drive and improved stabilization of rotational modes.

Scuffing Failure of Hydrodynamic Bearings Due to an Abrasive Contaminant Partially Penetrated in the Bearing Over-Layer

Scuffing Failure of Hydrodynamic Bearings Due to an Abrasive Contaminant Partially Penetrated in the Bearing Over-Layer

The effect of the quadratic gradient term on variable-rate well-tests

Conventional welltest models for liquid flow are not consistent with material balance. The quadratic gradient term in the non-linear diffusion equation is usually neglected in light of the slightly compressible fluid assumption. This approach is questionable for live oil and low permeability reservoirs. It is already known that linearization by neglecting terms may lead to errors for large values of time. The material balance error is compounded by the traditional skin model which implies the assumption of incompressible flow into the wellbore. A method that is consistent with material balance is proposed. All terms in the non-linear diffusion equation are retained. In addition a skin model that accommodates compressible flow across the skin zone is used. The conceptual skin models for incompressible and compressible flow are different, but they are characterized by the same numerical value. A short discussion of this difference is provided. The resulting model, which is based on source and Green's functions, is well suited for restricted entry problems. Results for a partially penetrated well in homogeneous reservoirs is presented. The effect of damage skin and wellbore storage is included. This study shows that the linearization error depends on: (1) the magnitude of wellbore damage, (2) the pseudo-skin resulting from partial penetration and (3) a non-linear flow parameter, α. The semi-log slope, which has traditionally been used to compute the reservoir permeability, may depend on the skin factor.

Spectral Lanczos decomposition method for solving single‐phase fluid flow porous media

AbstractA three‐dimensional well model (r − θ − z) for the simulation of single‐phase fluid flow in porous media is developed. Rather than directly solving the 3‐D parabolic PDE (partial differential equation) for fluid flow, the PDE is transformed to a linear operator problem that is defined as u = f(A)σ, where A is a real symmetric square matrix and σ is a vector. The linear operator problem is solved by using the spectral Lanczos decomposition method. This formulation gives continuous solutions in time. A 7‐point finite difference scheme is used for the spatial discretization. The model is useful for well testing problems as well as for the simulation of the wireline formation tester tool behavior in heterogeneous reservoirs. The linear operator formulation also permits us to obtain solutions in the Laplace domain, where the wellbore storage and skin can be incorporated analytically. The infinite‐conductivity (uniform pressure) wellbore condition is preserved when mixed boundary conditions, such as partial penetration, occur. The numerical solutions are compared with the analytical solutions for fully and partially penetrated wells in a homogeneous reservoir. © 1994 John Wiley & Sons, Inc.

New Skin and Wellbore Storage Type Curves for Partially Penetrated Wells

Summary An analytic solution is derived for the transient pressure behavior of a partially penetrated well when wellbore storage and skin effects are significant. New type curves, generated by this solution, enable the engineer to analyze well test data from partially penetrated wells and to discriminate between near-wellbore damage and pseudoskin caused by partial penetration.

Effect of Anisotropy and Stratification on Pressure Transient Analysis of Wells with Restricted Flow Entry

Effect of Anisotropy and Stratification on Pressure Transient Analysis of Wells with Pressure Transient Analysis of Wells with Restricted Flow Entry A numerical model, devised to study here the effect of anisotropy and stratification on pressure transient analysis of wells with restricted flow entry, utilizes a more realistic boundary condition than do the usual ones appearing in the literature. Nonetheless, the results from both types of models can be correlated. Introduction The effects of anisotropy and stratification on flow behavior and production performance of oil and gas wells have been studied by numerous authors. Lefkovits et al. studied the performance of totally penetrated, stratified bounded reservoirs with no penetrated, stratified bounded reservoirs with no crossflow. Others have studied a similar problem, but with crossflow; Russell and Prats have summarized the findings of these papers. Muskat studied the steady-state behavior of liquid flow for a partially penetrating well in an anisotropic system and penetrating well in an anisotropic system and concluded that the productivity weakly depended on the directional permeability ratios (k(z)/k(r) greater than 0.1). Nisle used the classical method of point source solution to the diffusivity equation to study the effect of partial penetration on pressure buildup of oil wells in an isotropic system. He found that the theoretical pressure buildup curves consisted of two straight pressure buildup curves consisted of two straight lines, the one at early buildup times having a slope proportional to the flow capacity of the open interval proportional to the flow capacity of the open interval (l-d)k(r) and the other having a slope proportional to the flow capacity of the entire formation hk(r). Later Brons and Marting supplemented the findings of Nisle and concluded that partial penetration gave rise to a pseudo damage, which reflected itself as a skin factor in pressure buildup calculations. Using the pseudo skin, they calculated the impairment of pseudo skin, they calculated the impairment of productivity of the production wells, which agreed well productivity of the production wells, which agreed well with the results of Muskat. Pizzi et al., using an electrical analog of a stratified system, concluded that a high pseudo damage resulted if the reservoir was partially penetrated. Harris" studied the optimum spacing and arrangement of perforations in cased holes. Hantush derived an expression for pressure distribution in an unbounded reservoir with restricted flow entry. Seth extended Hantush's work to a bounded reservoir. Odeh has studied a similar problem for steady-state conditions. problem for steady-state conditions. The purpose of this work was to investigate:the combined effects of anisotropy, stratification with crossflow, and restricted flow entry on pressure transient analysis of flow and buildup tests,the feasibility of calculating the horizontal permeabilities of intercommunicating stratified systems, andthe pressure interference tests in such systems. Theory The partial differential equation governing the isothermal flow of homogeneous fluids of constant compressibility is given by Eq. 1: ..............................(1) where The initial and the boundary conditions are: 1. The reservoir potential Phi is initially constant, say Phi i. JPT P. 639