Elastic Deformation Process Research Articles

Effects of Nonlinear Reservoir Compaction on Casing Behavior

Summary Depletion of overpressured, undercompacted reservoirs can cause large reservoir pressure drops and sediment compaction, which may result in casing deformation and well failure. To predict soil and casing deformation during depletion, a finite-element model was developed. Nonlinear elastic and plastic behavior of the soils and slippage along the wellbore boundary are major advancements in this study. This axisymmetric model is composed of casing wall, cement column, slippage interface, and sediments from 11,400 to 13,200 ft [3475 to 4025 m] in depth with a radius of 3,400 ft [1035 m]. This study features a process of concurrent fluid flow, nonlinear elastic and plastic soil deformation, slippage from the wellbore boundary, and casing deformation. The modeling results show that the decline in near-wellbore reservoir pressure during depletion causes vertical compaction in both the sand reservoirs and the confining shale formations. Slippage next to the wellbore decreases the axial shear load placed on the casing by the sediments. Nonlinear elastic and plastic soils show a greater tendency for casing deformation with depletion than do linear elastic soils. Axial strains in the casing above the yield strain eventually developed as near-wellbore reservoir pressure was allowed to decline to a minimum. Because this effect is quantified, the production rate may be held to a safe maximum so that the operating limits of the casing are not exceeded. Criteria are given to improve both completion design and production rate specification.

Description of the process of elastic deformation of layers in mulilayer metallic packets and vessels

Description of the process of elastic deformation of layers in mulilayer metallic packets and vessels

Molecular dynamics simulation in investigating mechanical properties

The use of the molecular dynamics method, advantageously combining features of experimental and theoretical approaches, makes it possible to reconstruct without application of any a priori schematicizing hypotheses the actual picture of behavior of atoms in a crystal, their behavior in thermal movement, the elementary acts of reconstruction and rupture of the bonds between them as a result of mechanical actions, the influence of the atoms of the medium, etc. A single approach proved to cover the processes of elastic and plastic deformation of the lattice, the formation of defects, local fracture, adsorption, and migration. Together with new quantitative determinations resulting from the micromechanism itself, the use of the molecular dynamics method led to a series of interesting conclusions of a qualitative character, both those expected a priori and those by no means obvious (which is related, in particular, to the “variability” of the observed micropicturea predetermined by the rules of random events, “elements of fluctuations,” in such small systems where not the averaged picture but individual elementary acts of the investigated phenomena are observed).

On the nature of deformation of a crystalline solid: II. the absolute strain rate in elastic deformation

Elastic deformation process in a crystalline solid is consideredab initio in terms of an idealized model. It is shown that the apparent time invariance of strain in a semi-infinite solid deformed at a surface velocityv is the result of neglecting to take into account the discrete nature of the deformation process. An absolute strain rate, έ0 =v/d, whered is the interplanar spacing in the direction of deformation, can be rigorously derived. It is also shown that the same absolute deformation rate governs the deformation behavior in an infinite plate specimen, thus permitting unified treatment of infinite and finite length specimen deformation.

On the nature of deformation of a crystalline solid: I. discontinuous nature of elastic deformation

The elastic deformation process in a periodic lattice is analyzed. It is concluded that the concepts developed to date for the treatment of high strain rate deformation are generally applicable, regardless of the magnitude of strain rate. Elastic deformation is shown to be fundamentally discontinuous, with very steep strain and stress gradients localized at the elastic wave front, which moves at sonic velocity. The observed strain is the sum of discrete steps, occurring in rapid succession, but explicitly determinable in time and location. It is pointed out that the externally applied deformation velocityv is the fundamental variable governing the deformation behavior. The relationship between strain, therefore also stress, and time of deformation is developed in terms ofv, the longitudinal wave velocityc, and length of a finite specimen.

Effect of the deformation of the film -substrate system on the physicochemical properties of films and their adhesion strength

It was shown that the mechanism of deformation of films of rigid crosslinked polymers (polyester, polyester imide, polyester cyanurate) is appreciably different from the deformation mechanism of free films: a forced highly elastic deformation takes place, sometimes even at an early stage, while the free films deform reversibly up to rupture. Explanations have been suggested for the characteristic features of deformation of films studied on a substrate. The forced highly elastic deformation process is related to the effect of orienting reinforcement of films. An increase in the adhesion strength in the film-substrate system during the deformation has been shown, and an explanation of this effect has been proposed.

Constitutive equations for elastic-plastic materials at finite strain

Constitutive equations are suggested for describing the behavior of elastic-plastic materials undergoing large strains. A special kinematical viewpoint is taken, so that the elastic and plastic deformation processes can be considered separately. This separation is also accommodated by a simplified thermodynamical theory of the deformation process. The elastic constitutive equation is written as a rate equation, after examining the interpretation of elastic isotropy in view of the particular kinematical description employed. To describe plastic deformation, a rate equation, which exhibits no dependence on the rate at which previous states have been traversed, is suggested. After the general relations have been put in appropriate form some simplifications based on physical assumptions are considered. The physical assumptions are based on the behavior of metals under large stress, high speed loading, such as in the penetration problem. Under these operating conditions, the thermoelastic effects dominate and plasticity plays a minor role. Consequently, a simple model of plastic deformation usually suffices. The analysis is presented in direct (matrix) notation and is valid for arbitrary stress states.

フェノールレジン積層板のせん断加工 (第 4 報)

The load distributions along the cutting edges were induced from mutual relations among shearing force, side force, holding force produced by a fixed stripper plate, axial force and bending moment in the case of low speed shearing at room temperature for the straight parallel cutting edges. As a result of this, mechanical characters of shearing phenomenon could be clarified. The results obtained are as follows : (1) In the shearing process of elastic deformation, the forces and the bending moments are proportional to the shearing force, and the ratios of these quantities to the shearing force are less than 0.25.(2) The principal components of the side forces are frictional forces produced by the vertical forces acting on the parts compressed by the cutting edges. Accordingly, it can be said that the portion between the edges of punch and die has a tendency to be extruded.(3) The vertical forces along to the parts compressed by the cutting edges act on those parts of which form are similar to triangle having an apex at the cutting edges.