The Pressure Transient Analysis Of Deformation Of Fractal Medium

The assumption of constant rock properties in pressure-transient analysis of stress-sensitive reservoirs can cause significant errors in the estimation of temporal and spatial variation of pressure. In this article, the pressure transient response of the fractal medium in stress-sensitive reservoirs was studied by using the self-similarity solution method and the regular perturbation method. The dependence of permeability on pore pressure makes the flow equation strongly nonlinear. The nonlinearities associated with the governing equation become weaker by using the logarithm transformation. The perturbation solutions for a constant pressure production and a constant rate production of a linear-source well were obtained by using the self-similarity solution method and the regular perturbation method in an infinitely large system, and inquire into the changing rule of pressure when the fractal and deformation parameters change. The plots of typical pressure curves were given in a few cases, and the results can be applied to well test analysis

Nanoindentation size effect interpreted by the dislocation nucleation mechanism

The instability criterion of atomic structure is used to investigate the nanoindentation size effect based on the dislocation nucleation mechanism. Both the dislocation nucleation location and the emission direction under indentation can be predicted. The nanoindentation size effect for hardness can be interpreted with a critical condition of the dislocation nucleation through adopting an Atomic Finite Element Method which is associated with the instability criterion. The present results agree well with the analytical solution based on the Rice model. The present results show that the nanoindentation size effect with the flat indenter can be expressed by using the dislocation nucleation concept. From dislocation nucleation point of view, the applied average force (hardness) required for dislocation emission is proportional to the inverse of square root of the width of the nano-indenter (contact zone size)

Mechanism of nucleation and precipitation in Li containing Al-Zn-Mg-Cu alloys

Investigations on the aging hardening behavior of four Al-Li-Zn-Mg-Cu alloys were carried out using differential scanning calorimetry, transmission electron microscopy and hardness measurement. It is shown that the addition of Li inhibits the formation of Zn-rich G.P. zones in Al-Zn-Mg-Cu alloys. The dominant aging hardening precipitates is delta'(Al3Li) phase. Coarse T ((AlZn)(49)Mg-32) phase, instead of MgZn2, precipitates primarily on grain boundaries, and provides little strengthening. The multi-stop aging involving plastic deformation introduces in the matrix a high concentration of structural defects. These defects play different role on the nucleation of Zn-rich G.P. zones in different alloys. For the Li free alloy, structural defects act as vacancy sinks and tend to suppress the homogeneous precipitation of G.P. zones, while for the Li containing alloys, these defects promote the heterogeneous nucleation of G.P. zones and metastable MgZn2. A significant aging hardening effect is attained in deformed Li containing alloys due to the extra precipitation of fine MgZn2 in the matrix combined with deformation hardening

A Model for the Elastic Modulus of Hydrate-Bearing Sediments

A model for the elastic modulus of hydrate-bearing sediment (HBS) is presented considering the variation of the hydrate saturation and hydrate occurrence mode. The model is based on the classical series and parallel modes, introducing a parameter of statistical force transfer paths among particles in HBS. Macro-triaxial compression tests and micro X-ray computed tomography (CT) observations of HBS in the gas-saturated formation mode were conducted. The applicability of the model was checked through the comparison between tests and theoretical results