Estimation of porosity, fluid bulk modulus, and stiff-pore volume fraction using a multi-trace Bayesian AVO petrophysics inversion in multi-porosity reservoirs

The estimation of petrophysical and fluid-filling properties of subsurface reservoirs from seismic data is a crucial component of reservoir characterization. Seismic amplitude variation with offset (AVO) inversion driven by rock physics is an effective approach to characterize reservoir properties. Generally, PP-wave reflection coefficients, elastic moduli and petrophysical parameters are nonlinearly coupled, especially in the multiple type pore-space reservoirs, which makes seismic AVO petrophysics inversion ill-posed. We propose a new approach that combines Biot-Gassmann’s poro-elasticity theory with Russell’s linear AVO approximation, to estimate the reservoir properties including elastic moduli and petrophysical parameters based on multi-trace probabilistic AVO inversion algorithm. We first derive a novel PP-wave reflection coefficient formulation in terms of porosity, stiff-pore volume fraction, rock matrix shear modulus, and fluid bulk modulus to incorporate the effect of pore structures on elastic moduli by considering the soft and stiff pores with different aspect ratios in sandstone reservoirs. Through the analysis of the four types of PP-wave reflection coefficients, the approximation accuracy and inversion feasibility of the derived formulation are verified. The proposed stochastic inversion method aims to predict the posterior probability density function in a Bayesian setting according to a prior Laplace distribution with vertical correlation and prior Gaussian distribution with lateral correlation of model parameters. A Metropolis-Hastings stochastic sampling algorithm with multiple Markov chains is developed to simulate the posterior models of porosity, stiff-pore volume fraction, rock-matrix shear modulus, and fluid bulk modulus from seismic AVO gathers. The applicability and validity of the proposed inversion method is illustrated with synthetic examples and a real data application.

Computational Homogenization of Cement-Based Porous Piezoelectric Composites with Random Structure

The finite element method (FEM) is used to characterize the effective thermo-electromechanical material properties of cement-based piezoelectric ceramic composites in this paper. The micromechanics representative volume element (RVE) approach is used with distribution of piezoelectric particles in the porous cement matrix. The effects of the piezoelectric particle volume fraction and pore volume fraction on the effective composite properties are determined using sets of different boundary conditions. Microscale homogenization is carried out through the analysis of particles which are randomly distributed in a homogenized matrix.

Synthesis of Porous Noble Metal Films With Tunable Porosity by Timed Dealloying

Nanoporous metal foams have an increasing importance in applications such as chemical catalysis, energy storage, and nanomedicine. This paper examines a simple strategy for controlling the pore volume fraction and pore size of nanoporous films synthesized by dealloying thin-films. By means of controlling the temperature and concentration of nitric acid in dealloying of AgAu thin-films, partially dealloyed AgAu nanoporous films are produced with a high degree of control over the pore size and pore volume fraction. Such capability enables the design of nanoporous metal catalysts materials with desired morphology.

Predicting the soil water characteristic curve from the particle size distribution based on a pore space geometry containing slit-shaped spaces

Abstract. Traditional models employed to predict the soil water characteristic curve (SWC) from the particle size distribution (PSD) always underestimate the water content in the dry range of the SWC. Using the measured physical parameters of 48 soil samples from the UNSODA unsaturated soil hydraulic property database, these errors were proven to originate from the underestimation of the pore volume fraction of the minimum pore diameter range. A method was therefore proposed to improve the estimation of the water content in the high suction range using a pore model comprising a circle-shaped central pore connected to slit-shaped spaces; in this model, the pore volume fraction of the minimum pore diameter range and the corresponding water content were accordingly increased. The SWCs predicted using the improved method reasonably approximated the measured SWCs, and which were more accurate than those obtained using traditional method in the dry range of the SWC.

Application of computed tomography for an analysis of composite with fine dispersive reinforcement made of the Fe65Co10Ni3W2B20 alloy

Purpose: The paper presents the results of microstructure and mechanical properties ofcomposites resulting from a combination of powders of metallic glasses with an epoxy resin(Epidian 100). The study was performed using computed tomography.Design/methodology/approach: The filler used was made of a Fe65Co10Ni3W2B20amorphous alloy based on, showing in the state after the formation the soft magneticproperties. The aim of the study was to determine the effect of the fraction of the compositepowders on the microstructure parameters (mean pore diameter and pore volume fraction)and the properties of the obtained composites.Findings: Based on the survey it was found out that size fraction used does not affectthe value of the modulus of elasticity linear composites studied. It was also shown that thecomposites analysed in an attempt to compress the cross cracked grain boundaries. Theinfluence fraction powders and change the share of the pore size depending on the fractionof the filler.Research limitations/implications: No studies of the magnetic properties determinethe usefulness of these materials in the electronics industry.Practical implications: Practical implications are to size the test specimens in the limitedrange of tests. In the future, it is planned to produce samples with a larger diameter.Originality/value: The paper presents a new group of composites-based metallic glassesconditions characterised by good properties produced a simple and inexpensive method.

Dynamic Mechanical Behavior of Additively Manufactured Ti6Al4V With Controlled Voids

The mechanical properties of additively manufactured (AM) dense and porous Ti6Al4V specimens were investigated under static and dynamic compression. The fully dense specimens were fabricated using laser melting process. The porous specimens contained spherical pores with full control on the geometry and location of the pores. The laser processed dense material exhibited superior strength in the static and dynamic tests, compared to the same conventional material, but the ductility of the two was comparable. Single pore specimens exhibited a linear relationship between the load and the pore volume fraction. The comparison between single- and double-pore specimens, at identical volume fractions, revealed the importance of the pores' orientation with respect to the applied load.