Umar Fauzi

3D FRACTAL DIMENSION AND FLOW PROPERTIES IN THE PORE STRUCTURE OF GEOLOGICAL ROCKS

Three-dimensional pore structure of four samples of geological rock was obtained using serial sectioning. Their fractal and flow properties have been successfully determined through image analysis. The measured 3D box counting fractal dimension of four geological rock samples are 2.59, 2.88, 2.88 and 2.29, which are not integer dimensions. This would imply that the structure of the four geological rock samples is fractal in nature. Porosity of the four rock samples are ranged from 0.18 to 0.31 and the specific surface area is ranged from 1.57 to 2.75 mm-1. Tortuosity estimated from image analysis of the four samples is ranged from 1.11 to 5.83 and varied in each fluid flow direction. This would imply that the rock samples are not uniform in its pore structure. The fractal dimension as a representation of the isotropic level of the pore structure is not clearly clarified and it still needs further investigation.

An Estimation of Rock Permeability and Its Anisotropy from Thin Sections Using a Renormalization Group Approach

Abstract A renormalization group approach was applied to estimate both permeability and anisotropy of several real rocks directly from the image of thin sections. Two-point correlation functions were applied to estimate both local porosity and local specific surface area. Local permeability was calculated using the Kozeny-Carman formula. The calculated permeability tended to the measured permeability as the renormalization step increased. The coefficient of anisotropy of the samples varied from around 1.0 to 1.8. Estimation of permeability using renormalization groups was also performed for pseudo 3-D sections.

To Divide or not to Divide: Simulation of Two‐Dimensional Stability of Three Grains using Molecular Dynamics

Simulation of three grains investigating system stability using molecular dynamics method implementing Gear predictor‐corrector algorithm of 5th order has been conducted. Linear spring‐dashpot model and short range cohesive Coulomb‐like force model are used as repeal and attractive force, respectively. Theoretical prediction, multiplied by a constant 0.02, agrees with the simulation results for lower layer consists of equal mass grains. Variations of mass of each grain in the lower layer and the results are also reported.

The effect of X-ray micro computed tomography image resolution on flow properties of porous rocks: MICRO COMPUTED TOMOGRAPHY IMAGE RESOLUTION

The study of digital rock physics has seen significant advances due to the development of X‐ray micro computed tomography scanning devices. One of the advantages of using such a device is that the pore structure of rock can be mapped down to the micrometre level in three dimensions. However, in providing such high‐resolution images (low voxel size), the resulting file sizes are necessarily large (of the order of gigabytes). Lower image resolution (high voxel size) produces smaller file sizes (of the order of hundreds of megabytes), but risks losing significant details. This study describes the effect of the image resolution obtained by means of hardware‐based and software‐based approach. Four samples of porous rock were scanned using a SkyScan 1173 High Energy Micro‐CT. We found that acquisition using increased pixel binning of the camera (hardware‐based resizing) significantly affects the calculated physical properties of the samples. By contrast, voxel resizing by means of a software‐based approach during the reconstruction process yielded less effect on the porosity and specific surface area of the samples. However, the decreasing resolution of the image obtained by both the hardware‐based and the software‐based approaches affects the permeability significantly. We conclude that simulating fluid flow through the pore space using the Lattice Boltzmann method to calculate the permeability has a significant dependency on the image resolution.

Two dimension porous media reconstruction using granular model under influence of gravity

Modeling of pores generation in 2-D with granular grains using molecular dynamics method is reported in this work. Grains with certain diameter distribution are let falling due to gravity. Three configurations (larger diameter in at upper layer, smaller diameter in at upper layer, and mixed) and two kinds of mixture (similar of grain density and mass) are used in the simulation. Mixture with heterogeneous density gives higher porosity than the homogeneous one for higher initial height, but change into opposite condition for lower initial height.

Molecular dynamics simulation on particular grain weighting in a granular pile: An attempt to induce an artificial micro-landslide

Weighting particular grain in granular pile can change the stability of the pile. In nature this weighting process is performed by increasing of water content due to rain or by agglomeration of several smaller grains into a larger one due to soil pressure. Four horizontal layers of hexagonal-packed grains are used in this simulation accompanied by one vertical layer acts as the left wall. From those four horizontal layers the lowest layer is defined as the floor. The left wall and the floor layers consist of fixed grains, while the other three layers are filled with movable grains. In the most top horizontal layer a particular grain is subjected to weighting process. It has been observed that during 200 s simulation time a micro-lanslide can occur if the minimum weighting is about 96 times of the original mass of the grain. As the weighting increasing the time needed for the micro-lanslide to emerge is decreasing. The position of the weighted grain is also play a role in introducing a micro-lanslide, the ...

Multiphase fluid simulations through porous rock using Shan-Chen type lattice Boltzmann method

Fluid flow with multiphase components is one of the daily problems that interesting to learn and widely used in various fields, one of them in rock physics. Euler approach and Lagrange approach, the two models are applied to study the fluid flow, which often known as the microscopic and macroscopic approaches. Lattice Boltzmann Method combines the advantages and appropriate of both approaches, that is used as a more efficient model approach, also known as mesoscopic. The LB method has been used to model the two-phase fluid flow with different viscosities using the Shan-Chen model, this model explain the interaction between two different fluid phases. Validated numerical models compiled using two ways, namely analytical models and physical models. Based on this research, numerical models are designed to meet the analytical model with an error on the lattice at the edge of the lattice. When compared with physical models, numerical models have qualitatively suitability. Based on the results of the validation...

Flow properties of the experimental and computer models of laminated rock

The existence of horizontal strata in sandstone has been identified by geologists. The thin layers are important in the way they affect some of the processes used to recover petroleum from the sandstone reservoir. In this research, we developed laboratory scale of laminated rock models as well as the computer models. The laboratory scale models were generated using sand with different grain size that was arranged into three layers. The computer models were generated using non-spherical grain model. The effects of variation of the laminae’s grain size and thickness were analyzed to identify the most significant feature of the layer. Flow properties of the laboratory scale models were conducted experimentally using falling-head method, while for the computer models; the permeability was calculated using Lattice Boltzmann Method. The result shows that the hydraulic conductivity of the laboratory scale models decreases as the thickness ratio of the laminae increases. For the computer models, the permeability ...

Parameterization of magnetic viscosity and its application in inferring magnetic grains in natural samples

Magnetic viscosity, also known as viscous magnetization, is one of the magnetic properties that rarely used in study of rock magnetism. The recent emergence of portable magnetic viscosity meter allows scientists to exploit that magnetic viscosity as the proxy parameters of processes recorded in natural materials. One of such instrument is MVM1, a new kind of magnetic viscosity meter which allow measurement of viscous magnetization to be conducted in 14 steps of time delay ranging from 10 to 100 µs. In this study, we have measured the changes of magnetic viscosity over the time delay and magnetic susceptibility in a suite of natural samples. The results show that viscous magnetization decays with time (in logarithmic scale or log t) which follows the trend of cubical-logarithmic decay. This is a unique response of fine magnetic grains, i.e. superparamagnetic grains, when that magnetization was measured in very short time delay. We then found the correlation between parameters of magnetic viscosity, S in sp...

Permeability anisotropy of layering rock model

Computer models of layering system were generated to analyze the effect of layering to the permeability anisotropy. Six layering models were created using non-spherical grain models. Each model consist of three layers with different thickness ratios. The permeability of the generated models were calculated using Lattice Boltzmann Method. Analysis of the flow properties shows that the permeability in the horizontal direction is greater than in the vertical direction. From the permeability anisotropy analysis, it is shown that in the horizontal direction, the models are generally considered as isotropic. This is confirmed by the anisotropy values, which are close to 1. The permeability anisotropy of the vertical direction to horizontal direction varies in the range of 0.32 – 0.45.