scholarly journals Evaluation of equivalent hydraulic aperture (EHA) for rough rock fractures

2019 ◽  
Vol 56 (10) ◽  
pp. 1486-1501 ◽  
Author(s):  
Fei Xiao ◽  
Zhiye Zhao
Keyword(s):  
Fluid Flow ◽  
Rock Fracture ◽  
Fluid Velocity ◽  
Surrogate Models ◽  
Rock Fractures ◽  
Parallel Plates ◽  
Characteristic Parameters ◽  
Fracture Roughness ◽  
Hydraulic Aperture ◽  
The Impact

Most existing models for fluid transportation within a single rock fracture tend to use a channel with two smooth parallel plates, whereas real fracture surfaces are usually rough and tortuous, which can produce a flow field significantly different from the smooth plate model. For fluid flow in a rough fracture, there are surface concave areas (SCA), where the fluid velocity is extremely low, contributing little to the fluid transportation. It is of great significance to quantitatively evaluate the impact of rough surfaces on fluid flow. Therefore, a numerical model for simulating Newtonian fluid through rough fractures is proposed, where synthetic surfaces are generated according to statistical analysis of natural rock fractures and can be quantified by several characteristic parameters. Equivalent hydraulic aperture (EHA) is proposed as one quantitative indicator for evaluating the impact of fracture roughness. Systematic studies were conducted for evaluating EHAs of rough fractures, which, combined with characteristic parameters of fractures, are used to build surrogate models for EHA prediction. It is found that the EHA is directly correlated with the fracture roughness, the mean mechanical aperture, and the standard deviation of aperture distribution. The developed surrogate models were verified to have a high accuracy for EHA prediction.

scholarly journals Analysis of Fracture Roughness Control on Permeability Using SfM and Fluid Flow Simulations: Implications for Carbonate Reservoir Characterization

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-19 ◽  
Author(s):  
Miller Zambrano ◽  
Alan D. Pitts ◽  
Ali Salama ◽  
Tiziano Volatili ◽  
Maurizio Giorgioni ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Reservoir Characterization ◽  
Flow Simulation ◽  
Carbonate Reservoir ◽  
Single Fracture ◽  
Parallel Plates ◽  
Surface Mapping ◽  
Navier Stokes Equation ◽  
Hydraulic Aperture ◽  
Fracture Modeling

Fluid flow through a single fracture is traditionally described by the cubic law, which is derived from the Navier-Stokes equation for the flow of an incompressible fluid between two smooth-parallel plates. Thus, the permeability of a single fracture depends only on the so-called hydraulic aperture which differs from the mechanical aperture (separation between the two fracture wall surfaces). This difference is mainly related to the roughness of the fracture walls, which has been evaluated in previous works by including a friction factor in the permeability equation or directly deriving the hydraulic aperture. However, these methodologies may lack adequate precision to provide valid results. This work presents a complete protocol for fracture surface mapping, roughness evaluation, fracture modeling, fluid flow simulation, and permeability estimation of individual fracture (open or sheared joint/pressure solution seam). The methodology includes laboratory-based high-resolution structure from motion (SfM) photogrammetry of fracture surfaces, power spectral density (PSD) surface evaluation, synthetic fracture modeling, and fluid flow simulation using the Lattice-Boltzmann method. This work evaluates the respective controls on permeability exerted by the fracture displacement (perpendicular and parallel to the fracture walls), surface roughness, and surface pair mismatch. The results may contribute to defining a more accurate equation of hydraulic aperture and permeability of single fractures, which represents a pillar for the modeling and upscaling of the hydraulic properties of a geofluid reservoir.

Investigation of Proppant Distributions in Rock Fractures With Applications to Hydraulic Fracturing

2021 ◽  
Author(s):  
Amir A. Mofakham ◽  
Farid Rousta ◽  
Dustin M. Crandall ◽  
Goodarz Ahmadi
Keyword(s):  
Fluid Flow ◽  
Hydraulic Fracturing ◽  
Oil And Gas ◽  
Fluid Dynamic ◽  
Rock Fracture ◽  
Experimental Investigations ◽  
Rock Fractures ◽  
Fracture Geometry ◽  
Injection Process ◽  
Fracking Fluid

Abstract Hydraulic fracturing or fracking is a procedure used extensively by oil and gas companies to extract natural gas or petroleum from unconventional sources. During this process, a pressurized liquid is injected into wellbores to generate fractures in rock formations to create more permeable pathways in low permeability rocks that hold the oil. To keep the rock fractures open after removing the high pressure, proppant, which typically are sands with different shapes and sizes, are injected simultaneously with the fracking fluid to spread them throughout rock fractures. The extraction productivity from shale reservoirs is significantly affected by the performance and quality of the proppant injection process. Since these processes occur under the ground and in the rock fractures, using experimental investigations to examine the process is challenging, if not impossible. Therefore, employing numerical tools for analyzing the process could provide significant insights leading to the fracking process improvement. Accordingly, in this investigation, a 4-way coupled Computational Fluid Dynamic and Discrete Element Method (CFD-DEM) code was used to simulate proppant transport into a numerically generated realistic rock fracture geometry. The simulations were carried out for a sufficiently long period to reach the fractures’ steady coverage by proppant. The proppant fracture coverage is a distinguishing factor that can be used to assess the proppant injection process quality. A series of simulations with different proppant sizes as well as various fracking fluid flow rates, were performed. The corresponding estimated fracture coverages for different cases were compared. The importance of proppant size as well as the fluid flow rate on the efficiency of the proppant injection process, were evaluated and discussed.

Parametric investigation of twin tube magnetorheological dampers using a new unsteady theoretical analysis

2019 ◽  
Vol 30 (6) ◽  
pp. 878-895
Author(s):  
Mohammad Mehdi Zolfagharian ◽  
Mohammad Hassan Kayhani ◽  
Mahmood Norouzi ◽  
Amir Jalali
Keyword(s):  
Fluid Flow ◽  
Pressure Drop ◽  
Static Analysis ◽  
Fluid Velocity ◽  
Magnetorheological Fluid ◽  
Magnetorheological Damper ◽  
Parallel Plates ◽  
Fluid Inertia ◽  
Time Duration ◽  
Inertia Term

In the present work, a new unsteady analytical model is developed for magnetorheological fluid flow through the annular gap which is opened on the piston head of twin tube magnetorheological damper, considering fluid inertia term into the momentum equation. This new unsteady model is based on Stokes’ second problem that is extended for magnetorheological fluid flow between finite oscillating parallel plates under the pressure gradient. A quasi-static analysis is also developed for magnetorheological fluid flow in twin tube damper, to compare its results with present unsteady solution and to show the effect of magnetorheological fluid inertia. The obtained results are validated experimentally and then, a parametric study is presented using both unsteady and quasi-static analysis. The effect of fluid inertia term is investigated on force–displacement and force–velocity loops, magnetorheological fluid velocity profile, pressure drop, phase difference between pressure drop and flow rate and change of plug thickness with time duration. According to the obtained results, quasi-static analysis included considerable error respect to new unsteady analysis as the gap height, magnetorheological fluid density, excitation frequencies and amplitudes are increased and yield stress is decreased. It is found that the plug thickness is considerably affected by inertia term of magnetorheological fluid.

scholarly journals An investigation into the controls on fracture tortuosity in rock sequences and the impact on fluid flow in the upper crust

2020 ◽  
Author(s):  
Nathaniel Forbes Inskip ◽  
Tomos Phillips ◽  
Kevin Bisdom ◽  
Georgy Borisochev ◽  
Andreas Busch ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Large Scale ◽  
Small Scale ◽  
Fine Scale ◽  
Geothermal Systems ◽  
Parallel Plates ◽  
Core Flooding ◽  
Fracture Surfaces ◽  
Fracture Orientation ◽  
The Impact

<p>Fractures are ubiquitous in geological sequences, and play an important role in the movement of fluids in the earth’s crust, particularly in fields such as hydrogeology, petroleum geology and volcanology. When predicting or analysing fluid flow, fractures are often simplified as a set of smooth parallel plates. In reality, they exhibit tortuosity on a number of scales: Fine-scale tortuosity, or roughness, is the product of the small-scale (µm – mm) irregularities in the fracture surface, whereas large-scale (> mm) tortuosity occurs as a result of anisotropy and heterogeneity within the host formation that leads to the formation of irregularities in the fracture surfaces. It is important to consider such tortuosity when analysing processes that rely on the movement (or hindrance) of fluids flowing through fractures in the subsurface. Such processes include fluid injection into granitic plutons for the extraction of heat in Engineered Geothermal Systems, or the injection of CO<sub>2</sub> into reservoirs overlain by fine-grained mudrocks acting as seals in Carbon Capture and Storage projects.</p><p>Although it is generally assumed that tortuosity is controlled by factors such as grain size, mineralogy and fracture mode, a systematic study of how these factors quantitatively affect tortuosity is currently lacking. Furthermore, in anisotropic rocks the fracture orientation with respect to any inherent anisotropy is also likely to affect tortuosity.</p><p>In order to address this gap, we have induced fractures in a selection of different rock types (mudrocks, sandstones and carbonates) using the Brazil disk method, and imaged the fracture surfaces using both a digital optical microscope and X-ray Computed Tomography. Using these methods we are able to characterise both the fine-scale (roughness) and large-scale tortuosity. In order to understand the effect of fracture orientation on tortuosity we have also analysed fractures induced at different angles to bedding in samples of a highly anisotropic mudrock taken from South Wales, UK. Results indicate that fine-scale tortuosity is highly dependent on the fracture orientation with regards to the bedding plane, with fractures normal to bedding being rougher than those induced parallel to bedding. Finally, in order to measure the effect of tortuosity on fluid flow, we have carried out a series of core flooding experiments on a subset of fractured samples showing that fracture transmissivity decreases with increasing tortuosity.</p>

scholarly journals Particle-fluid flow and transport within rough fractures

2020 ◽  
Vol 205 ◽  
pp. 08010
Author(s):  
Brian Yamashiro ◽  
Ingrid Tomac
Keyword(s):  
Surface Roughness ◽  
Fracture Surface ◽  
Rock Fracture ◽  
Rock Fractures ◽  
Rough Boundary ◽  
Fracture Surface Roughness ◽  
Flow And Transport ◽  
Fluid Systems ◽  
Transport Behaviour ◽  
The Impact

Proppant injection is an important part of a hydraulic fracturing programs in which fluid-particle slurry is injected into rock fractures. Injected particles are lodged between fracture surfaces during wall close-in thereby propping open the fracture, improving connectivity and production. This paper investigates behaviour of proppant particles within artificially generated rock fractures, providing insight into transport behavioural differences caused by realistic surface roughness. Better understanding of proppant behaviour within more realistic rough fracture conditions provides greater understanding of proppant transport as compared to past works where smooth walled fracture configurations were utilized. A clearer understanding is important in providing more accurate evaluation of realistic proppant flow and distribution and improving injection design. In this study a roughened surface, analogues to actual rock fracture surface, is artificially generated based on a rock surface’s fractal dimension and asperity height standard deviation. Computational representation of the rock surfaces and flow domain is generated. Resolved Discrete Element Method coupled with computational fluid dynamics (DEM-CFD) is implemented in this study to evaluate proppant particle transport behaviour within the fractures. This work highlights importance of considering fracture surface roughness in evaluating proppant flow and transport and more generally the impact of rough boundary conditions of particle-fluid systems.

scholarly journals Hydrodynamical Study of Creeping Maxwell Fluid Flow through a Porous Slit with Uniform Reabsorption and Wall Slip

Mathematics ◽  
2020 ◽  
Vol 8 (10) ◽  
pp. 1852
Author(s):  
Hameed Ullah ◽  
Dianchen Lu ◽  
Abdul Majeed Siddiqui ◽  
Tahira Haroon ◽  
Khadija Maqbool
Keyword(s):  
Fluid Flow ◽  
Physical Phenomenon ◽  
Fluid Velocity ◽  
Axial Flow ◽  
Maximum Velocity ◽  
Maxwell Fluid ◽  
Two Dimensional ◽  
Mathematical Basis ◽  
Analytical Technique ◽  
The Impact

The present theoretical study investigates the influence of velocity slip characteristics on the plane steady two-dimensional incompressible creeping Maxwell fluid flow passing through a porous slit with uniform reabsorption. This two-dimensional flow phenomenon is governed by the mathematical model having nonlinear partial differential equations together with non-homogeneous boundary conditions. An analytical technique, namely the recursive approach, is used successfully to find the solutions of the problem. The explicit expressions for stream function, velocity components, pressure distribution, wall shear stress and normal stress difference have been derived. The axial flow rate, leakage flux and fractional reabsorption are also found out. The points of maximum velocity are identified. Non-dimensionalization is carried out and graphs are portrayed at different positions of the channel to show the impact of pertinent parameters: slip parameter, Maxwell fluid parameter and absorption parameter, on flow variables and found that the fluid velocity is affected significantly due to these parameters. This study provides a mathematical basis to understand the physical phenomenon for fluid flows through permeable boundaries which exists in different problems like gaseous diffusion, filtration and biological mechanisms.

scholarly journals Numerical Simulation on Non-Darcy Flow in a Single Rock Fracture Domain Inverted by Digital Images

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-13 ◽  
Author(s):  
Jianli Shao ◽  
Qi Zhang ◽  
Wenbin Sun ◽  
Zaiyong Wang ◽  
Xianxiang Zhu
Keyword(s):  
Numerical Simulation ◽  
Fluid Flow ◽  
Digital Images ◽  
Rock Fracture ◽  
Inertial Force ◽  
Darcy Flow ◽  
Fracture Aperture ◽  
Rock Fractures ◽  
Single Rock Fracture ◽  
Fracture Domain

The influence of rock seepage must be considered in geotechnical engineering, and understanding the fluid flow in rock fractures is of great concern in the seepage effect investigation. This study is aimed at developing a model for inversion of rock fracture domains based on digital images and further study of non-Darcy flow. The visualization model of single rock fracture domain is realized by digital images, which is further used in flow numerical simulation. We further discuss the influence of fracture domain geometry on non-Darcy flow. The results show that it is feasible to study non-Darcy flow in rock fracture domains by inversion based on digital images. In addition, as the joint roughness coefficient (JRC) increases or the fracture aperture decreases, distortion of the fluid flow path increases, and the pressure gradient loss caused by the inertial force increases. Both coefficients of the Forchheimer equation decrease with increasing fracture aperture and increase with increasing JRC. Meanwhile, the critical Reynolds number tends to decrease when JRC increases or the fracture aperture decreases, indicating that the fluid tends to non-Darcy flow. This work provides a reference for the study of non-Darcy flow through rock fractures.

Magnetohydrodynamics Boundary Layer Slip Casson Fluid Flow over a Dissipated Stretched Cylinder

2019 ◽  
Vol 393 ◽  
pp. 73-82 ◽  
Author(s):  
M. Krishna Murthy ◽  
Chakravarthula S.K. Raju ◽  
V. Nagendramma ◽  
S.A. Shehzad ◽  
Ali J. Chamkha
Keyword(s):  
Boundary Layer ◽  
Fluid Flow ◽  
Skin Friction ◽  
Fluid Model ◽  
Fluid Velocity ◽  
Casson Fluid ◽  
Moving Cylinder ◽  
Casson Fluid Model ◽  
Mhd Boundary Layer ◽  
The Impact

Magnetohydrodynamics (MHD) boundary layer slip Casson fluid flow over a dissipated moving cylinder is explored. Casson fluid model is employed as a non-Newtonian material that demonstrates the phenomenon of yield stress. Blood material is considered to be an example of Casson liquid. The non-linear partial differential quantities are transformed into expressions of ordinary derivatives through transformation of similarity variables. These equations are computed for numeric solutions by using Runge-Kutta method along with shooting scheme. The impact of pertinent constraints on the fluid velocity and temperature are examined through graphs. The coefficient of the skin friction and the rate of heat transfer are found numerically. Comparing of the present study with the earlier results is also presented. We observed that the coefficient of skin friction increases for higher values of Hartmann number.

The Effect of Pore Water Velocity on the Spectral Induced Polarization Signature of Porous Media

2021 ◽  
Author(s):  
Nimrod Schwartz ◽  
Kuzma Tsukanov ◽  
Itamar Assa
Keyword(s):  
Porous Media ◽  
Relaxation Time ◽  
Fluid Flow ◽  
Driving Forces ◽  
Fluid Velocity ◽  
Synthetic Data ◽  
Induced Polarization ◽  
Bulk Fluid ◽  
Noninvasive Measurements ◽  
The Impact

<p>Induced polarization (IP) is increasingly applied for hydrological, environmental and agricultural purposes. Interpretation of IP data is based on understanding the relationship between the IP signature and the porous media property of interest. Mechanistic models on the IP phenomenon relay on the Poisson-Nernst-Plank equations, where diffusion and electromigration fluxes are the driving forces of charge transport, and are directly related to IP. However, to our knowledge, the impact of advection flux on IP was not investigated experimentally, and was not considered in any IP model. In this work, we measured the spectral IP (SIP) signature of porous media under varying flow conditions, in addition to developing and solving a model for SIP signature of porous media, which takes flow into consideration. The experimental and the model results demonstrate that as bulk velocity increases, polarization and relaxation time decrease. Using a numerical model, we established that fluid flow near the particle deforms the structure of the electrical double layer (EDL), accounting for the observed decrease in polarization. Using simple physical arguments, we developed a new model for the relaxation time, taking into account the impact of bulk fluid velocity. The model and the measured and synthetic data were found to be in good agreement. Overall, our results demonstrate the sensitivity of the SIP signature to fluid flow, highlighting the need for considering fluid velocity in the interpretation of the SIP signature of porous media, and opening an exciting new direction for noninvasive measurements of fluid flow at the EDL scale.     </p>

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