Semi‐automatic analysis of rock fracture orientations from borehole wall images

Geophysics ◽  
1997 ◽  
Vol 62 (1) ◽  
pp. 129-137 ◽  
Author(s):  
Bhaskar B. Thapa ◽  
Paul Hughett ◽  
Kenzi Karasaki
Keyword(s):  
Hough Transform ◽  
High Intensity ◽  
Input Data ◽  
Rock Fracture ◽  
Fracture Aperture ◽  
Test Cases ◽  
Rock Fractures ◽  
Tunnel Stability ◽  
Noisy Background ◽  
Intensity Contrast

We develop a semiautomatic method of identifying rock fractures and analyzing their orientations from digital images of borehole walls. This method is based on an algorithm related to the Hough transform which is modified to find sinusoidal rather than linear patterns. The algorithm uses the high‐intensity contrast between the fracture aperture and the rock wall, as well as the sinusoidal trajectory defined by the intersection of the borehole and the fracture. The analysis rate of the algorithm itself is independent of fracture contrast and network complexity. The method has successfully identified fractures both in test cases containing several fractures in a noisy background and in real borehole images. The analysis rate was 0.3–1.2 minutes/m of input data, compared to an average of 12 minutes/m using an existing interactive method. An automatic version under development should open new possibilities for site characterization, such as real‐time exploration and analysis of tunnel stability and support requirements as construction proceeds.

Coupled hydromechanical modeling of rock fractures under normal stress

2004 ◽  
Vol 41 (4) ◽  
pp. 686-697 ◽  
Author(s):  
M Bart ◽  
J F Shao ◽  
D Lydzba ◽  
M Haji-Sotoudeh
Keyword(s):  
Experimental Data ◽  
Normal Stress ◽  
Rock Fracture ◽  
Fluid Pressure ◽  
Fracture Aperture ◽  
Rock Fractures ◽  
Compression Tests ◽  
Void Space ◽  
Progressive Fracture ◽  
Single Rock Fracture

In this paper, a nonlinear poromechanical model is developed for a single rock fracture under normal stress. The fracture is represented by a set of voids, and the progressive fracture displacement is considered as a modification process of void space. Based on experimental data obtained from three representative rock fractures, the constitutive model is formulated through an extension of Biot poroelasticity theory to a saturated fracture. A generalized poroelastic coupling coefficient is introduced to describe the interaction between pore fluid pressure and fracture deformation. This coefficient is expressed as a function of fracture aperture. Five parameters involved in the model have been determined from mechanical and poromechanical compression tests. The validity of the model is checked on fluid flow tests under different normal stresses. Comparisons between numerical simulations and experimental data are provided.Key words: hydromechanical coupling, interfaces, joints, poroelasticity, rock mechanics, fractures.

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.

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.

Field Test of Ethanol/Bentonite Slurry Grouting into Rock Fracture

2006 ◽  
Vol 932 ◽  
Author(s):  
Motoyuki Asada ◽  
Hitoshi Nakashima ◽  
Takashi Ishii ◽  
Sumio Horiuchi
Keyword(s):  
Rock Fracture ◽  
Ground Surface ◽  
Rock Fractures ◽  
Natural Clay ◽  
Groundwater Seepage ◽  
Low Viscosity ◽  
Grouting Material ◽  
Bentonite Slurry ◽  
Bentonite Grout

ABSTRACTCrystalline rocks have fractures which may cause unexpected routes of groundwater seepage. Cement grouting is one of the most effective methods to minimize seepage; however, cement materials may not be suitable for the purpose of extra-long durability, because cement is neutralized or degraded by chemical and physical influence of chemical reaction.Natural clay like bentonite is one of the most promising materials for seepage barrier; however, water/bentonite grout is so viscous that enough amount of bentonite can not be grouted into rock fractures. To increase bentonite content in grout with low viscosity, the utilization of ethanol as a mixing liquid was studied. Ethanol suppresses bentonite swelling, and more bentonite can be injected more than that of water/bentonite slurry. In this paper, grouting into in-situ rock mass fracture from the ground surface was tested to investigate the barrier performance and workability of ethanol/bentonite slurry as a grouting material.

scholarly journals SOME STATISTICAL TECHNIQUES APPLIED TO ENGINEERING MECHANICS PROBLEMS

2020 ◽  
Vol 57 (6A) ◽  
pp. 10
Author(s):  
Tham Hong Duong
Keyword(s):  
Taguchi Method ◽  
Input Data ◽  
Technical Specification ◽  
Engineering Problem ◽  
Statistical Techniques ◽  
Test Cases ◽  
Statistical Tools ◽  
Technology Process ◽  
Engineering Problems ◽  
Engineering Mechanics

This article deals with statistical techniques normally used in Engineering. Variables or parameters in models of Engineering Mechanics always face data:  a) of materials (with technical specification); b) of analysing model using specific software; c) of measurement using variety of devices and approaches; and d) of the technology process of manufacture (outcome). An engineering object to be studied has k variables and each variable has m values or level of status, it will need mk cases to be solved. This has to conduct a very large number of test cases to be solved for target objective(s). A Taguchi Method will be applied for finding solution in which much less effort of computation is paid and other different conditions of noise could be taken into account. Besides, other statistical tools, ANOVA have also proved to be useful in quantifying uncertainties in engineering problems, both in aleatory (nature) and epistemic (knowledge and measurement) categories. A typical example of engineering problem is chosen to study using above-mentioned Taguchi method and statistical tools. This method is very useful for design of experiments, both in traditional laboratory and computer numerical modeling and it can used to optimize the set of input data for obtaining the best results of outcome product.

Transport of reactive tracers in rock fractures

1999 ◽  
Vol 378 ◽  
pp. 335-356 ◽  
Author(s):  
V. CVETKOVIC ◽  
J. O. SELROOS ◽  
H. CHENG
Keyword(s):  
Mass Transfer ◽  
Flow Equation ◽  
Transfer Reactions ◽  
Fracture Plane ◽  
Fracture Aperture ◽  
Rock Fractures ◽  
Advective Transport ◽  
Rock Matrix ◽  
Cubic Law ◽  
Diffusive Mass Transfer

Transport of tracers subject to mass transfer reactions in single rock fractures is investigated. A Lagrangian probabilistic model is developed where the mass transfer reactions are diffusion into the rock matrix and subsequent sorption in the matrix, and sorption on the fracture surface as well as on gauge (infill) material in the fracture. Sorption reactions are assumed to be linear, and in the general case kinetically controlled. The two main simplifying assumptions are that diffusion in the rock matrix is one-dimensional, perpendicular to the fracture plane, and the tracer is displaced within the fracture plane by advection only. The key feature of the proposed model is that advective transport and diffusive mass transfer are related in a dynamic manner through the flow equation. We have identified two Lagrangian random variables τ and β as key parameters which control advection and diffusive mass transfer, and are determined by the flow field. The probabilistic solution of the transport problem is based on the statistics of (τ, β), which we evaluated analytically using first-order expansions, and numerically using Monte Carlo simulations. To study (τ, β)-statistics, we assumed the ‘cubic law’ to be applicable locally, whereby the pressure field is described with the Reynolds lubrication equation. We found a strong correlation between τ and β which suggests a deterministic relationship β∼τ3/2; the exponent 3/2 is an artifact of the ‘cubic law’. It is shown that flow dynamics in fractures has a strong influence on the variability of τ and β, but a comparatively small impact on the relationship between τ and β. The probability distribution for the (decaying) tracer mass recovery is dispersed in the parameter space due to fracture aperture variability.

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