A Finite Element Model to Estimate In-Situ Stress and Fracture Toughness From a Step-Rate Test

1989 ◽  
Author(s):  
H.A. Khattab
Keyword(s):  
Fracture Toughness ◽  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
In Situ Stress ◽  
Step Rate ◽  
Rate Test

Finite Element Model Simulations Associated With Hydraulic Fracturing

1982 ◽  
Vol 22 (02) ◽  
pp. 209-218 ◽  
Author(s):  
Sunder H. Advani ◽  
J.K. Lee
Keyword(s):  
Finite Element ◽  
Hydraulic Fracturing ◽  
Finite Element Model ◽  
Hydraulic Fracture ◽  
Element Model ◽  
In Situ Stress ◽  
Fracture System ◽  
Model Simulations ◽  
Fracture Fluid

Abstract Recently emphasis has been placed on the development and testing of innovative well stimulation techniques for the recovery of unconventional gas resources. The design of optimal hydraulic fracturing treatments for specified reservoir conditions requires sophisticated models for predicting the induced fracture geometry and interpreting governing mechanisms. This paper presents methodology and results pertinent to hydraulic fracture modeling for the U.S. DOE's Eastern Gas Shales Program (EGSP). The presented finite-element model simulations extend available modeling efforts and provide a unified framework for evaluation of fracture dimensions and associated responses. Examples illustrating the role of multilayering, in-situ stress, joint interaction, and branched cracks are given. Selected comparisons and applications also are discussed. Introduction Selection and design of stimulation treatments for Devonian shale wells has received considerable attention in recent years1-3. The production of natural gas from such tight eastern petroliferous basins is dependent on the vertical thickness of the organically rich shale matrix, its inherent fracture system density, anisotropy, and extent, and the communication-link characteristics of the induced fracture system(s). The investigation of stimulation techniques based on resource characterization, reservoir property evaluation, theoretical and laboratory model simulations, and field testing is a logical step toward the development of commercial technology for optimizing gas production and related costs. This paper reports formulations, methodology, and results associated with analytical simulations of hydraulic fracturing for EGSP. The presented model extends work reported by Perkins and Kern,4 Nordgren,5 Geertsma and DeKlerk,6 and Geertsma and Haafkens.7 The simulations provide a finite-element model framework for studying vertically induced fracture responses with the effects of multilayering and in-situ stress considered. In this context, Brechtel et al.,8 Daneshy,9 Cleary,10 and Anderson et al.11 have done recent studies addressing specific aspects of this problem. The use of finite-element model techniques for studying mixed-mode fracture problems encountered in dendritic fracturing and vertical fracture/joint interaction also is illustrated along with application of suitable failure criteria. Vertical Hydraulic Fracture Model Formulations Coupled structural fracture mechanics and fracture fluid response models for predicting hydraulically induced fracture responses have been reported previously.12,13 These simulations incorporate specified reservoir properties, in-situ stress conditions, and stimulation treatment parameters. One shortcoming of this modeling effort is that finite-element techniques are used for the structural and stress intensity simulations, while a finite-difference approach is used to evaluate the leakoff and fracture-fluid response in the vertical crack. A consistent framework for conducting all simulations using finite-element modeling is formulated here.

Static and Dynamic Finite Element Model Updating of a Rigid Frame-Continuous Girders Bridge Based on Response Surface Method

2013 ◽  
Vol 639-640 ◽  
pp. 992-997 ◽  
Author(s):  
Jian Ping Han ◽  
Yong Peng Luo
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Response Surface ◽  
Test Data ◽  
Dynamic Test ◽  
Element Model ◽  
Surface Method ◽  
Rigid Frame ◽  
The Finite Element Model

Using the static and dynamic test data simultaneously to update the finite element model can increase the available information for updating. It can overcome the disadvantages of updating based on static or dynamic test data only. In this paper, the response surface method is adopted to update the finite element model of the structure based on the static and dynamic test. Using the reasonable experiment design and regression techniques, a response surface model is formulated to approximate the relationships between the parameters and response values instead of the initial finite element model for further updating. First, a numerical example of a reinforced concrete simply supported beam is used to demonstrate the feasibility of this approach. Then, this approach is applied to update the finite element model of a prestressed reinforced concrete rigid frame-continuous girders bridge based on in-situ static and dynamic test data. Results show that this approach works well and achieve reasonable physical explanations for the updated parameters. The results from the updated model are in good agreement with the results from the in-situ measurement. The updated finite element model can accurately represent mechanical properties of the bridge and it can serve as a benchmark model for further damage detection and condition assessment of the bridge.

Analytic and Numerical Solutions of Load and Stress of Casing and Cement in Cementing Section

2012 ◽  
Vol 268-270 ◽  
pp. 721-724
Author(s):  
Zhan Qu ◽  
Xiao Zeng Wang ◽  
Yi Hua Dou
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Analytical Solutions ◽  
Numerical Solutions ◽  
Element Model ◽  
In Situ Stress ◽  
Oil Field ◽  
Oil Well ◽  
Production Term

With the prolonged production term and the stimulation of the oil well in oil-field, the load which results from the in-situ stress is one of the main reasons to the casing damage. Taking the casing in Cementing section, the cement and the rock surrounding the cement into consideration, a mechanical model is established, while analytical solutions of displacement and stress distribution is obtained. The finite element method is adopted to obtain the numerical solutions of the mechanics model. The result shows that analytical solutions and finite element solutions are approximate. Finite element model of casing/cement/formation which is established in the paper can be used to analyze the load and stress distribution of worn casing with non-uniform in-situ stress.

Tribological Process Characterization With In-Situ Quantitative Nano-Scale Metrology

2005 ◽  
Author(s):  
Antanas Daugela ◽  
Alex Meyman ◽  
Vladimir Knyazik ◽  
Nikolai Yeremin
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Optical Microscope ◽  
Nano Scale ◽  
Process Characterization ◽  
Microscope Imaging

A novel quantitative nano+micro-tribometer with integrated nanoindenter, SPM and optical microscope imaging has been used to characterize mechanical properties of Cu coated Si wafers at various test stages. A 2D Finite Element Model was developed to study changes on workhardened contacts assessed via nanoindentation experiments.

Mesure de la déformabilité des sols in situ à l'aide d'un essai de chargement statique d'une pointe pénétrométrique

2006 ◽  
Vol 43 (4) ◽  
pp. 355-369 ◽  
Author(s):  
Hakim Arbaoui ◽  
Roland Gourvès ◽  
Philippe Bressolette ◽  
Laurent Bodé
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Static Loading ◽  
Initial Conditions ◽  
Deformation Modulus ◽  
Element Model ◽  
Rheological Parameters ◽  
Loading Test ◽  
Global Parameter

The penetrometers allow one to obtain a global parameter, which is the cone resistance; this one is related to the soil failure and not to its deformability. The idea is to use a penetrometer to measure in situ the deformability properties of the soils. A new method of soil deformability measurement is then presented in this article: a monotonic static loading test using a penetrometer. The main objective is to measure particularly the three mechanical parameters, which are Young's modulus E, the cohesion c, and the friction angle ϕ. This article describes the testing equipment and the tests performed by precise procedure. An interpretation of the obtained monotonic experimental curves is also presented. It is based on a mathematical regression by three coefficients. According to this study, conducted on a purely frictional soil, the test allows one to obtain by a simple, fast, and economic way, a relevant evaluation of the soil deformability properties and its resistance. An axisymmetric finite element model of the experimental test is proposed to identify the correlation between the three mathematical coefficients of the experimental curve and the three rheological parameters E, c, and ϕ. The initial conditions before the test, which are crucial, are simulated by performing an unloading–reloading loop. Interesting results are obtained with this simplified, but realistic, finite element model. However, a simulation considering large strain conditions is still needed.Key words: penetrometer, deformability, monotonic static loading, deformation modulus, finite element simulation.

scholarly journals In-situ Fluid Injections to Achieve Bio-Stimulated Calcite Precipitation in Expansive Soils

2020 ◽  
Author(s):  
Anish Pathak
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Expansive Soils ◽  
Element Model ◽  
Field Application ◽  
Engineering Properties ◽  
Swelling Potential ◽  
Calcite Precipitation ◽  
Low Pressures

Expansive soils undergo vast changes in volume when subject to change in water contents and cause damages to infrastructures across the world. Traditional methods of tackling the problem of expansive soils using cement or lime are environmentally unfriendly and expensive. Microbial Induced Calcite Precipitation (MICP) is a new method which uses bacteria in the soil to precipitate CaCO3 (calcite) and improve the engineering properties of soils. Various laboratory studies have shown that this method can be applied successfully to treat expansive soils, but the field application of the method have barely been studied. To study the applicability of MICP in field, a protocol was developed to perform in-situ chemical injections through a borehole and tests were conducted in Marsing, Idaho. Multiple rounds of chemical injections were performed, and soil samples were monitored for calcite content and swelling potential changes. Results showed an increase in calcite precipitation and decrease in swelling potential of the soil with each round of chemical treatment. Additional study to understand the influence distance of chemical injections in the soil were performed by injecting water into the soil and collecting moisture change data around the borehole. A finite element model was created in ABAQUS to establish the influence zone of the injections and verified against field data. The finite element model was then used to study the effects of pressure, permeability and sorption characteristics of soil in influence distance. Results suggest that, in soils with low permeabilities, such as in case of expansive soils, higher matric suction can result in greater influence distances over time. It was also seen that change in pressure of injection had minimal effect in influence distance. This suggests that it may be possible to implement MICP protocols in expansive soils by injecting solutions through boreholes at very low pressures and longer durations.

The Micromechanical Environment of Intervertebral Disc Cells Determined by a Finite Deformation, Anisotropic, and Biphasic Finite Element Model

2003 ◽  
Vol 125 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Anthony E. Baer ◽  
Tod A. Laursen ◽  
Farshid Guilak ◽  
Lori A. Setton
Keyword(s):  
Finite Element ◽  
Intervertebral Disc ◽  
Finite Element Model ◽  
Transition Zone ◽  
Nucleus Pulposus ◽  
Finite Deformation ◽  
Element Model ◽  
Constitutive Law ◽  
Anulus Fibrosus

Cellular response to mechanical loading varies between the anatomic zones of the intervertebral disc. This difference may be related to differences in the structure and mechanics of both cells and extracellular matrix, which are expected to cause differences in the physical stimuli (such as pressure, stress, and strain) in the cellular micromechanical environment. In this study, a finite element model was developed that was capable of describing the cell micromechanical environment in the intervertebral disc. The model was capable of describing a number of important mechanical phenomena: flow-dependent viscoelasticity using the biphasic theory for soft tissues; finite deformation effects using a hyperelastic constitutive law for the solid phase; and material anisotropy by including a fiber-reinforced continuum law in the hyperelastic strain energy function. To construct accurate finite element meshes, the in situ geometry of IVD cells were measured experimentally using laser scanning confocal microscopy and three-dimensional reconstruction techniques. The model predicted that the cellular micromechanical environment varies dramatically between the anatomic zones, with larger cellular strains predicted in the anisotropic anulus fibrosus and transition zone compared to the isotropic nucleus pulposus. These results suggest that deformation related stimuli may dominate for anulus fibrosus and transition zone cells, while hydrostatic pressurization may dominate in the nucleus pulposus. Furthermore, the model predicted that micromechanical environment is strongly influenced by cell geometry, suggesting that the geometry of IVD cells in situ may be an adaptation to reduce cellular strains during tissue loading.

Sign in / Sign up

Export Citation Format

Share Document