The interaction between deformation, fracture initiation and fracture propagation in two phase Co-CoAl alloys

1980 ◽  
Vol 11 (4) ◽  
pp. 643-652 ◽  
Author(s):  
M. A. Przystupa ◽  
M. G. Stout ◽  
T. H. Courtney
Keyword(s):  
Fracture Propagation ◽  
Fracture Initiation ◽  
Two Phase

Experiments and Modelling of Water Injection in Soft Heavy Oil Reservoirs

2015 ◽  
Author(s):  
C.J.. J. de Pater ◽  
Matthieu Brizard
Keyword(s):  
Water Injection ◽  
Fracture Propagation ◽  
Numerical Data ◽  
Water Flooding ◽  
Two Phase ◽  
Unconsolidated Sands ◽  
Coupled Numerical Model ◽  
Heavy Oil Reservoirs ◽  
Matrix Flow ◽  
Minimum Stress

Abstract Water flooding is often applied to increase the recovery of oil from reservoirs. In practice, the water injectivity below the fracture propagation pressure (at so called matrix flow), is usually too low, so that the pressure is increased and the well is fractured. The fracture behavior is however different for unconsolidated sands than for consolidated rock as higher pressures relative to the minimum stress are required to obtain fracture propagation. Injecting water at higher pressure will lead to higher recovery. Our aim was to gain experimental and numerical data to establish the transition from matrix flow to fracturing. We present a series of model tests on different unconsolidated materials using large cylindrical samples with a diameter of 0.4 m. We changed the permeability of the sample and investigated the effect of cohesion by adding cement to some of the samples. It appeared that fractures obtained in material without any cohesion are really complex. On the other hand, adding some small cohesion to the sample, we observed a fracture more like “classical” fractures in competent rocks. For interpreting the tests, we have developed a fully coupled numerical model taking into account the two phase flow of oil and water, and the deformation of the sample.

Thermal Effects of Liquid/Supercritical Carbon Dioxide Arising From Fluid Expansion in Fracturing

SPE Journal ◽  
2018 ◽  
Vol 23 (06) ◽  
pp. 2026-2040 ◽  
Author(s):  
Xiaojiang Li ◽  
Gensheng Li ◽  
Wei Yu ◽  
Haizhu Wang ◽  
Kamy Sepehrnoori ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Thermal Stress ◽  
Supercritical Carbon Dioxide ◽  
Hydraulic Fracturing ◽  
Thermal Effect ◽  
Fracture Propagation ◽  
Fracture Initiation ◽  
Thermodynamic Behavior ◽  
Fracture Complexity ◽  
Supercritical Carbon

Summary Liquid/supercritical carbon dioxide (L/SC-CO2) fracturing is an emerging technology for shale gas development because it can effectively overcome problems related to clay swelling and water scarcity. Recent applications show that L/SC-CO2 fracturing can induce variations in temperature. Understanding of this phenomenon is rudimentary and needs to be carefully addressed to improve the understanding of CO2 thermodynamic behavior, and thus helps to optimize CO2 fracturing in the field. In this paper, we develop a numerical model to assess the impact of thermal effect on fracture initiation during CO2 fracturing. The model couples fluid flow and heat transfer in the fracture, and is verified by a peer-reviewed solution and observation in laboratory experiments. The velocity, pressure, and temperature are calculated at various time to demonstrate the thermodynamic behavior during fracture initiation. A pseudo shock wave is observed, associated with a compression wave and an expansion wave, which finally leads to an increase in temperature in the new fracture and a decrease in temperature in the initial fracture. The thermal stress is derived to investigate the difference between hydraulic fracturing and CO2 fracturing. The results show that thermal stress, resulting from CO2 fracturing initiation, is comparable to the rock strength, which will help induce microfractures, and thus promote the fracture complexity. The formation pressure after CO2 fracturing is also calculated to evaluate the pressure-buildup potential. This work highlights the importance of CO2 expansion during and after fracturing. It is one of the unique features that differs from hydraulic fracturing. For field-design recommendations, to enhance the thermal effect of CO2 fracturing, it is a good strategy to pump CO2 at high pressure and low temperature into the reservoirs with high Young's modulus, low Poisson's ratio, low permeability, and high geothermal temperature (or large depth). This paper does not address the dynamics of fracture propagation under the influence of thermal effect. Rather, it intends to demonstrate the potential of the thermal effect of CO2 fluid in assisting the fracture propagation, and the importance of incorporating the compressibility of CO2 into fracture modeling and operation design. Failing to account for this thermal effect might underestimate the fracture complexity and stimulated reservoir volume.

scholarly journals The propagation saw test: slope scale validation and alternative test methods

2012 ◽  
Vol 58 (208) ◽  
pp. 407-416 ◽  
Author(s):  
Cameron K.H. Ross ◽  
Bruce Jamieson
Keyword(s):  
Scale Validation ◽  
Fracture Propagation ◽  
Fracture Initiation ◽  
Test Methods ◽  
Alternative Methods ◽  
Column Length ◽  
Layer Depth ◽  
Weak Layer ◽  
Predictive Skill ◽  
Alternative Test

AbstractThe propagation saw test (PST) is a recently developed snowpack test that enables assessment of the fracture propagation propensity of selected persistent weak-layer and slab combinations, which are known to release dry-slab avalanches. In this paper, we assess the slope- scale accuracy of the standard PST method at validated sites of observed weak-layer fracture initiation, with or without propagation. We also report on experiments with alternative test methods and varying saw thicknesses. Results show the standard PST method is comparably accurate to other common snowpack tests in predictive skill when predicting propagation propensity on the slope scale. Although a slight but significant dependence on saw thickness was found, it did not affect the interpretation in our validation study. Alternative methods such as scaling the test column length with weak-layer depth or leaving the upslope end of the column attached to the surrounding snowpack did not improve slope- scale accuracy and these tests were often more difficult to interpret.

scholarly journals NUMERICAL MODELLING APPLICATIONS ON FRACTURE PREDICTIONS: AN EXAMPLE FROM THE BLUE LIAS FORMATION IN KILVE, UK

2018 ◽  
Vol 28 (2) ◽  
pp. 193
Author(s):  
Adi Patria
Keyword(s):  
Finite Element Method ◽  
Tensile Stress ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Fracture Propagation ◽  
Fracture Initiation ◽  
Excess Pressure ◽  
Comsol Multiphysics ◽  
The Third ◽  
Set Up

Numerical modeling using Comsol Multiphysics, with Finite Element Method, has been carried out to study fracture initiation, linkage, and deflection of the Blue Lias Formation. Data were from outcrop observation where hydrofractures were well observed. Three models were set up to understand how fractures initiated, linked and arrested. The Young’s modulus of shales (Esh) was set with the value of 1 GPa, 5 GPa, and 10 GPa. The fluid excess pressure was applied with the value of 5 MPa, 10 MPa, and 15 MPa. The Young’s modulus of the limestone (Elst) was a constant at 10 GPa. The first model showed how the overburden induces fracture initiation. The results indicated that tensile stress concentrated only within limestone and favour to form fractures. The second model was about linking of fractures. The result explained that shear stress was dominantly concentrated in limestone layers. Previous hydrofractures possibly linked up forming shear fractures and en-echelon fractures. The third model was run to understand fracture propagation and deflection. The result was that tensile stress concentrated at the hydrofracture tips close to the contacts between limestone and shale. Hydrofractures were deflected, and in some places, hydrofractures were likely started to propagate through shale.Permodelan numerik dengan Comsol Multiphysics berdasarkan metode Elemen Terbatas  dilakukan untuk mempelajari inisiasi, hubungan, dan defleksi rekahan Formasi Blue Lias. Data berasal dari observasi singkapan dimana hydrofracture teramati. Tiga model dibuat untuk memahami bagaimana rekahan terinisiasi, terhubung, terambatkan dan terhenti. Modulus Young’s batulempung (Esh) diatur dengan nilai 1 GPa, 5GPa, dan 10 GPa. Tekanan kelebihan cairan (fluid excess pressure) yang diterapkan sebesar 5 MPa, 10 MPa, dan 15 MPa. Modulus Young’s batugamping (Elst) konstan sebesar 10 GPa. Model pertama menunjukkan bagaimana pembebanan mempengaruhi inisiasi rekahan. Hasil perhitungan menunjukkan bahwa tekanan tarik terkonsentrasi hanya pada lapisan batugamping dan memungkinkan terbentuknya rekahan. Model kedua mengenai hubungan rekahan. Model menunjukkan bahwa tekanan geser terkonsentrasi pada lapisan batugamping secara dominan. Hydrofracture yang telah ada akan terhubung membentuk rekahan geser and rekahan en-echelon. Model ketiga dihitung untuk memahami perambatan dan defleksi rekahan. Hasilnya menunjukkan bahwa tekanan tarik terkonsentrasi pada ujung hydrofracture dekat kontak lapisan batugamping dan batulempung. Hydrofracture terdefleksi dan pada beberapa titik mulai merambat menembus batulempung.

Full Fluid–Solid Cohesive Finite-Element Model to Simulate Near Wellbore Fractures

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Saeed Salehi ◽  
Runar Nygaard
Keyword(s):  
Finite Element ◽  
Hoop Stress ◽  
Fracture Propagation ◽  
Fracture Initiation ◽  
Element Model ◽  
Cohesive Elements ◽  
Element Simulation ◽  
Initiation And Propagation ◽  
Fracture Sealing ◽  
Wellbore Strengthening

This paper presents finite-element simulation for hydraulic fracture's initiation, propagation, and sealing in the near wellbore region. A full fluid solid coupling module is developed by using pore pressure cohesive elements. The main objective of this study is to investigate the hypothesis of wellbore hoop stress increase by fracture sealing. Anisotropic stress state has been used with assignment of individual criteria for fracture initiation and propagation. Our results demonstrate that fracture sealing in “wellbore strengthening” cannot increase the wellbore hoop stress beyond its upper limit when no fractures exist. However, this will help to restore part or all of the wellbore hoop stress lost during fracture propagation.

Numerical Simulations of Tensile Deformation Behavior in Two Phase α2 + γ Lamellar Tial Alloys

1994 ◽  
Vol 364 ◽  
Author(s):  
Bimal K. Kad ◽  
Ming Dao ◽  
Robert J. Asaro
Keyword(s):  
Volume Fraction ◽  
Tensile Deformation ◽  
Hydrostatic Stress ◽  
Fracture Initiation ◽  
Two Phase ◽  
Tial Alloys ◽  
Tensile Deformation Behavior ◽  
Mechanical Methods ◽  
Fully Lamellar ◽  
Stress Buildup

AbstractDeformation microstructures in γ-TiAl + α2Ti3Al based fully lamellar (FL) and nearly lamellar (NL) microstructures have been simulated using micro-mechanical methods. The deformation is extremely inhomogenous resulting in a large accumulation of hydrostatic stresses at the grain boundaries, thereby promoting intergranular fracture initiation. In particular, the increase in ductility with increasing equiaxed γ-grain volume fraction (with compliant deformation characteristics) in nearly lamellar alloys is explained by the reduction of the hydrostatic stress buildup at the boundaries, consequently mitigating fracture.

Review of Fracture Control Technology for Gas Transmission Pipelines

2014 ◽  
Author(s):  
Xian-Kui Zhu
Keyword(s):  
Ductile Fracture ◽  
Fracture Propagation ◽  
High Strength ◽  
Fracture Initiation ◽  
Alternative Methods ◽  
Opening Angle ◽  
Pipeline Steels ◽  
Control Plan ◽  
Fracture Control ◽  
Arrest Toughness

A fracture control plan is often required for a gas transmission pipeline in the structural design and safe operation. Fracture control involves technologies to control brittle and ductile fracture initiation, as well as brittle and ductile fracture propagation for gas pipelines, as reviewed in this paper. The approaches developed forty years ago for the fracture initiation controls remain in use today, with limited improvements. In contrast, the approaches developed for the ductile fracture propagation control has not worked for today’s pipeline steels. Extensive efforts have been made to this topic, but new technology still needs to be developed for modern high-strength pipeline steels. Thus, this is the central to be reviewed. In order to control ductile fracture propagation, Battelle in the 1970s developed a two-curve model (BTCM) to determine arrest toughness for gas pipeline steels in terms of Charpy vee-notched (CVN) impact energy. Practice showed that the BTCM is viable for pipeline grades X65 and below, but issues emerged for higher grades. Thus, different corrections to improve the BTCM and alternative methods have been proposed over the years. This includes the CVN energy-based corrections, the drop-weight tear test (DWTT) energy-based correlations, the crack-tip opening angle (CTOA) criteria, and finite element methods. These approaches are reviewed and discussed in this paper, as well as the newest technology developed to determine fracture arrest toughness for high-strength pipeline steels.

scholarly journals Towards a field test for fracture propagation propensity in weak snowpack layers

2006 ◽  
Vol 52 (176) ◽  
pp. 164-168 ◽  
Author(s):  
Dave Gauthier ◽  
Bruce Jamieson
Keyword(s):  
Field Test ◽  
Fracture Propagation ◽  
Field Tests ◽  
Fracture Initiation ◽  
Bimodal Distribution ◽  
Test Method ◽  
Flexural Wave ◽  
Weak Layer ◽  
Columbia Mountains ◽  
Initiation And Propagation

AbstractSlab avalanche release requires fracture initiation and propagation in a weak snowpack layer. While field tests of weak-layer strength are useful for fracture initiation, the challenge remains to find a verified field test for fracture propagation. We introduce the two current versions of a field test for fracture propagation propensity, and report results of testing conducted in the Columbia Mountains of British Columbia, Canada, during the winter of 2005. By extending the column of a stability test approximately 3 m in the downslope direction, the test method allows for the development of a flexural wave in the slab, and thereby maintains the contribution of this wave and the associated weak-layer collapse to the fracture process. Fracture lengths collected on a day and location where the propagation propensity of the snowpack was locally high show a bimodal distribution, with approximately 50% of observed fractures similar to those collected in stable snowpacks, and approximately 50% with much longer fracture lengths.

scholarly journals Model of Fracture Propagation in Hydraulic Isolation of the Wellbore

2020 ◽  
Vol 18 (1) ◽  
pp. 36-49
Author(s):  
V. N. Lapin
Keyword(s):  
Propagation Velocity ◽  
Numerical Experiments ◽  
Fracture Propagation ◽  
Fracture Initiation ◽  
Reservoir Pressure ◽  
Initiation And Propagation ◽  
The Stability ◽  
Prestressed State ◽  
Cement Plug

A model of fracture initiation and propagation along the boundary of a cement plug and a steel casing in a plugged wellbore is proposed. The model allows predicting the conditions of hydraulic isolation failure of a cement plug induced by reservoir pressure. The model describes the stress state of the cement and it’s breakaway from the steel casing caused by the pressure of the pore fluid flowing into the fracture. Numerical experiments show that the fracture propagation velocity and the stability of the hydraulic isolation are sensitive to the reservoir pressure and to the prestressed state of the cement. It is shown also that the quality of cement adhesion to steel and the size of the initial cementing defects have little effect on the initiation conditions and fracture propagation velocity.

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