Numerical simulation of fracture initiation, propagation and fracture complexity in the presence of multiple perforations

2020 ◽  
Vol 83 ◽  
pp. 103486 ◽  
Author(s):  
Qiang Wang ◽  
Yongquan Hu ◽  
Jinzhou Zhao ◽  
Shengnan Chen ◽  
Chenghao Fu ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Fracture Initiation ◽  
Fracture Complexity

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.

Experimental and Numerical Study of Ductile Fracture Initiation in Aluminum 6061-T6

2015 ◽  
Author(s):  
W. Rekik ◽  
O. Ancelet ◽  
C. Gardin
Keyword(s):  
Numerical Simulation ◽  
Ductile Fracture ◽  
Void Growth ◽  
Numerical Study ◽  
Micromechanical Model ◽  
Stress Triaxiality ◽  
Fracture Initiation ◽  
Compact Tension ◽  
Growth Ratio ◽  
Ductile Fracture Initiation

This work deals with the characterization of ductile damage in Aluminum 6061-T6 alloy. In this paper we discuss the stress triaxiality effect on the initiation and the evolution of damage through a sequence of tensile tests conducted on round specimens with different rate of trixialities and tearing tests on precracked Compact Tension specimens. Scattering of ductility and toughness values was highlighted between the three characteristic directions studied in this topic. Based on the experimental results, numerical simulation has been performed in order to analyze and predict ductile fracture initiation of this aluminum alloy by simulating void growth according to the Rice-Tracey micromechanical model. The numerical simulation was conducted in two steps: first the critical void growth ratio (R / R0)c was evaluated for tensile cylindrical specimens with different degrees of triaxiality and then used to analyze crack growth initiation on Compact Tension specimen. Due to the Al-6061-T6 highly sensitivity to triaxiality, a necessary adaptation of the Rice-Tracey model’s coefficient was made.

Numerical Simulation and Laboratory Experiments of Hydraulic Fracturing of Highly Deviated Well

2013 ◽  
Vol 275-277 ◽  
pp. 278-281 ◽  
Author(s):  
Hai Yan Zhu ◽  
Jing Gen Deng ◽  
Song Yang Li ◽  
Zi Jian Chen ◽  
Wei Yan ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Hydraulic Fracturing ◽  
Fracture Initiation ◽  
Element Model ◽  
Simulation Method ◽  
Horizontal Stress ◽  
Initiation Point ◽  
Strength Failure ◽  
Fluid Penetration ◽  
Maximum Horizontal Stress

Considering the combined action of the fluid penetration and the casing, the seepage coupled deformation finite element model of the highly deviated casing perforation well is established by using the tensile strength failure criterion and applied on the BZ25-1 oil filed. The results show that the increasing of the perforation angle and the well azimuth and the decreasing of the inclination would lead to a higher fracture initiation pressure. The fracture initiation point always locates on the wellbore face when the influence of the casing is considered. When the casing is ignored: when the perforation angle is 0°-45°, the fracture initiation point locates on the root of the tunnel; when the angle is 45°-90°, the fracture initiation point may be on the wellbore face or the perforation biased toward the maximum horizontal stress direction; when the angle is near to 90°, the hydraulic fracturing difficultly fractures the rock through the perforation tunnels. The laboratory hydraulic fracturing simulation experiments of 45° deviated well are carried through 400mm3 cement specimen so as to obtain the fracture initiation point and geometric shape under different perforation angles, the results verify the accuracy of the numerical simulation method.

scholarly journals Analysis of Crack Initiation and Propagation Thresholds of Inclined Cracks under High-Pressure Grouting in Ordovician Limestone

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 360
Author(s):  
Bin Xu ◽  
Shuning Dong ◽  
Shangxian Yin ◽  
Shuxia Li ◽  
Yanling Xu ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Mixed Mode ◽  
Crack Opening ◽  
Pressure Coefficient ◽  
Water Channel ◽  
Fracture Initiation ◽  
Simulation Software ◽  
Mode I ◽  
Ordovician Limestone ◽  
Grouting Pressure

Control of the grouting pressure within the critical grouting pressure for crack propagation in Ordovician limestone can not only ensure grout penetration length, but also prevent the risk of creating an artificial water channel. Based on the fracture mechanics theory, a formula was proposed to calculate the critical grouting pressure of mixed mode I-II cracks in Ordovician limestone. The necessary conditions for tilted crack opening, the rationality of the existing empirical value of the maximum allowable grouting pressure was investigated based on the mechanical model. The RFPA2D-Flow numerical simulation software was used to evaluate the deduced theory. The research results show that the deduced theoretical calculation formula of the critical grouting pressure agrees with the numerical simulation results; when the mixed mode I-II fracture initiation occurs, the grouting pressure exceeds the perpendicular stress of the overlying rock; the greater the density of the overlying rock mass, the greater the value of grouting pressure for fracture initiation; when the side pressure coefficient was ≥1, crack dip angle increased and the grouting pressure for fracture initiation tended to decrease; and the empirical grouting pressure at the maximum allowable grouting pressure is 2.0–2.5 pw, which will not cause propagation and failure of the existing crack.

scholarly journals Extension of grouting-induced splitting fractures in materials similar to coal rocks containing prefabricated fractures

2020 ◽  
Author(s):  
Chao Liu ◽  
Xiaosheng Huang ◽  
Wenping Yue ◽  
Chao Zhang
Keyword(s):  
Numerical Simulation ◽  
Decisive Role ◽  
Fracture Initiation ◽  
Whole Process ◽  
Physical Experiments ◽  
Fracture Splitting ◽  
Orienting Effect ◽  
Similar Materials ◽  
Coal Rock ◽  
Extension Direction

Abstract To reveal the influence of prefabricated fractures (PFs) with different parameters on the extension of grouting-induced splitting fractures, a combination of numerical simulation and physical experiments were used to carry out grouting trials on similar materials to coal rock. The RFPA software was used to simulate the whole process of fracture initiation and expansion of coal rock with PFs during grouting. In the experiment, acoustic emission (AE) technology was used to monitor the extension process of grouting-induced splitting fractures. The results demonstrated that when the PFs do not intersect with the grouting holes, the extension of grouting-induced splitting fractures in rocks containing PFs experienced four stages: splitting and penetrating, slurry filling, fracture splitting and splitting extension. PFs have an orienting effect on the direction of grouting fracture extension and the size of the PFs influenced the extension of the grouting-induced splitting fractures: the larger the size, the easier the surrounding rocks were ruptured, the easier the connection was formed of channels between the grouting-induced splitting fractures and the PFs were formed, and the more complex the secondary splitting pattern in the PFs. This indicated that the angle of PFs played a decisive role in determining the extension direction of grouting-induced splitting fractures. The extension of grouting-induced splitting fractures during grouting of rock mass with different parameters is revealed by numerical simulation and experimental results.

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