Study on the Mechanisms of Hydraulic Fracturing Crack Initiation and Propagating

2012 ◽  
Vol 188 ◽  
pp. 101-105
Author(s):  
G. Li ◽  
Lian Chong Li ◽  
Chun An Tang
Keyword(s):  
Crack Initiation ◽  
Hydraulic Fracturing ◽  
Water Pressure ◽  
Influencing Factor ◽  
Injection Rate ◽  
Initial Water ◽  
Core Content ◽  
Minimum Principal Stress ◽  
Analysis Experiment ◽  
Stress Plane

The hydraulic fracturing technology is widely used in the forefront of engineering and production, the mechanisms of hydraulic fracturing crack initiation and propagating are the core content of hydraulic fracturing research. We explain the tensile mechanism of rock under the hydraulic effect, give the two forms of the crack initial water pressure (total stress and effective stress expression) in detail. From the results of theoretical analysis, experiment and numerical simulation we discriminate the mechanisms of hydraulic fracturing crack propagating, which show that cracks are distributed in the minimum principal stress plane under different stress situations. Furthermore, the injection rate is an important influencing factor. The study is valuable to the engineering design of hydraulic fracturing.

scholarly journals Mechanisms of Crack Initiation and Propagation in Dense Linear Multihole Directional Hydraulic Fracturing

2019 ◽  
Vol 2019 ◽  
pp. 1-15
Author(s):  
Jiangwei Liu ◽  
Changyou Liu ◽  
Qiangling Yao
Keyword(s):  
Rock Mass ◽  
Crack Initiation ◽  
Hydraulic Fracturing ◽  
Principal Stress ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Crack Initiation And Propagation ◽  
Initiation And Propagation ◽  
Coal Rock

Artificially fracturing coal-rock mass serves to form break lines therein, which is related to the distribution of cracked boreholes. For this reason, we use physical experiments and numerical simulations to study the crack initiation and propagation characteristics of dense linear multihole drilling of fractured coal-rock mass. The results indicate that only in the area between the first and last boreholes can hydraulic fracturing be controlled by dense linear multihole expansion along the direction of the borehole line; in addition, no directional fracturing occurs outside the drilling section. Upon increasing parameters such as the included angle θ between the drilling arrangement line and the maximum principal stress σ1 direction, the drilling spacing D, the difference Δσ in principal stress, etc., the effect of directional fracture is gradually weakened, and the hydraulic fractures reveal three typical cracking modes: cracking along the borehole line, bidirectional cracking (along the borehole line and perpendicular to the minimum principal stress σ3), and cracking perpendicular to σ3. Five propagation modes also appear in sequence: propagating along borehole line, step-like propagation, S-shaped propagation, bidirectional propagation (along the borehole line and perpendicular to σ3), and propagation perpendicular to σ3. Based on these results, we report the typical characteristics of three-dimensional crack propagation and discuss the influence of the gradient of pore water pressure. The results show clearly that crack initiation and propagation are affected by both the geostress field and the pore water pressure. The pore water pressure will exhibit a circular-local contact-to-integral process during crack initiation and expansion. When multiple cracks approach, the superposition of pore water pressure at the tip of the two cracks increases the damage to the coal rock, which causes crack reorientation and intersection.

Simulation of proppant transport and fracture plugging in the framework of a radial hydraulic fracturing model

2020 ◽  
Vol 35 (6) ◽  
pp. 325-339
Author(s):  
Vasily N. Lapin ◽  
Denis V. Esipov
Keyword(s):  
Numerical Model ◽  
Hydraulic Fracturing ◽  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Injection Rate ◽  
Fluid Injection ◽  
Subtraction Technique ◽  
Gas Industry ◽  
Proppant Transport ◽  
Hydraulic Fracture Propagation

AbstractHydraulic fracturing technology is widely used in the oil and gas industry. A part of the technology consists in injecting a mixture of proppant and fluid into the fracture. Proppant significantly increases the viscosity of the injected mixture and can cause plugging of the fracture. In this paper we propose a numerical model of hydraulic fracture propagation within the framework of the radial geometry taking into account the proppant transport and possible plugging. The finite difference method and the singularity subtraction technique near the fracture tip are used in the numerical model. Based on the simulation results it was found that depending on the parameters of the rock, fluid, and fluid injection rate, the plugging can be caused by two reasons. A parameter was introduced to separate these two cases. If this parameter is large enough, then the plugging occurs due to reaching the maximum possible concentration of proppant far from the fracture tip. If its value is small, then the plugging is caused by the proppant reaching a narrow part of the fracture near its tip. The numerical experiments give an estimate of the radius of the filled with proppant part of the fracture for various injection rates and leakages into the rock.

The Prediction of Wellhead Pressure of Hydraulic Fracturing

2013 ◽  
Vol 405-408 ◽  
pp. 3323-3327
Author(s):  
Feng Shen ◽  
Zhou Wu ◽  
Nan Wang ◽  
Yong Ming Li
Keyword(s):  
Hydraulic Fracturing ◽  
Influencing Factor ◽  
Case Analysis ◽  
Fluid Density ◽  
Interaction Theory ◽  
Breakdown Pressure ◽  
Two Phase ◽  
Wellhead Pressure ◽  
Computing Method ◽  
Calculation Software

The accurate prediction of wellhead pressure in process of hydraulic fracturing is a keypoint to guide the design and construction of the fracturing, and does help in choosing appropriate wellhead equipment and pipeline. This paper calculates the formation breakdown pressure by using a self-made formation stress calculation software, analyzes perforation friction and near-wellbore friction on the basis of Michael theory, eatablishes a model of wellbore friction through Darcy-Weisbach equation and the momentum interaction theory of two-phase flow, and according to the composition of wellhead pressure, makes calculation software which can also analyze the influencing factor of wellbore friction, such as delivery rate, pipe diameter, fracturing fluid density and proppant size. Finally, case analysis verifies the accuracy of the computing method.

scholarly journals Comparison of Local Load Influence on Crack Evolution of Coal and Briquette Coal Samples

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Hongbao Zhao ◽  
Tao Wang ◽  
Huan Zhang ◽  
Ziqiang Wei
Keyword(s):  
Crack Initiation ◽  
Crack Growth ◽  
Influencing Factor ◽  
Local Load ◽  
End Effect ◽  
Crack Evolution ◽  
Systematic Analysis ◽  
Effect Factor ◽  
Factors Influencing ◽  
Major Factors

Taking raw coal and briquette coal samples with preset center holes as research objects, this paper makes a systematic analysis and research of crack evolution laws of the two different coal samples under the local load. The results show that the raw coal and briquette coal samples are different mainly in number, dimension, and complexity of the internal microstructures, so it is not right to replace raw coal with briquette coal when performing observational study of the crack evolution of microstructures; under the effect of local load, local property, randomness of crack initiation position, and crack initiation stress of raw coal samples are greater than those of briquette coal samples; law of instantaneous maximum effective cut-through rate of raw coal samples is more complex than that of briquette coals; under the effect of uniformly distributed load, end effect factor Fe, sample microstructure influencing factor Fs, and preset center hole factor Fh are the major factors influencing crack growth, among which the amplified end effect factor Fe and sample microstructure influencing factor Fs are dominant factors; under the effect of local load, local load influencing factor Fp, end effect factor Fe, sample microstructure influencing factor Fs, and preset center hole factor Fs are the major factors influencing crack growth, among which the local load influencing factor Fp, end effect factor Fe, and sample microstructure influencing factor Fs are dominant factors. Compared with briquette coal samples, raw coal samples are more sensitive to influencing factors, such as local load influencing factor Fp, end effect factor Fe, sample microstructure influencing factor Fs, and preset center hole factor Fh, and can aggravate the influence of these factors on the crack growth; the paper also puts forward a method for describing local load based on a coupling mechanical model of uniaxial compression and local shear.

scholarly journals Effect of Water Infiltration, Injection Rate and Anisotropy on Hydraulic Fracturing Behavior of Granite

2018 ◽  
Vol 52 (2) ◽  
pp. 575-589 ◽  
Author(s):  
Li Zhuang ◽  
Kwang Yeom Kim ◽  
Sung Gyu Jung ◽  
Melvin Diaz ◽  
Ki-Bok Min
Keyword(s):  
Hydraulic Fracturing ◽  
Injection Rate ◽  
Water Infiltration ◽  
Effect Of Water

scholarly journals Experimental Study on Hydraulic Fracturing of High Asphalt Concrete Core Rock-Fill Dam

2019 ◽  
Vol 9 (11) ◽  
pp. 2285 ◽  
Author(s):  
Zhengxing Wang ◽  
Jutao Hao ◽  
Jian Yang ◽  
Yan Cao ◽  
Xiulin Li ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Hydraulic Fracture ◽  
Asphalt Concrete ◽  
Water Pressure ◽  
Concrete Core ◽  
Mix Proportion ◽  
Local Shear ◽  
Test Result ◽  
Rule Out ◽  
Shear Dilatancy

In this paper, we experiment on the hydraulic fracturing of asphalt concrete with a voids content higher than 3%, which has arisen from the possible local shear dilatancy of Quxue asphalt’s core wall of concrete core dam, the highest one of the sort constructed in the world. The model test has shown that under the sole water pressure 0.13 MPa—relevant to the pressure where the dilatancy could appear at core wall of Quxue dam—the asphalt concrete with a voids content of 3.5% underwent hydraulic fracturing. Furthermore, the asphalt concrete with a voids content of 3.0% was tested for nearly 500 h and no sign of hydraulic fracturing was found, which again confirmed the threshold requirement for a 3% voids content to the impervious asphalt concrete to the hydraulic fracture concern. According to the analysis of the test result, the theory of fracture mechanics could be applied to the hydraulic fracture of asphalt concrete with a voids content between 3.4~4.0%, which behaved during hydraulic fracturing like a quasi-brittle material, similar to concrete. Because the hydraulic fracturing could occur in the shear dilatant asphalt concrete, a proper mix proportion of asphalt concrete to a project with adverse stress state should be carefully designed to rule out the possibility of shear dilatancy.

The Study of Fractured Rock Mass Instability of the Law Based on the Hydraulic Fracturing

2012 ◽  
Vol 496 ◽  
pp. 538-541
Author(s):  
Zhi Qiang Kang ◽  
Wein Jie Li ◽  
Yu Bo Jia
Keyword(s):  
Rock Mass ◽  
Hydraulic Fracturing ◽  
Hydraulic Fracture ◽  
Fractured Rock ◽  
Water Pressure ◽  
Overburden Rock ◽  
Fractured Rock Mass ◽  
Water Seepage ◽  
Vertical Loading ◽  
The Law

Fractured rock mass, Hydraulic fracture, RFPA2D-Flow, Instability of the law. Abstract. Based on the theory of fluid-solid coupling, Studying on the effect of permeability about damage and stress, Analysis of influence factors what hydraulic fracturing process, fracture propagation pattern, and influencing factors including shape and magnitude of inlet hole, stress conditions, and specimen strength were investigated. Application of rock failure process analysis software coupled seepage-stress F-RFPA2D, numerical simulated rock water pressure to cause crack rupture instability process, research the fracture law of the rock on water pressure and vertical loading. Combine similar physical experiment model, contrast analysis of two broken results and stress-strain curve, reveals instability mechanical behavior of rock hydraulic fracture process. Obtain deep mining in the process of mine water seepage and water extrude, overburden rock crack up, expand, water seepage, water extrude, instability rupture process rules.

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