scholarly journals Study on Synchronous Propagation Behavior of Hydraulic Fractures and Cementing Interfacial Cracks during Fracturing of Shale Horizontal Wells

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 4) ◽  
Author(s):  
Fuping Feng ◽  
Xu Han ◽  
Yu Suo ◽  
Heyuan Wang ◽  
Qinyou Ye ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Hydraulic Fracturing ◽  
Large Scale ◽  
Propagation Model ◽  
Displacement Discontinuity ◽  
Hydraulic Fractures ◽  
Cement Slurry ◽  
Interface Failure ◽  
Propagation Length ◽  
Interfacial Cracks

Abstract Large-scale staged hydraulic fracturing stimulation technology is an effective method to increase shale oil and gas recovery. However, cracks will appear along with the cementing interface and expand under the drive of fluid while hydraulic fracturing, failing wellbore sealing. To solve this problem, the synchronous propagation model of hydraulic fractures and cementing interfacial cracks in hydraulic fracturing is established. The Newton iteration method and displacement discontinuity method are used to solve the propagation length of each fracture, and the effects of cement sheath parameters and fracture parameters on the interface failure range are studied. The results show that when multiple hydraulic fractures expand, the interfacial cracks are also affected by “stress shadow,” offering an asymmetric expansion, and the cementing interfacial cracks in the area between hydraulic fractures are easier to expand. The failure range of interface between the hydraulic fractures expands rapidly if the cement elastic modulus increases from 5 GPa to 10 GPa; while the cement elastic modulus is higher than 10 GPa, the failure area is mainly affected by the number of hydraulic fractures; the failure range is not affected by the number of hydraulic fractures if the hydraulic fracture spacing is less than 10 m or more than 30 m; while the crack spacing is between 10 m and 30 m, the more the number of hydraulic fractures, the easier it is to cause the interface failure range to increase and connect. The research results can provide a theoretical basis for the optimization of cement slurry systems and fracturing parameters.

Modeling of fiber-optic strain responses to hydraulic fracturing

Geophysics ◽  
2020 ◽  
Vol 85 (6) ◽  
pp. A45-A50
Author(s):  
Zhishuai Zhang ◽  
Zijun Fang ◽  
Joe Stefani ◽  
James DiSiena ◽  
Dimitri Bevc ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Strain Rate ◽  
Fiber Optic ◽  
Low Frequency ◽  
Displacement Discontinuity ◽  
Hydraulic Fractures ◽  
Quantitative Interpretation ◽  
Current Application ◽  
Monitoring Well ◽  
And Inversion

We modeled cross-well strain/strain rate responses of fiber optic sensing, including distributed strain sensing (DSS) and low-frequency distributed acoustic sensing (DAS), to hydraulic stimulation. DSS and low-frequency DAS have been used to measure strain or the strain rate to characterize hydraulic fractures. However, the current application of DSS/DAS is limited to acquisition, processing, and qualitative interpretations. The lack of geomechanical models hinders the development of the technology toward quantitative interpretation and inversion. We have developed a strategy to use the displacement discontinuity method to model the strain field around kinematically propagating fractures. For a horizontal monitoring well, modeling results were able to explain the heart-shaped extending pattern before a fracture hit, the polarity flip due to fracture interaction during stimulation, and the V-shaped pattern when a fracture does not intersect with the monitoring well. For a vertical monitoring well, modeling shows the different characters of strain rate responses when a fracture is near and far away from a vertical monitoring well. We also investigated the effects of fractures with various geometries such as elliptic and layered fractures. We compared and verified the modeling with field data from the Hydraulic Fracturing Test Site 2, a research experiment performed in the Permian Basin. Our modeling work can be used to identify patterns in field observations. The results also help to improve acquisition design and lay the groundwork for quantitative interpretation and inversion.

scholarly journals Experimental and Numerical Evaluation of Hydraulic Fracturing under High Temperature and Embedded Fractures in Large Concrete Samples

Water ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 3171
Author(s):  
Liangliang Guo ◽  
Zihong Wang ◽  
Yanjun Zhang ◽  
Zhichao Wang ◽  
Haiyang Jiang
Keyword(s):  
Numerical Simulation ◽  
High Temperature ◽  
Hydraulic Fracturing ◽  
Laboratory Test ◽  
High Temperatures ◽  
Large Scale ◽  
Hydraulic Fractures ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Fracture Density

In order to study the mechanism of hydraulic fracturing in enhanced geothermal systems, we analyzed the influence of high temperatures and embedded fractures on the initiation and propagation of hydraulic fractures using a laboratory test and numerical simulation. The analysis was conducted via large-scale true triaxial hydraulic fracturing tests with acoustic emission monitoring. Moreover, we discussed and established the elastic-plastic criterion of hydraulic fracturing initiation. The corresponding fracturing procedure was designed and embedded into the FLAC3D software. Then, a numerical simulation was conducted and compared with the laboratory test to verify the accuracy of the fracturing procedure. The influence of high temperatures on hydraulic fracturing presented the following features. First, multi-fractures were created, especially in the near-well region. Second, fracturing pressure, extension pressure, and fracture flow resistance became larger than those at room temperature. 3D acoustic fracturing emission results indicated that the influence of the spatial distribution pattern of embedded fractures on hydraulic fracturing direction was larger than that of triaxial stress. Furthermore, the fracturing and extension pressures decreased with the increase of embedded fracture density. For hydraulic fracturing in a high temperature reservoir, a plastic zone was generated near the borehole, and this zone increased as the injection pressure increased until the well wall failed.

Simultaneous Multifracture Treatments: Fully Coupled Fluid Flow and Fracture Mechanics for Horizontal Wells

SPE Journal ◽  
2014 ◽  
Vol 20 (02) ◽  
pp. 337-346 ◽  
Author(s):  
Kan Wu ◽  
Jon E. Olson
Keyword(s):  
Fluid Flow ◽  
Fracture Propagation ◽  
Horizontal Wells ◽  
Gas Production ◽  
Propagation Model ◽  
Displacement Discontinuity ◽  
Hydraulic Fractures ◽  
Multiple Fractures ◽  
Frictional Pressure Drop ◽  
Horizontal Wellbore

Summary Successfully creating multiple hydraulic fractures in horizontal wells is critical for unconventional gas production economically. Optimizing the stimulation of these wells will require models that can account for the simultaneous propagation of multiple, potentially nonplanar, fractures. In this paper, a novel fracture-propagation model (FPM) is described that can simulate multiple-hydraulic-fracture propagation from a horizontal wellbore. The model couples fracture deformation with fluid flow in the fractures and the horizontal wellbore. The displacement discontinuity method (DDM) is used to represent the mechanics of the fractures and their opening, including interaction effects between closely spaced fractures. Fluid flow in the fractures is determined by the lubrication theory. Frictional pressure drop in the wellbore and perforation zones is taken into account by applying Kirchoff's first and second laws. The fluid-flow rates and pressure compatibility are maintained between the wellbore and the multiple fractures with Newton's numerical method. The model generates physically realistic multiple-fracture geometries and nonplanar-fracture trajectories that are consistent with physical-laboratory results and inferences drawn from microseismic diagnostic interpretations. One can use the simulation results of the FPM for sensitivity analysis of in-situ and fracture treatment parameters for shale-gas stimulation design. They provide a physics-based complex fracture network that one can import into reservoir-simulation models for production analysis. Furthermore, the results from the model can highlight conditions under which restricted width occurs that could lead to proppant screenout.

scholarly journals An Analytical Framework for Stress Shadow Analysis During Hydraulic Fracturing – Applied to the Bakken Formation, Saskatchewan, Canada

2021 ◽  
Author(s):  
Mostafa Gorjian ◽  
Sepidehalsadat Hendi ◽  
Christopher D. Hawkes
Keyword(s):  
Hydraulic Fracturing ◽  
Large Scale ◽  
Shear Failure ◽  
Microseismic Monitoring ◽  
Natural Fracture ◽  
Hydraulic Fractures ◽  
Natural Fractures ◽  
Bakken Formation ◽  
Stress Shadow

Abstract. This paper presents selected results of a broader research project pertaining to the hydraulic fracturing of oil reservoirs hosted in the siltstones and fine grained sandstones of the Bakken Formation in southeast Saskatchewan, Canada. The Bakken Formation contains significant volumes of hydrocarbon, but large-scale hydraulic fracturing is required to achieve economic production rates. The performance of hydraulic fractures is strongly dependent on fracture attributes such as length and width, which in turn are dependent on in-situ stresses. This paper reviews methods for estimating changes to the in-situ stress field (stress shadow) resulting from mechanical effects (fracture opening), poro-elastic effects, and thermo-elastic effects associated with fluid injection for hydraulic fracturing. The application of this method is illustrated for a multi-stage hydraulic fracturing operation, to predict principal horizontal stress magnitudes and orientations at each stage. A methodology is also presented for using stress shadow models to assess the potential for inducing shear failure on natural fractures. The results obtained in this work suggest that thermo and poro-elastic stresses are negligible for hydraulic fracturing in the Bakken Formation of southeast Saskatchewan, hence a mechanical stress shadow formulation is used for analyzing multistage hydraulic fracture treatments. This formulation (and a simplified version of the formulation) predicts an increase in instantaneous shut-in pressure (ISIP) that is consistent with field observations (i.e., ISIP increasing from roughly 21.6 MPa to values slightly greater than 26 MPa) for a 30-stage fracture treatment. The size of predicted zones of shear failure on natural fractures are comparable with the event clouds observed in microseismic monitoring when assumed values of 115°/65° are used for natural fracture strike/dip; however, more data on natural fracture attributes and more microseismic monitoring data for the area are required before rigorous assessment of the model is possible.

scholarly journals Developing Upscaling Approach for Swarming Hydraulic Fractures Observed at Hydraulic Fracturing Test Site through Multiscale Simulations

SPE Journal ◽  
2021 ◽  
pp. 1-15
Author(s):  
Wei Fu ◽  
Joseph P. Morris ◽  
Pengcheng Fu ◽  
Jixiang Huang ◽  
Christopher S. Sherman ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Hydraulic Fracture ◽  
Fracture Propagation ◽  
Test Site ◽  
Hydraulic Fractures ◽  
Single Fracture ◽  
Multiscale Simulations ◽  
Field Scale ◽  
Propagation Length ◽  
Microseismic Data

Summary This work aims to address a challenge posed by recent observations of tightly spaced hydraulic fractures in core samples from the hydraulic fracturing test site (HFTS) in the Middle Wolfcamp Formation. Many fractures in retrieved cores have subfoot spacing, which is at odds with conventional models in which usually one hydraulic fracture is initiated per cluster. Models assuming a single fracture at each cluster, although a common practice, often predict excessive fracture propagation that is inconsistent with microseismic observation. Here, we aim to develop a numerical approach to effectively account for densely spaced hydraulic fractures in field-scale simulations. Because it is impractical to explicitly model all aforementioned fractures, we develop a new upscaling law that enables existing simulation tools to predict reservoir response to fracture swarms. The upscaling law is derived based on an energy equivalence argument and validated through multiscale simulations using a high-fidelity code, GEOS. The swarming fractures are first modeled with a spacing that is much smaller than the cluster spacing; these fractures are then approximated by an upscaled, single fracture based on the proposed upscaling law. The upscaled fracture is shown to successfully match the energy input rate and produce the total fracture aperture and average propagation length of the explicitly simulated swarm. Afterward, the upscaling approach is further implemented in 3D field-scale simulations and validated against the HFTS microseismic data of a horizontal well. Our results show that hydraulic fracture swarming can significantly affect fracture propagation behaviors compared with the propagation of single fractures as assumed by conventional modeling approaches. Under the considered situations, the conventional treatment yields fast propagation speed that far exceeds that indicated by the microseismic data. We also illustrate that this discrepancy can be reduced readily through the implementation of the upscaling law. Our results demonstrate the importance of accounting for the fracture swarming effect in field-scale simulations and the efficacy of this approach to enable realistic predictions of reservoir responses to fracture swarms, without the need to model tightly spaced fractures individually.

scholarly journals Application of Symmetry Law in Numerical Modeling of Hydraulic Fracturing by Finite Element Method

Symmetry ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1122 ◽  
Author(s):  
Shanhui Sun ◽  
Meihua Zhou ◽  
Wei Lu ◽  
Afshin Davarpanah
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Hydraulic Fracturing ◽  
Fluid Pressure ◽  
Hydraulic Fractures ◽  
Propagation Length ◽  
Fracture Fluid ◽  
Fracture Opening ◽  
Influential Parameters ◽  
Element Method

In this paper, influential parameters on the hydraulic fracturing processes in porous media were investigated. Besides, the simultaneous stimulation of solids, fluids and fractures geomechanical equations were numerically analyzed as a developed 3D model. To do this, the Abacus software was used as a multi-objective program to solve the physical-mechanical symmetry law governing equations, according to the finite element method. Two different layers, A (3104–2984 m) and B (4216–4326 m), are considered in the model. According to the result of this study, the maximum fracture opening length in the connection of the wall surface is 10 and 9 mm for layer B and layer A, respectively. Moreover, the internal fracture fluid pressure for layer B and layer A is 65 and 53 Mpa. It is indicated that fracture fluid pressure reduced with the increase in fracture propagation length. Consequently, the results of this study would be of benefit for petroleum industries to consider several crucial geomechanical characteristics in hydraulic fractures simultaneously as a developed numerical model for different formation layers to compare a comprehensive analysis between each layer.

scholarly journals Experimental and Numerical Investigation on Basic Law of Dense Linear Multihole Directional Hydraulic Fracturing

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-19
Author(s):  
Xin Zhang ◽  
Yuqi Zhang
Keyword(s):  
Hydraulic Fracturing ◽  
Hydraulic Fracture ◽  
Large Scale ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
In Situ Stress ◽  
Hydraulic Fractures ◽  
Directional Hydraulic Fracturing ◽  
Basic Law

Using the dense linear multihole to control the directional hydraulic fracturing is a significant technical method to realize roof control in mining engineering. By combining the large-scale true triaxial directional hydraulic fracturing experiment with the discrete element numerical simulation experiment, the basic law of dense linear holes controlling directional hydraulic fracturing was studied. The results show the following: (1) Using the dense linear holes to control directional hydraulic fracturing can effectively form directional hydraulic fractures extending along the borehole line. (2) The hydraulic fracturing simulation program is very suitable for studying the basic law of directional hydraulic fracturing. (3) The reason why the hydraulic fracture can be controlled and oriented is that firstly, due to the mutual compression between the dense holes, the maximum effective tangential tensile stress appears on the connecting line of the drilling hole, where the hydraulic fracture is easy to be initiated. Secondly, due to the effect of pore water pressure, the disturbed stress zone appears at the tip of the hydraulic fracture, and the stress concentration zone overlaps with each other to form the stress guiding strip, which controls the propagation and formation of directional hydraulic fractures. (4) The angle between the drilling line and the direction of the maximum principal stress, the in situ stress, and the hole spacing has significant effects on the directional hydraulic fracturing effect. The smaller the angle, the difference of the in situ stress, and the hole spacing, the better the directional hydraulic fracturing effect. (5) The directional effect of synchronous hydraulic fracturing is better than that of sequential hydraulic fracturing. (6) According to the multihole linear codirectional hydraulic fracturing experiments, five typical directional hydraulic fracture propagation modes are summarized.

scholarly journals Fully three-dimensional propagation model of horizontal borehole hydraulic fractures in strata under the effect of bedding planes

2018 ◽  
Vol 36 (5) ◽  
pp. 1189-1209 ◽  
Author(s):  
Bingxiang Huang ◽  
Jiangwei Liu
Keyword(s):  
Hydraulic Fracturing ◽  
Hydraulic Fracture ◽  
Three Dimensional ◽  
Fracture Morphology ◽  
Bedding Plane ◽  
Propagation Model ◽  
Tensile Failure ◽  
Propagation Mechanism ◽  
Hydraulic Fractures ◽  
Bedding Planes

The bedding plane effect will occur when hydraulic fractures propagate to the bedding plane in sedimentary strata, resulting in the “≠,” “工,” or “/” shaped fracture morphology. Based on previous physical experiments results, this article analyzed the mecroscopic propagation mechanism of tensile failure and the mechanical conditions for main hydraulic fracture and the bedding plane fracture propagating, proposing the criteria for hydraulic fracture to penetrate through the bedding plane. A fully three-dimensional model of hydraulic fracture morphology in horizontal borehole hydraulic fracturing is established with the vertical water flow, water leak-off, and bedding plane effect taken into consideration. Basic equations of continuity, pressure decline, hydraulic fracture morphology, and others are solved. After that, true triaxial hydraulic fracturing experiments with samples containing bedding planes are conducted to verify the aperture, length, width, and height of hydraulic fractures in this model. The model is proved to be accurate and reliable.

scholarly journals Experimental Study on Crack Extension Rules of Hydraulic Fracturing Based on Simulated Coal Seam Roof and Floor

Geofluids ◽  
2022 ◽  
Vol 2022 ◽  
pp. 1-12
Author(s):  
Lu Gao ◽  
Xiangtao Kang ◽  
Gun Huang ◽  
Ziyi Wang ◽  
Meng Tang ◽  
...  
Keyword(s):  
Coal Seam ◽  
Hydraulic Fracturing ◽  
Principal Stress ◽  
Hydraulic Fracture ◽  
Large Scale ◽  
Confining Pressure ◽  
Maximum Principal Stress ◽  
Hydraulic Fractures ◽  
True Triaxial ◽  
Extension Direction

Hydraulic fracturing can increase the fracture of coal seams, improve the permeability in the coal seam, and reduce the risk of coal and gas outburst. Most of the existing experimental specimens are homogeneous, and the influence of the roof and floor on hydraulic fracture expansion is not considered. Therefore, the hydraulic fracturing test of the simulated combination of the coal seam and the roof and floor under different stress conditions was carried out using the self-developed true triaxial coal mine dynamic disaster large-scale simulation test rig. The results show that (1) under the condition of triaxial unequal pressure, the hydraulic fractures are vertical in the coal seam, and the extension direction of hydraulic fractures in the coal seam will be deflected, with the increase of the ratio of the horizontal maximum principal stress to the horizontal minimum principal stress. The angle between the extension direction of the hydraulic fracture and the horizontal maximum principal stress decreases. (2) Under the condition of triaxial equal confining pressure, the extension of hydraulic fractures in the coal seam are random, and the hydraulic fracture will expand along the dominant fracture surface and form a unilateral expansion fracture when a crack is formed. (3) When the pressure in one direction is unloaded under the condition of the triaxial unequal pressure, the hydraulic fractures in the coal seam will reorientate, and the cracks will expand in the direction of the decreased confining pressure, forming almost mutually perpendicular turning cracks.

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