DEM modeling of hydraulic fracturing in fractured shale formation: Effect of inherent anisotropy and induced anisotropy

2016 ◽  
pp. 247-253 ◽  
Author(s):  
K Duan ◽  
C Kwok
Keyword(s):  
Hydraulic Fracturing ◽  
Induced Anisotropy ◽  
Inherent Anisotropy ◽  
Shale Formation

scholarly journals A hyperelastic model for soils with stress-induced and inherent anisotropy

2021 ◽  
Author(s):  
Marcin Cudny ◽  
Katarzyna Staszewska
Keyword(s):  
Small Strain ◽  
Induced Anisotropy ◽  
Dynamic Simulations ◽  
Inherent Anisotropy ◽  
Directional Model ◽  
Model Response ◽  
Hyperelastic Model ◽  
Stress Induced Anisotropy ◽  
Stress Invariant ◽  
Independent Model

AbstractIn this paper, modelling of the superposition of stress-induced and inherent anisotropy of soil small strain stiffness is presented in the framework of hyperelasticity. A simple hyperelastic model, capable of reproducing variable stress-induced anisotropy of stiffness, is extended by replacement of the stress invariant with mixed stress–microstructure invariant to introduce constant inherent cross-anisotropic component. A convenient feature of the new model is low number of material constants directly related to the parameters commonly used in the literature. The proposed description can be incorporated as a small strain elastic core in the development of some more sophisticated hyperelastic-plastic models of overconsolidated soils. It can also be used as an independent model in analyses involving small strain problems, such as dynamic simulations of the elastic wave propagation. Various options and features of the proposed anisotropic hyperelastic model are investigated. The directional model response is compared with experimental data available in the literature.

scholarly journals Study on Fracture Morphological Characteristics of Refracturing for Longmaxi Shale Formation

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-13 ◽  
Author(s):  
Yintong Guo ◽  
Lei Wang ◽  
Xin Chang ◽  
Jun Zhou ◽  
Xiaoyu Zhang
Keyword(s):  
Hydraulic Fracturing ◽  
Morphological Characteristics ◽  
Test Method ◽  
Pressure Curve ◽  
Natural Fractures ◽  
True Triaxial ◽  
Bedding Planes ◽  
Initiation And Propagation ◽  
Longmaxi Shale ◽  
Shale Formation

Refracturing technology has become an important means for the regeneration of old wells reconstruction. It is of great significance to understand the formation mechanism of hydraulic fracturing fracture for the design of hydraulic fracturing. In order to accurately evaluate and improve fracturing volume after refracturing, it is necessary to understand the mechanism of refracturing fracture in shale formation. In this paper, a true triaxial refracturing test method was established. A series of large-scale true triaxial fracturing experiments were carried out to characterize the refracturing fracture initiation and propagation. The results show that for shale reservoirs with weak bedding planes and natural fractures, hydraulic fracturing can not only form the main fracturing fracture, which is perpendicular to horizontal minimum principal stress, but it can also open weak bedding plane or natural fractures. The characteristics of fracturing pump curve indicated that the evolution of fracturing fractures, including initiation and propagation and communication of multiple fractures. The violent fluctuation of fracturing pump pressure curve indicates that the sample has undergone multiple fracturing fractures. The result of refracturing shows that initial fracturing fracture channels can be effectively closed by temporary plugging. The refracturing breakdown pressure is generally slightly higher than that of initial fracturing. After temporary plugging, under the influence of stress induced by the initial fracturing fracture, the propagation path of the refracturing fracture is deviated. When the new fracturing fracture communicates with the initial fracturing fracture, the original fracturing fracture can continue to expand and extend, increasing the range of the fracturing modifications. The refracturing test results was shown that for shale reservoir with simple initial fracturing fractures, the complexity fracturing fracture can be increased by refracturing after temporary plugging initial fractures. The effect of refracturing is not obvious for the reservoir with complex initial fracturing fractures. This research results can provide a reliable basis for optimizing refracturing design in shale gas reservoir.

scholarly journals Regulation Requires Records: Access to Fracking Information in the Marcellus/Utica Shale Formations

2018 ◽  
Vol 2 ◽  
pp. 3 ◽  
Author(s):  
Eira Tansey
Keyword(s):  
Hydraulic Fracturing ◽  
Water Supply ◽  
Environmental Regulation ◽  
Economic Activity ◽  
Fossil Fuel ◽  
Shale Formations ◽  
Utica Shale ◽  
The World ◽  
Shale Formation ◽  
Records Access

In the world of environmental regulation, records are the foundation on which all further regulatory action takes place. From permits that give industry permission to pollute in the name of economic activity, to annual production reports documenting how much fossil fuel is taken out of the ground, notices of violation issued by regulators, to complaints filed by citizens noticing contaminants in their water supply, recordkeeping is fundamental to regulation. Even as records are critical to understanding and contextualizing environmental problems, accessing and interpreting this information is an exceptionally difficult experience. This article will consider the regulatory recordkeeping context of hydraulic fracturing (fracking) in Ohio, Pennsylvania, and West Virginia, the three most productive states in the Marcellus/Utica shale formation.

scholarly journals Numerical Study on the Effects of Imbibition on Gas Production and Shut-In Time Optimization in Woodford Shale Formation

Energies ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 3222 ◽  
Author(s):  
Zhou Zhou ◽  
Shiming Wei ◽  
Rong Lu ◽  
Xiaopeng Li
Keyword(s):  
Numerical Model ◽  
Hydraulic Fracturing ◽  
Field Data ◽  
Gas Production ◽  
Model Parameters ◽  
Water Recovery ◽  
Woodford Shale ◽  
Capillary Suction ◽  
Shale Formation ◽  
The Relationship

In shale gas formations, imbibition is significant since the tight pore structure causes a strong capillary suction pressure. After hydraulic fracturing, imbibition during the period of shut-in affects the water recovery of flowback. Although there have been many studies investigating imbibition in shale formations, few papers have studied the relationship between gas production and shut-in time under the influence of imbibition. This paper developed a numerical model to investigate the effect of imbibition on gas production to optimize the shut-in time after hydraulic fracturing. This numerical model is a 2-D two-phase (gas and water) imbibition model for simulating an imbibed fluid flow and its effect on permeability, flowback, and water recovery. The experimental and field data from the Woodford shale formation were matched by the model to properly configure and calibrate the model parameters. The experimental data consisted of the relationship between the imbibed fluid volume and permeability change, the relative permeability, and the capillary pressure for the Woodford shale samples. The Woodford field data included the gas production and flowback volume. The modeling results indicate that imbibition can be a beneficial factor for gas production, since it can increase rock permeability. However, the gas production would be reduced when excessive fluid is imbibed by the shale matrix. Therefore, the shut-in time after hydraulic fracturing, when the imbibition happens in shale, could be optimized to maximize the gas production.

Impact of the stress state and the natural network of fractures/faults on the efficiency of hydraulic fracturing operations in the Goldwyer Shale Formation

2020 ◽  
Vol 60 (1) ◽  
pp. 163
Author(s):  
Partha Pratim Mandal ◽  
Reza Rezaee ◽  
Joel Sarout
Keyword(s):  
Stress State ◽  
Hydraulic Fracturing ◽  
Pore Pressure ◽  
Cost Effective ◽  
Fracture Network ◽  
Fault Reactivation ◽  
Hydraulic Fractures ◽  
Natural Fractures ◽  
Future Production ◽  
Shale Formation

Cost-effective hydrocarbon production from low-permeability unconventional reservoirs requires multi-stage hydraulic fracturing (HF) operations. Each HF stage aims to generate the most spatially extended fracture network, giving access to the largest volume of reservoir possible (stimulated volume) and allowing hydrocarbons to flow towards the wellbore. The size of the stimulated volume, and therefore, the efficiency of any given HF stage, is governed by the rock’s deformational behaviour and presence of pre-existing natural fractures/faults. Naturally elevated pore pressures at depth not only help to reduce the injection energy required to generate hydraulic fractures but can also induce slip along pre-existing fractures/faults, and therefore, enhance production rates. Here we analyse borehole image, density, resistivity and sonic logs available from a vertical exploration well in the Goldwyer Shale Formation (Canning Basin) to (i) characterise the pre-existing network of natural fractures; and (ii) estimate the in-situ pore pressure and stress state at depth. The aim of such an analysis is to evaluate the possibility of fracture/fault reactivation (slip) during and following HF operations. Based on this analysis, we found that an increase in the formation's pore pressure by only a few MPa (typically ~5–10 MPa) could lead to slip along pre-existing fractures/faults, provided they are favourably oriented with respect to the prevalent stress field for future production. We also found that slip along the horizontal or sub-horizontal bedding of the Goldwyer Formation is unlikely in view of the prevalent strike-slip faulting regime, unless an extremely large overpressure exists within the reservoir.

Seismic inversion of shale reservoir properties using microseismic-induced guided waves recorded by distributed acoustic sensing (DAS)

Geophysics ◽  
2021 ◽  
pp. 1-58
Author(s):  
Bin Luo ◽  
Ariel Lellouch ◽  
Ge Jin ◽  
Biondo Biondi ◽  
James Simmons
Keyword(s):  
Hydraulic Fracturing ◽  
Guided Waves ◽  
Wave Dispersion ◽  
Seismic Inversion ◽  
Dispersion Relations ◽  
Guided Wave ◽  
Low Velocity ◽  
Propagator Matrix ◽  
Shale Formation ◽  
Shale Reservoir

Shale formation properties are crucial for the hydrocarbon production performance of unconventional reservoirs. Microseismic-induced guided waves, which propagate within the low-velocity shale formation, are an ideal candidate for accurate estimation of the shale thickness, velocity, and anisotropy. A DAS fiber deployed along the horizontal section of a monitor well can provide a high-resolution recording of guided waves excited by microseismic events during hydraulic fracturing operations. These guided waves manifest a highly dispersive behavior that allows for seismic inversion of the shale formation properties. An adaptation of the propagator matrix method is presented to estimate guided wave dispersion curves and its accuracy is validated by comparison to 3-D elastic wavefield simulations. The propagator matrix formulation holds for cases of vertical transverse isotropy (VTI) as well. A sensitivity analysis of the theoretical dispersion relations of the guided waves shows that they are mostly influenced by the thickness and S-wave velocity of the low-velocity shale reservoir. The VTI parameters of the formation are also shown to have an impact on the dispersion relations. These physical insights provide the foundation for a dispersion-based model inversion for a 1-D depth-dependent structure of the reservoir and its surroundings. The inversion procedure is validated in a synthetic case and applied to the field records collected in an Eagle Ford hydraulic fracturing project. The inverted structure agrees well with a sonic log acquired several hundred meters away from the monitor well. Seismic inversion using guided wave dispersion therefore shows promise to become a novel and cost-effective strategy for in-situ estimation of reservoir structure and properties, which complements microseismic-based interpretation and production-related information.

Discrete-Element-Method/Computational-Fluid-Dynamics Coupling Simulation of Proppant Embedment and Fracture Conductivity After Hydraulic Fracturing

SPE Journal ◽  
2017 ◽  
Vol 22 (02) ◽  
pp. 632-644 ◽  
Author(s):  
Fengshou Zhang ◽  
Haiyan Zhu ◽  
Hanguo Zhou ◽  
Jianchun Guo ◽  
Bo Huang
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Hydraulic Fracturing ◽  
Discrete Element Method ◽  
Discrete Element ◽  
Particle Assembly ◽  
Fracture Conductivity ◽  
Shale Formation ◽  
Proppant Embedment ◽  
Element Method

Summary In this paper, an integrated discrete-element-method (DEM)/computational-fluid-dynamics (CFD) numerical-modeling work flow is developed to model proppant embedment and fracture conductivity after hydraulic fracturing. Proppant with diameter from 0.15 to 0.83 mm was modeled as a frictional particle assembly, whereas shale formation was modeled as a bonded particle assembly by using the bonded-particle model in PFC3D (Itasca Consulting Group 2010). The mechanical interaction between proppant pack and shale formation during the process of fracture closing was first modeled with DEM. Then, fracture conductivity after the fracture closing was evaluated by modeling fluid flow through the proppant pack by use of DEM coupled with CFD. The numerical model was verified by laboratory fracture-conductivity experiment results and the Kozeny-Carman equation. The simulation results show that the fracture conductivity increases with the increase of proppant concentration or proppant size, and decreases with the increase of fracture-closing stress or degree of shale hydration; shale-hydration effect was confirmed to be the main reason for the large amount of proppant embedment.

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