scholarly journals Lattice Numerical Simulations of Hydraulic Fracture Propagation and Their Geometry Evolution in Transversely Isotropic Formations

2021 ◽  
Vol 9 ◽  
Author(s):  
Dezhi Qiu ◽  
Jun Zhang ◽  
Yinhe Lin ◽  
Jinchuan Liu ◽  
Minou Rabiei ◽  
...  
Keyword(s):  
Hydraulic Fracture ◽  
Numerical Models ◽  
Fractured Reservoirs ◽  
Fracture Propagation ◽  
Propagation Mechanism ◽  
Fracture Aperture ◽  
Natural Interfaces ◽  
Fracture Geometry ◽  
Hf Propagation ◽  
The Impact

Accurate prediction of the fracture geometry before the operation of a hydraulic fracture (HF) job is important for the treatment design. Simplified planar fracture models, which may be applicable to predict the fracture geometry in homogeneous and continuous formations, fail in case of fractured reservoirs and laminated formations such as shales. To gain a better understanding of the fracture propagation mechanism in laminated formations and their vertical geometry to be specific, a series of numerical models were run using XSite, a lattice-based simulator. The results were studied to understand the impact of the mechanical properties of caprock and injection parameters on HF propagation. The tensile and shear stimulated areas were used to determine the ability of HF to propagate vertically and horizontally. The results indicated that larger caprock Young’s modulus increases the stimulated area (SA) in both vertical and horizontal directions, whereas it reduces the fracture aperture. Also, larger vertical stress anisotropy and tensile strength of caprock and natural interfaces inhibit the horizontal fracture propagation with an inconsiderable effect in vertical propagation, which collectively reduces the total SA. It was also observed that an increased fluid injection rate suppresses vertical fracture propagation with an insignificant effect on horizontal propagation. The dimensionless parameters defined in this study were used to characterize the transition of HF propagation behavior between horizontal and vertical HFs.

scholarly journals Numerical Investigation of Hydraulic Fracture Propagation in Naturally Fractured Reservoirs Based on Lattice Spring Model

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Kaikai Zhao ◽  
Pengfei Jiang ◽  
Yanjun Feng ◽  
Xiaodong Sun ◽  
Lixing Cheng ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Hydraulic Fracture ◽  
Fractured Reservoirs ◽  
Fracture Propagation ◽  
Maximum Principal Stress ◽  
Injection Rate ◽  
Naturally Fractured Reservoirs ◽  
Fluid Viscosity ◽  
Global Orientation ◽  
Hf Propagation

Hydraulic fracturing has been extensively employed for permeability enhancement in low-permeability reservoirs. The geometry of the hydraulic fracture network (HFN) may have implications for the optimization of hydraulic fracturing operations. Various parameters, including the in situ stress, treatment parameters (injection rate and fluid viscosity), and orientation of natural fractures (NFs), can significantly affect the interactions between hydraulic fracture (HF) and NFs and the final HFN. In this study, a lattice-spring code was employed to determine the impact of various parameters on the geometry of the HFN. The modelling results indicated that with a large stress difference, the global orientation of the fracture propagation was restricted to the direction of maximum principal stress, and the number of fracture branches was reduced. The geometry of the HFN changed from circular to elliptical. In contrast, with an increase in the fluid viscosity/injection rate, the evolution of the geometry of the HFN exhibited the opposite trend. The global orientation of HF propagation tended to remain parallel to the direction of maximum principal stress, regardless of the branching and tortuosity of the fracture. The variations in the ratio of tensile fracture (HF) to shear fracture (shear slip on NF) can be significant, depending on the stress state, treatment parameters, and preexisting NF network, which determine the dominant stimulation mechanism. This study provides insight into the HF propagation in naturally fractured reservoirs.

The Impact of Laminated Rock on Hydraulic Fracture Propagation in Unconventional Resources

2014 ◽  
Author(s):  
B.V. V Cherian ◽  
S.. Higgins-Borchardt ◽  
G.A.. A. Bordakov ◽  
A.. Yunuskhojayev ◽  
Z.. Al-Jalal ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Hydraulic Fracture ◽  
Fracture Propagation ◽  
Unconventional Reservoirs ◽  
Accurate Estimation ◽  
Earth Model ◽  
Propagation Mechanism ◽  
Hydraulic Fractures ◽  
Facies Classification ◽  
The Impact

Abstract As unconventional reservoirs continue to be discovered and appraised, an ever increasing challenge is to understand the productive mechanism that unlocks the potential of these reservoirs. Since most unconventional reservoirs have some degree of lamination (varying from a few hundreds of an inch to a couple of feet), a technical hurdle exists in understanding the integration of conventional logging (using up-scaled measurements), modeling software (assumptions, gridding, numerical/P3D) and fine scale measurements (core measurements). Laminated reservoirs pose many challenges in the decision making process especially when a model centric, data driven approach is utilized. These challenges can be reduced to two categories: (1) challenges in understanding fracture propagation mechanism and (2) challenges in reservoir characterization. This paper focuses on a procedure to capture the former. The early phase of gathering measurements is frequently executed with data sets and measurements that are incomplete and insufficient to understand the production mechanism in these low porosity environments. In an engineering analysis, this data may be utilized only to a limited extent, due to the inconsistences in the measurements gathered at various scales. To overcome these inconsistencies a novel approach to estimate mechanical properties with sub-sonic resolution through integration of sonic logs, high resolution logs, and facies classification has been developed. The use of traditional workflows to derive mechanical properties has led to overestimating and/or underestimating rock strength and stress in the different layers. This, historically, has resulted in inconsistent conclusions across various disciplines and unexplainable well performance. Furthermore, the process of matching hydraulic fracture net-pressure using conventional workflows can result in the complication of fracture propagation process or incorrect calibration of the Mechanical Earth Model used to estimate earth stresses. We have demonstrated that the presented workflow allows for more accurate estimation of the mechanical properties profile in thin bed formations and consequently more effective use of those estimates to design hydraulic fractures and analyze the results.

Investigation of Rupture and Slip Mechanisms of Hydraulic Fractures in Multiple-Layered Formations

SPE Journal ◽  
2019 ◽  
Vol 24 (05) ◽  
pp. 2292-2307 ◽  
Author(s):  
Jizhou Tang ◽  
Kan Wu ◽  
Lihua Zuo ◽  
Lizhi Xiao ◽  
Sijie Sun ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Hydraulic Fracture ◽  
Fracture Propagation ◽  
Propagation Model ◽  
Rock Deformation ◽  
Hydraulic Fractures ◽  
Fracture Geometry ◽  
Fracture Width ◽  
Hydraulic Fracture Propagation ◽  
Fracture Height

Summary Weak bedding planes (BPs) that exist in many tight oil formations and shale–gas formations might strongly affect fracture–height growth during hydraulic–fracturing treatment. Few of the hydraulic–fracture–propagation models developed for unconventional reservoirs are capable of quantitatively estimating the fracture–height containment or predicting the fracture geometry under the influence of multiple BPs. In this paper, we introduce a coupled 3D hydraulic–fracture–propagation model considering the effects of BPs. In this model, a fully 3D displacement–discontinuity method (3D DDM) is used to model the rock deformation. The advantage of this approach is that it addresses both the mechanical interaction between hydraulic fractures and weak BPs in 3D space and the physical mechanism of slippage along weak BPs. Fluid flow governed by a finite–difference methodology considers the flow in both vertical fractures and opening BPs. An iterative algorithm is used to couple fluid flow and rock deformation. Comparison between the developed model and the Perkins–Kern–Nordgren (PKN) model showed good agreement. I–shaped fracture geometry and crossing–shaped fracture geometry were analyzed in this paper. From numerical investigations, we found that BPs cannot be opened if the difference between overburden stress and minimum horizontal stress is large and only shear displacements exist along the BPs, which damage the planes and thus greatly amplify their hydraulic conductivity. Moreover, sensitivity studies investigate the impact on fracture propagation of parameters such as pumping rate (PR), fluid viscosity, and Young's modulus (YM). We investigated the fracture width near the junction between a vertical fracture and the BPs, the latter including the tensile opening of BPs and shear–displacement discontinuities (SDDs) along them. SDDs along BPs increase at the beginning and then decrease at a distance from the junction. The width near the junctions, the opening of BPs, and SDDs along the planes are directly proportional to PR. Because viscosity increases, the width at a junction increases as do the SDDs. YM greatly influences the opening of BPs at a junction and the SDDs along the BPs. This model estimates the fracture–width distribution and the SDDs along the BPs near junctions between the fracture tip and BPs and enables the assessment of the PR required to ensure that the fracture width at junctions and along intersected BPs is sufficient for proppant transport.

scholarly journals Hydraulic Fracture Propagation and Permeability Evolution in the Composite Thin Coal Seam

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Shenglong Liu ◽  
Bingxiang Huang ◽  
Weiyong Lu ◽  
Haoze Li ◽  
Ding Li ◽  
...  
Keyword(s):  
Coal Seam ◽  
Hydraulic Fracturing ◽  
Hydraulic Fracture ◽  
Water Pressure ◽  
Fracture Propagation ◽  
Injection Pressure ◽  
Unstable Fracture ◽  
Permeability Evolution ◽  
Thin Coal Seam ◽  
Hf Propagation

Hydraulic fracturing can improve the permeability of composite thin coal seam. Recently, characterizing hydraulic fracture (HF) propagation inside the coal seam and evaluating the permeability enhancement with HF extension remain challenging and crucial. In this work, based on the geological characteristics of the coal seam in a coal mine of the southwest China, the RFPA2D-Flow software is employed to simulate the HF propagation and its permeability-increasing effect in the composite thin coal seam, and a couple of outcomes were obtained. (1) Continuous propagation of the hydraulic microcrack-band is the prominent characteristic of HF propagation. With the increment of the injection-water pressure, HF generation in the composite thin coal seam can be divided into three stages: stress accumulation, stable fracture propagation, and unstable fracture propagation. (2) The hydraulic microcrack-band propagates continuously driven by the fluid-injection pressure. The microcrack-band not only cracks the coal seam but also fractures the gangue sandwiched between the coal seams. (3) The permeability in the composite thin coal seam increases significantly with the propagation of hydraulic microcrack-band. The permeability increases by 1~2 magnitudes after hydraulic fracturing. This study provides references to the field applications of hydraulic fracturing in the composite thin coal seam, such as optimizing hydraulic fracturing parameters, improving gas drainage, and safe-efficient mining.

scholarly journals Geomechanical key parameters of the process of hydraulic fracturing propagation in fractured medium

2019 ◽  
Vol 74 ◽  
pp. 58 ◽  
Author(s):  
Rouhollah Basirat ◽  
Kamran Goshtasbi ◽  
Morteza Ahmadi
Keyword(s):  
Hydraulic Fracturing ◽  
Numerical Models ◽  
Fractured Reservoirs ◽  
Natural Fracture ◽  
Propagation Path ◽  
Fracture Density ◽  
Strength Parameters ◽  
Propagation Process ◽  
Fractured Medium ◽  
Hf Propagation

Hydraulic Fracturing (HF) is a well-stimulation technique that creates fractures in rock formations through the injection of hydraulically pressurized fluid. Because of the interaction between HF and Natural Fractures (NFs), this process in fractured reservoirs is different from conventional reservoirs. This paper focuses mainly on three effects including anisotropy in the reservoir, strength parameters of discontinuities, and fracture density on HF propagation process using a numerical simulation of Discrete Element Method (DEM). To achieve this aim, a comprehensive study was performed with considering different situations of in situ stress, the presence of a joint set, and different fracture network density in numerical models. The analysis results showed that these factors play a crucial role in HF propagation process. It also was indicated that HF propagation path is not always along the maximum principal stress direction. The results of the numerical models displayed that the affected area under HF treatment is decreased with increasing the strength parameters of natural fracture and decreasing fracture intensity.

Validation of flow capacity and state-of-stress models in unconventional reservoirs by implementation of numerical models of diagnostic fracture injection tests

2019 ◽  
Vol 38 (6) ◽  
pp. 465-472
Author(s):  
Hernán Buijs ◽  
Jorge Ponce ◽  
Paul Veeken
Keyword(s):  
Development Strategy ◽  
Hydraulic Fracture ◽  
Reservoir Characterization ◽  
Numerical Models ◽  
Solution Space ◽  
Production Performance ◽  
Fracture Geometry ◽  
Field Development ◽  
Flow Capacity ◽  
Planar Shear

Diagnostic fracture injection tests contain critical information for reservoir characterization and hydraulic fracturing design, defining every input and output of the simulation modeling process. They help to assess the expected fracture geometry, proppant pack conductivity, formation flow capacity, and optimum hydraulic fracture design. At the same time, these data provide the necessary means to place a frac job adequately. However, interpretation challenges and inherent modeling nonuniqueness demonstrate the need for more constraints to reduce the solution space. Proprietary workflows have been applied using a 3D planar shear decoupled hydraulic fracture simulator to several vertical wells in the Vaca Muerta play in Argentina. The generated information makes it possible to build models consistent with multiple independent measurements from bottom-hole gauges, near wellbore, and far-field assessments of fracture geometry, which permit us to better understand production performance of the wells. The proposed workflow can be utilized to collapse the learning curve in a significant and meaningful way, playing a vital role in the optimization of horizontal wells and the field development strategy.

scholarly journals Adaptive Finite Element-Discrete Element Analysis for Microseismic Modelling of Hydraulic Fracture Propagation of Perforation in Horizontal Well considering Pre-Existing Fractures

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Yongliang Wang ◽  
Yang Ju ◽  
Yongming Yang
Keyword(s):  
Finite Element ◽  
Hydraulic Fracture ◽  
Horizontal Well ◽  
Numerical Models ◽  
Fracture Propagation ◽  
Discrete Element ◽  
Hydraulic Fractures ◽  
Adaptive Finite Element ◽  
Naturally Fractured ◽  
Hydraulic Fracture Propagation

Hydrofracturing technology of perforated horizontal well has been widely used to stimulate the tight hydrocarbon reservoirs for gas production. To predict the hydraulic fracture propagation, the microseismicity can be used to infer hydraulic fractures state; by the effective numerical methods, microseismic events can be addressed from changes of the computed stresses. In numerical models, due to the challenges in accurately representing the complex structure of naturally fractured reservoir, the interaction between hydraulic and pre-existing fractures has not yet been considered and handled satisfactorily. To overcome these challenges, the adaptive finite element-discrete element method is used to refine mesh, effectively identify the fractures propagation, and investigate microseismic modelling. Numerical models are composed of hydraulic fractures, pre-existing fractures, and microscale pores, and the seepage analysis based on the Darcy’s law is used to determine fluid flow; then moment tensors in microseismicity are computed based on the computed stresses. Unfractured and naturally fractured models are compared to assess the influences of pre-existing fractures on hydrofracturing. The damaged and contact slip events were detected by the magnitudes, B-values, Hudson source type plots, and focal spheres.

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