An Experimental And Numerical Investigation Into Hydraulic Fracture Propagation In Naturally Fractured Shale Gas Reservoirs
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An Experimental And Numerical Investigation Into Hydraulic Fracture Propagation In Naturally Fractured Shale Gas Reservoirs
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Author : Betul Yildirim
language : en
Publisher:
Release Date : 2019
An Experimental And Numerical Investigation Into Hydraulic Fracture Propagation In Naturally Fractured Shale Gas Reservoirs written by Betul Yildirim and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019 with categories.
Geomechanics And Hydraulic Fracturing For Shale Reservoirs
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Author : Yu Wang
language : en
Publisher: Scientific Research Publishing, Inc. USA
Release Date : 2020-07-01
Geomechanics And Hydraulic Fracturing For Shale Reservoirs written by Yu Wang and has been published by Scientific Research Publishing, Inc. USA this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020-07-01 with Art categories.
This book is intended as a reference book for advanced graduate students and research engineers in shale gas development or rock mechanical engineering. Globally, there is widespread interest in exploiting shale gas resources to meet rising energy demands, maintain energy security and stability in supply and reduce dependence on higher carbon sources of energy, namely coal and oil. However, extracting shale gas is a resource intensive process and is dependent on the geological and geomechanical characteristics of the source rocks, making the development of certain formations uneconomic using current technologies. Therefore, evaluation of the physical and mechanical properties of shale, together with technological advancements, is critical in verifying the economic viability of such formation. Accurate geomechanical information about the rock and its variation through the shale is important since stresses along the wellbore can control fracture initiation and frac development. In addition, hydraulic fracturing has been widely employed to enhance the production of oil and gas from underground reservoirs. Hydraulic fracturing is a complex operation in which the fluid is pumped at a high pressure into a selected section of the wellbore. The interaction between the hydraulic fractures and natural fractures is the key to fracturing effectiveness prediction and high gas development. The development and growth of a hydraulic fracture through the natural fracture systems of shale is probably more complex than can be described here, but may be somewhat predictable if the fracture system and the development of stresses can be explained. As a result, comprehensive shale geomechanical experiments, physical modeling experiment and numerical investigations should be conducted to reveal the fracturing mechanical behaviors of shale.
Fracture Propagation In Naturally Fractured Reservoirs
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Author : Hunjoo Peter Lee
language : en
Publisher:
Release Date : 2015
Fracture Propagation In Naturally Fractured Reservoirs written by Hunjoo Peter Lee and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
Investigations of hydrocarbons in tight formations require understanding of hydraulic fracturing in order to optimize the production and recovery of oil and natural gas. The classic description of hydraulic fracture is a single bi-wing planar feature, however, field observations show that hydraulic fracture growth in naturally fractured formations like shale is complex. Lack of knowledge concerning the remote stress impact and the interaction with planes of weakness on a fracture propagation trajectory leads to inaccurate predictions of the fracture geometry and the surface area required for the production estimation. Most studies in engineering mechanics extended the standard mixed-mode fracture propagation models, based on the near tip approximations, to include the impact of the tensile crack-parallel stress on the fracture propagation path. However, for fractures in the subsurface, the remote stress is compression, and internal fluid pressure or frictional stress become important in the near-tip stress field and the propagation trajectory. The Modified Maximum Tangential Principal Stress criterion (MMTPS-criterion) was introduced to address and evaluate the remote and internal crack stresses in the propagation path. The predictions of the fracture propagation angles by the MMTPS-criterion agreed with published experimental results of fractures propagating under both tensile and compressive external loads. In addition, the predictions matched well with uniaxial compression tests on hydrostone samples with the critical radial distance, defined by the process zone size, for open fractures that satisfy the Small Scale Yielding conditions. For short open fractures, a larger critical radial distance was required to correspond with the experimental results. The MMTPS-criterion was also capable of predicting lower propagation angles for closed cracks with higher friction coefficients. Preexisting discontinuities in shale, including natural fractures and bedding, act as planes of weakness that divert fracture propagation. To investigate the influences of weak planes on hydraulic fracture propagation, I performed Semi-Circular Bend (SCB) tests on Marcellus shale core samples containing calcite-filled natural fractures (veins). The approach angle of the induced fracture to the veins and the thickness of the veins had a strong influence on propagation. As the apprach angle became more oblique to the induced fracture plane, and as the vein got thicker, the induced fracture was more likely to divert into the vein. Microstructural analysis of tested samples showed that the induced fracture propagated in the middle of the vein rahter than the interface between vein and the rock matrix. Cleavage planes and fluid inclusion trails in the vein cements exerted some control on the fracture path. By combining the experimental results with theoretical fracture-mechanics arguments, the fracture toughness of the calcite veins was estimated to range from 0.99 MPa [square root of m] to 1.14 MPa [square root of m], depending on the value used for the Young's modulus of the calcite vein material. Measured fracture toughness of unfractured Marcellus shale was 0.64 MPa [square root of m]. A Discrete Element Method (DEM) based numerical modeling software, Particle Flow Code in three-dimensions (PFC3D), was utilized to reproduce and analyze the experimental results of Marcellus shale samples. The trend of numerical results correlated with the interaction feature of the experimental results for various approach angel and thickness (i.e., aperture) of the vein. Further sensitivity analysis on vein properties indicated that veins with lower stranght and higher stiffness contribute to more fracture diversion than veins with higher strenght and lower stiffness. Additionally, parallel bond breakages in the model show that microcracks were generated inside the vein before the induced fracture encountered the vein especially for the veins with higher stiffnesses when compared to the rock matrix. Most of the bond failure mode inside the vein and the induced fracture was tensile rather that shear mode.
Numerical Simulation In Hydraulic Fracturing Multiphysics Theory And Applications
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Author : Xinpu Shen
language : en
Publisher: CRC Press
Release Date : 2017-03-27
Numerical Simulation In Hydraulic Fracturing Multiphysics Theory And Applications written by Xinpu Shen and has been published by CRC Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017-03-27 with Science categories.
The expansion of unconventional petroleum resources in the recent decade and the rapid development of computational technology have provided the opportunity to develop and apply 3D numerical modeling technology to simulate the hydraulic fracturing of shale and tight sand formations. This book presents 3D numerical modeling technologies for hydraulic fracturing developed in recent years, and introduces solutions to various 3D geomechanical problems related to hydraulic fracturing. In the solution processes of the case studies included in the book, fully coupled multi-physics modeling has been adopted, along with innovative computational techniques, such as submodeling. In practice, hydraulic fracturing is an essential project component in shale gas/oil development and tight sand oil, and provides an essential measure in the process of drilling cuttings reinjection (CRI). It is also an essential measure for widened mud weight window (MWW) when drilling through naturally fractured formations; the process of hydraulic plugging is a typical application of hydraulic fracturing. 3D modeling and numerical analysis of hydraulic fracturing is essential for the successful development of tight oil/gas formations: it provides accurate solutions for optimized stage intervals in a multistage fracking job. It also provides optimized well-spacing for the design of zipper-frac wells. Numerical estimation of casing integrity under stimulation injection in the hydraulic fracturing process is one of major concerns in the successful development of unconventional resources. This topic is also investigated numerically in this book. Numerical solutions to several other typical geomechanics problems related to hydraulic fracturing, such as fluid migration caused by fault reactivation and seismic activities, are also presented. This book can be used as a reference textbook to petroleum, geotechnical and geothermal engineers, to senior undergraduate, graduate and postgraduate students, and to geologists, hydrogeologists, geophysicists and applied mathematicians working in this field. This book is also a synthetic compendium of both the fundamentals and some of the most advanced aspects of hydraulic fracturing technology.
Formation Evaluation And Numerical Modeling On Hydraulic Fracturing For An Emerging Marine Shale Gas Reservoir
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Author : Chenji Wei
language : en
Publisher:
Release Date : 2013
Formation Evaluation And Numerical Modeling On Hydraulic Fracturing For An Emerging Marine Shale Gas Reservoir written by Chenji Wei and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with Hydraulic fracturing categories.
Shale gas development has more than 3 decades of history and remains one of the hottest topics in the petroleum industry. Shale gas development in China is underway. Our study focuses on an emerging marine shale gas reservoir in southern China, with its huge reserves that have attracted strong attention. The first part of this dissertation is the petrophysical characterization, which is an important step for a new shale gas play to better understand the geology of the formation, and it provides vital data to optimize a production plan and stimulation design. A systematic petrophysical study was conducted for the marine shale gas reservoir by conducting a series of 6 parallel experiments for 12 groups of samples to measure the total organic content (TOC), vitrinite reflectance (Ro), porosity, permeability, mineralogy, and gas content. Second, the extra-low porosity and permeability of shale formations complicate the mechanisms of shale gas storage and flow. Understanding the microstructure is significant for evaluating a new shale gas play toward accurate reserve estimation and recovery prediction. Both physical measurement (nitrogen adsorption experiment) and visualization technology (Scanning Electron Microscope) were used to characterize the nanopore structure of the Longmaxi Shale. Isotherms were obtained from adsorption experiments, and specific surface area and pore size distribution were calculated from the experimental results. Combining with the TOC, gas content, and mineralogy of the Longmaxi Shale, the significance and the controlling factors of the specific surface area and the nanopore volume were discussed. In addition, various types of porosity and several microfractures were observed from SEM images. Third, preliminary interpretation of the imaging logs revealed natural fractures in the formation that can significantly affect the production performance of shale gas wells since preexisting natural fractures will influence hydraulic fracture propagation. Thus, numerical simulation was conducted focusing on the interaction between hydraulically induced fractures and preexisting natural fractures. A hydraulic fracturing model considering the in-situ stress response to turbulent flow process was developed and validated with regression tests of a bi-wing hydraulic fracture model. Field-scale simulation results indicate that our model is capable of capturing the interactions between hydraulic fractures and the preexisting natural fractures defined by the initial fracture maps. Finally, a new model was built to model the actual network of hydraulic and preexisting fractures from geological interpretations and microseismic mapping results. The discrete fracture modeling (DFM) approach was applied to represent each fracture individually and explicitly. The near-well effects were modeled in detail by refining the unstructured 3D grid to the point where we fully resolve stimulated fractures. Simulations of the detailed model of an actual shale gas reservoir considered various mechanisms including adsorption/desorption, matrix/fracture transfer, and non-Darcy effects. Furthermore, the dissertation illustrates upscaling from the discrete fracture model to a coarse continuum model using multiple subregion (MSR), and the high degree of accuracy provided by this technique is demonstrated by comparing the solution of the upscaled model with the corresponding fine-grid solution for a synthetic case.
The Combined Finite Discrete Element Method
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Author : Antonio A. Munjiza
language : en
Publisher: John Wiley & Sons
Release Date : 2004-04-21
The Combined Finite Discrete Element Method written by Antonio A. Munjiza and has been published by John Wiley & Sons this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004-04-21 with Technology & Engineering categories.
The combined finite discrete element method is a relatively new computational tool aimed at problems involving static and / or dynamic behaviour of systems involving a large number of solid deformable bodies. Such problems include fragmentation using explosives (e.g rock blasting), impacts, demolition (collapsing buildings), blast loads, digging and loading processes, and powder technology. The combined finite-discrete element method - a natural extension of both discrete and finite element methods - allows researchers to model problems involving the deformability of either one solid body, a large number of bodies, or a solid body which fragments (e.g. in rock blasting applications a more or less intact rock mass is transformed into a pile of solid rock fragments of different sizes, which interact with each other). The topic is gaining in importance, and is at the forefront of some of the current efforts in computational modeling of the failure of solids. * Accompanying source codes plus input and output files available on the Internet * Important applications such as mining engineering, rock blasting and petroleum engineering * Includes practical examples of applications areas Essential reading for postgraduates, researchers and software engineers working in mechanical engineering.
Numerical Investigation Of Interaction Between Hydraulic Fractures And Natural Fractures
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Author : Wenxu Xue
language : en
Publisher:
Release Date : 2011
Numerical Investigation Of Interaction Between Hydraulic Fractures And Natural Fractures written by Wenxu Xue and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
Hydraulic fracturing of a naturally-fractured reservoir is a challenge for industry, as fractures can have complex growth patterns when propagating in systems of natural fractures in the reservoir. Fracture propagation near a natural fracture (NF) considering interaction between a hydraulic fracture (HF) and a pre-existing NF, has been investigated comprehensively using a two dimensional Displacement Discontinuity Method (DDM) Model in this thesis. The rock is first considered as an elastic impermeable medium (with no leakoff), and then the effects of pore pressure change as a result of leakoff of fracturing fluid are considered. A uniform pressure fluid model and a Newtonian fluid flow model are used to calculate the fluid flow, fluid pressure and width distribution along the fracture. Joint elements are implemented to describe different NF contact modes (stick, slip, and open mode). The structural criterion is used for predicting the direction and mode of fracture propagation. The numerical model was used to first examine the mechanical response of the NF to predict potential reactivation of the NF and the resultant probable location for fracture re-initiation. Results demonstrate that: 1) Before the HF reaches a NF, the possibility of fracture re-initiation across the NF and with an offset is enhanced when the NF has weaker interfaces; 2) During the stage of fluid infiltration along the NF, a maximum tensile stress peak can be generated at the end of the opening zone along the NF ahead of the fluid front; 3) Poroelastic effects, arising from fluid diffusion into the rock deformation can induce closure and compressive stress at the center of the NF ahead of the HF tip before HF arrival. Upon coalescence when fluid flows along the NF, the poroelastic effects tend to reduce the value of the HF aperture and this decreases the tension peak and the possibility of fracture re-initiation with time. Next, HF trajectories near a NF were examined prior to coalesce with the NF using different joint, rock and fluid properties. Our analysis shows that: 1) Hydraulic fracture trajectories near a NF may bend and deviate from the direction of the maximum horizontal stress when using a joint model that includes initial joint deformation; 2) Hydraulic fractures propagating with higher injection rate or fracturing fluid of higher viscosity propagate longer distance when turning to the direction of maximum horizontal stress; 3) Fracture trajectories are less dependent on injection rate or fluid viscosity when using a joint model that includes initial joint deformation; whereas, they are more dominated by injection rate and fluid viscosity when using a joint model that excludes initial joint deformation.
Hydraulic Fracture Modeling
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Author : Yu-Shu Wu
language : en
Publisher: Gulf Professional Publishing
Release Date : 2017-11-30
Hydraulic Fracture Modeling written by Yu-Shu Wu and has been published by Gulf Professional Publishing this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017-11-30 with Technology & Engineering categories.
Hydraulic Fracture Modeling delivers all the pertinent technology and solutions in one product to become the go-to source for petroleum and reservoir engineers. Providing tools and approaches, this multi-contributed reference presents current and upcoming developments for modeling rock fracturing including their limitations and problem-solving applications. Fractures are common in oil and gas reservoir formations, and with the ongoing increase in development of unconventional reservoirs, more petroleum engineers today need to know the latest technology surrounding hydraulic fracturing technology such as fracture rock modeling. There is tremendous research in the area but not all located in one place. Covering two types of modeling technologies, various effective fracturing approaches and model applications for fracturing, the book equips today’s petroleum engineer with an all-inclusive product to characterize and optimize today’s more complex reservoirs. Offers understanding of the details surrounding fracturing and fracture modeling technology, including theories and quantitative methods Provides academic and practical perspective from multiple contributors at the forefront of hydraulic fracturing and rock mechanics Provides today’s petroleum engineer with model validation tools backed by real-world case studies
The Effect Of Cemented Natural Fractures On Hydraulic Fracture Propagation
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Author : Weiwei Wang
language : en
Publisher:
Release Date : 2017
The Effect Of Cemented Natural Fractures On Hydraulic Fracture Propagation written by Weiwei Wang and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.
Microseismic events, which are generated during hydraulic fracturing treatments, suggest that a complicated fracture network develops in many naturally−fractured unconventional reservoirs. Deformation along weak planes, such as cemented natural fractures, has been proposed as one of the possible reasons for fracture network complexity. Cemented natural fractures widely exist in shale reservoirs. They are diverse in composition and size, depending on the burial condition, the composition of the rock matrix, and the geochemical environment. The interaction between cemented natural fractures with hydraulic fractures generated as part of the reservoir stimulation are thought to impact hydraulic fracture propagation. Previous studies mostly treated natural fractures as frictional interfaces without considering the actual cement fillings. In this study, I analyzed the effect of cemented natural fractures on hydraulic fracture propagation by considering natural fracture thickness, mechanical properties and rock−cement interface bond strength. Firstly, I conducted a series of semi−circular bend (SCB) tests and corresponding numerical simulations to study the interaction between hydraulic and natural fractures. The SCB tests are attractive in general because of their simple setup with consistent results. The experimental results also served as a validation for numerical model. Two drawbacks of the SCB tests include that the test is unconfined and there is no fluid component. Numerical modeling can then be applied to extend results beyond these shortcomings. Synthetic hydrostone samples with embedded inclusions of different mechanical properties were used to mimic rock with cemented natural fractures. Experimental results identified several parameters that could be used to explain hydraulic fractures interaction with cemented natural fractures. The SCB test conditions that promoted fracture crossing were near−orthogonal approach angles, small natural fracture thicknesses, and strong rock−cement interfaces. Such conditions in a reservoir would promote long hydraulic fractures and less complicated fracture networks. In contrast, the SCB test conditions that caused fracture diverting were more oblique approach angles, large natural fracture thicknesses, and weak rock−cement interfaces, resulting in short hydraulic fractures and more complicated fracture networks. The SCB tests using synthetic rock samples provided insights into the hydraulic fracture propagation in naturally−fractured reservoirs. Through the numerical modeling with the finite element code in Abaqus, the impact of fluid driven fracturing on fracture−fracture interaction was investigated. Fracture propagation in two dimensions was modeled using the cohesive elements and anisotropic compressive remote stress conditions. Results suggest that if the natural fracture thickness is considered, the commonly used fracture crossing/diverting criterion will overestimate the hydraulic fracture crossing scenario. Factors including modulus contrast and coefficient of friction also influence hydraulic fracture interaction with natural fractures. An application of this work is the case of how bedding−parallel veins will affect hydraulic fracture height growth. Such natural fractures are abundant in the unconventional resource play in the Vaca Muerta formation in Argentina. When the rock−cement coefficient of friction is around 0.4−0.5, which most likely represents shale reservoirs, hydraulic fracture crossing behavior is affected by the modulus contrast between natural fractures and host rock as well as the natural fracture thickness.
New Numerical Approaches To Model Hydraulic Fracturing In Tight Reservoirs With Consideration Of Hydro Mechanical Coupling Effects
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Author : Lei Zhou
language : en
Publisher: Cuvillier Verlag
Release Date : 2014-03-20
New Numerical Approaches To Model Hydraulic Fracturing In Tight Reservoirs With Consideration Of Hydro Mechanical Coupling Effects written by Lei Zhou and has been published by Cuvillier Verlag this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014-03-20 with Technology & Engineering categories.
In this dissertation, two new numerical approaches for hydraulic fracturing in tight reservoir were developed. A more physical-based numerical 3D-model was developed for simulating the whole hydraulic fracturing process including fracture propagation, closure and contact as well as proppant transport and settling. In this approach rock formation, pore and fracture systems were assembled together, in which hydro-mechanical coupling effect, proppant transport and settling as well as their influences on fracture closure and contact were fully considered. A combined FDM and FVM schema was used to solve the problem. Three applications by using the new approach were presented. The results illustrated the whole hydraulic fracturing process well and seemed to be logical, which confirmed the ability of the developed approach to model the in-situ hydraulic fracturing operation from injection start till fully closure. In order to investigate the orientation problem of hydraulic fracturing in tight reservoir, a new approach for simulating arbitrary fracture propagation and orientation in 2D was developed. It was solved by a hybrid schema of XFEM and FVM. Three numerical studies were illustrated, which proved the ability of the developed approach to solve the orientation problem in field cases.