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Mining Publications

Five Things You Didn’t Want to Know about Hydraulic Fractures
M.C. Vincent
Book Title / Journal: Effective and Sustainable Hydraulic Fracturing - Chapter 4
Year: 2013
Mining
  • Description
    • It is common to envision and design hydraulic fractures as if they were simple, planar features that are relatively consistent in width and durable in their flow capacity. Production forecasting is frequently based on a simplified description of the reservoir as a homogene‐ ous single productive layer. In rare instances the pay intervals may be simulated with as many as a dozen layered strata, but even the most meticulous reservoir engineer may mis‐ takenly assign each layer a highly conductive, durable connection with the wellbore. When analyzing the resulting production data, similar assumptions are made, which can errone‐ ously reinforce these misconceptions. This paper examines five limitations of hydraulic fractures and interpretation techniques, and describes the increases in well productivity that can be achieved when efforts are made to address and compensate for these deficiencies.
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EGS — Goodbye or Back to the Future
R. Jung
Book Title / Journal: Effective and Sustainable Hydraulic Fracturing - Chapter 5
Year: 2013
Mining
  • Description
    • The heat content of the crystalline basement is by far the biggest energy resource of the earth crust. First attempts to access this resource date back to the early 1970´th and more than a dozen research and industrial projects have been performed since than in various countries. But still the technique, known as HDR (Hot-Dry-Rock) or EGS (Enhanced-Geothermal-Systems) is not mature and the thermal power achieved so far does not meet economical standards. In addition further development is now hindered by the risk of induced earthquakes.
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Understanding Hydraulic Fracture Growth, Effectiveness, and Safety Through Microseismic Monitoring
N.R. Warpinski
Book Title / Journal: Effective and Sustainable Hydraulic Fracturing - Chapter 6
Year: 2013
Mining
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Development of Fracture Networks Through Hydraulic Fracture Growth in Naturally Fractured Reservoirs
X. Zhang ; R. Jeffrey
Book Title / Journal: Effective and Sustainable Hydraulic Fracturing - Chapter 7
Year: 2013
Discrete Element ; Mining
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Hydraulic Fracture Propagation Across a Weak Discontinuity Controlled by Fluid Injection
D. Chuprakov ; O. Melchaeva ; R. Prioul
Book Title / Journal: Effective and Sustainable Hydraulic Fracturing - Chapter 8
Year: 2013
Rock Mechanics ; Mining
  • Description
    • The present chapter investigates the problem of a hydraulic fracture propagation through a weakly cohesive frictional discontinuity for different conditions of fracture toughness, in situ stresses, fracture intersection angle, injection parameters and permeability of the pre-existing fracture. The parametric sensitivity of the fracture interaction process, in terms of crossing versus arresting of the hydraulic fracture at the discontinuity, was performed using numerical simulations through an extensive parameter space representative of hydraulic fracturing field conditions. The effect of the pre-existing fracture permeability on the crossing behavior was analyzed using a simple analytical model. We showed that the injection rate and viscosity of fracturing fluid are the key parameters controlling the crossing/non-crossing interaction behavior, in addition to already known fracture interaction angle and in-situ stress parameters. We have also found that the pre-existing fracture hydraulic aperture, when as large as that of the hydraulic fracture aperture, has significant influence on the interaction and may more likely cause the hydraulic fracture to arrest.
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Effect of Flow Rate and Viscosity on Complex Fracture Development in UFM Model
O. Kresse ; X. Weng ; D. Chuprakov ; R. Prioul ; C. Cohen
Book Title / Journal: Effective and Sustainable Hydraulic Fracturing - Chapter 9
Year: 2013
Rock Mechanics ; Mining
  • Description
    • In this paper we present the results of several test cases showing the influence of injection rate and fluid viscosity on the generated hydraulic fracture footprint in formations with preexisting natural fractures. The influence of the stress field anisotropy, intersection angle, as well as natural fractures properties are also important and are discussed. The results are then compared with the simulations using a crossing model which does not account for the influence of fluid properties.
  • Abstract

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Hydrochemical and Hydrogeological Impact of Hydraulic Fracturing in the Karoo, South Africa
G. Steyl ; G.J. van Tonder
Book Title / Journal: Effective and Sustainable Hydraulic Fracturing - Chapter 10
Year: 2013
Rock Mechanics ; Mining
  • Description
    • Hydraulic fracturing has become a prevalent public and regulatory issue in most countries developing shale gas. South Africa has only recently been exposed to terrestrial gas resource development and this has created unique regulatory issues which are currently being resolved. One of the key issues under debate is the protection of groundwater resources in rural areas, since most of South Africa’s rural and some inland cities are dependent on groundwater for potable water supply. A second concern is the infrastructure requirements to handle the material movement processes during the development of each wellfield and subsequent processing of waste generated on site. Regarding the waste material production, a phased approach is required which considers the initial well development activities, production and subsequent well abandonment. Each phase has a unique risk associated with it and thus would require different management options. At the current stage most of the focus is on the initial stages of well development but the long term view has been neglected to some extent. Due to the unique geological structure of the Karoo, the presence of dolerite structures, a number of risk mitigation methods might be required to succesfully develop hydraulically fractured wells. In all aspects the chemical and hydrogeological impacts related to wellfield development cannot be ignored in the Karoo aquifer system, as it may directly influence human and environmental health. This paper will present chemical perspective on the hydraulic fracturing perspective that will deal with the impact of hydraulic fracturing fluid and flowback water. Additionally, the interaction of wellfield development and hydrogeology of the Karoo area will be discussed and how it relates to future water quality issues.
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Regulatory Nirvana for Hydraulic Fracture Stimulation
B. Goldstein ; M. Malavazos ; A. Wickham ; M Jarosz ; D. Pepicelli ; Mi Webb ; D Wenham
Book Title / Journal: Effective and Sustainable Hydraulic Fracturing - Chapter 11
Year: 2013
Mining
  • Description
    • Government are challenged to deploy trustworthy regulation to enable profitable and environmentally sustainable unconventional petroleum projects. A key activity under scrutiny during the development of these projects is hydraulic fracture stimulation. Regulatory ‘Nirvana’ for unconventional projects and conventional projects alike entails: • Pragmatic licence tenure; • Regulatory certainty and efficiency without taint of capture; • Regulators and licensees with trustworthy competence and capacity; • Effective stakeholder consultation well-ahead of land access; • Public access to details of significant risks and reliable research to backup risk management strategies so the basis for regulation is contestable anytime, everywhere; • Timely notice of entry with sufficient operational details to effectively inform stakeholders; • Potentially affected people and organisations can object to land access - without support for vexatious objections; • Fair and expeditious dispute resolution processes; • Fair compensation to affected land-users; • Risks are reduced to low or as low as reasonably practicable (ALARP) while also meeting community expectations for net outcomes; • Licensees monitor and report on the efficacy of their risk management, and the regulator probes same; • Regulator can prevent and stop operations, require restitution, levy fines and cancel licences; and • Industry compliance records are public, so the efficacy of regulation is transparent. These principles are deployed in South Australia where: • 24 unconventional gas plays are being explored, each with giant gas potential; • Hundreds of wells have been safely hydraulically fracture stimulated; The introduction of new energy development technologies is inevitable, so regulatory Nir‐ vana requires adaptive learning so that the previously mentioned principles are maintained. Expeditious, welcomed access to land for compatible, multiple uses is the metric for per‐ formance, and leading practice is based on the principle that trust is the most valuable lead factor and lag outcome in sustaining land access for resource exploration, development and production.
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How Can Understanding Community Concerns About Hydraulic Fracturing Help to Address Them?
S.T. Cham ; P. Stone
Book Title / Journal: Effective and Sustainable Hydraulic Fracturing - Chapter 12
Year: 2013
Mining
  • Description
    • Hydraulic fracturing has been the focal point of widespread and global public debate. While the resources sector typically sees hydraulic fracturing as a low-risk method for accessing the coal seam and shale gas reserves required to meet growing public demand for energy, some in the community perceive it as an unmanageable and unacceptable risk. Concerns about hydraulic fracturing and the coal seam gas (CSG) industry include the health impacts of chemicals used, contamination of water supplies from fugitive gas after hydraulic fracturing, equity of land and water access, long term impacts on groundwater, and the full life cycle emission of greenhouse gases from CSG compared to that of coal. This paper highlights the main psychological drivers behind some of these concerns and a possible approach to effectively address them.
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Numerical Study of Interaction Between Hydraulic Fracture and Discrete Fracture Network
A. Riahi ; B. Damjanac
Book Title / Journal: Effective and Sustainable Hydraulic Fracturing - Chapter 13
Year: 2013
Rock Mechanics ; Mining
  • Description
    • This paper discusses the interaction between hydraulic fracturing and the pre-existing dis‐ crete fracture network (DFN) in a rock mass subject to in–situ stresses. Two–dimensional computational model studies have been used in an initial attempt towards understanding how reservoir response to fluid injection is affected by some of the DFN characteristics and to operational variables such as injection rate.
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Hydraulic Fracturing in Formations with Permeable Natural Fractures
O. Kresse ; X. Weng
Book Title / Journal: Effective and Sustainable Hydraulic Fracturing - Chapter 14
Year: 2013
Rock Mechanics ; Mining
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Injection Modeling and Shear Failure Predictions in Tight Gas Sands — A Coupled Geomechanical Simulation Approach
A. Islam ; A- Settari
Book Title / Journal: Effective and Sustainable Hydraulic Fracturing - Chapter 15
Year: 2013
Numerical & Constitutive Modeling ; Mining
  • Description
    • This work presents theory for modeling of fracture propagation within reservoir simulator, history matching of field injection pressure using uncoupled and fully coupled geomechanical injection models, and sensitivity study of various parameters such as permeability enhancement/reduction functions, limiting length of fracture propagation, stress factor, and Biot’s constant. Two wells completed in tight gas sands in Western Canadian sedimentary basin were studied. The wells were fractured with different techniques (i.e., X-link gelled water fracs (Well A) and un-gelled slick water fracs (Well B)) and were both successfully matched with coupled geomechanical model.
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The Role of Natural Fractures in Shale Gas Production
I. Walton ; J. McLennan
Book Title / Journal: Effective and Sustainable Hydraulic Fracturing - Chpater 16
Year: 2013
Mining ; Other Geotechnical
  • Description
    • In this paper we investigate the role played by natural fractures in the gas production process. By applying a new model of the production process to data from many shale gas wells across a number of shale plays in North America, we can for the first time begin to sort out assertion from inference in the role that these fractures play. Specifically, we are able to estimate the magnitude of the fracture surface through which gas is actually produced. We are able to demonstrate that although it may be commensurate with the expected surface area of open natural fractures for the ultra-low permeability shallow gas shales, it is in fact com‐ mensurate with a very much smaller area for the deeper gas shales such as the Barnett. Furthermore, given a typical value of the matrix permeability, almost all the gas between the fractures would have been produced in an uncharacteristically short period of time unless the producing fractures are 100s of feet apart. The implications of these findings for completion and stimulation strategies will be discussed.
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Do Perforated Completions Have Value for Engineered Geothermal Systems
W. Glauser ; J. McLennan ; I. Walton
Book Title / Journal: Effective and Sustainable Hydraulic Fracturing - Chapter 17
Year: 2013
Mining ; Other Geotechnical ; Geothermal
  • Description
    • A comparative and realistic analysis is done to assess the impact of perforation skin, tortuosity associated with shear fractures intersecting the wellbore and relative economics associated with perforating and cementing geothermal wells
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Initiation and Breakdown of an Axisymmetric Hydraulic Fracture Transverse to a Horizontal Wellbore
S. Abbas ; B. Lecampion
Book Title / Journal: Effective and Sustainable Hydraulic Fracturing - Chapter 19
Year: 2013
Mining ; Other Geotechnical
  • Description
    • We investigate the initiation and early-stage propagation of an axi-symmetric hydraulic fracture from a wellbore drilled in the direction of the minimum principal stress in an elastic and impermeable formation. Such a configuration is akin to the case of a horizontal well and a hydraulic fracture transverse to the well axis in an open hole completion. In addition to the effect of the wellbore on the elasticity equation, the effect of the injection system compressi‐ bility is also taken into account. The formulation accounts for the strong coupling between the elasticity equation, the flow of the injected fluid within the newly created crack and the fracture propagation condition. Dimensional analysis of the problem reveals that three di‐ mensionless parameters control the entire problem: the ratio of the initial defect length over the wellbore radius, the ratio between the wellbore radius and a length-scale associated with the fluid stored by compressibility in the injection system during the well pressurization, and finally the ratio of the time-scale of transition from viscosity to toughness dominated propagation to the time-scale associated with compressibility effects. A fully coupled nu‐ merical solver is presented, and validated against solutions for a radial hydraulic fracture propagating in an infinite medium. The influence of the different parameters on the transi‐ tion from the near-wellbore to the case of a hydraulic fracture propagating in an infinite me‐ dium is fully discussed.
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