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Vladimir Grechka - One of the best experts on this subject based on the ideXlab platform.
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Characterization of Multiple Fracture Sets at Rulison Field, Colorado, USA
EAGE SEG Research Workshop on Fractured Reservoirs - Integrating Geosciences for Fractured Reservoirs Description, 2007Co-Authors: Vladimir Grechka, Ivan VasconcelosAbstract:Conventional Fracture-characterization methods assume the presence of a single set of cracks in the subsurface. We relax this assumption and demonstrate the feasibility of seismic characterization of Multiple Fracture sets. Our technique relies on recent findings indicating that Multiple, differently oriented, possibly intersecting cracks embedded in an otherwise isotropic host rock result in nearly orthotropic effective media. Here, we estimate the governing parameters of crack-induced orthotropy from 3D, wide-azimuth, multicomponent seismic reflection data acquired over the tight-gas Rulison Field in Colorado. We translate azimuthal variations of the normal-moveout velocities into interval crack densities, Fracture orientations, type of fluid infill, and velocities of P- and S-waves in an unFractured rock. Our inversion procedure identifies one set of cracks in the western part of the study area and Multiple, likely intersecting Fractures in its eastern part. We validate both our underlying theoretical model and the obtained estimates by two independent measurements: the estimated fluid-infill parameter indicates dry cracks as expected for the gas-producing sandstones at Rulison; and the obtained crack orientations are supported by well observations. As a by-product of Fracture characterization, we build an orthorhombic velocity model of the Rulison reservoir.
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seismic characterization of Multiple Fracture sets at rulison field colorado
Geophysics, 2007Co-Authors: Ivan Vasconcelos, Vladimir GrechkaAbstract:Conventional Fracture-characterization methods assume the presence of a single set of aligned, vertical cracks in the subsur-face. We relax this assumption and demonstrate the feasibility of seismic characterization of Multiple Fracture sets. Our technique relies on recent numerical findings indicating that Multiple, differently oriented, possibly intersecting planar cracks embedded in an otherwise isotropic host rock result in a nearly orthorhombic (or orthotropic) effective medium. Here, the governing parameters of crack-induced orthotropy are estimated from 3D, wide-azimuth, multicomponent seismic reflection data acquired over the tight-gas Rulison Field in Colorado. We translate strong azimuthal variations of the normal-moveout velocities intointerval crack densities, Fracture orientations, type of fluid infill, and velocities of P- and S-waves in an unFractured rock. Our inversion procedure identifies a set of cracks aligned in approximately west northwest-east southeast direction in the western part...
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Seismic characterization of Multiple Fracture sets at Rulison Field, ColoradoFracture characterization at Rulison
GEOPHYSICS, 2007Co-Authors: Ivan Vasconcelos, Vladimir GrechkaAbstract:Conventional Fracture-characterization methods assume the presence of a single set of aligned, vertical cracks in the subsur-face. We relax this assumption and demonstrate the feasibility of seismic characterization of Multiple Fracture sets. Our technique relies on recent numerical findings indicating that Multiple, differently oriented, possibly intersecting planar cracks embedded in an otherwise isotropic host rock result in a nearly orthorhombic (or orthotropic) effective medium. Here, the governing parameters of crack-induced orthotropy are estimated from 3D, wide-azimuth, multicomponent seismic reflection data acquired over the tight-gas Rulison Field in Colorado. We translate strong azimuthal variations of the normal-moveout velocities intointerval crack densities, Fracture orientations, type of fluid infill, and velocities of P- and S-waves in an unFractured rock. Our inversion procedure identifies a set of cracks aligned in approximately west northwest-east southeast direction in the western part...
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Seismic characterization of Multiple Fracture sets: Does orthotropy suffice?
GEOPHYSICS, 2006Co-Authors: Vladimir Grechka, Mark KachanovAbstract:As geophysicists rely increasingly on effective media theories to characterize naturally Fractured reservoirs, they become more and more interested in evaluating the accuracy of different theories, estimating their limits of applicability, and assessing their usefulness for practice. With this in mind, we compare two popular seismological theories of Hudson and Schoenberg with the theory of Kachanov developed in the context of mechanics of materials. By performing finite-element simulations of effective media for models that contain several sets of nonintersecting, circular, vertical Fractures embedded in otherwise isotropic host rock, we examine the accuracy of these theories. Our numeric study reveals that predictions of both the first- and second-order Hudson's theories are typically inferior to those of others, especially when the Fractures are dry. While, on average, the theories of Schoenberg and Kachanov fit finite-element computations with comparable accuracy, the latter appears to be more useful ...
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Feasibility of seismic characterization of Multiple Fracture sets
GEOPHYSICS, 2003Co-Authors: Vladimir Grechka, Ilya TsvankinAbstract:Estimation of parameters of Multiple Fracture sets is often required for successful exploration and development of naturally Fractured reservoirs. The goal of this paper is to determine the maximum number of Fracture sets of a certain rheological type which, in principle, can be resolved from seismic data. The main underlying assumption is that an estimate of the complete effective stiffness tensor has been obtained, for example, from multiazimuth, multicomponent surface seismic and vertical seismic profiling (VSP) data. Although typically only a subset of the stiffness elements (or some of their combinations) may be available, this study helps to establish the limits of seismic Fracture-detection algorithms. The number of uniquely resolvable Fracture systems depends on the anisotropy of the host rock and the rheology and orientation of the Fractures. Somewhat surprisingly, it is possible to characterize fewer vertical Fracture sets than dipping ones, even though in the latter case the Fracture dip has to be found from the data. For the simplest, rotationally invariant Fractures embedded in either isotropic or transversely isotropic with a vertical symmetry axis (VTI) host rock, the stiffness tensor can be inverted for up to two vertical or four dipping Fracture sets. In contrast, only one Fracture set of the most general (microcorrugated) type, regardless of its orientation, is constrained by the effective stiffnesses. These results can be used to guide the development of seismic Fracture-characterization algorithms that should address important practical issues of data acquisition, processing, and inversion for particular Fracture models.
L. A. Berglund - One of the best experts on this subject based on the ideXlab platform.
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A Multiple Fracture test for strain to failure distribution in wood
Wood Science and Technology, 1998Co-Authors: F. Thuvander, L. A. BerglundAbstract:The tensile strain to failure of small wood samples is a desirable property in studies where the effect of small differences in microstructure on failure is of interest. However, the scatter in data is usually significant and only one data is obtained per specimen. For this reason, a new Multiple Fracture test for measurement of the strain to failure distribution was designed. Wood samples were bonded between two transparent PVC layers with higher strain to failure than the wood. Multiple Fractures were then observed in single wood samples during tensile loading. This behavior is already utilized in tests in the field of synthetic composite materials. It was possible to conveniently register Multiple Fracture events as a function of strain by visual observation through the transparent PVC layers. The data were used to compare two different wood materials and to determine their Weibull distribution functions.
Ivan Vasconcelos - One of the best experts on this subject based on the ideXlab platform.
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Characterization of Multiple Fracture Sets at Rulison Field, Colorado, USA
EAGE SEG Research Workshop on Fractured Reservoirs - Integrating Geosciences for Fractured Reservoirs Description, 2007Co-Authors: Vladimir Grechka, Ivan VasconcelosAbstract:Conventional Fracture-characterization methods assume the presence of a single set of cracks in the subsurface. We relax this assumption and demonstrate the feasibility of seismic characterization of Multiple Fracture sets. Our technique relies on recent findings indicating that Multiple, differently oriented, possibly intersecting cracks embedded in an otherwise isotropic host rock result in nearly orthotropic effective media. Here, we estimate the governing parameters of crack-induced orthotropy from 3D, wide-azimuth, multicomponent seismic reflection data acquired over the tight-gas Rulison Field in Colorado. We translate azimuthal variations of the normal-moveout velocities into interval crack densities, Fracture orientations, type of fluid infill, and velocities of P- and S-waves in an unFractured rock. Our inversion procedure identifies one set of cracks in the western part of the study area and Multiple, likely intersecting Fractures in its eastern part. We validate both our underlying theoretical model and the obtained estimates by two independent measurements: the estimated fluid-infill parameter indicates dry cracks as expected for the gas-producing sandstones at Rulison; and the obtained crack orientations are supported by well observations. As a by-product of Fracture characterization, we build an orthorhombic velocity model of the Rulison reservoir.
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seismic characterization of Multiple Fracture sets at rulison field colorado
Geophysics, 2007Co-Authors: Ivan Vasconcelos, Vladimir GrechkaAbstract:Conventional Fracture-characterization methods assume the presence of a single set of aligned, vertical cracks in the subsur-face. We relax this assumption and demonstrate the feasibility of seismic characterization of Multiple Fracture sets. Our technique relies on recent numerical findings indicating that Multiple, differently oriented, possibly intersecting planar cracks embedded in an otherwise isotropic host rock result in a nearly orthorhombic (or orthotropic) effective medium. Here, the governing parameters of crack-induced orthotropy are estimated from 3D, wide-azimuth, multicomponent seismic reflection data acquired over the tight-gas Rulison Field in Colorado. We translate strong azimuthal variations of the normal-moveout velocities intointerval crack densities, Fracture orientations, type of fluid infill, and velocities of P- and S-waves in an unFractured rock. Our inversion procedure identifies a set of cracks aligned in approximately west northwest-east southeast direction in the western part...
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Seismic characterization of Multiple Fracture sets at Rulison Field, ColoradoFracture characterization at Rulison
GEOPHYSICS, 2007Co-Authors: Ivan Vasconcelos, Vladimir GrechkaAbstract:Conventional Fracture-characterization methods assume the presence of a single set of aligned, vertical cracks in the subsur-face. We relax this assumption and demonstrate the feasibility of seismic characterization of Multiple Fracture sets. Our technique relies on recent numerical findings indicating that Multiple, differently oriented, possibly intersecting planar cracks embedded in an otherwise isotropic host rock result in a nearly orthorhombic (or orthotropic) effective medium. Here, the governing parameters of crack-induced orthotropy are estimated from 3D, wide-azimuth, multicomponent seismic reflection data acquired over the tight-gas Rulison Field in Colorado. We translate strong azimuthal variations of the normal-moveout velocities intointerval crack densities, Fracture orientations, type of fluid infill, and velocities of P- and S-waves in an unFractured rock. Our inversion procedure identifies a set of cracks aligned in approximately west northwest-east southeast direction in the western part...
F. Thuvander - One of the best experts on this subject based on the ideXlab platform.
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A Multiple Fracture test for strain to failure distribution in wood
Wood Science and Technology, 1998Co-Authors: F. Thuvander, L. A. BerglundAbstract:The tensile strain to failure of small wood samples is a desirable property in studies where the effect of small differences in microstructure on failure is of interest. However, the scatter in data is usually significant and only one data is obtained per specimen. For this reason, a new Multiple Fracture test for measurement of the strain to failure distribution was designed. Wood samples were bonded between two transparent PVC layers with higher strain to failure than the wood. Multiple Fractures were then observed in single wood samples during tensile loading. This behavior is already utilized in tests in the field of synthetic composite materials. It was possible to conveniently register Multiple Fracture events as a function of strain by visual observation through the transparent PVC layers. The data were used to compare two different wood materials and to determine their Weibull distribution functions.
Jon Olson - One of the best experts on this subject based on the ideXlab platform.
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Characterization of hydraulic Fracture geometry in shale rocks through physical modeling
International Journal of Fracture, 2019Co-Authors: Weihong Wang, Kan Wu, Jon OlsonAbstract:In unconventional shale reservoirs, the presence of natural Fractures is common and widespread. Multi-stage hydraulic Fracture treatments are used to generate complex Fracture geometry and stimulate reservoirs to unlock hydrocarbon in unconventional reservoirs. Natural Fractures further complicate the complexity of the Fracture geometry. In this paper, the objective is to investigate the impact of natural Fractures on Multiple hydraulic Fracture propagation using an in-house Fracture propagation model. We have developed a complex hydraulic Fracture model to simulate Multiple Fracture propagation in naturally Fractured reservoirs. The model can calculate partitioning of fluid between Multiple Fractures, Fracture interaction within a stage and between stages, as well as the interaction between hydraulic and natural Fractures. For simultaneous Multiple Fracture propagation, the exterior Fractures generally take the majority of fluid and propagate at the expense of the interior Fractures. Natural Fractures can retard the growth of hydraulic Fractures and change the fluid distribution between Fractures and propagation trajectories of hydraulic Fractures. In a reservoir with a heterogeneous natural Fracture distribution, the interruption of natural Fractures can complicate Fracture geometry. The higher density or smaller spacing of natural Fractures can mitigate stress shadow effects and favor more fluid flowing into the inner Fractures. Due to the uncertainty of natural Fracture distribution, the reliability of the complex Fracture geometry provided by numerical models has been challenged. This paper demonstrates the potential of incorporating diagnostic results to constrain numerical results. Through combining diagnostic results with the Fracture model, the accuracy of predicted Fracture geometry can be improved.
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Numerical Analysis for Promoting Uniform Development of Simultaneous Multiple-Fracture Propagation in Horizontal Wells
SPE Production & Operations, 2016Co-Authors: Jon Olson, Matthew T. BalhoffAbstract:Summary Multistage hydraulic fracturing, together with horizontal drilling, plays an important role in the economic development of unconventional reservoirs. However, according to field analysis of stimulation effectiveness, only a small percentage of perforation clusters contribute to most of the well production. One reason for this low effectiveness is that Multiple Fractures do not take the same amount of fluid and proppant because of the interaction between hydraulic Fractures (i.e., stress-shadow effects). Unfortunately, how best to minimize the negative effects of stress shadowing is still not fully understood in the petroleum industry. In this paper, we analyze this problem to promote more-uniform Fracture growth by use of a complex hydraulic-Fracture-development model. We use our Fracture-propagation model, which couples rock deformation and fluid flow in the Fracture and horizontal wellbore. The model assumes homogeneous linear-elastic rock medium and does not consider proppant transport in Multiple Fractures. Partitioning of flow rate between Multiple Fractures is calculated by use of the principles of flow through an electric-circuit network. Fracture development is dominated by flow-rate distribution, which is controlled by flow resistance within the Fractures. For simultaneous Multiple-Fracture propagation, nonuniform flow-rate distribution is induced because stress-shadow effects exert additional flow resistance on the interior Fractures. To balance the extra resistance introduced by the effects, we investigated two adjustment approaches to promote uniform Fracture development. The first approach was to adjust perforation number or diameter to increase flow resistance entering the exterior Fractures. The second was to mitigate stress-shadow effects through management of nonuniform Fracture spacing. We found that decreasing perforation diameter or the number of exterior Fractures can divert fluid into the interior Fractures and promote even Fracture growth. Stress-shadow effects can be mitigated by moving the two interior Fractures away from each other and toward the exterior Fractures. The key mechanism is to maintain even flow resistance within each Fracture and facilitate Fractures to obtain the same amount of injection fluid. Furthermore, flow resistance is affected by near-wellbore Fracture tortuosity, natural Fractures, and stress heterogeneity in the reservoirs. These factors might also be effectively controlled by adding extra flow resistance to pass perforations, provided that this extra resistance is larger than the extra resistance introduced by the factors. This work analyzes the problem of uneven development of Multiple Fractures along the horizontal wellbore and provides new insights into how to control simultaneous Multiple-Fracture propagation. It offers potential approaches for engineers to apply in the field to optimize hydraulic-fracturing-treatment design, thereby maximizing well production cost-effectively.