Recent Advances in the Characterization of Unconventional Reservoirs with Wide-Azimuth Seismic Data

Bachrach, Ran; Sayers, Colin M.; Dasgupta, Sagnik; Silva, Josimar; Volterrani, Stefano

doi:10.1190/urtec2013-030

Cited by 25 publications

(6 citation statements)

References 14 publications

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“…The workflow used to determine in-situ stress, stress anisotropy, geomechanical properties, and the density and orientation of natural fractures in unconventional reservoirs is shown in figure 1. An essential component of this workflow is the use of seismic AVOAz (Amplitude Variation with Offset and Azimuth) inversion (Bachrach et al, 2013). During the presentation, this workflow will be illustrated using examples from the Middle East and North America.…”

Section: Methodsmentioning

confidence: 99%

Seismic Inversion for Engineering Applications in Unconventional Reservoirs

Sayers¹,

Dasgupta²,

Boer³

et al. 2017

Proceedings

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SummaryEconomic production from unconventional reservoirs requires increasing the surface area in contact with the reservoir via hydraulic fracturing. Important to the design of efficient hydraulic fractures is knowledge of the orientation and magnitude of principal stresses, geomechanical rock properties, and the density and orientation of any natural fractures. The use of seismic AVOAz (Amplitude Variation with Offset and Azimuth) inversion to determine fracture density and orientation as well as horizontal stress anisotropy and the orientation of the principal stresses is illustrated using examples from the Middle East and North America. An example is shown of using the results of seismic AVOAz inversion calibrated to geomechanical measurements on cores, to build a 3D MEM (Mechanical Earth Model) for an area in North America. The variation in principal stresses over the area is evaluated using the Finite Element Method. Computed stresses are found to be consistent with variability in production over the area and show stress rotations near faults in agreement with microseismic data.

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Section: Methodsmentioning

confidence: 99%

Seismic Inversion for Engineering Applications in Unconventional Reservoirs

Sayers¹,

Dasgupta²,

Boer³

et al. 2017

Proceedings

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“…(Bachrach et al ., ). It then follows from equations and that

\begin{matrix} true \\ right R_{PP} (θ, ϕ) & = & left R_{italicPP}^{VTI} (θ) + \frac{1}{4} (normalΔ Γ_{x}^{'} - normalΔ Γ_{y}^{'}) prefixcos 2 ϕ {sin}^{2} θ \\ left + \frac{1}{4} (normalΔ ε_{x}^{'} - normalΔ ε_{y}^{'}) prefixcos 2 ϕ {sin}^{2} θ {tan}^{2} θ . \end{matrix}

…”

Section: Fracture Compliance From Seismic Amplitude Variation With Ofmentioning

confidence: 97%

Constructing a discrete fracture network constrained by seismic inversion data

Boer

Sayers

2017

Geophysical Prospecting

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A B S T R A C TRock fractures are of great practical importance to petroleum reservoir engineering because they provide pathways for fluid flow, especially in reservoirs with low matrix permeability, where they constitute the primary flow conduits. Understanding the spatial distribution of natural fracture networks is thus key to optimising production. The impact of fracture systems on fluid flow patterns can be predicted using discrete fracture network models, which allow not only the 6 independent components of the second-rank permeability tensor to be estimated, but also the 21 independent components of the fully anisotropic fourth-rank elastic stiffness tensor, from which the elastic and seismic properties of the fractured rock medium can be predicted. As they are stochastically generated, discrete fracture network realisations are inherently nonunique. It is thus important to constrain their construction, so as to reduce their range of variability and, hence, the uncertainty of fractured rock properties derived from them. This paper presents the underlying theory and implementation of a method for constructing a geologically realistic discrete fracture network, constrained by seismic amplitude variation with offset and azimuth data. Several different formulations are described, depending on the type of seismic data and prior geologic information available, and the relative strengths and weaknesses of each approach are compared. Potential applications of the method are numerous, including the prediction of fluid flow, elastic and seismic properties of fractured reservoirs, model-based inversion of seismic amplitude variation with offset and azimuth data, and the optimal placement and orientation of infill wells to maximise production.

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“…The Hough transform (Duda and Hart 1972) is named after Hough from the patent he filed in 1962 (Hough 1962) to recognize linear patterns in a 2D space. One can easily extend this method to 3D space for any parameterized shape (Woodford et al 2011) such as planes (Borrmann et al 2011). In a 3D Cartesian space, knowing the azimuth u and dip h of the normal vector and the distance r to the origin of the coordinate system uniquely defines a plane.…”

Section: Hough Transform For Pattern Recognitionmentioning

confidence: 99%

“…Such an analytical approach more closely approximates the full Radon transform solution in the case of incomplete information . The way commonly used in pattern recognition is to make the continuous space discrete and solve it numerically by introducing a voting mechanism (Borrmann et al 2011). Thus, the Hough-parameter space is divided into a discrete grid.…”

Section: Hough Transform For Pattern Recognitionmentioning

confidence: 99%

“…Some methods describe the DFN in a statistical way, such as inferring the fracture intensity and orientation from horizontal anisotropy measured by wide azimuthal seismic data (Bachrach et al 2013;Far et al 2013) or 3D vertical seismic profiling (Misaghi et al 2005), whereby it is assumed the anisotropy is correlated with the fracture profile. More-explicit ways to derive a DFN would include extracting fault geometry from the seismic data with anttracking algorithms (Hu et al 2014) or finding discontinuities in the seismic image (Yan et al 2011).…”

Section: Introductionmentioning

confidence: 99%

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Discrete-Fracture-Network Generation From Microseismic Data by Use of Moment-Tensor- and Event-Location-Constrained Hough Transforms

Rutledge

Leaney

et al. 2016

SPE Journal

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Reservoir simulation and prediction of production associated with hydraulic-fracturing require the input of the fracture geometry and the fracture properties such as the porosity and retained permeability. Various methods were suggested and applied for deriving discrete fracture networks (DFNs) from microseismic data as a framework for modeling reservoir performance. Although microseismic data are the best diagnostics for revealing the volume of rock fractured, its incompleteness in representing the deformation induced presents a challenge to calibrate and represent complex fracture networks created and connected during hydraulic-fracture stimulation. We present an automated method to generate DFN models constrained by the microseismic locations and fracture plane orientations derived from moment-tensor analysis. We use a Hough-transform technique to find significant planar features from combinations of the microseismic source locations. We have modified the technique with an equal-probability voting scheme to remove an inherent bias for horizontal planes. The voting mechanism is a general grid search in the space of fracture strike, dip, and location (u; h; r, respectively) with grid-cell sizes scaled by uncertainty estimates of u; h; r. We constrain fracture orientations with weighting on the basis of the moment-tensor orientations of neighboring events and their associated uncertainties. With two case studies, we demonstrate that our automated technique can reliably extract the complex fracture network on the basis of good matches with the event-cloud trends and the input moment-tensor orientations. We also tested the sensitivity of the technique to event-location uncertainty. With increasing location uncertainty, the details of the fracture network extracted are diminished with events grouping to larger-scale features, but the general shape and orientation of the fracture network obtained are insensitive to the location uncertainty.

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Recent Advances in the Characterization of Unconventional Reservoirs with Wide-Azimuth Seismic Data

Cited by 25 publications

References 14 publications

Seismic Inversion for Engineering Applications in Unconventional Reservoirs

Seismic Inversion for Engineering Applications in Unconventional Reservoirs

Constructing a discrete fracture network constrained by seismic inversion data

Discrete-Fracture-Network Generation From Microseismic Data by Use of Moment-Tensor- and Event-Location-Constrained Hough Transforms

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