Fractal modeling of natural fracture networks. Final report, June 1994--June 1995

The creation of large complex fracture networks by hydraulic fracturing is imperative for enhanced oil recovery from tight sand or shale reservoirs, tight gas extraction, and Hot-Dry-Rock (HDR) geothermal systems to improve the contact area to the rock matrix. Although conventional fracturing treatments may result in bi-wing fractures, there is evidence by microseismic mapping that fracture networks can develop in many unconventional reservoirs, especially when natural fracture systems are present and the differences between the principle stresses are low. However, not much insight is gained about fracture development as well as fluid and proppant transport in naturally fractured tight formations. In order to clarify the relationship between rock and treatment parameters, and resulting fracture properties, numerical simulations were performed using a commercial Discrete Fracture Network (DFN) simulator. A comprehensive sensitivity analysis is presented to identify typical fracture network patterns resulting from massive water fracturing treatments in different geological conditions. It is shown how the treatment parameters influence the fracture development and what type of fracture patterns may result from different treatment designs. The focus of this study is on complex fracture network development in different natural fracture systems. Additionally, the applicability of the DFN simulator for modeling shale gas stimulation and HDR stimulation is critically discussed. The approach stated above gives an insight into the relationships between rock properties (specifically matrix properties and characteristics of natural fracture systems) and the properties of developed fracture networks. Various simulated scenarios show typical conditions under which different complex fracture patterns can develop and prescribe efficient treatment designs to generate these fracture systems. Hydraulic stimulation is essential for the production of oil, gas, or heat from ultratight formations like shales and basement rocks (mainly granite). If natural fracture systems are present, the fracturing process becomes more complex to simulate. Our simulation results reveal valuable information about main parameters influencing fracture network properties, major factors leading to complex fracture network development, and differences between HDR and shale gas/oil shale stimulations.

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Characterizing flow in natural fracture networks

Groundwater in Fractured Rocks ◽

10.1201/9780203945650.ch29 ◽

2007 ◽

pp. 437-449 ◽

Cited By ~ 1

Author(s):

Philippe Davy ◽

Jean Raynald De Dreuzy ◽

Tanguy Le Borgne ◽

Olivier Bour

Keyword(s):

Natural Fracture ◽

Fracture Networks

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Interaction of Hydraulic and Natural Fracture Networks Inferred by Integrating Microseismic and Geomechanical Techniques

10.1190/segam2012-1577.1 ◽

2012 ◽

Cited By ~ 1

Author(s):

Andreas Wuestefeld ◽

J-. Michael Kendall ◽

Ted Urbancic

Keyword(s):

Natural Fracture ◽

Fracture Networks

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An Integrated Study to Characterize and Model Natural Fracture Networks of Gas Condensate Carbonate Reservoirs, Onshore Abu Dhabi, UAE

10.2118/186043-ms ◽

2017 ◽

Author(s):

Budour Ateeq ◽

Mohamed El Gohary ◽

Khalid Al Ammari ◽

Rashad Masoud ◽

Abdelwahab Noufal ◽

...

Keyword(s):

Gas Condensate ◽

Carbonate Reservoirs ◽

Natural Fracture ◽

Abu Dhabi ◽

Fracture Networks ◽

Integrated Study

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Acid Penetration in Natural Fracture Networks

10.2118/68927-ms ◽

2001 ◽

Cited By ~ 3

Author(s):

Chengli Dong ◽

D. Zhu ◽

A.D. Hill

Keyword(s):

Natural Fracture ◽

Fracture Networks

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Modelling large-scale fractured reservoirs efficiently for geothermal energy and groundwater flow

10.5194/egusphere-egu2020-9278 ◽

2020 ◽

Author(s):

Simon Oldfield ◽

Mikael Lüthje ◽

Michael Welch ◽

Florian Smit

Keyword(s):

Fluid Flow ◽

Geothermal Energy ◽

Large Scale ◽

Fractured Reservoirs ◽

Fracture Network ◽

Natural Fracture ◽

Fracture Networks ◽

Persistent Problem ◽

Fracture Evolution ◽

Rapid Generation

Large scale modelling of fractured reservoirs is a persistent problem in representing fluid flow in the subsurface. Considering a geothermal energy prospect beneath the Drenthe Aa area, we demonstrate application of a recently developed approach to efficiently predict fracture network geometry across an area of several square kilometres.Using a strain based method to mechanically model fracture nucleation and propagation, we generate a discretely modelled fracture network consisting of individual failure planes, opening parallel and perpendicular to the orientation of maximum and minimum strain. Fracture orientation, length and interactions vary following expected trends, forming a connected fracture network featuring population statistics and size distributions comparable to outcrop examples.Modelled fracture networks appear visually similar to natural fracture networks with spatial variation in fracture clustering and the dominance of major and minor fracture trends.Using a network topology approach, we demonstrate that the predicted fracture network shares greater geometric similarity with natural networks. Considering fluid flow through the model, we demonstrate that hydraulic conductivity and flow anisotropy are strongly dependent on the geometric connection of fracture sets.Modelling fracture evolution mechanically allows improved representation of geometric aspects of fracture networks to which fluid flow is particularly sensitive. This method enables rapid generation of discretely modelled fractures over large areas and extraction of suitable summary statistics for reservoir simulation. Visual similarity of the output models improves our ability to compare between our model and natural analogues to consider model validation.

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Predictive Modelling of Naturally Fractured Reservoirs Using Geomechanics and Flow Simulation

GeoArabia ◽

10.2113/geoarabia060127 ◽

2001 ◽

Vol 6 (1) ◽

pp. 27-42

Author(s):

Stephen J. Bourne ◽

Lex Rijkels ◽

Ben J. Stephenson ◽

Emanuel J.M. Willemse

Keyword(s):

Fractured Reservoirs ◽

Flow Simulation ◽

Naturally Fractured Reservoirs ◽

Natural Fracture ◽

Production Data ◽

Well Test ◽

Fracture Networks ◽

Field Scale ◽

Fracture Permeability ◽

Naturally Fractured

ABSTRACT To optimise recovery in naturally fractured reservoirs, the field-scale distribution of fracture properties must be understood and quantified. We present a method to systematically predict the spatial distribution of natural fractures related to faulting and their effect on flow simulations. This approach yields field-scale models for the geometry and permeability of connected fracture networks. These are calibrated by geological, well test and field production data to constrain the distributions of fractures within the inter-well space. First, we calculate the stress distribution at the time of fracturing using the present-day structural reservoir geometry. This calculation is based on a geomechanical model of rock deformation that represents faults as frictionless surfaces within an isotropic homogeneous linear elastic medium. Second, the calculated stress field is used to govern the simulated growth of fracture networks. Finally, the fractures are upscaled dynamically by simulating flow through the discrete fracture network per grid block, enabling field-scale multi-phase reservoir simulation. Uncertainties associated with these predictions are considerably reduced as the model is constrained and validated by seismic, borehole, well test and production data. This approach is able to predict physically and geologically realistic fracture networks. Its successful application to outcrops and reservoirs demonstrates that there is a high degree of predictability in the properties of natural fracture networks. In cases of limited data, field-wide heterogeneity in fracture permeability can be modelled without the need for field-wide well coverage.

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Clustering, Connectivity and Flow Responses of Deterministic Fractal-Fracture Networks

Advances in Geosciences ◽

10.5194/adgeo-54-149-2020 ◽

2020 ◽

Vol 54 ◽

pp. 149-156

Author(s):

Ajay K. Sahu ◽

Ankur Roy

Keyword(s):

Fractal Dimension ◽

Spatial Clustering ◽

Flow Behavior ◽

Flow Simulation ◽

Fractal Dimensions ◽

Fracture Network ◽

Natural Fracture ◽

Fracture Networks ◽

Fracture Models ◽

Fractal Fracture

Abstract. It is well known that fracture networks display self-similarity in many cases and the connectivity and flow behavior of such networks are influenced by their respective fractal dimensions. In the past, the concept of lacunarity, a parameter that quantifies spatial clustering, has been implemented by one of the authors in order to demonstrate that a set of seven nested natural fracture maps belonging to a single fractal system, but of different visual appearances, have different clustering attributes. Any scale-dependency in the clustering of fractures will also likely have significant implications for flow processes that depend on fracture connectivity. It is therefore important to address the question as to whether the fractal dimension alone serves as a reasonable proxy for the connectivity of a fractal-fracture network and hence, its flow response or, if it is the lacunarity, a measure of scale-dependent clustering, that may be used instead. The present study attempts to address this issue by exploring possible relationships between the fractal dimension, lacunarity and connectivity of fractal-fracture networks. It also endeavors to study the relationship between lacunarity and fluid flow in such fractal-fracture networks. A set of deterministic fractal-fracture models generated at different iterations and, that have the same theoretical fractal dimension are used for this purpose. The results indicate that such deterministic synthetic fractal-fracture networks with the same theoretical fractal dimension have differences in their connectivity and that the latter is fairly correlated with lacunarity. Additionally, the flow simulation results imply that lacunarity influences flow patterns in fracture networks. Therefore, it may be concluded that at least in synthetic fractal-fracture networks, rather than fractal dimension, it is the lacunarity or scale-dependent clustering attribute that controls the connectivity and hence the flow behavior.

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A Peridynamics Model for the Propagation of Hydraulic Fractures in Heterogeneous, Naturally Fractured Reservoirs

10.2118/spe-173361-ms ◽

2015 ◽

Author(s):

Hisanao Ouchi ◽

Amit Katiyar ◽

John T. Foster ◽

Mukul M. Sharma

Keyword(s):

Hydraulic Fracturing ◽

Hydraulic Fracture ◽

Fracture Propagation ◽

Two Dimensions ◽

Natural Fracture ◽

Hydraulic Fractures ◽

Natural Fractures ◽

Fracture Networks ◽

Complex Fracture ◽

Nonlocal Continuum Theory

Abstract A novel fully coupled hydraulic fracturing model based on a nonlocal continuum theory of peridynamics is presented and applied to the fracture propagation problem. It is shown that this modeling approach provides an alternative to finite element and finite volume methods for solving poroelastic and fracture propagation problems and offers some clear advantages. In this paper we specifically investigate the interaction between a hydraulic fracture and natural fractures. Current hydraulic fracturing models remain limited in their ability to simulate the formation of non-planar, complex fracture networks. The peridynamics model presented here overcomes most of the limitations of existing models and provides a novel approach to simulate and understand the interaction between hydraulic fractures and natural fractures. The model predictions in two-dimensions have been validated by reproducing published experimental results where the interaction between a hydraulic fracture and a natural fracture is controlled by the principal stress contrast and the approach angle. A detailed parametric study involving poroelasticity and mechanical properties of the rock is performed to understand why a hydraulic fracture gets arrested or crosses a natural fracture. This analysis reveals that the poroelasticity, resulting from high fracture fluid leak-off, has a dominant influence on the interaction between a hydraulic fracture and a natural fracture. In addition, the fracture toughness of the rock, the toughness of the natural fracture, and the shear strength of the natural fracture also affect the interaction between a hydraulic fracture and a natural fracture. Finally, we investigate the interaction of multiple completing fractures with natural fractures in two-dimensions and demonstrate the applicability of the approach to simulate complex fracture networks on a field scale.

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