Coupled Numerical Evaluations of the Geomechanical Interactions Between a Hydraulic Fracture Stimulation and a Natural Fracture System in Shale Formations

Nagel, N.B.; Sanchez-Nagel, Marisela; Zhang, Fengshou; García, Xavier; Lee, B.

doi:10.1007/s00603-013-0391-x

Cited by 173 publications

(53 citation statements)

References 35 publications

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“…DFNs are often characterized by several statistical parameters, among them, fracture orientation distribution, fracture spacing distribution, fracture length distribution and fracture persistence of each fracture set, etc. [3,[29][30][31][32]. The combinations of these statistical characteristics that describe the geometrical properties of a DFN defined by the macro-scale connectivity and directional flow preference of the DFN are essential for the fluid transport characterization of an unconventional reservoir.…”

Section: Discrete Fracture Network Realizationmentioning

confidence: 99%

Numerical Modeling of Variable Fluid Injection-Rate Modes on Fracturing Network Evolution in Naturally Fractured Formations

2016

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Abstract:In this study, variable injection-rate technology was numerically investigated in a pre-existing discrete fracture network (DFN) formation, the Tarim Basin in China. A flow-stressdamage (FSD) coupling model has been used in an initial attempt towards how reservoir response to variable injection-rates at different hydraulic fracturing stages. The established numerical model simultaneously considered the macroscopic and microscopic heterogeneity characteristics. Eight numerical cases were studied. Four cases were used to study the variable injection-rate technology, and the other four cases were applied for a constant injection-rate in order to compare with the variable injection-rate technology. The simulation results show that the variable injection-rate technology is a potentially good method to a form complex fracturing networks. The hydraulic fracturing effectiveness when increasing the injection-rate at each stage is the best, also, the total injected fluid is at a minimum. At the initial stage, many under-fracturing points appear around the wellbore with a relatively low injection-rate; the sudden increase of injection rate drives the dynamic propagation of hydraulic fractures along many branching fracturing points. However, the case with decreasing injection rate is the worst. By comparing with constant injection-rate cases, the hydraulic fracturing effectiveness with variable flow rate technology is generally better than those with constant injection-rate technology. This work strongly links the production technology and hydraulic fracturing effectiveness evaluation and aids in the understanding and optimization of hydraulic fracturing simulations in naturally fractured reservoirs.

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Section: Discrete Fracture Network Realizationmentioning

confidence: 99%

Numerical Modeling of Variable Fluid Injection-Rate Modes on Fracturing Network Evolution in Naturally Fractured Formations

2016

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“…In ultra-low permeability formations, complex leakoff models are essential for accurate results and should be used for all shale plays (Savitski et al, 2013). Previous shale gas modeling efforts have represented the complex interactions of the created hydraulic fracture with natural fractures using a traditional finite element approach by treating the natural fractures as a simplified equivalent continuum or damage zone around the single, main hydraulic fracture (Nagel et al, 2012b).…”

Section: Unconventional Modelingmentioning

confidence: 99%

“…The numerical model must represent the two types of mechanical behavior, first the behavior of the solid material of blocks, and second the behavior of the discontinuities or fractures. The continuum models are ill-suited for addressing the explicit mechanical behavior of discontinuities and fractures since they must recognize the existence and behavior of interfaces between the discrete blocks that comprise the rock system (Nagel et al, 2012b). Therefore, distinct element modeling is often regarded as the best practice for incorporating the discrete behaviors of fractures into reservoir simulators in order to properly characterize the transmission of fluid from matrix to fracture blocks.…”

Section: Complex Fracture Modelingmentioning

confidence: 99%

“…This technology based need stems from the inability of former conventional reservoir models to accurately predict and represent the behavior of these very low permeability reservoirs (Warpinksi et al, 2009). For instance, most numerical simulators developed for sandstones assume bi-planar fracture development under almost constant leakoff whereas complex fracture networks and leakoff into fractures and fissures need to be accounted for in shale reservoirs (Nagel et al, 2012b).…”

Section: Introduction To Hydraulic Fracture Modelingmentioning

confidence: 99%

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Coupled Geomechanics and Fluid Flow Model for Production Optimization in Naturally Fractured Shale Reservoirs

Curnow

Tutuncu

2015

SEG Technical Program Expanded Abstracts 2015

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The benefits of hydraulic fracturing horizontal wells in unconventional reservoirs for production enhancement are evident; however, the best methods to truly increase recovery efficiency through these stimulations are still under great examination.Analogous to how operators and service companies discovered that Barnett-style slickwater treatments were not successful in all reservoirs, companies are beginning to recognize the importance of engineered stimulations, specifically in regard to geomechanics. Rather than perforating for only production purposes, hydraulic fracturing design has now turned its focus to perforating for reservoir rock stimulation.Enhanced fracture network complexity through induced fractures greatly increases the contact area and reservoir drainage for maximum productivity. However, to accomplish the stimulation of both primary and secondary fracture networks, the coupled behaviors of geomechanics and fluid flow in response to the hydraulic fracturing operations must be considered.This research details the development of a coupled geomechanics and fluid flow model for the purpose of hydraulic fracture design optimization through the evaluation of different stimulation patterns. The patterns under consideration include the Zipper, Texas Two-Step, and Modified Zipper designs. Furthermore within these patterns, the well locations and hydraulic fracture properties are analyzed to determine the most ideal design for a shale oil reservoir based on recovery efficiency and economic viability.

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“…Numerous studies have been carried out to explore the mechanism of hydraulic fracturing, mainly focusing on the interactions between artificial and natural fractures in naturally fractured reservoirs [3,4]. Experiments have showed thatbecause of the complex influences of various factors, such as far-field stress, loading pressure and inclusions -a reservoir may present different fracture mechanisms or patterns [5][6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Hydraulic Fracturing Mechanism in Reservoirs with a Linear Inclusion Fissure

Wang¹,

Zhu

et al. 2016

J. Eng. Technol. Sci.

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Abstract. Hydraulic fracturing technology is widely used in most oil-water wells to improve production. However, the mechanism of fracturing in a reservoir with inclusion fissures is still unclear. In this study, a theoretical model was developed to determine the stress distribution during hydraulic fracturing. The line inclusion fissure was regarded as a thin bar and the stress around the artificial fracture, which is affected by a single line inclusion, was determined using the Eshelby equivalent inclusion theory. Stress intensity factors at the tip of both the artificial fracture and the inclusion were achieved, and initiation of the fracture was predicted. Furthermore, to validate the theoretical model, refracturing experiments were performed on a large-scale tri-axial system. The results showed that the defects reduce the intensity of the rock, which introduces the possibility that more complex fractures emerge in the reservoir. The results also showed that the fracture direction is governed by far-field stress. The obtained conclusions are helpful to better understand the mechanism of hydraulic fracturing in reservoirs.

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Coupled Numerical Evaluations of the Geomechanical Interactions Between a Hydraulic Fracture Stimulation and a Natural Fracture System in Shale Formations

Cited by 173 publications

References 35 publications

Numerical Modeling of Variable Fluid Injection-Rate Modes on Fracturing Network Evolution in Naturally Fractured Formations

Numerical Modeling of Variable Fluid Injection-Rate Modes on Fracturing Network Evolution in Naturally Fractured Formations

Coupled Geomechanics and Fluid Flow Model for Production Optimization in Naturally Fractured Shale Reservoirs

Hydraulic Fracturing Mechanism in Reservoirs with a Linear Inclusion Fissure

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