Modeling of Hydraulic-Fracture-Network Propagation in a Naturally Fractured Formation

Weng, Xiaowei; Kresse, Olga; Cohen, C.; Wu, R.; Gu, Hongren

doi:10.2118/140253-pa

Cited by 284 publications

(132 citation statements)

References 25 publications

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“…In particular, we demonstrated that the stress contrast in the infill region reaches its lowest value exactly at the onset time of stress reversal halfway between the producing wells. Weng et al (2011) showed that interactions between hydraulic and natural fractures are largely influenced by the stress regime in which the induced fracture propagates. If the difference between minimum and maximum horizontal stresses is small, an induced fracture will have a larger tendency to branch-out when intersecting natural fractures, thus forming more complex fracture networks.…”

Section: Timing Of Infill Operationsmentioning

confidence: 99%

Hydraulic Fracture Propagation from Infill Horizontal Wells

Roussel

Florez

Rodríguez

2013

Day 3 Wed, October 02, 2013

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As pressure increases or decreases non-uniformly as a result of well injection/production, stresses vary anisotropically in the reservoir. The principal stresses, which govern the propagation direction of hydraulic fractures, are thus modified not only in magnitude but also in direction. Previous modeling efforts and field observations have demonstrated the impact of stress reorientation on the refracturing of vertical wells and the multi-stage fracturing of horizontal wells.Using a state-of-the-art coupled symmetric Galerkin boundary-element method (SGBEM) and finite-element method (FEM) model, we simulate the impact of prior production from offset wells on the propagation direction of fractures initiated from an infill horizontal well. Geomechanical calculations demonstrate the occurrence of stress reversal in the infill region following a period of production from the offset wells in the order of years. The numerically simulated hydraulic fracture network in the infill well is shown to contact a smaller reservoir area past the onset time of stress reversal, as the induced fractures gradually turn to orient parallel to the infill well. The risk is to see the performance of the infill well drop compared to the offset wells. On the other hand, a window of opportunity exists when the horizontal stress contrast is reduced compared to in-situ, thus favoring the interaction with natural fractures and enhancing fracture complexity.These new observations have significant implications for field development strategies, hydraulic fracturing design, well placement and spacing, as well as the timing of infill-well stimulation, especially in shale plays where poroelastic stress reorientation is sustained over the life of the reservoir. SPE 166503bigger role than fluid flow interference depends largely on the value of the in situ stress contrast. In cases featuring large in situ horizontal anisotropy, stress reversal is unlikely to occur and fluid flow interference is then likely to dominate.Studying of the impact of pressure-induced stress changes on fracture propagation direction is by no means of recent interest (Berchenko and Detournay 1997). In tight gas plays, poroelastic stress interference has been investigated and applied to the refracturing of vertical wells (Roussel 2011;Roussel and Sharma 2010a, 2010b;Siebrits and Elbel 1998;Warpinski and Branagan 1989;Weng and Siebrits 2007). In the case of a previously fractured well, it is possible to create a secondary fracture that is perpendicular to the first. Thus, refracturing makes it possible to access zones of the reservoirs that were previously unstimulated or understimulated. Initially, the direction of maximum horizontal stress is aligned with the initial vertical fracture. During production, the maximum horizontal stress decreases faster than the minimum horizontal stress, causing principal stresses to be reversed in the vicinity of the fracture. As a result, the second fracture may propagate orthogonal to the initial fracture. Past the isotropic point (L f '), the...

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Section: Timing Of Infill Operationsmentioning

confidence: 99%

Hydraulic Fracture Propagation from Infill Horizontal Wells

Roussel

Florez

Rodríguez

2013

Day 3 Wed, October 02, 2013

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“…The interaction between a hydraulic fracture (HF) and natural fracture (NF) can lead to the propagation of a fracture network (Jang et al 2015;Cai et al 2017), which is also influenced by heterogeneity of reservoir layers, irregular distribution of natural fractures and especially the in situ stress field (Olson 2008;Olson and Taleghani 2009). Weng et al (2011) and Weng (2015) developed an unconventional fracture model (UFM) and considered stress field, the orientation of the NF and rock deformation, which is very powerful to describe the hydraulic fracture propagation using an unstructured grid. On the other hand, the wiremesh model (Xu et al 2009(Xu et al , 2010Meyer and Bazan 2011) utilizes two orthogonal sets of planar elements to represent the area of the fracture network and stimulated reservoir volume (SRV), which is simple but effective for network modeling (Weng et al 2011).…”

Section: Introductionmentioning

confidence: 99%

“…Weng et al (2011) and Weng (2015) developed an unconventional fracture model (UFM) and considered stress field, the orientation of the NF and rock deformation, which is very powerful to describe the hydraulic fracture propagation using an unstructured grid. On the other hand, the wiremesh model (Xu et al 2009(Xu et al , 2010Meyer and Bazan 2011) utilizes two orthogonal sets of planar elements to represent the area of the fracture network and stimulated reservoir volume (SRV), which is simple but effective for network modeling (Weng et al 2011). Fracture spacing, the complexity of the fracture network and the grid's properties are considered during the hydraulic fracture propagation.…”

Section: Introductionmentioning

confidence: 99%

Performance-based fractal fracture model for complex fracture network simulation

Wang

Zhang

Xiang³

et al. 2017

Pet. Sci.

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The paper presents a novel hydraulic fracturing model for the characterization and simulation of the complex fracture network in shale gas reservoirs. We go beyond the existing method that uses planar or orthogonal conjugate fractures for representing the ''complexity'' of the network. Bifurcation of fractures is performed utilizing the Lindenmayer system based on fractal geometry to describe the fracture propagation pattern, density and network connectivity. Four controlling parameters are proposed to describe the details of complex fractures and stimulated reservoir volume (SRV). The results show that due to the multilevel feature of fractal fractures, the model could provide a simple method for contributing reservoir volume calibration. The primary-and second-stage fracture networks across the overall SRV are the main contributions to the production, while the induced fracture network just contributes another 20% in the late producing period. We also conduct simulation with respect to different refracturing cases and find that increasing the complexity of the fracture network provides better performance than only enhancing the fracture conductivity.

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“…There are some mathematic models to present the complex shale fracture morphological characteristics. For example, Weng et al (2011) presented the Unconventional Fracture Model (UFM), which can simulate complex-fracture-network propagation in a formation with preexisting natural fractures. Wenyue Xu et al (2009) put forward Wire-mesh model, which was fully constrained when accounting for mechanical interactions between injected fluid and fracture walls and among nearby fractures and when satisfying observation data including wellbore pressure and microseismic event distribution.…”

Section: Introductionmentioning

confidence: 99%

New Design Method of Multi-Stage Hydraulic Fracturing in Shale Horizontal Well

Guo

Gou

et al. 2014

All Days

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As the growth of energy demands, development of shale oil/gas resources has become major focus in China in the recent years. At the early stage, many fracturing technologies being popular with North America were directly brought in and applied to shale horizontal wells in China. However, some problems have shown up due to its own complex reservoir characteristics. It is necessary to seek for economic staged fracturing design based on specific shale reservoir characteristics and actual situation.This paper presents a mathematical model to investigate the relationship between the parameters of a treatment design and complex fracture network which is treated as a high permeability zone (HPZ). A novel three-step design method for multistage hydraulic fracturing is proposed on the basis of the model. Firstly, hydraulic fracture morphology is investigated through the analysis of brittleness index, stress interference caused by creation of hydraulic fractures and natural fractures. Then, the feature parameters of HPZ are optimized by utilizing numerical simulation based on the shale reservoir model that is built on the horizontal well data. At last, treatment parameters (the amount of proppant, the number of perforation clusters and position, displacement and fracturing fluids volum et al.) are determined by the model and fractuting simulator incorporated with reservoir property and the results of numerical reservoir simulation.The new design method is applied to the first shale oil horizontal Q2 well in Jianghan Basin. And the evaluation of postfracture data indicates that the new design method is proper and easy to use. This paper describes a new and convenient design method of multi-stage hydraulic fracturing in shale reservoirs. The method can also be extended to tight oil/gas reservoirs for horizontal staged-fracturing to maximize the stimulation reservoir volume.

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Modeling of Hydraulic-Fracture-Network Propagation in a Naturally Fractured Formation

Cited by 284 publications

References 25 publications

Hydraulic Fracture Propagation from Infill Horizontal Wells

Hydraulic Fracture Propagation from Infill Horizontal Wells

Performance-based fractal fracture model for complex fracture network simulation

New Design Method of Multi-Stage Hydraulic Fracturing in Shale Horizontal Well

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