Volume fracturing technology of unconventional reservoirs: Connotation, design optimization and implementation

Wu, Qi; Xu, Yizhuang; Wang, Xiaoquan; Wang, Tengfei; Zhang, Shouliang

doi:10.1016/s1876-3804(12)60054-8

Cited by 169 publications

(50 citation statements)

References 21 publications

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“…After volume fracturing treatment, a certain stimulated region composed of hydraulic fractures, natural fractures and shear cracks is created near the wellbore. This reduces the flow resistance and thus improves the wells' production [1,2]. However, it is difficult to test and evaluate the productivity under such complex fracture network conditions caused by volume fracturing.…”

Section: Introductionmentioning

confidence: 99%

Rate Decline Analysis for Modeling Volume Fractured Well Production in Naturally Fractured Reservoirs

et al. 2018

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Based on the property discontinuity in the radial direction, this paper develops a new composite model to simulate the productivity of volume fractured wells in naturally fractured reservoirs. The analytical solution of this model is derived in detail and its accuracy is verified by the same model's numerical solution. Detailed analyses of the traditional transient and cumulative rate are provided for the composite model. Results show that volume fracturing mainly contributes to the early-flow period's production rate. As interregional diffusivity ratio increases or interregional conductivity ratio decreases, the transient rate at the same wellbore pressure increases. Three characteristic decline stages may be observed on transient rate curves and the shape of traditional rate curves in the middle-and late-flow periods depends on naturally fractured medium and boundary condition. By introducing a new pseudo-steady constant, new Blasingame type curves are also established and their features are more salient than those of traditional rate curves. Five typical flow regimes can be observed on these new type curves. Sensitivity analysis indicates that new Blasingame type curves for varied interregional diffusivity ratio, interregional conductivity ratio, interporosity coefficient and dimensionless reservoir radius, except storativity ratio, will normalize in the late-flow period.

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Section: Introductionmentioning

confidence: 99%

Rate Decline Analysis for Modeling Volume Fractured Well Production in Naturally Fractured Reservoirs

et al. 2018

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“…Volume stimulation drives these natural fractures to expand continuously and introduce shear slip in brittle rocks, thus forming complicated networks of intersecting natural fractures and artificial fractures that further increase the stimulated volume [2]. Therefore, the volume stimulation method has become one of the key technologies in unconventional oil and gas development [3]. However, simulation hydraulic fracturing in the presence of natural fracture network is a challenging task, owing to the complex interactions between fracturing fluid, rock matrix, and rock interfaces, as well as the mechanical behaviors before, during, and after the intersections between hydraulic fractures and preexisting natural fractures [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Deformation Behavior between Hydraulic and Natural Fractures Using Fully Coupled Hydromechanical Model with XFEM

Liu¹,

Luo

Sang³

et al. 2017

Mathematical Problems in Engineering

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There has been a growing consensus that preexisting natural fractures play an important role during stimulation. A novel fully coupled hydromechanical model using extended finite element method is proposed. This directly coupled scheme avoids the cumbersome process during calculating the fluid pressure in complicated fracture networks and translating into an equivalent nodal force. Numerical examples are presented to simulate the hydraulic fracture propagation paths for simultaneous multifracture treatments with properly using the stress shadow effects for horizontal wells and to reveal the deformation response and interaction mechanism between hydraulic induced fracture and nonintersected natural fractures at orthotropic and nonorthotropic angles. With the stress shadow effects, the induced hydraulic flexural fracture deflecting to wellbore rather than transverse fracture would be formed during the progress of simultaneous fracturing for a horizontal well. The coupled hydromechanical simulation reveals that the adjacent section to the intersection is opened and the others are closed for orthogonal natural fracture, while the nonorthogonal natural fracture is activated near the intersection firstly and along the whole section with increasing perturbed stresses. The results imply that the induced hydraulic fracture tends to cross orthotropic natural fracture, while it is prior to being arrested by the nonorthotropic natural fracture.

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“…As a reliable and economic formation stimulation technology, it has been successfully used in shale gas reservoirs. Due to low matrix porosity and low permeability of shale gas reservoirs, to make long well lengths for effective drainage areas in traditional designs, it is not practical for tight shales (Zhou et al 2010;Zeng et al 2010;Wu et al 2011Wu et al , 2012Wang et al 2014a). In order to create complex fractures in shale reservoirs through multi-stage hydraulic fracturing in horizontal wells, analysis of stage spacing and stress interference among fractures needs to be done.…”

Section: Introductionmentioning

confidence: 99%

Stress redistribution in multi-stage hydraulic fracturing of horizontal wells in shales

Zeng

Zhang

2015

Pet. Sci.

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Multi-stage hydraulic fracturing of horizontal wells is the main stimulation method in recovering gas from tight shale gas reservoirs, and stage spacing determination is one of the key issues in fracturing design. The initiation and propagation of hydraulic fractures will cause stress redistribution and may activate natural fractures in the reservoir. Due to the limitation of the analytical method in calculation of induced stresses, we propose a numerical method, which incorporates the interaction of hydraulic fractures and the wellbore, and analyzes the stress distribution in the reservoir under different stage spacing. Simulation results indicate the following: (1) The induced stress was overestimated from the analytical method because it did not take into account the interaction between hydraulic fractures and the horizontal wellbore. (2) The hydraulic fracture had a considerable effect on the redistribution of stresses in the direction of the horizontal wellbore in the reservoir. The stress in the direction perpendicular to the horizontal wellbore after hydraulic fracturing had a minor change compared with the original in situ stress. (3) Stress interferences among fractures were greatly connected with the stage spacing and the distance from the wellbore. When the fracture length was 200 m, and the stage spacing was 50 m, the stress redistribution due to stage fracturing may divert the original stress pattern, which might activate natural fractures so as to generate a complex fracture network.

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Volume fracturing technology of unconventional reservoirs: Connotation, design optimization and implementation

Cited by 169 publications

References 21 publications

Rate Decline Analysis for Modeling Volume Fractured Well Production in Naturally Fractured Reservoirs

Rate Decline Analysis for Modeling Volume Fractured Well Production in Naturally Fractured Reservoirs

Deformation Behavior between Hydraulic and Natural Fractures Using Fully Coupled Hydromechanical Model with XFEM

Stress redistribution in multi-stage hydraulic fracturing of horizontal wells in shales

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