Modelling hydraulic fracturing in a complex-fracture-network reservoir with the DDM and graph theory

2017 ◽  
Vol 47 ◽  
pp. 73-82 ◽  
Author(s):  
Wan Cheng ◽  
Rongjing Wang ◽  
Guosheng Jiang ◽  
Jingyu Xie
Keyword(s):  
Graph Theory ◽  
Hydraulic Fracturing ◽  
Fracture Network ◽  
Complex Fracture ◽  
Complex Fracture Network

Induced Stress and Interaction of Fractures During Hydraulic Fracturing in Shale Formation

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Desheng Zhou ◽  
Peng Zheng ◽  
Jiao Peng ◽  
Pei He
Keyword(s):  
Hydraulic Fracturing ◽  
Principal Stress ◽  
Hydraulic Fracture ◽  
Fracture Network ◽  
Hydraulic Fractures ◽  
Single Fracture ◽  
Complex Fracture ◽  
Induced Stress ◽  
Transverse Distance ◽  
Complex Fracture Network

Creating complex fracture network by hydraulic fracturing operation in unconventional reservoir development is the key factor of effective exploitation. The mechanism of creating a fracture network is not clear up to today. Conventional hydraulic fracturing theory is based on tensile failure of a rock, and a hydraulic fracture is widely accepted as propagating along the direction of in situ maximum horizontal principal stress in the industry. Based on rock elastic mechanics and fracture mechanics, considering combined tensile and shear failures, the maximum circumferential strain criterion and boundary element method (BEM), the paper studies the induced stress and its variation during a fracture propagation, the interaction between two or more hydraulic fractures, and the interaction between a hydraulic fracture and a natural crack. The paper shows that a propagating fracture will produce induced stresses on surrounding rock and form a stress shadow. Instead of propagation along the direction of maximum horizontal principal stress as a single fracture, the outside two fractures of two or more hydraulic fractures are exclusive and turning away from each other. A natural crack may be awaked and extend at its both tips by a propagating hydraulic fracture before their intersection, and the hydraulic fracture may deflect toward the natural crack. The interaction between a hydraulic fracture and a natural crack depends on the transverse distance between them and the initial length of the crack. The shorter the transverse distance and the longer the crack length are, the higher the possibility of the crack to be awaked is. The research results are helpful in understanding complex fracture network and may be used in determining hydraulic fracture places to create a complex fracture network.

scholarly journals A New Method to Improve the Fracturing Effect of Coal Seams by Using Preset Slots and Induced Stress Shadows

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Li Li ◽  
Lei Zhou ◽  
Honglian Li ◽  
Binwei Xia ◽  
Junping Zhou
Keyword(s):  
Coal Seam ◽  
Hydraulic Fracturing ◽  
Fracture Network ◽  
Coal Bed ◽  
Hydraulic Fractures ◽  
Large Area ◽  
Multiple Fractures ◽  
Complex Fracture ◽  
Induced Stress ◽  
Complex Fracture Network

Efficient extraction of coal bed methane before coal mining is essential to eliminate the risk of coal-gas outbursts. However, stimulation technologies should be implemented to enhance the conductivity of the coal seam. In this study, we propose a novel method to create a complex fracture network in underground coal mines with the integration of multiple hydraulic slotting and hydraulic fracturing. In this method, hydraulic slots are used to direct hydraulic fractures and initialize branch fractures, while hydraulic fracturing is used to extend the fractures. Given the mutually exclusive and attractive propagation of multiple fractures, a relatively evenly distributed fracture network can be generated. The results show that (1) the dynamically induced stress shadows of hydraulic fractures can cause exclusive and attractive propagation of multiple hydraulic fractures; (2) a preset slot that deviates from the principal stress can direct hydraulic fractures to a certain extent and generate branch fractures; and (3) with a staggered distribution of preset slots, a relatively large volume of the coal seam in both the minimum and maximum horizontal stress directions can be stimulated, creating a complex fracture network including many vertical branch fractures and a large area of horizontally layered directional fractures.

scholarly journals Experimental Investigation on Hydraulic Fractures in the Layered Shale Formation

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Jingyin Wang ◽  
Ying Guo ◽  
Kaixun Zhang ◽  
Guangying Ren ◽  
Jinlong Ni
Keyword(s):  
Acoustic Emission ◽  
Hydraulic Fracturing ◽  
Fracture Network ◽  
Injection Rate ◽  
Vertical Stress ◽  
Hydraulic Fractures ◽  
Stress Difference ◽  
Complex Fracture ◽  
Fracturing Process ◽  
Complex Fracture Network

Multistage fracturing of horizontal wells to form a complex fracture network is an essential technology in the exploitation of shale gas. Different from the conventional reservoirs, the mechanical characteristics of shale rock have significant heterogeneity due to the existence of beddings, which makes it difficult to predict the fracture geometry in the shale reservoir. Based on the laboratory experiments, the factors that affect fracture propagation were analyzed. The experimental results revealed that the hydraulic fracture would cross the beddings under the high vertical stress difference, while it would propagate along with the bedding under the low vertical stress difference; besides, the low injection rate and viscosity of the fracturing fluid were beneficial to generate a complex fracture network. Under the high injection rate and viscosity, a planar fracture was created, while a nonplanar fracture was observed under the low injection rate and viscosity, and branch fracture was created. According to the acoustic emission events, the shear events were the main events that occurred during the hydraulic fracturing process, and the acoustic emission events could be adopted to describe the fracture network. Lastly, the supercritical carbon dioxide fracturing was more effective compared with the hydraulic fracturing because the fracture network was more complex.

Numerical Simulation of Complex Fracture Network Development by Hydraulic Fracturing in Naturally Fractured Ultratight Formations

2013 ◽  
Author(s):  
Hannes Hofmann ◽  
Tayfun Babadagli ◽  
Günter Zimmermann
Keyword(s):  
Fracture Network ◽  
Natural Fracture ◽  
Fracture Networks ◽  
Network Development ◽  
Complex Fracture ◽  
Fracture Patterns ◽  
Fracture Systems ◽  
Fracture Development ◽  
Complex Fracture Network ◽  
Treatment Designs

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.

scholarly journals Performance-based fractal fracture model for complex fracture network simulation

2017 ◽  
Vol 15 (1) ◽  
pp. 126-134 ◽  
Author(s):  
Wen-Dong Wang ◽  
Yu-Liang Su ◽  
Qi Zhang ◽  
Gang Xiang ◽  
Shi-Ming Cui
Keyword(s):  
Network Simulation ◽  
Fracture Network ◽  
Fracture Model ◽  
Complex Fracture ◽  
Complex Fracture Network ◽  
Fractal Fracture

scholarly journals A New Approach for Automatic Optimization of Complex Fracture Network in Shale Reservoirs

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 1) ◽  
Author(s):  
Haibo Wang ◽  
Tong Zhou ◽  
Fengxia Li
Keyword(s):  
Shale Gas ◽  
Flow Model ◽  
Optimization Method ◽  
Fracture Network ◽  
Gas Reservoirs ◽  
Fracture Length ◽  
Complex Fracture ◽  
Shale Gas Reservoirs ◽  
Automatic Optimization ◽  
Complex Fracture Network

Abstract Shale gas reservoirs have gradually become the main source for oil and gas production. The automatic optimization technology of complex fracture network in fractured horizontal wells is the key technology to realize the efficient development of shale gas reservoirs. In this paper, based on the flow model of shale gas reservoirs, the porosity/permeability of the matrix system and natural fracture system is characterized. The fracture network morphology is finely characterized by the fracture network expansion calculation method, and the flow model was proposed and solved. On this basis, the influence of matrix permeability, matrix porosity, fracture permeability, fracture porosity, and fracture length on the production of shale gas reservoirs is studied. The optimal design of fracture length and fracture location was carried, and the automatic optimization method of complex fracture network parameters based on simultaneous perturbation stochastic approximation (SPSA) was proposed. The method was applied in a shale gas reservoir, and the results showed that the proposed automatic optimization method of the complex fracture network in shale gas reservoirs can automatically optimize the parameters such as fracture location and fracture length and obtain the optimal fracture network distribution matching with geological conditions.

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