Application of Simulation of Coupled Hydraulic Fracture Propagation by Implementing Natural Fracture Modeling in Shale Oil Reservoir- A Case Study from Junggar Basin, China

Abstract The interaction mode of induced fracture and natural fracture plays an important role in prediction of hydraulic fracture propagation. In this paper, a two-dimensional hydromechanical coupled discrete element model is first introduced in the framework of particle flow simulation, which can well take into account mechanical and hydraulic properties of rock samples with natural fracture. The model’s parameters are strictly calibrated by conducting numerical simulations of uniaxial compression test and direct tensile and shear tests, as well as fluid flow test. The effectiveness of coupled model is also assessed by describing hydraulic fracture propagation in two representative cases, respectively, rock samples with and without preexisting fracture. With this model in hand, the effects of interaction between induced and natural fractures with different approach angles and differential stresses on fluid injection pressure and fracture propagation patterns are investigated and discussed. Results suggest that the interaction modes mainly involve three basic behaviors including the arrested, captured with offset, and directly crossing. For a given differential stress, the captured offset of hydraulic fracture by natural fracture gradually decreases with the approach angle increase, while for a fixed approach angle, that captured offset increases with differential stress decrease.

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Numerical simulation study on hydraulic fracture propagation in heavy oil reservoir with THM coupling

International Journal of Oil Gas and Coal Technology ◽

10.1504/ijogct.2020.10028253 ◽

2020 ◽

Vol 24 (2) ◽

pp. 179

Author(s):

Yong Zhang ◽

Chun Mao ◽

Jinzhou Zhao ◽

Ziyi Guo ◽

Qiang Wang ◽

...

Keyword(s):

Numerical Simulation ◽

Simulation Study ◽

Hydraulic Fracture ◽

Heavy Oil ◽

Fracture Propagation ◽

Oil Reservoir ◽

Hydraulic Fracture Propagation ◽

Heavy Oil Reservoir

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Numerical Simulation of Hydraulic Fracture Propagation in Coal Seams with Discontinuous Natural Fracture Networks

Processes ◽

10.3390/pr6080113 ◽

2018 ◽

Vol 6 (8) ◽

pp. 113 ◽

Cited By ~ 12

Author(s):

Shen Wang ◽

Huamin Li ◽

Dongyin Li

Keyword(s):

Hydraulic Fracture ◽

Fracture Propagation ◽

Fracture Network ◽

Natural Fracture ◽

Cohesive Element ◽

Natural Fractures ◽

Fracture Networks ◽

Coal Seams ◽

Hydraulic Fracture Network ◽

Hydraulic Fracture Propagation

To investigate the mechanism of hydraulic fracture propagation in coal seams with discontinuous natural fractures, an innovative finite element meshing scheme for modeling hydraulic fracturing was proposed. Hydraulic fracture propagation and interaction with discontinuous natural fracture networks in coal seams were modeled based on the cohesive element method. The hydraulic fracture network characteristics, the growth process of the secondary hydraulic fractures, the pore pressure distribution and the variation of bottomhole pressure were analyzed. The improved cohesive element method, which considers the leak-off and seepage behaviors of fracturing liquid, is capable of modeling hydraulic fracturing in naturally fractured formations. The results indicate that under high stress difference conditions, the hydraulic fracture network is spindle-shaped, and shows a multi-level branch structure. The ratio of secondary fracture total length to main fracture total length was 2.11~3.62, suggesting that the secondary fractures are an important part of the hydraulic fracture network in coal seams. In deep coal seams, the break pressure of discontinuous natural fractures mainly depends on the in-situ stress field and the direction of natural fractures. The mechanism of hydraulic fracture propagation in deep coal seams is significantly different from that in hard and tight rock layers.

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Numerical Simulation of the Influence of Natural Fractures on Hydraulic Fracture Propagation

Geofluids ◽

10.1155/2020/8878548 ◽

2020 ◽

Vol 2020 ◽

pp. 1-12 ◽

Cited By ~ 1

Author(s):

Song Yaobin ◽

Lu Weiyong ◽

He Changchun ◽

Bai Erhu

Keyword(s):

Tensile Strength ◽

Principal Stress ◽

Hydraulic Fracture ◽

Fracture Propagation ◽

Natural Fracture ◽

Hydraulic Fractures ◽

Stress Difference ◽

Natural Fractures ◽

Approach Angle ◽

Hydraulic Fracture Propagation

According to the theory of plane mechanics involving the interaction of hydraulic and natural fractures, the law of hydraulic fracture propagation under the influence of natural fractures is verified using theoretical analysis and RFPA2D-Flow numerical simulation approaches. The shear and tensile failure mechanisms of rock are simultaneously considered. Furthermore, the effects of the approach angle, principal stress difference, tensile strength and length of the natural fracture, and elastic modulus and Poisson’s ratio of the reservoir on the propagation law of a hydraulic fracture are investigated. The following results are obtained: (1) The numerical results agree with the experimental data, indicating that the RFPA2D-Flow software can be used to examine the hydraulic fracture propagation process under the action of natural fractures. (2) In the case of a low principal stress difference and low approach angle, the hydraulic fracture likely causes shear failure along the tip of the natural fracture. However, under a high stress difference and high approach angle, the hydraulic fracture spreads directly through the natural fracture along the original direction. (3) When natural fractures with a low tensile strength encounter hydraulic fractures, the hydraulic fractures likely deviate and expand along the natural fractures. However, in the case of natural fractures with a high tensile strength, the natural fracture surface is closed, and the hydraulic fracture directly passes through the natural fracture, propagating along the direction of the maximum principal stress. (4) Under the same principal stress difference, a longer natural fracture corresponds to the easier initiation and expansion of a hydraulic fracture from the tip of the natural fracture. However, when the size of the natural fracture is small, the hydraulic fracture tends to propagate directly through the natural fracture. (5) A smaller elastic modulus and larger Poisson’s ratio of the reservoir result in a larger fracture initiation pressure. The presented findings can provide theoretical guidance regarding the hydraulic fracturing of reservoirs with natural fractures.

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Characteristics of Fracture Propagation Induced by Supercritical CO2 in Inter-Salt-Shale Reservoir

Geofluids ◽

10.1155/2019/7132843 ◽

2019 ◽

Vol 2019 ◽

pp. 1-9 ◽

Cited By ~ 1

Author(s):

Yixiang Zhang ◽

Jianming He ◽

Fengxia Li ◽

Xin Fan ◽

Xiao Li

Keyword(s):

Rock Salt ◽

Fracture Propagation ◽

Natural Fracture ◽

Lake Basin ◽

Oil Reservoir ◽

Shale Oil ◽

Ct Scanner ◽

Breakdown Pressure ◽

Average Width ◽

Fracture Width

Hydraulic fracturing using freshwater is difficult for the commercial exploitation of a shale oil reservoir in Jianghan Basin with a continental saline lake basin sedimentary background. Supercritical CO2 (SC-CO2) is a promising fracturing fluid under consideration for the reservoir stimulation, especially in the case of the presence of water sensible salt layers. In this study, SC-CO2 fracturing experiments on the inter-salt-shale and salt specimens, which were obtained from the drilling well, were carried out in the laboratory. The characteristics of fracture propagation, including morphology and width variation, were analyzed based on the observations of a stereoscopic microscope, X-ray micro-CT scanner, and 3D scanner. The existing weak planes in the shale can really impact the fracture propagation in SC-CO2 fracturing. Deflection, branching, and approaching can occur during the process of fracture propagation. The average width value of the reactivated natural fracture is bigger than that of a newly created fracture. In addition, the fracturing results indicate the greater breakdown pressure of rock salt if compared with the inter-salt-shale. The induced fractures in the salt specimen are compact and smaller in average width than those in the shale specimen. The higher breakdown pressure and relatively smaller fracture width of rock salt are real challenges for the fracturing of an inter-salt-shale oil reservoir.

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