Optimal spacing of staged fracturing in horizontal shale-gas well

LIU, Chuang; Liu, He; Zhang, Yongping; Deng, Dawei; Wu, HengAn

doi:10.1016/j.petrol.2015.05.011

Cited by 58 publications

(19 citation statements)

References 51 publications

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“…Two main integration methods, including full integration (C3D8P) and reduced integration (C3D8RP) are provided to solve the problems coupling multiple factors. However, the sensitivity of mesh size and the accuracy of integration method were not verified in previous studies [3,11,13,31]. In this paper, we use a single layer whose thickness is 0.5 m. Then, the size of horizontal is refined for four types as shown in Figure 4.…”

Section: Model Construction and Verificationmentioning

confidence: 96%

Comparison of Different Hydraulic Fracturing Scenarios in Horizontal Wells Using XFEM Based on the Cohesive Zone Method

Wen

Hao³

et al. 2019

Energies

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Multistage hydraulic fracturing is a highly effective method for creating multiple transverse fractures to improve gas and oil reservoir production. It is critical to minimize the fracture spacing while also ensuring transverse propagation of fractures in multi-fractured horizontal wells. In this paper, a 3D fully coupled pore pressure-stress model based on the extended finite element method (XFEM) combined with the cohesive zone method is established to simulate five different fracturing scenarios in close spacing. The sensitivity of mesh size and the integration method are optimal, which are verified by the highly accurate traditional cohesive zone method. Then, the effect of five different fracturing scenarios on fracture geometries is compared. It is shown that spacing is a key parameter controlling fracture geometries in all fracturing scenarios. Alternative sequential and modified two-step fracturing can significantly reduce the influence of stress shadowing to generate more transverse fractures and form longer effective fractures. The sequential and two-step fracturing see an obvious improvement with increased fracture effective length when the spacing increases. The simultaneous fracturing technique can result in excessive closure of the middle fractures, which causes serious insertion of proppants. These results offer a new insight on optimization of hydraulic fracturing and can be a guidance for typical field cases.

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Section: Model Construction and Verificationmentioning

confidence: 96%

Comparison of Different Hydraulic Fracturing Scenarios in Horizontal Wells Using XFEM Based on the Cohesive Zone Method

Wen

Hao³

et al. 2019

Energies

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“…The quantitative relationship of the effect of different crack angles and the number of rock mechanical properties was analyzed. 3,[11][12][13][14][15][16] Effect of crack angle on the rock mechanical properties. Cracks with different angles are formed in the rock in the volume fracturing process.…”

Section: Study On the Change Of Fissured Rock Mechanical Properties Amentioning

confidence: 99%

Casing failure mechanism during volume fracturing: A case study of shale gas well

Lin

Lian

et al. 2017

Advances in Mechanical Engineering

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A large number of casing failures occur during the volume fracturing operation of shale gas, making normal completion stimulations impossible. To solve this problem, rock mechanical experiments and numerical simulation experiments are carried out in this article. It is found that the macroscopic rock mechanical strength reduces most when the crack angle of fissured rock in Longmaxi Formation is 45°, and it reduces stably when the number of cracks increases to 8. The elasticity modulus ratio, yield strength ratio, and compressive strength ratio are 0.70, 0.71, and 0.68, respectively, based on which this article establishes the finite element model for shale gas well X201. Then, the secondary development realizes the dynamic adjustment of the rock mechanical properties during the fracturing. The correctness of method and model in the article is verified through comparing the simulated calculation of casing deformation and the field multi-arm caliper logging data. The casing failure mechanism is revealed, providing a theoretical basis for the prevention of casing failure caused by shale gas fracturing.

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“…Secondly, artificial fractures will cause reorientation of in situ stresses in hydraulic fracturing area. As a result, fracture initiation will be modified . Currently, influences of natural fracture and artificial fracture have been studies separately, whereas no much attention has been given to this coupling effect from natural fracture and artificial fracture.…”

Section: Introductionmentioning

confidence: 99%

A novel analytical model of initial fracture pressure for horizontal staged fracturing in fractured reservoir

Liang

Ding

Liu

et al. 2019

Energy Science & Engineering

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The horizontal well-staged fracturing technology has been widely used in many oilfields to enhance well production by creating fracture network. Accurate prediction of fracture initiation is significant for successful hydraulic fracturing operation. However, hydraulic fracture initiation in fractured reservoir is highly tricky due to its rich natural fractures and artificial fractures previously created during staged fracturing. These fractures are thought to be major factors in conducting efficient staged fracturing in fractured reservoir. Therefore, in this paper, induced stress from artificial fractures has been analyzed by using two-dimensional analytical model. Besides, based on the assumption that rock in the formation is composed by rock matrix and fracture plane, considering tensile and shear failure type, failure criterion with multiple natural fracture planes has been developed. By combining impacts from natural fractures and artificial fractures, we establish an analytical model to calculate initial fracture pressure for horizontal staged fracturing in fractured reservoir. These results demonstrate that induced stress is associated with artificial fractures' location, height, and number. This induced stress leads to increment of initial fracture pressure, restricting fracture initiation. Due to natural fractures, there are three types of initiation, which are tensile failure along rock matrix, tensile failure along natural fracture, and shear failure along natural fracture plane. When rock failure is related to natural fracture, initial fracture pressure decreases and is variable with natural fracture plane occurrence. Especially, with large number of natural fractures, only one initiation type exists, which is tensile failure along natural fracture. Additionally, for horizontal borehole, influencing extent of fracture planes is associated with wellbore trajectory. The case study proves the applicability of this analytical model, meaning it can be used to guide horizontal staged fracturing in oilfield. K E Y W O R D Sartificial fracture, fracture initiation, fractured reservoir, natural fractures, staged fracturing

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Optimal spacing of staged fracturing in horizontal shale-gas well

Cited by 58 publications

References 51 publications

Comparison of Different Hydraulic Fracturing Scenarios in Horizontal Wells Using XFEM Based on the Cohesive Zone Method

Comparison of Different Hydraulic Fracturing Scenarios in Horizontal Wells Using XFEM Based on the Cohesive Zone Method

Casing failure mechanism during volume fracturing: A case study of shale gas well

A novel analytical model of initial fracture pressure for horizontal staged fracturing in fractured reservoir

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