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Hou B.,State Key Laboratory of Petroleum Resources and Prospecting | Cheng W.,State Key Laboratory of Petroleum Resources and Prospecting | Jin Y.,State Key Laboratory of Petroleum Resources and Prospecting | Diao C.,State Key Laboratory of Petroleum Resources and Prospecting | And 2 more authors.
ISRM International Symposium - 8th Asian Rock Mechanics Symposium, ARMS 2014 | Year: 2014

Horizontal-well multi-stage fracturing was an effective stimulation technique, which was commonly used in unconventional reservoir. The complex interactions between multiple hydraulic fractures were believed to have a significant impact on fracture geometry inside the rock mass. Many theoretical models proposed to predict the hydraulic fracture geometry and stress interference in multi-stage fracturing had not been experimentally proved. In this study, a multi-stage fracturing test utilizing gal solution as fracturing fluid were conducted utilizing tri-axial fracturing system. Multi fractures were observed in a cubic rock sample. Experimental results showed that first stage fracture was a planar fracture while the second stage fracture was a concave fracture (bowl-shaped fracture). Stress interference between those two main fractures caused the growing of secondary cracks which were parallel to the simulated wellbore, but decreasing the width of sequent main fractures. Penny-shaped fracture model was believed to be more suitable than rectangular fracture model to simulate the real hydraulic fracture geometry in horizontal well. Fracture spacing design should be a significant work in multi-stage fracturing in horizontal well. © 2014 by Japanese Committee for Rock Mechanics.


Cheng W.,State Key Laboratory of Petroleum Resources and Prospecting | Jin Y.,State Key Laboratory of Petroleum Resources and Prospecting | Chen Y.,State Key Laboratory of Petroleum Resources and Prospecting | Zhang Y.,State Key Laboratory of Petroleum Resources and Prospecting | And 2 more authors.
ISRM International Symposium - 8th Asian Rock Mechanics Symposium, ARMS 2014 | Year: 2014

The complex interaction between hydraulic and natural fracture was believed to have a significant impact on hydraulic fracture complexity. Extensive theoretical and experimental works had proved this interaction was affected by several parameters, such as stress difference, approaching angle, frictional coefficient and fracturing parameters etc. However, only engineering parameters, such as pump displacement and viscosity of fracturing fluid, could be controlled by field engineers. How these two parameters affect the interaction remain poorly understood. In this study, a piece of white paper with the dimensions of 200 mm×150 mm×0.1 mm was spread to simulate a planar naturalfracture in the specimen. Two groups of fracturing tests were conducted under tri-axial stresses in large-sized fracturing system. In the first group, different pump displacements with the same viscosity of fracturing fluid were applied. In the second group, fracturing fluid with different viscosities was applied while pump displacement were strictly the same. Experimental results showed that hydraulic fracture can cross the natural fracture under large pump displacement and high viscosity. A critical pump displacement and a critical viscosity were observed respectively. Above this critical displacement or above this critical viscosity, hydraulic fracture can cross the natural fracture; below this critical displacement or below this critical viscosity, hydraulic fracture only propagates along the plane of the nature fracture to its ends rather than cross it. These two critical values can help field engineer design the fracturing parameters. © 2014 by Japanese Committee for Rock Mechanics.


Tang M.,China University of Petroleum - Beijing | Wang Z.,China University of Petroleum - Beijing | Ding G.,Langfang Branch of Research Institute of Petroleum Exploration and Development
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2010

For investigation on the mechanical characteristics of layered salt rocks in Huai'an Salt Mine, Jiangsu Province, and in consideration of the laminative geological structural character of most salt mines in China, experimental studies of uniaxial and triaxial compressions are carried out on three kinds of rock samples which are rock salt, mudstone and salt-mudstone interlayer. The experiment results indicate that: (1) The strain-stress relationship of rock salt and salt-mudstone interlayer under uniaxial compression or triaxial compression performs obviously strain hardening-softening properties. (2) The rock salt and salt-mudstone interlayer have obvious plastic deformation ability. The elastic modulus measured by the cycle loading-unloading curve is better than that measured directly from the primeval loading curve. (3) For the rock salt, the cohesive force is getting smaller and smaller while the internal friction angle first increases and then decreases with the plastic shear deformation increasing. (4) The presence of mudstone interlayer affects the mechanical characteristics of samples remarkably. The primary phenomenon is the strength's increasing. The failure modes of the mudstone interlayer rock salt are determined by their states.


Zhang H.,China University of Petroleum - Beijing | Wang Z.,China University of Petroleum - Beijing | Zheng Y.,China University of Geosciences | Zheng Y.,Langfang Branch of Research Institute of Petroleum Exploration and Development | And 2 more authors.
Safety Science | Year: 2012

To evaluate the effect of the long-term operation of a salt cavern in a given construction on rock deformation and its stability, tri-axial creep tests to the glauberite, anhydrite, and argillaceous rock salt are conducted, from which the creep curves as well as exponential functions of strain rate during the steady creep stage and creep constitutive equations of different rock salt in the experimental process derived are obtained. The study results show that: (i) Under the same deviatoric stress, the strain rate of argillaceous rock salt is lower than the glauberite and anhydrite, and the difference becomes larger with the increase of the deviatoric stress; (ii) The creep constitutive equations of different kinds of rock salt are in good agreement with the Burgers model, besides which the respective characteristics of these two creep models are compared. The change of creep parameters also illustrates the discrepancy of rock salt. The researching results can provide some references for long-term stability analysis of gas storage in salt caverns. © 2011 Elsevier Ltd.


Hou B.,China University of Petroleum - Beijing | Chen M.,China University of Petroleum - Beijing | Li Z.,China University of Petroleum - Beijing | Wang Y.,Langfang Branch of Research Institute of Petroleum Exploration and Development | Diao C.,China University of Petroleum - Beijing
Petroleum Exploration and Development | Year: 2014

Based on hydraulic fracturing experiments in laboratory, the hydraulic fracture propagation in shale is analyzed, a method for evaluating the fracture propagation extent is proposed, and the effects of geological factors and engineering factors on fracture propagation are studied. "Stimulated Rock Area (. SRA)" is proposed as an evaluation index for the hydraulic fracturing results. By analyzing the experiment results, it is found that hydraulic fracturing in shale reservoirs can generate a complex fracture network; a lower stress difference in brittle shale formation and a shorter distance between hydraulic fracture and bedding plane lead to a larger SRA and more complex fracture geometry; a fracture network is more likely to generate in the case that the angle between horizontal maximum stress direction and bedding plane is 90° or large enough, or the approaching angle between hydraulic fracture and well-opened natural fracture is close to 90° a higher brittle mineral content leads to better fracturing ability; low fluid viscosity and high flow rate lead to a large SRA; a variable flow rate increases the possibility that the hydraulic fracture communicates with bedding planes and natural fractures. © 2014 Research Institute of Petroleum Exploration & Development, PetroChina.

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