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RISS 인기검색어
- 검색키워드
- 저자 : Hai Y. Zhu (검색결과 2 건)
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Cementing failure of the casing-cement-rock interfaces during hydraulic fracturing
Hai Y. Zhu,Jin G. Deng,Jun Zhao,Hu Zhao,Hai L. Liu,Teng Wang 사단법인 한국계산역학회 2014 Computers and Concrete, An International Journal Vol.14 No.1
Using the principle of damage mechanics, zero-thickness pore pressure cohesive elements(PPCE) are used to simulate the casing-cement interface (CCI) and cement-rock interface (CRI). The traction-separation law describes the emergence and propagation of the PPCE. Mohr-coulomb criteria determines the elastic and plastic condition of cement sheath and rock. The finite element model (FEM) of delamination fractures emergence and propagation along the casing-cement-rock (CCR) interfaces during hydraulic fracturing is established, and the emergence and propagation of fractures along the wellbore axial and circumferential direction are simulated. Regadless of the perforation angle (the angle between the perforation and the max. horizontal principle stress), mirco-annulus will be produced alonge the wellbore circumferential direction when the cementation strength of the CCI and the CRI is less than the rock tensile strength; the delamination fractures are hard to propagate along the horizontal wellbore axial direction; emergence and propagation of delamination fractures are most likely produced on the shallow formationwhen the in-situ stresses are lower; the failure mode of cement sheath in the deep well is mainly interfaces seperation and body damange caused by cement expansion and contraction, or pressure testing and well shut-in operations.
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Hydraulic fracturing experiments of highly deviated well with oriented perforation technique
Zhu, Hai Y.,Deng, Jin G.,Liu, Shu J.,Wen, Min,Peng, Cheng Y.,Li, Ji R.,Chen, Zi J.,Hu, Lian B.,Lin, Hai,Guang, Dong Techno-Press 2014 Geomechanics & engineering Vol.6 No.2
In order to investigate the effect of different perforation angles (the angle between the perforation direction and the maximum horizontal principal stress) on the fracture initiation and propagation during hydraulic fracturing of highly deviated well in oil & gas saturated formation, laboratory experiments of the hydraulic fracturing had been carried out on the basis of non-dimensional similar criteria by using 400^3 $mm^3$ cement cubes. A plane fracture can be produced when the perforations are placed in the direction of the maximum horizontal principal stress. When the perforation angle is $45^{\circ}$, the fractures firstly initiate from the perforations at the upper side of the wellbore, and then turn to the maximum horizontal principal stress direction. When the well deviation angle and perforation angle are both between $45^{\circ}$ and $90^{\circ}$, the fractures hardly initiate from the perforations at the lower side of the wellbore. Well azimuth (the angle between the wellbore axis and the maximum horizontal principal stress) has a little influence on the fracture geometries; however it mainly increases the fracture roughness, fracture continuity and the number of secondary fractures, and also increases the fracture initiation and propagation pressure. Oriented perforating technology should be applied in highly deviated well to obtain a single plane fracture. If the well deviation angle is smaller, the fractures may link up.
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