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Computers and Concrete
  Volume 14, Number 1, July 2014 , pages 091-107

Cementing failure of the casing-cement-rock interfaces during hydraulic fracturing
Hai Y. Zhu, Jin G. Deng, Jun Zhao, Hu Zhao, Hai L. Liu and Teng Wang

    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 formation when 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.
Key Words
    delamination fractures; cement; interface; hydraulic fracturing; failure
Hai Y. Zhu and Teng Wang: State Key Laboratory of Oil & Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China

Jin G. Deng and Hai L. Liu: State Key Laboratory of Petroleum Resource and Prospecting (China University of Petroleum, Beijing), Beijing 102249, China

Jun Zhao and Hu Zhao: Oilfield Chemicals R & D Institute,COSL,Beijing East Yanjiao,065200,China

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