Fracturing Failure Mechanism of Porous Cement Sheath under Triaxial Stress
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摘要: 针对多孔水泥环的井下失效问题,制备了液硅水泥环岩心试样,开展了力学性能测试试验,同时利用Flac 3D自编程序构建了多孔“单层水泥环”和“水泥环/套管/水泥环”模型,模拟深部地应力作用下水泥环的压裂过程,探明在水压和地应力耦合作用下水泥环的变形破坏机制。研究表明:单层水泥环在应力作用下表现为脆性破坏,外层套管和水泥环的保护能有效提高水泥环的峰值载荷。研究结果为揭示水泥环密封失效的破坏机理提供了理论基础。Abstract: The liquid silicon cement sheath samples were prepared, and the mechanical property testing experiments were carried out. Aiming at the problem of downhole failure of porous cement sheath, the porous “single-layer cement sheath” and “cement sheath-casing-cement sheath” models were established by using Flac 3D self-programming program to simulate the cement sheath fracturing process under the action of deep in-situ stress, and the deformation and failure laws of cement sheath under the coupling action of hydraulic pressure and in-situ stress were proved. The research shows that the single-layer cement sheath exhibits brittle failure under the action of stress, while under the protection of the outer casing and the cement sheath, the peak load of the cement sheath can be effectively increased. The research results provide a theoretical basis for revealing the failure mechanism of cement ring seal failure.
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表 1 液硅水泥环的物理力学参数
Table 1. Physical and mechanical parameters of liquid silica cement sheath
Tensile strength/
MPaUniaxial compressive strength/MPa Modulus of elasticity/GPa Poisson’s ratio Cohesion/
MPaInternal friction angle/(°) 4.8 54.31 3.56 0.15 7.8 35 -
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