分段压裂过程中射孔段水泥环密封完整性的数值模拟

水平井射孔段井筒由于孔眼的存在，在分段压裂过程中应力集中现象极易加剧固井水泥环的破坏。此外，由于高压压裂液直接作用在水泥环孔眼壁面上，使其完整性在压裂过程中遭受的挑战更大。本文建立了热流固耦合数值模型旨在分析分段压裂过程中射孔段水泥环内部的温度与应力变化，研究了套管内压、压裂液排量、水泥弹性模量、孔径与孔密对于水泥环密封完整性的影响规律。计算结果表明，压裂过程中水泥环一界面、二界面以及孔眼处均会产生剪切破坏。考虑瞬态力热耦合作用时，水泥环孔眼处失封风险提高。压裂液排量、孔径与孔密对水泥环切向应力影响较小；套管内压与水泥环弹性模量的降低虽然可在一定程度降低剪切破坏系数，但难以避免射孔段水泥环压裂初期的剪切破坏。

Numerical Simulation of Perforated Cement Sheath Integrity During Staged Fracturing

The stress concentration could easily aggravate the damage of perforated cement sheath due to the perforation hole in horizontal wells during staged fracturing. In addition, the wall of perforation hole was directly pressed by the high-pressure fracturing fluid, making cement integrity more challenged. A fully coupled thermo -hydro-mechanical model was set up to simulate the temperature and the stress variation of the cement sheath during fracturing, and the influence of casing pressure, fracturing fluid displacement, cement elastic modulus, hole diameter and density on the cement integrity was analyzed. The results show that there is shear failure on casing/cement interface, cement/rock interface and the hole wall during fracturing process. Considering the coupling of transient temperature and pressure, the risk of failure at the cement hole is increased. The fracturing fluid displacement, hole diameter and density have little effect on the tangential stress of the cement sheath; although a lower casing pressure and cement elastic modulus can reduce the shear failure coefficient to some extent, it is difficult to avoid the shear failure at the initial stage of hydraulic fracturing.