史密斯膨胀锥整形临界参数指标研究

Research on the critical indexes for casing dressing by Smith expansion cone

鉴于目前对整形工具的选用规格和避免套管损伤的最大整形量还没有明确定论的现状,通过显式动力有限元程序LS-DYNA模拟膨胀锥整形过程,分析套管和水泥环的应力扩张趋势,确定了整形过程中膨胀锥应用规格和最大可整形量等临界指标。建模时切向接触条件使用Cou-lomb摩擦模型,在模型的顶面边界和底面边界施加垂直方向约束。研究结果认为,屈服强度和工程需求内径是决定膨胀锥整形临界指标的主要因素,修套过程中膨胀锥对套管和水泥环造成的破坏较大,相对于套管,水泥环更容易发生破坏。

There is currently no definite conclusion for the indexes for selecting the casing swage as well as the maximum plastic amount for avoiding casing damage. Therefore, the explicit dynamic finite element software LS-DYNA was adopted to simulate the casing dressing process by the expansion cone,analyze the expansion tendency of casing and cement sheath,and determine the critical indexes, such as the cone applicationspecification and the maximum plastic amount. The Coulomb friction model was used as the condition for tangent contact in modeling and the vertical restraint was applied on both top and bottom boundaries of the model. The findings show that the yield strength and the internal diameter required by engineering are the major factors to determine the dressing critical indexes of the cone. The cone does remarkable damage to casing and cement sheath in the process of casing repair. Compared with casing, cement sheath is more easily subject to damage.