围压条件下水泥封固长度对封隔能力的影响规律

The Influence of Cement Sealing Length on Sealing Capability under Confining Pressure

油气井固井质量关系到油气井使用寿命及油气田勘探开发的整体效果,油田公司也规定了必须要达到的固井连续优质段长度。为了探寻水泥封固长度对水泥封隔能力的影响规律,采用Cohesive黏聚力模型描述固井界面胶结特性,考虑水泥环界面初始应力,利用环空气体突破水泥环界面的压力来衡量水泥封隔能力,建立了环空气体突破水泥环的三维有限元数值模型,研究了不同气体黏度、界面胶结强度及水泥环初始应力条件下,固井封固长度对其封隔能力的影响规律,并通过水泥环密封完整性评价试验对数值模拟结果进行了验证。研究结果表明:随着水泥封固长度的增加,水泥封隔能力呈现线性增大的趋势;不同气体黏度对环空气体突破压力影响不大;在不同的界面胶结强度以及水泥环初始应力条件下,水泥封固长度与水泥封隔能力呈线性关系。研究结果对于油气井固井质量评价具有一定的参考作用。

The cementing quality is related to the service life of oil and gas wells and the overall effect of oil and gas field exploration and development.Oilfield companies stipulate the length of continuous high-quality cementing sections that must be achieved.In order to explore the influence of the cement sealing length on the cement sealing ability,the Cohesive cohesion model is used to describe the cementing characteristics of the cementing interface.Considering the initial stress of the cement sheath interface,and using the pressure of the annular air breaking through the cement sheath interface to measure the cement sealing,the three-dimensional finite element numerical model of the annulus air breaking through the cement sheath is established.The influence of the cement sealing length on the sealing capability of the cement sheath under different gas viscosities,interfacial bonding strengths and cement sheath initial stresses is studied.The research results show that with the increase of the cement sealing length,the cement sealing capacity presents a linear increase trend.The gas viscosity has little effect on the breakthrough pressure of the annulus air.For different interface bonding strengths and the initial cement sheath stress,the cement sealing length has a linear relationship with the cement sealing capacity.The research results have a certain reference for the evaluation of cementing quality of oil and gas wells.