窄安全压力窗口地层精细控压下套管技术研究

针对窄安全压力窗口地层下套管存在高漏失风险的问题，以瞬态波动压力为基础，建立了窄安全压力窗口地层下套管过程井筒压力控制模型，进而提出了精细控压下套管方法。利用瞬态波动压力模型进行了下套管过程波动压力敏感性分析，结果表明，套管下放速度越大、套管下入深度越深、钻井液密度越大、环空间隙越小，下套管引起的井底波动压力越大。精细控压下套管实例应用表明，该方法既能保证套管下放速度，又能有效避免窄安全压力窗口地层下套管漏失的发生。此外，通过实例对比精细控压下套管与常规下套管发现，套管下放到井底附近，采用常规方法下套管时套管下放最大速度调节范围非常窄，很难将井筒压力维持在安全压力窗口内。

Research on Managed Pressure Casing Technology in Narrow Safety Pressure Window Formation

Aiming at the problem of high loss risk of casing running in narrow safety pressure window formation, based on transient surge pressure, a wellbore pressure control model for casing running in narrow safety pressure window formation is established, and then a precise pressure control method for casing running is proposed. Firstly, the sensitivity analysis of casing surge pressure is carried out by using the transient surge pressure model. The results show that the higher the casing running speed, the deeper the casing sinking depth, the greater the drilling fluid density and the smaller the annulus clearance, the greater the bottom-hole surge pressure caused by casing. A case study of casing running under precise pressure control shows that this method can not only ensure casing running speed, but also effectively avoid loss in narrow safe pressure window formation. In addition, by comparing the precise pressure control casing running with the conventional casing running, it is found that the maximum speed adjustment range of casing running is very narrow when the casing running with the conventional method is near the bottom of the well, which makes it difficult to maintain the wellbore pressure within the safety pressure window.