固井安全下套管速度分析

Velocity Analysis of the Safety of Casing in Cementing Operation

在固井作业下套管过程中,控制井底压力平衡是安全下套管的关键。套管在下入过程中会产生激动压力,在上提过程中会产生抽汲压力。在套管下入过程中如果激动压力和井内液柱压力之和大于地层破裂压力就可能发生井漏事故;在上提套管过程中如果抽汲压力和井内液柱压力之和小于地层压力可能发生溢流、井喷等事故。建立安全下套管的速度计算模型,以DXHW某井为实例计算出安全下套管速度应≤1.8m/s,上提套管速度应≤0.5m/s,为现场施工提供参考。

Controlling downhole pressure balance is the key of safety casing. Casing will produce surge pressure while casing lift will produce swabbing pressure. If surge pressure plus borehole fluid column pressure is larger than for-mation fracture pressure, leakage will occur in casing. If swabbing pressure plus borehole fluid column pressure is less than formation pressure, overflow or blowout will occur in casing lift. Taking DXHW Well as an example, this paper works out its safety casing velocity less than or equal to 1.8 m/s based on velocity calculation model and its casing lift velocity less than or equal to 0. 5 m/s, which provide a reference for site operation.