欠平衡钻井溢流风险分析方法

川渝地区采用欠平衡钻井技术提速效果明显，但在钻进过程中，易发生发现气层后关井不及时，压井循环排气套压过高的问题。对欠平衡钻井溢流风险进行评估，可以为每口欠平衡井制订安全预案提供理论依据。为此，利用实钻资料，对欠平衡钻井潜在的溢流风险进行了分析，提出了欠平衡钻井前开展溢流风险分析的方法。其核心是：根据欠平衡井钻遇的地层特性，预测不同欠压值下的地层出气量，再通过压井计算确定循环排气时的最大套压值，最后判定允许的溢流量及关井时间。以四川盆地合川构造的合川X井为实例进行了计算，计算结果与实钻结果相符，证明上述欠平衡钻井溢流风险分析方法是切实可行的，并提出了控制欠平衡钻井溢流风险的对策与措施。通过分析欠平衡钻井溢流风险、规范欠平衡操作、明确施工细节，可以确保及时发现溢流、及时关井、严格控制溢流量，进而实现快速安全钻井。

Underbalanced drilling kick risk analysis

Underbalanced drilling(UBD) could obviously improve the ROP in the Sichuan Basin but such problems easily occurred like that the well could not be shut in as soon as the pay zone was touched,or that the casing pressure became extremely high when circulating out the gas during killing process.In view of this,through evaluation on the UBD kick risks,theoretical foundation can be provided for a contingency planning made properly for each UBD well.Then based on the actual drilling data,potential kick risks are ...