液相欠平衡钻井合理欠压值设计方法

Designing method for reasonable negative pressure value in liquid underbalanced drilling

 窦亮彬 李天太 张明 毕刚

 （西安石油大学石油工程学院，陕西 西安 710065）

 (School of Petroleum Engineering, Xi′an Shiyou University, Xi′an 710065, China)

 液相欠平衡钻井井底欠压值的确立和控制直接决定着钻井的成败。目前钻井行业井底欠压值确立方法一般基于现场经验，误差较大，在现场应用时，其控制调节缺乏理论依据。欠压值过大，易导致井壁失稳，出现井控风险及速敏、应力敏感等储层伤害问题；欠压值过小，易导致钻井液进入储层，无法实现有效保护储层及提高机械钻速的目的。为此，利用井眼力学稳定及井控风险分析确定欠压值上限，利用储层毛细管力确立欠压值下限，建立液相欠平衡钻井合理欠压值设计新方法，并结合塔里木盆地塔北地区X井现场数据进行分析优化。结果表明，此欠压值设计新方法能够为欠平衡钻井现场设计提供理论指导，避免了单纯依靠经验值确立欠平衡钻井欠压值导致的钻井事故或储层保护效果不好等问题。

 Reasonable negative pressure value of the bottom hole is the key to the success of liquid underbalanced drilling (UBD). Negative pressure value is based primarily on on-site experience in the oilfield, which has a bigger error and is unfavorable to regulating the value. High negative pressure value easily leads to wellbore instability, well control accidents, and the permeability damage caused by velocity and stress sensitivity. Small negative pressure value will not protect reservoir and improve the penetration rate. A new designing method for reasonable negative pressure value in liquid UBD is given, in which the maximum negative pressure value is determined by wellbore stability calculation and well control analysis, and the minimum negative pressure value is determined by capillary force analysis. The method was analyzed and optimized by X well data in the northern area of Tarim Basin. The new method provides the guidance for reasonable negative pressure value design in liquid UBD and avoids a series of UBD problems based on experience.

10.6056/dkyqt201702024