大牛地气田欠平衡水平井井壁稳定性分析

Well stability analysis of underbalanced horizontal well in Daniudi gas field

为有效开发大牛地气田低孔、特低渗储层,在盒1储层试点推行了欠平衡钻水平井技术。井壁稳定性分析是欠平衡钻井技术的关键因素。结合大牛地气田实际地质情况,利用有限元分析的方法研究了盒1储层在氮气、泡沫和充气液欠平衡方式下水平井的井壁稳定性问题。计算结果表明,不论是在常规的φ215.9mm的井眼中,还是在φ152.4mm的井眼中应用上述3种欠平衡方式进行水平井钻井均不会发生井壁失稳问题,这与DP4井、DP14井和DP19井的实钻情况完全相吻合,为大牛地气田欠平衡钻水平井的井壁稳定性分析提供了理论依据。

In order to effectively develop the reservoirs of low porosity and super-low permeability in Daniudi gas field,the underbalanced horizontal well technology drilling is used to the He1 reservoir.Well stability analysis is the key of the technology.Combining with the actual geological conditions of the gas field,the finite element analysis method is used to study the well stability of horizontal wells at He1 reservoir with nitrogen,foam and gassy liquid underbalanced drilling.The results show that case well instability will not occur either in theφ215.9 mm well or in theφ152.4 mm well when applying the three ways of drilling underbalanced horizontal wells.This is entirely consistent with the real drilling situation of DP4 well,DP14 well and DP19 well.The results provide an important theoretical basis for the stability analyisis of underbalanced horizontal wells in the Daniudi gas field.