永301井井壁稳定钻井液技术

Drilling Fluid Technology for Borehole Stability at Yong 301 Well

永301井位于准噶尔盆地车莫古隆起南翼,是永进油田的一口重点评价直井。永进油田地质构造复杂,上部地层棕红色泥岩易吸水膨胀缩径,导致起下钻不畅;疏松砂岩易形成虚厚泥饼,造成起下钻阻卡;二开大井眼长裸眼井段井壁稳定难度大;侏罗系发育超压,地层层理及微裂缝发育严重,井壁稳定性差,钻井液稳定井壁技术难度大。通过优选聚胺强抑制防塌钻井液体系和合成基钻井液体系,针对不同地层岩性采用相应的井壁稳定对策及维护处理工艺,保证了工程施工的顺利进行,达到了良好的提速提效目的。

Yong 301 Well is at the south wing of Che-Mo Palaeohigh of Junggar Basin, and it is an important vertical well for evaluation in Yongjin Oilfield. Geological structure is complex at Yongjin Oilfield. The brownish red mudstone in upper formation is prone to absorb water, causing hole shrinkage by expansion accordingly, which would make tripping difficult. Unconsolidated sandstone is prone to form loose mud cakes which would cause blockage during tripping. The wellbore stability operation is difficult for big and long open hole section during second spuding. Stratification and microfractures develop seriously in formation because of overpressure in Jurassic System, leading to poor wellbore stability and difficult technical problem regarding stabilizing wellbore with drilling fluid. A polyamine strong inhibition anti-collapse drilling fluid system and a synthetic base drilling fluid system were chosen through optimization and relevant wellbore stability and maintenance measures were taken for different formation lithology to ensure successful construction and increase drilling speed and efficiency.