黔西南地区煤系地层井壁稳定技术探讨

Wellbore stabilization techniques in coal-bearing formation in Southwestern Guizhou

井壁稳定性问题对黔西南地区煤系气的勘探开发效果至关重要。对泥页岩和煤岩井壁失稳的机理进行了分析,从化学、力学和化学与力学耦合等方面,探讨了煤泥互层段井壁失稳的对策。结合黔西南地区煤系地层煤层气井的实例,分析了井壁失稳对井径大小及岩心采取率的影响,发现煤泥互层段的井径扩大率较大而相应的岩心采取率较小。尽可能准确地预测探井的地层压力、选用合理的钻井液体系和密度、采用合理的钻井工艺有助于维持黔西南地区煤系地层井壁稳定。

Maintaining wellbore stability in unconventional gas wells is much important to the exploration and production of natural gas in coal-bearing formation in the southwestern region of Guizhou Province.This paper investigates the wellbore failure mechanism in coal and mud shale formation,and finds out that the two kinds of wellbore failure mechanisms are essentially different.In addition,solutions for wellbore instability are investigated in terms of chemistry,mechanics and mechanics coupled with chemistry.Influence of wellbore instability on well-radius variations and core recovery is analyzed in the context of a CBM well in Zhina Coalfield,leading to the finding that wellbore enlargement is greater with lower core recovery over the coal-mudstone section.Predicting accurately the formation pressures of exploration wells,optimizing the drilling fluid system and density,and choosing the right drilling techniques contribute to CBM wellbore stability in the southwestern region of Guizhou Province.