气体钻井转换钻井液井壁稳定技术

Enhancing Wellbore Stability by Gas-Liquid Drilling Fluids Replacement in Gas Drilling

气体钻井可以提高机械钻速、预防井漏,川东北地区上部陆相地层采用该技术钻进,加快了施工速度,大大缩短了钻井周期。但在气体钻井结束,转换为钻井液钻进后经常出现井壁失稳问题。分析了川东北地区气液转换过程中井壁失稳的原因,主要是该地区复杂的地质特点、干燥井壁吸水和钻井液冲刷。针对干燥井壁吸水,提出以润湿反转剂作为前置液的技术措施;针对该地区的地质特点和钻井液冲刷制定了符合川东北地质特点的气液转换施工工艺。在P204-2井和其他井的应用结果表明,以润湿反转剂作为前置液的技术措施和制定的气液转换施工工艺能减少由气液转换井壁失稳造成的井下复杂情况,避免恶性钻井事故的发生。

Gas drilling, which can increase penetration rate and prevent lost circulation, was useo m upper terrestrial formation in Northeast Sichuan area to increase drilling speed and reduce gas drilling cycle. However, at the end of gas drilling, wellbore collapse occurs frequently when substituting liquid drilling fluids for gas fluids. The reasons for wellhore collapse occurred during fluid-gas replacement were ana- lyzed, including complex formation, wellbore water absorption and drilling fluid erosion. For wellbore water absorption, the reverse wetting agent was used as lead fluids. For the formation characteristics and drilling fluid erosion, the corresponding gas-liquid replacement technique was designed. The applications in Well P204-2 and in other wells suggest that the proposed techniques can reduce downhole problems and avoid drilling accidents