破碎松软地层取心钻头孔底流场数值模拟及应用

Numerical Stimulation of Bottom Flow Field of Core Bit in Broken Soft Formation and the Application

摘要:

复杂地层取心和孔壁稳定一直是困扰地质钻探界的2大技术难题。以汶川地震科钻为例，5个钻孔都在断裂带上，地层极破碎、松软。针对部分孔段取心率低问题，设计一种新型阶梯式隔水底喷取心钻头，利用CFD技术对钻头孔底流场进行数值分析，优化钻头排水槽结构、泥浆性能和水力参数，寻找一种最佳组合，为提高岩心采取率、预防堵心，提高孔壁的稳定性奠定基础。

关键词:破碎松软地层;防冲蚀取心钻头;金刚石钻头;流场;数值模拟;结构优化

Abstract:

Coring and keeping the stability hole wall in complex formation are technical difficulties in geological drilling circles. In Wenchuan Earthquake Fault Scientific Drilling (WFSD), 5 boreholes were in the fault zone and the formation was extremely broken and soft. A new type of stepped bottom jetting anti-erosion core bit was designed, numerical analysis was made on bottom flow field by CFD technology to optimize drainage groove structure, mud properties and hydraulic parameters in order to fine the best combination to lay foundations for core recovery rate improvement, core blockage prevention and higher hole wall stability.

Key words:broken and soft formation; anti-erosion core bit; diamond bit; flow field numerical simulation; structure optimization