中文摘要：

螺杆钻具虽然应用广泛，但使用螺杆钻具条件下的钻井水力参数优化设计方法还不完善。为了指导钻井现场应用，以螺杆钻具的推荐工作参数为约束条件，应用数学规划方法建立了钻井液排量和钻头压降优选模型，给出了实用的钻井水力参数优化设计方法。研究表明，使用螺杆钻具时，应在螺杆钻具推荐工作参数内，以钻头水功率与螺杆钻具水功率之和最大为指标优选钻井水力参数；为了获得最优水力参数，螺杆钻具工作压降尽可能采用推荐工作压降，钻头压降尽可能接近螺杆钻具传动轴限定的最大钻头压降。

英文摘要：

Although positive displacement dow n-hole motor （PDM ）is commonly used in directional drilling at present ,not much effort has been made in research on the optimization methods for drilling hy-draulic parameters when using a PDM .An optimization model in drilling fluid rate and drill bit nozzle pres-sure-drop selection has been established by mathematical programming method w hile taking PDM ’s recom-mended operating parameters as constrain conditions .T he research results show that hydraulic parameters should be optimized within PDM ’s recommended operating parameters while taking maximum total hy-draulic power designated to drill bit and PDM as the target .To obtain optimum drilling hydraulic parame-ters ,the PDM’s working pressure-drop should be within the recommended working pressure-drop while bit nozzle pressure-drop is close to the maximum of that transmission shaft of the down hole motor allows to .