螺杆钻具最大机械钻速优化方法研究

Method of Optimizing Motor and Bit Performance for Maximum ROP

螺杆钻具配合PDC钻头进行钻进,可以大大地提高机械钻速、降低成本、缩短钻井周期。螺杆钻具的高转速可以为PDC钻头提高切削速度提供井下动力保障。在螺杆钻具与PDC钻头配合钻进时,首先选择配合较好的螺杆钻具和PDC钻头,然后根据其性能和要求选择合适的地层。本文介绍了螺杆钻具钻井参数的优化方法,此方法将螺杆工作特性方程与钻头机械钻速模型相结合,推导出了根据地层情况为达到最大机械钻速计算最佳钻压公式,并且将钻头磨损考虑在钻头机械钻速模型之中。同时本文模拟了在不同地层情况下2种螺杆钻具组合的钻进性能,并对比了计算结果。结果证明钻头磨损系数、钻进的长度和地层岩石强度值都会影响优化结果。为达到最大机械钻速,本文方法也可以用于选择最佳的螺杆和钻头组合。

By PDM(positive displacement mud motor)matching with PDC drilling bits,drilling rates are able to be increased greatly,drilling costs are decreased greatly,and the drilling cycles are shortened.High rotate speeds of PDM can improve PDC bit’S cutting rates,and also can provide downhole motives.When PDC bits.,are matched with PDM,PDC bits matching with PDM should be better optimized.And then in terms of PDC bit’S performance and requirement.suitable formation should be selected optimally.In this paper,the method of PDC bits optimization matching with PDM are discussed in detail,which discusses how motor performance equation,coupled with an ROP model,can predict the optimal WOB(weight—on—hit)required to derive maximum ROP for fl given section of a hole to be drilled.Bit wear is also included in the ROP model and an analysis is performed tO optimize a given interval.The optimization approach is illustrated with two examples for different formation types comparing the performance of two motors with PDC bits.It is shown that the bit wear coefficient,length of the interval and interval rock strength values affect the simulation results.This analytical approach can also be used tO determine the optimum PDM/PDC bit combination to achieve maximum ROP.