Management of equivalent circulating density (ECD) is one of the key issues in designing and drilling extended reach well (ERW). The paper focuses on ECD fluctuation occurred while repeated formation and erosion of cuttings deposit bed in drilling ERW. Numerical studies of hydraulics calculation were carried out in combination with cuttings transport model along the whole trajectory of ERW. While the cause of ECD fluctuation is primarily thought to be the mud pumps being turned on and off, our calculations showed that repeated formation and erosion of cuttings deposit bed, due to the repetition of drilling and drilling interruption for making a connection, causes a significant level of irregular fluctuation of ECD. To avoid severe unexpected ECD fluctuation in drilling ERW, the authors recommend that the schedule of mud circulation operations for hole cleaning and ROP management should be carefully designed by hydraulics calculations in consideration of transient behavior of cuttings transport.

You can access this article if you purchase or spend a download.